Influence of standing estrus before an injection of GnRH during a beef cattle fixed-time AI protocol on LH release, subsequent concentrations of progesterone, and steriodogenic enzyme expression.

Beef cows that exhibit estrus before fixed-time AI have been reported to have increased pregnancy success and increased concentrations of progesterone during the subsequent estrous cycle. Therefore, these experiments were conducted to evaluate if initiation of standing estrus before an injection of GnRH during a fixed-time AI protocol affected LH pulses, subsequent concentrations of progesterone, and luteal steroidogenic enzyme expression. In Experiments 1 and 2, cows were treated with the CO-Synch protocol (100 µg GnRH day -9, 25 mg PGF(2α) day -2, and 100 µg GnRH day 0) and allotted to one of two treatments: 1) cows that initiated estrus before GnRH on day 0 (estrus; n = 5) or 2) cows that did not initiate estrus and were induced to ovulate by the GnRH on day 0 (no estrus; n = 5). In Experiment 1, blood samples were collected at 15-min intervals from 0 to 6 (bleed 1), 12 to 20 (bleed 2), 26 to 34 (bleed 3), and 40 to 48 (bleed 4) h after GnRH. Daily blood samples were collected for 17 d. Initiation of estrus before the GnRH injection had no effect on LH release or the pattern of progesterone increase; however, cows detected in estrus had overall increased (P = 0.002) concentrations of progesterone compared with cows not in estrus. In Experiment 2, estrus was detected with the HeatWatch system. Location and size of the ovulatory follicle was determined on day 0 by transrectal ultrasonography at time of injection with GnRH. Blood samples were collected on days 3, 4, 5, 7, and 9; luteal tissue was collected on day 10 (n = 4 estrus and n = 9 no estrus) from corpus luteum (CL) originating from similar-sized follicles (13.0 to 16.0 mm). Total cellular RNA was extracted, and relative mRNA levels were determined by real-time reverse transcription PCR and corrected for GAPDH. There was no effect of estrus on CL weight or concentrations of progesterone. In addition, there was no effect of estrus, follicle size, or CL weight on luteal expression of LH receptor, StAR, CYP11A1, or 3ßHSD. However, there was a correlation between follicle size and CL weight (P = 0.01; R(2) = 0.43); for every increase of 1 mm in follicle size, CL weight increased by 1.5 g. In summary, estrus did not influence release of LH, CL weight, progesterone concentrations, or expression of steriodogenic enzymes. However, as follicle size increased, CL weight increased; therefore, both follicle size and CL weight were associated with progesterone concentrations.

Endocrine actions of interferon-tau in ruminants.

The ovine conceptus releases interferon-tau (IFNT), which prevents upregulation of the endometrial estrogen receptor (ESR1) and, consequently, oxytocin receptor (OXTR), thereby disrupting pulsatile release of prostaglandin F2alpha (PGF) in response to oxytocin. IFNT, through paracrine action on the endometrium, protects the corpus luteum (CL) during maternal recognition of pregnancy. Pregnancy also induces IFN stimulated genes (ISGs) in peripheral blood mononuclear cells (PBMCs), which is interpreted to reflect a "prompted" antiviral and immune cell response peripherally in ruminants. IFNT was recently demonstrated to be released from the uterus in amounts of 200 microg (2 x 10(7) U)/24 h via the uterine vein and to induce ISGs in the CL during maternal recognition of pregnancy. Delivery of recombinant ovine (ro) IFNT into the uterine vein in a location that is upstream of the utero-ovarian plexus from Day 10 to 17 maintained serum progesterone concentrations and extended normal 16-17 d estrous cycles to beyond 32 d. It is concluded from these studies that IFNT is released into the uterine vein and initiates a peripheral antiviral response to protect pregnancy from maternal viral infection. It also may have endocrine action through inducing luteal resistance to PGF and longer-term survival of the CL and maintenance of pregnancy.

A proposed role for VEGF isoforms in sex-specific vasculature development in the gonad.

Many scientists have expended efforts to determine what regulates development of an indifferent gonad into either a testis or ovary. Expression of Sry and upregulation of Sox9 are factors that initiate formation of the testis-specific pathway to allow for both sex-specific vasculature and seminiferous cord formation. Migration of mesonephric precursors of peritubular myoid cells and endothelial cells into the differentiating testis is a critical step in formation of both of these structures. Furthermore, these events appear to be initiated downstream from Sry expression. Sertoli cell secretion of growth factors acts to attract these mesonephric cells. One hypothesis is that a growth factor specific for these cell linages act in concert to coordinate migration of both peritubular and endothelial cells. A second hypothesis is that several growth factors stimulate migration and differentiation of mesonephric 'stem-like' cells to result in migration and differentiation into several different cell lineages. While the specific mechanism is unclear, several growth factors have been implicated in the initiation of mesonephric cell migration. This review will focus on the proposed mechanisms of a growth factor, Vascular Endothelial Growth Factor, and how different angiogenic and inhibitory isoforms from this single gene may aid in development of testis-specific vascular development.

