Mice that are ets variant gene 5 (ETV5) null (Etv5(-/-)) undergo the first wave of spermatogenesis but lose all spermatogonial stem cells (SSCs) during this time. The SSC loss in Etv5(-/)-mice begins during the neonatal period, suggesting a role for ETV5 in SSC self-renewal during this period. Herein, we show that Etv5 mRNA was present in perinatal mouse testis and that ETV5 was expressed in fetal Sertoli cells and by germ cells and Sertoli cells during the neonatal period. Transplantation of Etv5(-/)-germ cells failed to establish spermatogenesis in W/W-v mice testes, indicating that germ cell ETV5 has a key role in establishment or self-renewal of transplanted SSCs. The SSC self-renewal is stimulated by glial cell-derived neurotrophic factor (GDNF) acting through the RET/GDNF family receptor alpha 1 (GFRA1) receptor complex in SSCs. Immunohistochemistry, quantitative PCR, and laser capture microdissection revealed decreased RET mRNA and protein expression in spermatogonia of neonatal Etv5-/-mice by Postnatal Days 4-8, indicating that disrupted GDNF/RET/GFRA1 signaling may occur before initial spermatogonial stem/progenitor cell decrease. Etv5(-/)-spermatogonia had reduced proliferation in vivo and in vitro. Decreased cell proliferation may cause the observed decreases in the number of type A spermatogonia (Postnatal Day 17) and daily sperm production (Postnatal Day 30) in Etv5(-/)-mice, indicating quantitative impairments in the first wave of spermatogenesis. In conclusion, ETV5 is expressed beginning in fetal Sertoli cells and can potentially have effects on neonatal Sertoli cells and germ cells. In addition, ETV5 has critical effects on neonatal spermatogonial proliferation, which may involve impaired signaling through the RET receptor.

The transcription factor Ets-variant gene 5 (ETV5) is essential for spermatogonial stem cell (SSC) self-renewal, as the targeted deletion of the Etv5 gene in mice (Etv5(-/-)) results in only the first wave of spermatogenesis. Reciprocal transplants of neonatal germ cells from wild-type (WT) and Etv5(-/-) testes were performed to determine the role of ETV5 in Sertoli cells and germ cells. ETV5 appears to be needed in both cell types for normal spermatogenesis. In addition, Etv5(-/-) recipients displayed increased interstitial inflammation and tubular involution after transplantation. Preliminary studies suggest that the blood-testis barrier (Sertoli-Sertoli tight junctional complex) is abnormal in the Etv5(-/-) mouse.

In some species such as flies, worms, frogs and fish, the key to forming and maintaining early germ cell populations is the assembly of germ plasm, microscopically distinct egg cytoplasm that is rich in RNAs, RNA-binding proteins and ribosomes. Cells which inherit germ plasm are destined for the germ cell lineage. In contrast, in mammals, germ cells are formed and maintained later in development as a result of inductive signaling from one embryonic cell type to another. Research advances, using complementary approaches, including identification of key signaling factors that act during the initial stages of germ cell development, differentiation of germ cells in vitro from mouse and human embryonic stem cells and the demonstration that homologs of germ plasm components are conserved in mammals, have shed light on key elements in the early development of mammalian germ cells. Here, we use FRET (Fluorescence Resonance Energy Transfer) to demonstrate that living mammalian germ cells possess specific RNA/protein complexes that contain germ plasm homologs, beginning in the earliest stages of development examined. Moreover, we demonstrate that, although both human and mouse germ cells and embryonic stem cells express the same proteins, germ cell-specific protein/protein interactions distinguish germ cells from precursor embryonic stem cells in vitro; interactions also determine sub-cellular localization of complex components. Finally, we suggest that assembly of similar protein complexes may be central to differentiation of diverse cell lineages and provide useful diagnostic tools for isolation of specific cell types from the assorted types differentiated from embryonic stem cells.

This review addresses the concept that essential trace minerals play a vital role in many enzymatic and metabolic pathways that are critical for conceptus development during pregnancy in livestock species. The conceptus relies entirely on the maternal system for a sufficient supply of trace minerals and other nutrients needed for normal development. If this supply is inadequate, growth and/or health of the conceptus can be affected adversely, and many of these effects carry over into the neonatal period. Information, accumulated in our laboratory and presented herein, indicates that zinc, copper and manganese are among the trace minerals that have the greatest impact on reproduction. For example, levels of zinc, copper and manganese were several fold greater in the conceptus than in other reproductive tissues, indicating that the conceptus preferentially accumulates these minerals, an action that may be important for conceptus development, growth and survival. Moreover, some recent results indicate that increasing the biological availability of zinc, copper and manganese, by attachment to short peptide chains (i.e., proteinated trace minerals) can enhance reproductive performance of swine. Mineral concentrations in conceptuses from female pigs consuming proteinated trace minerals were greater than those from females that consumed only inorganic mineral salts. Elucidating the mechanisms whereby conceptus development and survival are enhanced by essential trace minerals may lead to development of specific feeding programs to increase the number and health of offspring at parturition, thereby allowing for further improvements in production efficiency in animal agriculture.

