Archive for the ‘Prostaglandin’ Category


Prostaglandin F2a-Induced Luteolysis: DISCUSSION(3)

Jan 7, 2013 Author: Walter Mcneil | Filed under: Prostaglandin

Relaxin does not seem to be required for the release of PRL because the PRL in hysterectomized pigs did not respond to the programmed peak of relaxin. Our results indicated that PGF2(1 caused peak release of PRL, but we do not know if PGF2„ contributes to the rise of PRL in pregnant and lactating pigs. Estrogens are potent stimulators of PRL secretion, and progesterone has an inhibitory effect on PRL secretion by counteracting estrogen action in the anterior pituitary, where it depletes nuclear estrogen receptors. The decrease of progesterone by PGF2a in hysterectomized pigs does not seem to cause the release of PRL, for the decreased level of progesterone from Day 114 to Day 118 failed to induce PRL release.

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  • Prostaglandin F2a-Induced Luteolysis: DISCUSSION(2)

    Jan 6, 2013 Author: Walter Mcneil | Filed under: Prostaglandin

    DISCUSSION(2)

    The results of this study indicate that the CL in hysterectomized gilts secrete peak quantities of relaxin on about Day 113 (Fig. lb), the same time as do those in pregnant gilts, even though these CL can persist to Day 150. The aging porcine CL may be genetically programmed to release relaxin as a result of an inherent life span, defined through evolutionary development of the reproductive cycle as the duration of gestation of about 114 days. How the aging porcine luteal cell autonomously signals itself for the timed release of relaxin and coincident decrease in progesterone, however, remains to be further investigated. PGF2a treatment at Day 113 in these hysterectomized gilts caused a relaxin release at a peak (range 38-142 ng/ml) similar to that seen in pregnant sows, and was followed by an abrupt decrease to basal levels from Days 114 to 120 (Fig. lb). It is clear that elevated PGF2„ along with luteal cell death may be an overriding cause of the higher peak release of relaxin in late pregnancy and in PGF2a-treated hysterectomized gilts compared with the coincident, but lower, relaxin peak in PBS-treated hysterectomized gilts. Thereafter, relaxin remained low (< 3 ng/ml) in PGF2a-treated hysterectomized gilts, similar to that seen during lactation. The results clearly indicate a trigger mechanism of PGF2„ on parturition: one injection of PGF2q on Day 113 in hysterectomized animals simulated the pattern of progesterone and relaxin secretory change seen at normal parturition. flovent inhaler

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  • Prostaglandin F2a-Induced Luteolysis: DISCUSSION(1)

    Jan 5, 2013 Author: Walter Mcneil | Filed under: Prostaglandin

    We have demonstrated the same pattern of hormonal change in hysterectomized gilts given PGF2o, as seen during normal late pregnancy and parturition. Increasing production and secretion of PGF2a could signal decreasing production and secretion of progesterone and the release of relaxin. Whether the progesterone decrease signals relaxin release is unresolved. In late pregnant sows, progesterone administered from Days 110 to 113 or 115 significantly delayed parturition but did not alter the time of relaxin release on Days 112.9 and 112.6, compared with Day 113.0, in the vehicle-treated controls. It was not determined in that study whether the daily injection of progesterone altered the time for regression of the CL and relaxin release by the ovaries of these animals. When the progesterone antagonist RU-486 was orally administered on Days 111 and 112, it abruptly decreased progesterone secretion and caused a significantly earlier relaxin release than seen in control sows. Whether ovarian progesterone secretion signals the timing of relaxin release in hysterectomized gilts is unknown. However, when RU-486 was orally administered to hysterectomized gilts from Days 111 to 115, circulating blood concentrations of progesterone were significantly increased in a dose-dependent manner, and relaxin release was significantly delayed. buy ortho tri-cyclen

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  • Prostaglandin F2a-Induced Luteolysis: RESULTS(2)

    Jan 4, 2013 Author: Walter Mcneil | Filed under: Prostaglandin

    RESULTS(2)

    PRL Concentrations in Peripheral Plasma

    PRL plasma concentration remained consistently low (i.e., 5-8 ng/ml) from Day 100 to Day 120 in unmated hysterectomized gilts given PBS (Fig. lc), whereas it increases markedly (i.e., 30-60 ng/ml) during late pregnancy and early lactation. PGF2e, treatment on Day 113 in hysterectomized gilts caused a PRL increase (peak 32 ng/ml) similar to that seen in late pregnancy (Fig. lc) (p < 0.01).

