Preimplantation development in ungulates: a 'ménage à quatre' scenario.

In ungulates, early embryonic development differs dramatically from that of mice and humans and is characterized by an extended period of pre- and peri-implantation development in utero. After hatching from the zona pellucida, the ungulate blastocyst will stay free in the uterus for many days before implanting within the uterine wall. During this protracted peri-implantation period, an intimate dialog between the embryo and the uterus is established through a complex series of paracrine signals. The blastocyst elongates, leading to extreme growth of extra-embryonic tissues, and at the same time, the inner cell mass moves up into the trophoblast and evolves into the embryonic disc, which is directly exposed to molecules present in the uterine fluids. In the peri-implantation period, uterine glands secrete a wide range of molecules, including enzymes, growth factors, adhesion proteins, cytokines, hormones, and nutrients like amino and fatty acids, which are collectively referred to as histotroph. The identification, role, and effects of these secretions on the biology of the conceptus are still being described; however, the studies that have been conducted to date have demonstrated that histotroph is essential for embryonic development and serves a critical function during the pre- and peri implantation periods. Here, we present an overview of current knowledge on the molecular dialogue among embryonic, extraembryonic, and maternal tissues prior to implantation. Taken together, the body of work described here demonstrates the extent to which this dialog enables the coordination of the development of the conceptus with respect to the establishment of embryonic and extra-embryonic tissues as well as in preparation for implantation.

Production of collared peccary (Pecari tajacu Linnaeus, 1758) parthenogenic embryos following different oocyte chemical activation and in vitro maturation conditions.

To optimize the protocols for assisted reproductive techniques (ARTs) in collared peccary (Pecari tajacu Linnaeus, 1758), we evaluated various conditions for oocyte in vitro maturation (IVM) and chemical activation. Initially, we assessed the IVM rates, cumulus-oocyte complex (COC) quality, and oocyte morphometry in the absence or presence of epidermal growth factor (EGF). There was no difference between the COCs matured in absence or presence of EGF for the expansion of cumulus cells (97.6% ±â€¯1.2 vs. 100% ±â€¯0.0), presence of first polar body (65.9% ±â€¯1.2 vs. 70.5% ±â€¯1.8), nuclear status in second metaphase (62.5% ±â€¯11.6 vs. 68.4% ±â€¯4.9), cytoplasmic maturation (100.0% ±â€¯0.7 vs. 75.0% ±â€¯0.7), reactive oxygen species levels (0.5 ±â€¯0.2 vs. 0.3 ±â€¯0.1), and mitochondrial membrane potential (1.1 ±â€¯0.2 vs. 1.1 ± 0.1). However, the zona pellucida thickness of matured COCs was reduced in the presence of EGF. Thus, the EGF group was used for further experiments. The oocytes were artificially activated with ionomycin and four secondary activator combinations [6-dimethylaminopurine (6D), 6D and cytochalasin B (6D + CB), cycloheximide (CHX), and CHX and CB (CHX + CB)]. The effect of immature COCs based on cumulus cell layers and cytoplasm homogeneity (GI and GII or GIII COCs) on embryonic development and quality was evaluated. There was no difference in the cleavage rates among the groups of secondary activators. The cleavage rates of embryos derived from GI/GII and GIII COCs were greater than 72.2% and 25.0%, respectively. Moreover, treatment with CHX showed a reduction in the cleavage rate of embryos derived from GIII COCs when compared to the cleavage rate of embryos derived from GI/GII COCs (P < 0.05). Nevertheless, higher rates of blastocyst/total GI and GII COCs were observed in the 6D group (27.6% ± 0.3) compared to CHX group (6.9% ± 0.3). Additionally, only 6D treatment resulted in the production of embryos derived from GIII COCs (25.0% ± 0.2). The percentage of the ICM/total cell ratio was also greater in blastocysts derived from 6D (42.5% ± 19.0), 6D + CB (37.9% ± 21.9), and CHX + CB (43.8% ± 19.6) groups when compared to CHX (3.6% ± 0.1) group. Thus, the combination of ionomycin and 6D could produce collared peccary embryos by activation of both GI/GII COCs and GIII COCs. These optimized IVM conditions using EGF and chemical activation using ionomycin and 6D in collared peccaries form the first steps for establishing ARTs to conserve this species.

Embryonic and fetal development of the collared peccary (Pecari tajacu).

