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PubMed1999

Surgical treatment of DeBakey type I aortic dissection using the "elephant trunk technique".

OBJECTIVES: To review the indications, operative methods and postoperative management of the "elephant trunk technique", and to report two cases of DeBakey type I aortic dissection treated with the "elephant trunk technique". METHODS: Two cases of DeBakey type I aortic dissection were operated with selective cerebral perfusion via the right subclavian artery. At the first stage, a tubular dangling aortic graft prosthesis ("elephant trunk") was inserted into the distal aorta while replacing the ascending aorta and aortic arch. The distal elephant trunk prosthesis was then used at the second stage involving the replacement of the sections of the distal aorta via a left-sided thoracotomy. RESULTS: The two operations were successful. Ultrafast computed tomograph (UFCT) showed that the two patients were cured after the first stage operation, and the second stage procedure could have been avoided. CONCLUSIONS: The "elephant trunk technique" is a multiple stage approach in the treatment of extensive aneurysmal diseases of the aorta. The procedure is indicated for patients who have combined diseases of both ascending aorta plus aortic arch segments and descending aortic aneurysm. It can also be used for patients with DeBakey type I aortic dissection. Some patients can be cured after the first stage operation.

Aortic Dissection↗
PubMed1996

The sensorineural specializations of the trunk tip (finger) of the Asian elephant, Elephas maximus.

BACKGROUND: The dorsal extension of the tip of the trunk of Asian elephants (Elephas maximus), often referred to as "the finger," possesses remarkable mechanical dexterity and is used for a variety of special behaviors including grasping food and tactile and ultimately chemosensory recognition via the vomeronasal organ. The present study describes a unique sensory innervation of this specialized region of the trunk. METHODS: The tip of the dorsal aspect of the trunk is referred to as the trunk tip finger and has been studied grossly in 13 living elephants. One tip from a male Asian elephant was obtained for histologic study when it was accidentally severed. The tissue was fixed in 10% neutral buffered formalin, and portions were either sectioned frozen or embedded in paraffin and serial sectioned. Sections were stained with silver in both cases. RESULTS: The skin of the trunk tip finger differs from that of the surrounding areas; it contains a high density of free nerve endings, numerous convoluted branched small corpuscles, and vellus vibrissae that resemble vellus hairs, which do not protrude beyond the skin surface. The finger is thus densely innervated with three distinctive types of sensory terminals. Corpuscular receptors consist of small Pacinian corpuscles and convoluted branched simple corpuscles. Both are present in the superficial dermis. Abundant regular vibrissae are present in the skin surrounding the trunk tip finger. Short vibrissae that do not protrude from the skin surface, referred to as vellus vibrissae, are abundant in the finger tip. Both types of vibrissae are innervated by hundreds of axons resembling the mystacial vibrissae of rodents. Free nerve endings are numerous in the superficial dermis, often making intimate contact with the basal cells of rete pegs. CONCLUSIONS: The dorsal finger of the trunk tip of Asian elephants has a unique sensory innervation that resembles aspects of sensory innervation of mystacial skin of rodents or lip tissue of monkeys. This dense sensory innervation can be correlated with the tactile ability of these animals to use the trunk finger to grasp small objects for feeding and to insert chemically active samples into the ductal orifices of the vomeronasal organ for subsequent chemosensory processing.

Animals↗
PubMed1999

Serum prolactin concentrations in the captive female African elephant (Loxodonta africana): potential effects of season and steroid hormone interactions.