Oxytocin (OT) stimulates pulsatile secretion of uterine PGF2 alpha in ruminants, but the role of OT in regulation of the estrous cycle of pigs is not clear. four experiments were performed to examine the effect of exogenous OT on interestrous interval of intact cyclic and hysterectomized gilts. In Exp. 1, i.v. injections of 20 USP units (equivalent to 20 IU) of OT, once/day via an ear vein on d 10, 12, 14, and 16 after estrus, decreased (P < .01) interestrous interval (19.9 +/- .2 d) compared with vehicle-injected control gilts (20.8 +/- .2 d), without affecting ovulation rate (12.1 vs. 12.0 +/- .7 corpora lutea; OT vs control gilts) at subsequent estrus. In Exp. 2, i.v. infusions of 20 USP units of OT, twice/day via an indwelling jugular catheter on d 10 to 16 after estrus, did not alter interestrous interval (20.6 +/- .3 d) compared with control gilts (20.4 +/- .3 d). Concentrations of progesterone in jugular vein plasma did not differ between treatment groups on d 9 to 21 after estrus. In Exp. 3, i.m. injections of 20 USP units of OT, twice/day on d 10 to 16 after estrus, decreased (P < .05) interestrous interval (20.6 +/- .4 d) compared with control gilts (22.3 +/- .4 d). In Exp. 4, i.m. injections of 20 USP units of OT, twice/day on d 10 to 16 after estrus, decreased (P < .05) interestrous interval (20.7 +/- .3 d) compared with control injections in uterine-intact gilts (21.8 +/- .3 d). None of the gilts hysterectomized on d 7 and treated on d 10 to 16 after estrus with either OT or control injections returned to estrus by d 28, and all had increased plasma progesterone on d 21 to 27. Mean weight of individual corpora lutea (502 vs 449 +/- 28 mg; OT vs control gilts) and total weight of corpora lutea (5,758 vs. 5,126 +/- 298 mg; OT vs control gilts) of hysterectomized gilts did not differ between treatment groups at ovariectomy on d 28. These results indicate that 1) exogenous OT administered on d 10 to 16 shortened the interestrous interval of intact cyclic gilts and 2) the effect of OT was uterine-dependent.

Oxytocin (OT) stimulates phosphoinositide (PI) hydrolysis and prostaglandin (PG) F2 alpha secretion from the endometrium of cyclic pigs, but the presence of specific endometrial receptors for OT has not been demonstrated in this species. Two experiments were performed to detect the presence of functional OT receptors on endometrium collected 15 days post estrus from cyclic gilts. OT receptor density and Kd were determined by receptor assay and Scatchard analysis. Hydrolysis of PI (i.e., incorporation of [3H]inositol into total inositol phosphates) and PGF2 alpha secretion were studied with use of incubations of endometrial explants. Concentrations of PGF2 alpha were log-transformed for analysis of variance and are expressed as means +/- standard error of log-transformed data. In experiment 1, mean density and mean Kd of OT receptors on endometrium of gilts were 29.2 +/- 5.54 fmol/mg protein and 1.59 +/- 0.23 nM, respectively. OT receptor density was significantly correlated with the ability of 100 nM OT to stimulate PI hydrolysis (r = 0.83, p < 0.05) and PGF2 alpha secretion (r = 0.87, p < 0.10), but was not highly correlated with receptor Kd (r = -0.08, p = 0.85). In contrast, OT receptor Kd was not highly correlated with OT-stimulated PI hydrolysis (r = -0.19, p = 0.68) or OT-stimulated PGF2 alpha secretion (r = 0.14, p = 0.86). OT-stimulated PI hydrolysis was also significantly correlated (r = 0.80, p < 0.05) with OT-stimulated PGF2 alpha secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

The ability of recombinant ovine interferon-tau (roIFNtau) to extend the interestrous interval (IEI) in sheep was studied. Ewes were fitted with bilateral uterine catheters 7 or 8 days post estrus and were assigned to receive either 10 or 20 million antiviral (AV) units/day i.u. (approximately 100 or 200 ug) of roIFNtau or ovine conceptus secretory proteins containing equivalent AV units of native oIFNtau (noIFNtau; 4 ewes/treatment). Four control ewes received ovine serum proteins (SP). Total protein injected was 6 mg per day, half at 0700 hours and half at 1730 hours. The treatments were administered from Day 11.5 (estrus=Day 0) to Day 16. Blood samples were collected by jugular vienipuncture daily from Day 11 until ewes returned to estrus. concentrations of progesterone (P) in plasma were determined by RIA. Treatment with either noIFNtau or roIFNtau extended IEI beyond that of SP-treated ewes (19.1 vs 31.2+/-3.4 days P<0.03). Of the ewes receiving 100 mug/day of oIFNtau, 2 of 4 receiving noIFNtau (23.6+/-5.2 days) and 3 of 4 receiving roIFNtau (34.2+/-5.2 days) had an extended IEI. All ewes receiving 200 mug/day of noIFNtau or roIFNtau had an extended IEI (28.8 and 38.5+/-5.2 days, respectively). Ewes receiving roIFNtau had a longer IEI than those receiving noIFNtau (36.7 vs 26.2+/-3.4 days; P=0.07). Ewes with an extended IEI had functional corpora lutea, as assessed by P production. The results demonstrate that 10 or 20 million AV units (approximately 100 or 200 ug) of roIFNtau extends the IEI and that the length of the IEI is longer for ewes receiving roIFNtau than noIFNtau following injection of equivalent AV units.