The relative timing of the main fetal development events in species determine the extent of fetal development at birth, which range along a gradient of having altricial and precocial traits. The results from this study allow for description of important fetal developments in collared peccary (Pecari tajacu) using data from 118 embryo/fetuses from 68 pregnant peccaries obtained over a period of 15 years through collaborative methods with local hunters in the Amazon. The chronological order of emergence of external characteristics in relation to the total dorsal length (TDL) was: differentiated genitalia, limbs and eyelid buds (TDL ≥ 4.5 cm), fusioned eyelids and outer ear (TDL ≥ 5.6 cm), dorsal gland (TDL ≥ 7.3 cm), skin (TDL ≥ 9.2 cm), tactile pelage (TDL ≥ 12.9 cm), coverage pelage (TDL ≥ 17.0 cm), opened eyelids (TDL ≥ 21.5 cm) and tooth eruption (TDL ≥ 24.5 cm). The formula of fetal age was ∛W = 0.079 (t - 27.6), with a linear relationship between TDL and gestational age. The relative weight of tubular gastrointestinal organs, lungs, spleen and thymus increased during fetal development. In contrast, the relative weight of kidneys and liver consistently decreased during the fetal development period. Results of this study indicate the collared peccary is a precocial species and that changes during fetal development are very similar to those in other Suiform species.

Embryonic and fetal development of the white-lipped peccary (Tayassu pecari).

The white-lipped peccary (Tayassu pecari) is an endangered large-sized Neotropical ungulate that is one of the most hunted mammals in the Amazon. Here, we used two embryos and 102 white-lipped peccary fetuses originated from animals hunted for subsistence in the Peruvian and Brazilian Amazon to describe the intrauterine development of external and internal morphology of this Neotropical ungulate. Logistic regressions were used to estimate the probability of occurrence of main external characteristics in relation to the total dorsal length (TDL), while multiple linear and non-linear regressions were conducted to assess the relationship between external and visceral biometry with TDL. External characteristics appeared in the following chronological order: limbs, differentiated genitalia and opened eyelids (≥5.1 cm TDL), fused eyelids (≥6.2 cm TDL), hooves and outer ear (≥7.9 cm TDL), dorsal gland (≥9.4 cm TDL), skin (≥11.5 cm TDL); tactile pelage (≥13.8 cm TDL), covering pelage (≥20.9 cm TDL), tooth eruption (≥26.4 cm TDL) and opened eyelids (≥27.8 cm TDL). The formula of fetal age was ∛W = 0.084 (t - 31.80), with a high linear relationship between TDL and gestational age. All external biometric parameters and absolute volume of visceral organs showed strong positive relationship with TDL. Except for the liver, we found differences in the relative volume of most visceral organs between advanced fetuses (≥34.2 cm TDL) and adults. The most important events during the intrauterine development in the white-lipped peccary show that, in contrast with the domestic pig, it is a highly precocial species producing newborns with a high fetal growth velocity which allows newborns to achieve an early autonomous functionality. Our results are relevant to improve imaging techniques and assist the reproductive and clinical management for the white-lipped peccary both in captivity and in the wild.

The entotympanic in late fetal Artiodactyla (Mammalia).

The entotympanic is a neomorphic component of the bulla tympanica of placental mammals. Ontogenetically, its rostral component seems to be derived from the tubal cartilage, whereas its caudal component is normally connected with the sheath of the tympanohyal; the present study indicates additional sources of the caudal entotympanic. The entotympanics develop in late fetal or early postnatal life as cartilaginous structures, but in most taxa they ossifiy endochondrally as "os bullae". This skeletal element is absent only in a few placental orders, among them the Artiodactyla. Because it is present in their sister taxa within the Scrotifera, it is likely to be reduced secondarily in the even-toed mammals. The study of histological serial sections of late fetal stages of several artiodactyl species shows that vestigial cartilaginous homologues of the entotympanics are invariably present, contrary to statements in the literature. In a few perinatal stages even secondary ossifications or calcifications of the entotympanic cartilages can be observed. The tubal cartilage of artiodactyls also continues into an anterior tegmen tympani (new term) that forms the floor of the fossa muscularis major.

Macroscopic and microscopic aspects of collared peccary and white-lipped peccary placenta.