Research was conducted to determine whether seasonal changes in prolactin secretion occur in nonpregnant female African elephants and to examine potential functional interrelationships between secretion of prolactin, cortisol, and progesterone. Weekly blood samples were taken for 18 months from four female African elephants and the sera were analyzed by RIA for progesterone, cortisol, and prolactin concentrations. There was no significant effect of season on serum concentrations of prolactin. Estrous cycles averaged 14 weeks in length and were composed of a 9-week luteal phase and a 5-week follicular phase (based on progesterone concentrations consistently >200 and <200 pg/ml, respectively). Estrous cycle synchronicity was evident between pairs of elephants. Serum concentrations of prolactin (3.91 +/- 0.69 ng/ml; range: 0.84-15.8 ng/ml) were significantly lower during the luteal, compared with the follicular, phase (P < 0.0001; t test) and were positively correlated with serum concentrations of cortisol (r = 0.14; P < 0.05). Mean (+/-SE) serum concentration of cortisol was 5.7 +/- 1.3 ng/ml (range: 1.4-19.3 ng/ml), and concentrations of this adrenal steroid were negatively correlated with progesterone concentrations (r = -0.15; P < 0.01). Increased serum concentrations of prolactin detected during the follicular phase suggest that this hormone may be regulated by ovarian estrogens and may play a role in modulating ovarian function in the elephant.

Animals↗
PubMed2006

Detection of fetal gender differences in maternal serum progesterone concentrations of Asian elephants (Elephas maximus).

Previous studies have analyzed total testosterone concentrations in maternal serum for a reliable method of fetal gender determination in Asian elephants (Elephas maximus). The present study investigated the possibility that progesterone concentrations in maternal serum may reflect these testosterone patterns. Weekly serum samples were collected from 17 pregnancies in captive Asian elephants and analyzed via radioimmunoassay (RIA) for progesterone concentrations. Nine and eight cows carried male and female calves, respectively. Mean progesterone concentrations in maternal serum of elephants carrying male calves were greater than in those carrying female calves (P<0.01). Mean progesterone concentrations (based on 5-week means) in maternal serum were greater at weeks 20-55 (P<0.01) and 60-65 (P<0.05) for elephants carrying male calves.

Animals↗
PubMed2004

Elephant albumin: a multipurpose pheromone shuttle.

(Z)-7-dodecenyl acetate (Z7-12:Ac) is present in the urine of female Asian elephants (Elephas maximus) approaching ovulation and functions as a female-to-male sex pheromone. Here we show that a significant fraction of the pheromone in the urine is bound to a protein, elephant serum albumin (ESA), and provide evidence for key physiological functions of urinary ESA. Our biochemical and behavioral experiments suggest a three-fold role of ESA in pheromone signaling: (1) transporting Z7-12:Ac from serum into urine; (2) extending the presence of the pheromone in the environment without hampering detection; and (3) targeting pheromone delivery to chemosensory organs through localized release of the ligand induced by a pH change. The exploitation of albumin in pheromone transport clearly distinguishes the elephant from other mammals studied, and complements the uniqueness of elephant anatomy, physiology, and behavior.

Acetates↗
PubMed2005

Sexual differentiation in three unconventional mammals: spotted hyenas, elephants and tammar wallabies.

The present review explores sexual differentiation in three non-conventional species: the spotted hyena, the elephant and the tammar wallaby, selected because of the natural challenges they present for contemporary understanding of sexual differentiation. According to the prevailing view of mammalian sexual differentiation, originally proposed by Alfred Jost, secretion of androgen and anti-Mullerian hormone (AMH) by the fetal testes during critical stages of development accounts for the full range of sexually dimorphic urogenital traits observed at birth. Jost's concept was subsequently expanded to encompass sexual differentiation of the brain and behavior. Although the central focus of this review involves urogenital development, we assume that the novel mechanisms described in this article have potentially significant implications for sexual differentiation of brain and behavior, a transposition with precedent in the history of this field. Contrary to the "specific" requirements of Jost's formulation, female spotted hyenas and elephants initially develop male-type external genitalia prior to gonadal differentiation. In addition, the administration of anti-androgens to pregnant female spotted hyenas does not prevent the formation of a scrotum, pseudoscrotum, penis or penile clitoris in the offspring of treated females, although it is not yet clear whether the creation of masculine genitalia involves other steroids or whether there is a genetic mechanism bypassing a hormonal mediator. Wallabies, where sexual differentiation occurs in the pouch after birth, provide the most conclusive evidence for direct genetic control of sexual dimorphism, with the scrotum developing only in males and the pouch and mammary glands only in females, before differentiation of the gonads. The development of the pouch and mammary gland in females and the scrotum in males is controlled by genes on the X chromosome. In keeping with the "expanded" version of Jost's formulation, secretion of androgens by the fetal testes provides the best current account of a broad array of sex differences in reproductive morphology and endocrinology of the spotted hyena, and androgens are essential for development of the prostate and penis of the wallaby. But the essential circulating androgen in the male wallaby is 5alpha androstanediol, locally converted in target tissues to DHT, while in the pregnant female hyena, androstenedione, secreted by the maternal ovary, is converted by the placenta to testosterone (and estradiol) and transferred to the developing fetus. Testicular testosterone certainly seems to be responsible for the behavioral phenomenon of musth in male elephants. Both spotted hyenas and elephants display matrilineal social organization, and, in both species, female genital morphology requires feminine cooperation for successful copulation. We conclude that not all aspects of sexual differentiation have been delegated to testicular hormones in these mammals. In addition, we suggest that research on urogenital development in these non-traditional species directs attention to processes that may well be operating during the sexual differentiation of morphology and behavior in more common laboratory mammals, albeit in less dramatic fashion.