Judge, jury and executioner: the auto-regulation of luteal function.

Experiments were conducted to further our understanding of the cellular and molecular mechanisms that regulate luteal function in ewes. Inhibition of protein kinase A (PKA) reduced (P < 0.05) secretion of progesterone from both small and large steroidogenic luteal cells. In addition, the relative phosphorylation state of steriodogenic acute regulatory protein (StAR) was more than twice as high (P < 0.05) in large vs small luteal cells. Large steroidogenic luteal cells appear to contain constitutively active PKA and increased concentrations of phosphorylated StAR which play a role in the increased basal rate of secretion of progesterone. To determine if intraluteal secretion of prostaglandin (PG) F2alpha was required for luteolysis, ewes on day 10 of the estrous cycle received intraluteal implants of a biodegradable polymer containing 0, 1 or 10 mg of indomethacin, to prevent intraluteal synthesis of PGF2alpha. On day 18, luteal weights in ewes receiving 1 mg of indomethacin were greater (P < 0.05) than controls and those receiving 10 mg were greater (P < 0.05) than either of the other two groups. Concentrations of progesterone in serum were also increased (P < 0.05) from days 13 to 16 of the estrous cycle in ewes receiving 10 mg of indomethacin. Although not required for decreased production of progesterone at the end of the cycle, intraluteal secretion of PGF2alpha appears to be required for normal luteolysis. To ascertain if oxytocin mediates the indirect effects of PGF2alpha on small luteal cells, the effects of 0, 0.1, 1 or 10 mM oxytocin on intracellular concentrations of calcium were quantified. There was a dose-dependent increase (P < 0.05) in the number of small luteal cells responding to oxytocin. Thus, oxytocin induces increased calcium levels and perhaps apoptotic cell death in small luteal cells. Concentrations of progesterone, similar to those present in corpora lutea (approximately 30 microg/g), prevented the increased intracellular concentrations of calcium (P < 0.05) stimulated by oxytocin in small cells. In large luteal cells the response to progesterone was variable. There was no consistent effect of high quantities of estradiol, testosterone or cortisol in either cell type. It was concluded that normal luteal concentrations of progesterone prevent the oxytocin and perhaps the PGF2alpha-induced increase in the number of small and large luteal cells which respond to these hormones with increased intracellular concentrations of calcium. In summary, large ovine luteal cells produce high basal levels of progesterone, at least in part, due to a constituitively active form of PKA and an enhanced phosphorylation state of StAR. During luteolysis PGF2alpha of uterine origin reduces the secretion of progesterone from the corpus luteum, but intraluteal production of PGF2alpha is required for normal luteolysis. Binding of PGF2alpha to receptors on large luteal cells stimulates the secretion of oxytocin which appears to activate PKC and may also inhibit steroidogenesis in small luteal cells. PGF2alpha also activates COX-2 in large luteal cells which leads to secretion of PGF2alpha. Once intraluteal concentrations of progesterone have decreased, oxytocin binding to its receptors on small luteal cells also results in increased levels of intracellular calcium and presumably apoptosis. Increased secretion of PGF2alpha from large luteal cells activates calcium channels which likely results in apoptotic death of this cell type.

Two crystal polymorphs of a flavonoid from Melicope ellyrana.

The crystal structure determinations of two crystalline components of the hexane extract of the fruit of the indigenous Australian tree Melicope ellyrana have shown them to be polymorphs of the same compound, namely the flavonoid 4',5-dihydroxy-3,3',8-trimethoxy-7-(3-methylbut-2-enyloxy)flavone [systematic name: 5-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-3,8-dimethoxy-7-(3-methylbut-2-enyloxy)-4H-1-benzopyran-4-one], C(23)H(24)O(8). The two polymorphs, one monoclinic (polymorph A) and the other triclinic (polymorph B), show significant conformational differences, particularly in the enyloxy side chain, while only one (polymorph A) shows intermolecular hydrogen bonding.

The 1:1 adduct of 4-aminobenzoic acid with 4-aminobenzonitrile.

The 1:1 adduct of 4-aminobenzoic acid (PABA) with 4-am-inobenzonitrile (PABN), C(7)H(7)NO(2).C(7)H(6)N(2), consists of a primary centrosymmetric cyclic hydrogen-bonded PABA dimer interaction [O.O 2.640 (3) A] peripherally linked into chains by weaker hydrogen bonds via a head-to-tail PABN interaction [N.N 3.179 (4) and N.O 3.062 (4) A], and is linked between the chains by amine-N (PABN) to amine-N (PABA) interactions [N.N 3.233 (5) A]. No proton transfer occurs.