This study examines middle and late gestational placentae from 13 Tayassu tajacu (collared peccary) and 3 Tayassu pecari (white-lipped peccary), which are Artiodactyla belonging to the Family Tayassuidae. The chorionic sac of Tayassu species is diffuse and chorioallantoic. These epitheliochorial placentae show no trophoblast invasion into the uterine epithelium and there is interdigitation between fetal and maternal microvilli. Two distinct regions of the fetomaternal interface can be identified: the interareolar and the areolar regions. The uterine epithelium has eosinophilic cytoplasm with dispersed, basophilic and electron-dense granules. Trophoblast cells are irregularly cuboidal on top of the fetal ridges and columnar on troughs, where cells have cytoplasmic vesicles and large basal vacuoles, surrounded by whorls of smooth membranes. Capillaries indent the trophoblast cells forming a placental barrier 3 microm or less thick. The columnar uterine glandular epithelium has a subpopulation of granules staining with Perl's Prussian blue reaction, suggesting iron secretion. In areolar areas, the trophoblast cells show apical microvilli, a basophilic cytoplasm with electron-dense intracellular vacuoles and cisternae. The placenta can therefore be classified as non-deciduate. The ultrastructural aspects of this study reveal features that have not previously been described and extend our knowledge of functions relating to materno-fetal transport in these species.

Cryopreservation of gametes and embryos of non-domestic species.

Many species of mammals are threatened or endangered. Methods of assisted reproduction that are being used with increasing frequency to produce offspring of domestic animals and humans are often viewed as offering innovative ways to reproduce non-domestic species as well. Uncounted millions of live young of domestic or laboratory species have been produced from gametes and embryos stored at -70 degrees C or below, sometimes for as long as 25 to 35 yrs. Such methods of cryopreservation are now being applied with increasing frequency and urgency to preserve gametes and embryos of non-domestic and threatened species to establish "genome resource banks" or "frozen zoos." But levels of success to produce live young from such cryopreserved gametes or embryos vary considerably from species to species, as well as from individual to individual. It is sometimes thought that differences among species in fundamental characteristics of their gametes may determine the efficacy of cryopreservation and the production of live young. However, it may not be that ineffective cryopreservation is responsible for low success rates. Rather, the limiting factor may be insufficient information and knowledge of the most basic reproductive biology of such non-domestic species. Even standard methods of cryopreservation may be completely adequate to act as a "temporary" expedient to preserve germplasm of non-domestic species to permit time to acquire a fuller understanding of the biology and behavior of non-domestic species.

Comparative anatomy of the foramen ovale in the Suina.

The structure of the foramen ovale from six species of Suina was studied using the scanning electron microscope. In each species, the foramen ovale, when viewed from the terminal part of the caudal vena cava had the appearance of a short tunnel. In the domestic pig (Sus scrofa), the wart hog (Phacochoerus aethiopicus) and the bush pig (Potamochoerus porcus) a fold of tissue projected from the caudal edge of the foramen ovale into the lumen of the left atrium. It constituted a large proportion of the tube, and its distal end was generally straight-edged. In some domestic pig hearts small holes were found in the fold, and single threads of tissue arose from its trailing edge. These were not found in specimens from the other pigs or from the collared peccary (Tayassu tajacu), which had a thin unfenestrated tissue fold ending in a straight edge. In both species of hippopotamidae, the hippopotamus (Hippopotamus amphibius) and the pigmy hippopotamus (Choeropsis liberiensis) the fold of tissue was tubular, with strands of tissue extending from the atrial wall to insert on the outer surface of its proximal half. This tube was orientated at an angle of approximately 90 degrees to the caudal vena cava. Its walls were unfenestrated proximally and fenestrated distally, the latter forming a network over the end of the tube. The knotted appearance of the fold after birth suggested that the strands of the network had shortened and coalesced.

Age-related changes in the seminal vesicles of a Brazilian (Nelore) zebu.

Age changes in the structure of the seminal vesicles and in the rate of production of fructose and citric acid have been studied in a Brazilian (Nelore) zebu, from the fetal period to 36 months of age. At 3 and 6 months, the microscopic anatomy of the gland resembled that of the fetus; the tubules of the seminal vesicles had a reduced diameter and a low epithelial layer; only a few presented traces of secretion, and tissue contents of fructose and citric acid were accordingly low. At 12 months, the tubules were more ramified and had a larger diameter. In the 18-month-old animals the seminal vesicles presented substantial modifications; the tubules were large, with irregular lumina and surrounded by narrow stroma, the epithelial layer was higher than that of previous stages and its columnar cells had nuclei located basally. Tissue levels of fructose increased rapidly between 12 and 18 months. At 24 months, the seminal vesicles had reached the adult condition characterized by intense proliferation of tubules with irregular lumina and abundant secretory material. Numerous dark columnar cells were found in the epithelium. Seminal vesicles of Nelore zebus contain less fructose and citric acid than those of taurine bulls of comparable age.