Androgens↗
PubMed2003

Non-invasive assessment of adrenocortical function in the male African elephant (Loxodonta africana) and its relation to musth.

Adult male elephants periodically show the phenomenon of musth, a condition associated with increased aggressiveness, restlessness, significant weight reduction and markedly elevated androgen levels. It has been suggested that musth-related behaviours are costly and that therefore musth may represent a form of physiological stress. In order to provide data on this largely unanswered question, the first aim of this study was to evaluate different assays for non-invasive assessment of adrenocortical function in the male African elephant by (i) characterizing the metabolism and excretion of [3H]cortisol (3H-C) and [14C]testosterone (14C-T) and (ii) using this information to evaluate the specificity of four antibodies for determination of excreted cortisol metabolites, particularly with respect to possible cross-reactions with androgen metabolites, and to assess their biological validity using an ACTH challenge test. Based on the methodology established, the second objective was to provide data on fecal cortisol metabolite concentrations in bulls during the musth and non-musth condition. 3H-C (1 mCi) and 14C-T (100 microCi) were injected simultaneously into a 16 year old male and all urine and feces collected for 30 and 86 h, respectively. The majority (82%) of cortisol metabolites was excreted into the urine, whereas testosterone metabolites were mainly (57%) excreted into the feces. Almost all radioactive metabolites recovered from urine were conjugated (86% 3H-C and 97% 14C-T). In contrast, 86% and >99% of the 3H-C and 14C-T metabolites recovered from feces consisted of unconjugated forms. HPLC separations indicated the presence of various metabolites of cortisol in both urine and feces, with cortisol being abundant in hydrolysed urine, but virtually absent in feces. Although all antibodies measured substantial amounts of immunoreactivity after HPLC separation of peak radioactive samples and detected an increase in glucocorticoid output following the ACTH challenge, only two (in feces against 3alpha,11-oxo-cortisol metabolites, measured by an 11-oxo-etiocholanolone-EIA and in urine against cortisol, measured by a cortisol-EIA) did not show substantial cross-reactivity with excreted 14C-T metabolites and could provide an acceptable degree of specificity for reliable assessment of glucocorticoid output from urine and feces. Based on these findings, concentrations of immunoreactive 3alpha,11-oxo-cortisol metabolites were determined in weekly fecal samples collected from four adult bulls over periods of 11-20 months to examine whether musth is associated with increased adrenal activity. Results showed that in each male levels of these cortisol metabolites were not elevated during periods of musth, suggesting that in the African elephant musth is generally not associated with marked elevations in glucocorticoid output. Given the complex nature of musth and the variety of factors that are likely to influence its manifestation, it is clear, however, that further studies, particularly on free-ranging animals, are needed before a possible relationship between musth and adrenal function can be resolved. This study also clearly illustrates the potential problems associated with cross-reacting metabolites of gonadal steroids in EIAs measuring glucocorticoid metabolites. This has to be taken into account when selecting assays and interpreting results of glucocorticoid metabolite analysis, not only for studies in the elephant but also in other species.

Adrenal Cortex↗
PubMed2003

The use of low-frequency vocalizations in African elephant(Loxodonta africana) reproductive strategies.

Fertility-advertisement calls in females are predicted to occur in nonmonogamous species where males and females are widely separated in space. In African elephants, low-frequency vocalizations have thus been suggested as a reproductive strategy used by fertile females to attract mates. This study examined the use of low-frequency vocalizations with respect to different phases of the estrous cycle in African elephants by simultaneously monitoring vocalizations, behavior, and hormonal profiles. Subjects were one male and six female African elephants housed at Disney's Animal Kingdom. No acoustically distinct vocalizations were restricted to the ovulatory follicular phase. However, overall rate of low-frequency vocalization as well as the rate of one acoustically distinct vocalization changed over the estrous cycle, with highest rates of calling related to the first period of follicular growth, or anovulatory follicular phase. Elevated rates of vocalization thus were not restricted to behavioral estrus and occurred much earlier in the estrous cycle than in most species that produce fertility-advertisement calls. Both herd composition and elephant identity also affected rates of vocalization. Vocalizations therefore may not be reliable signals of actual fertility. However, the increase in vocalizations in advance of estrus may attract males to the herd prior to ovulation, facilitating both male-male competition and female choice. Once present in the herd, males may then switch strategies to use more reliable chemical and visual cues to detect ovulating females.

Animals↗
PubMed1997

Neuroendocrine-associated behavioral patterns in the male Asian elephant (Elephas maximus).

Steroid-responsive behaviors have been reported in various species; however, the reports thus far on the male Asian elephant (bull) during musth are few in number and most have been conducted on single captive animals for short time periods. The purpose of this investigation was to perform a longitudinal study on steroid-responsive behavior in 3 male Asian elephants from a captive herd of 11 male Asian elephants in Nepal. Male Asian elephants were 18, 25, and 43 years old. The animals had serum collected for 11 months and were observed on a daily basis for aggressive behavior according to the Species Survival Plan (SSP) collection protocol on SSP data sheets. Testosterone (T) and dihydrotestosterone (DHT) were measured in each animal by radioimmunoassay. Testosterone levels rose during musth 26-fold compared to nonmusth, and DHT was elevated 12-fold in musth. Maximal aggressive behavior episodes occurred during peak elevations of T and DHT, with correlation coefficients of 0.82 and 0.89, respectively. Therefore, we suggest that the aggressive episodes are dependent on elevated circulating androgens acting on androgen-responsive neural tissues.

Animals↗
PubMed1998

Endocrinology of the ovarian cycle and pregnancy in the Asian (Elephas maximus) and African (Loxodonta africana) elephant.

In reviewing the literature, this paper assesses the current level of understanding of the hormonal control of the ovarian cycle and pregnancy in the elephant. Data are compiled from two genera, Elephas maximus and Loxodonta africana, recognizing differences where known to exist. Measurements of various steroid and peptide hormones, but most notably immunoreactive progesterone (iP), indicate an overall cycle length of 15-16 weeks, comprising an 8-11-week luteal phase and a shorter inter-luteal (follicular) period of 4-6 weeks. Oestrogen related phenomena suggest the occurrence of two (possibly more) waves of follicular development with a 3-week periodicity, although oestrogen levels are low and fluctuate without clear pattern. The inter-luteal period is characterized by two discrete LH peaks also 3 weeks apart, but only the second is associated with an iP rise. Ovulation rate is variable and additional luteal structures lacking ovulation points are probably formed each cycle. The post-ovulatory period is associated with elevated progestogen levels, mainly 5alpha-reduced compounds, while progesterone itself is a minor secretory product. A revised model for the elephant ovarian cycle is presented. Detailed information on the endocrinology of pregnancy is lacking. Elevated progestins beyond the normal luteal phase indicate that conception extends the functional lifespan of the CL, with maximum steroidogenic activity between 3-15 months. The nature of the luteotrophic support is not known and placental gonadotrophins have not been conclusively demonstrated. Progestins fluctuate at or slightly above luteal phase values throughout pregnancy. There is a marked increase in prolactin levels after 16-24 weeks and a relationship with oestrogen secretion may exist since circulating and urinary levels show a progressive increase from 6-8 months. A placental contribution to progestin secretion is likely, although direct evidence is lacking. Considerable enlargement of foetal gonads during the second half of pregnancy in African elephants suggests a possible steroidogenic function, but none has been defined. The endocrine events leading to parturition are unknown. In the Asian elephant, a fall in iP precedes parturition; oestrogen levels decline and cortisol increases at the time of birth. The paper concludes with a brief selection of priorities for future research.

Animals↗
PubMed2003

Arterial blood gas control in the upright versus recumbent Asian elephant.

In the elephant, there is concern that lateral recumbency (LR) impairs respiratory muscle and lung function resulting in clinically significant arterial hypoxemia. Using healthy adult female Asian elephants (Elephas maximus, n=6), the hypothesis was tested that, given the O(2) binding characteristics of elephant blood, substantial reductions in arterial O(2) pressure (Pa(O(2))) in LR could be tolerated without lowering arterial O(2) content appreciably. Fifteen minutes of LR decreased Pa(O(2)) from 103+/-2 (upright, U) to 77+/-4 mmHg (P<0.05) and hemoglobin O(2) saturation (U, 97.8+/-0.1, LR, 95.3+/-0.5%, P<0.05). However, due to a recumbency-induced hemoconcentration, arterial O(2) content was unchanged (U, 18.2+/-2.4, LR, 18.3+/-2.1 ml O(2) per 100 ml). In addition, there was a mild hyperventilation in LR that reduced arterial CO(2) pressure (P(CO(2))) from 39.4+/-0.3 to 37.1+/-1.0 mmHg (P<0.05). These data indicate that the Asian elephant can endure at least short periods of LR without lowering arterial O(2) content.

Acid-Base Equilibrium↗
PubMed2006

Do Asian elephants (Elephas maximus) apply causal reasoning to tool-use tasks?

Two experiments addressed contradictory claims about causal reasoning in elephants. In Experiment 1, 4 Asian elephants (Elephas maximus) were pretrained to remove a lid from the top of a bucket and retrieve a food reward. Subsequently, in the first 5 critical trials, when the lid was placed alongside the bucket and no longer obstructed access to the reward, each elephant continued to remove the lid before retrieving the reward. Experiment 2, which involved 11 additional elephants and variations of the original design, yielded similarly counterintuitive observations. Although the results are open to alternative interpretations, they appear more consistent with associative learning than with causal reasoning. Future applications of Fabrean methodologies (J. H. Fabre, 1915) to animal cognition are proposed.

Age Factors↗
PubMed2003

Estimating population sizes for elusive animals: the forest elephants of Kakum National Park, Ghana.

African forest elephants are difficult to observe in the dense vegetation, and previous studies have relied upon indirect methods to estimate population sizes. Using multilocus genotyping of noninvasively collected samples, we performed a genetic survey of the forest elephant population at Kakum National Park, Ghana. We estimated population size, sex ratio and genetic variability from our data, then combined this information with field observations to divide the population into age groups. Our population size estimate was very close to that obtained using dung counts, the most commonly used indirect method of estimating the population sizes of forest elephant populations. As their habitat is fragmented by expanding human populations, management will be increasingly important to the persistence of forest elephant populations. The data that can be obtained from noninvasively collected samples will help managers plan for the conservation of this keystone species.

Animals↗
PubMed2004

Assigning African elephant DNA to geographic region of origin: applications to the ivory trade.

Resurgence of illicit trade in African elephant ivory is placing the elephant at renewed risk. Regulation of this trade could be vastly improved by the ability to verify the geographic origin of tusks. We address this need by developing a combined genetic and statistical method to determine the origin of poached ivory. Our statistical approach exploits a smoothing method to estimate geographic-specific allele frequencies over the entire African elephants' range for 16 microsatellite loci, using 315 tissue and 84 scat samples from forest (Loxodonta africana cyclotis) and savannah (Loxodonta africana africana) elephants at 28 locations. These geographic-specific allele frequency estimates are used to infer the geographic origin of DNA samples, such as could be obtained from tusks of unknown origin. We demonstrate that our method alleviates several problems associated with standard assignment methods in this context, and the absolute accuracy of our method is high. Continent-wide, 50% of samples were located within 500 km, and 80% within 932 km of their actual place of origin. Accuracy varied by region (median accuracies: West Africa, 135 km; Central Savannah, 286 km; Central Forest, 411 km; South, 535 km; and East, 697 km). In some cases, allele frequencies vary considerably over small geographic regions, making much finer discriminations possible and suggesting that resolution could be further improved by collection of samples from locations not represented in our study.

Africa↗
PubMed1995

A double mutant of sperm whale myoglobin mimics the structure and function of elephant myoglobin.

The functional, spectral, and structural properties of elephant myoglobin and the L29F/H64Q mutant of sperm whale myoglobin have been compared in detail by conventional kinetic techniques, infrared and resonance Raman spectroscopy, 1H NMR, and x-ray crystallography. There is a striking correspondence between the properties of the naturally occurring elephant protein and those of the sperm whale double mutant, both of which are quite distinct from those of native sperm whale myoglobin and the single H64Q mutant. These results and the recent crystal structure determination by Bisig et al. (Bisig, D. A., Di Iorio, E. E., Diederichs, K., Winterhalter, K. H., and Piontek, K. (1995) J. Biol. Chem. 270, 20754-20762) confirm that a Phe residue is present at position 29 (B10) in elephant myoglobin, and not a Leu residue as is reported in the published amino acid sequence. The single Gln64(E7) substitution lowers oxygen affinity approximately 5-fold and increases the rate of autooxidation 3-fold. These unfavorable effects are reversed by the Phe29(B10) replacement in both elephant myoglobin and the sperm whale double mutant. The latter, genetically engineered protein was originally constructed to be a blood substitute prototype with moderately low O2 affinity, large rate constants, and increased resistance to autooxidation. Thus, the same distal pocket combination that we designed rationally on the basis of proposed mechanisms for ligand binding and autooxidation is also found in nature.

Amino Acid Sequence↗
PubMedDate not supplied

Structure and history of African elephant populations: I. Eastern and southern Africa.

Patterns of restriction site variation within mitochondrial DNA (mtDNA) of 270 individuals were used to examine the current structure of savanna elephant populations and to infer historical patterns of gene flow across eastern and southern Africa. Elephants have a complex population structure characterized by marked subdivision at the continental level (Fst = 0.39; 95% confidence interval 0.19-0.58), and isolation by distance at the regional level. However, phylogeographic analysis revealed evidence of protracted gene flow across the continent. First, one relatively derived haplotype was found at all sampling locations. Second, haplotypes representing exceptionally divergent (up to 8.3%) mitochondrial clades were found to coexist at distant (> 2,000 km) sampling locations. In the few other species characterized by sympatric individuals bearing such divergent haplotypes, all such individuals were found to coexist within limited geographical regions. Accordingly, pronounced mitochondrial divergence within populations is often attributed to ancestral isolation in allopatry, followed by secondary contact. The patterns within elephants do not accord with ancestral isolation in allopatry. Given the exceptional mobility of elephants, a geographical barrier is unlikely to have obstructed gene flow between regions for long enough to produce the observed mitochondrial divergence. Rather, the patterns are consistent with the more parsimonious hypothesis, based on neutral coalescent theory, that gene flow has maintained a sufficiently large effective population size (> 50,000 females) for representatives of clades that diverged at least 4 million years ago to have persisted by chance within a population that was subdivided, but not strictly isolated in allopatry.

Africa, Eastern↗
PubMed1996

Nonluteal estrous cycles of 3-week duration are initiated by anovulatory luteinizing hormone peaks in African elephants.

Previous attempts to characterize the estrous cycle of elephants have yielded conflicting estimates of cycle length and LH profiles. In order to establish artificial breeding programs in this species, resolution of these issues is needed. Therefore, four female African elephants housed at the Indianapolis Zoo were studied for approximately 6 mo beginning in December 1994. Blood was collected weekly, and the serum was immediately analyzed for progesterone (P4). Whenever the weekly concentration of P4 was found to be low, blood was collected one or four times per day. All serum samples were assayed for LH, and the daily samples were assayed for P4 and estradiol. Transient increases of serum LH (designated as peaks) were observed four times in each of the four females. Of these 16 LH peaks, 8 were classified as ovulatory LH (ovLH) peaks and 8 were classified as anovulatory LH (anLH) peaks. Peaks designated ovLH averaged 3.60 +/- 0.67 ng/ml (mean +/- SEM); serum P4 measured during these peaks began to increase 2-3 days before each ovLH peak and continued to increase for several weeks thereafter, reaching a peak of 675 +/- 35 pg/ml. The eight other LH peaks, designated anLH peaks, were of similar (p > 0.05) magnitude averaging 3.07 +/- 0.72 ng/ml, but the serum concentration of P4 remained very low (< 80 pg/ml) during and for several weeks after these peaks. Six peaks designated anLH occurred an average of 12.2 +/- 1.4 days after serum P4 had declined below 80 pg/ml. In each elephant, there was a regular sequence in which each ovLH peak was followed by a luteal-active period lasting about 60 days and then about 12 days later by one anLH peak. Each anLH peak was followed 19-22 days later by one ovLH peak, but serum P4 remained at nonluteal levels throughout this interval between peaks. The authors propose to designate this interval after the anLH peak and before the next ovLH peak as a nonluteal (i.e., low P4) estrous cycle of only 3-wk duration. Following each short nonluteal estrous cycle, there was a single ovLH peak that initiated one luteal-active estrous cycle lasting 10-11 wk until terminated by the next anLH peak. The present results demonstrate that nonpregnant African elephants, housed in the absence of males, alternate between short nonluteal estrous cycles and long luteal-active estrous cycles. Daily measurements of serum P4 can be used to distinguish between the two types of estrous cycles and thereby provide a clinical prediction about the optimum time for artificial insemination.

Animals↗
PubMed1998

Influence of gestation on uterine endometrial steroid receptor concentrations in the African elephant, Loxodonta africana.

The modulatory effects of gestational age and circulating concentrations of progesterone, 5alpha-pregnane-3,20-dione, and estradiol-17beta on the uterine sex steroid hormone receptor levels of the African elephant were investigated. Uterine tissue biopsies and blood samples were obtained from animals culled in the Kruger National Park. Estrogen and progesterone receptor concentrations were determined in uterine biopsies from subadult, lactating, early-, mid-, and late-pregnant elephants, by equilibrium binding assays. Circulating estradiol-17beta and progesterone concentrations were measured by means of RIAs, while plasma concentrations of 5alpha-pregnane-3,20-dione were determined with an amplified ELISA. Significant inverse correlations of the concentrations of estrogen and progesterone receptors with the gestational stage of the elephants were observed. Pregnant uterine horns of individual animals contained lower levels of estrogen and progesterone receptors than the nonpregnant horns of the same animals. A strong positive correlation existed between uterine estrogen and progesterone receptors levels. Circulating concentrations of 5alpha-pregnane-3,20-dione and progesterone decreased with an increase in the concentrations of progesterone receptors as well as with fetal age. We conclude that the progesterone receptor concentrations are down-regulated with progressing gestation in the African elephant. This down-regulation appears to be linked to an increase in circulatory 5alpha-pregnane-3,20-dione concentration in the plasma of pregnant animals.

5-alpha-Dihydroprogesterone↗