    GH Concentrations in Peripheral Plasma

    GH plasma concentrations remained consistently low (12 ng/ml) from Day 100 to Day 120 in unmated hysterectomized gilts given PBS (Fig. Id). There was an abrupt increase in GH (> 5 ng/ml; p < 0.05) in the PGF2a-treated group, but a return to basal levels from Day 115 to Day 120.

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  • Prostaglandin F2a-Induced Luteolysis: RESULTS(1)

    Jan 3, 2013 Author: Walter Mcneil | Filed under: Prostaglandin

    Progesterone Concentrations in Peripheral Plasma

    In hysterectomized gilts given PBS, progesterone blood levels gradually decreased from Day 108 (31 ± 3.6 ng/ml) to Day 114 (17 ± 4.3 ng/ml) (Fig. la). This programmed decrease by half in progesterone blood level occurs in hysterectomized gilts at the expected time of normal parturition (Day 114) in pregnant animals. The CL in hysterectomized gilts can be maintained to Day 150. In this study, none of the hysterectomized gilts given PGF2a or PBS expressed behavioral estrus by Day 125. The CL in both groups were maintained, but they appeared less vascular in animals given PGF2a treatment than those in the PBS-injected controls. Aging CL in hysterectomized gilts are acutely responsive to the luteolytic action of PGF2o (Fig. la). PGF2a treatment on Day 113 caused an abrupt decrease (p < 0.01) in plasma progesterone (4.8 ± 0.14 ng/ml) on Day 113 and a further decrease to basal level (0.7 ± 0.08 ng/ml) by Day 116 in these hysterectomized animals that resulted in hormone levels similar to those seen in the early postpartum period.

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  • Prostaglandin F2a-Induced Luteolysis: MATERIALS AND METHODS(3)

    Jan 2, 2013 Author: Walter Mcneil | Filed under: Prostaglandin

    MATERIALS AND METHODS(3)

    Plasma progesterone was extracted from 100 |xl plasma with a benzene-hexane mixture by using a modified version of the procedure described by Louis et al.. One hundred microliters of plasma was extracted in duplicate. A third replicate (100 (xl) served as a recovery for determining procedural losses by the addition of 5000 cpm [2,3,6,7-N-3H]progesterone (97.0 Ci/mmol; NEN Research Products, Boston, MA). Plasma extracts were assayed for progesterone by a modification of the RIA procedure described by Anderson et al. using a fully characterized antibody (GDN antiprogesterone-11-BSA 337; a gift from G.D. Niswender, Colorado State University, Fort Collins, CO). The sensitivity of the progesterone RIA was 50 pg/tube. The intraassay CV was 7.4% (n = 6 samples), and the interassay CV was 14.8% (n = 5 assays/sample). Mean recovery of progesterone after benzene-hexane extraction was 90%.

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  • Prostaglandin F2a-Induced Luteolysis: MATERIALS AND METHODS(2)

    Jan 1, 2013 Author: Walter Mcneil | Filed under: Prostaglandin

    Experimental Protocol

    Hysterectomized gilts were randomly assigned to either the PGF2u-treated group (n = 5) or hysterectomized control group with PBS treatment (n = 11). Two days before beginning blood sampling on Day 100 after estrus, gilts were anesthetized with an ear vein injection of sodium thiopental and maintained on a closed circuit system of halothane and oxygen. Catheterization (i.d., 1.27 mm; o.d., 2.29 mm diameter; Tygon microbore tubing; Fisher Scientific, Pittsburgh, PA) of the anterior vena cava was performed to allow for repeated blood sampling. Blood samples were collected daily from the anterior vena cava from Day 98 to Day 107, and collected twice daily (0800 and 2000 h) from Day 108 to Day 120. Additionally on Days 112, 113, 114, and 115, the gilts were bled sequentially every 20 min for 180 min beginning at 1200 h to closely monitor the hormone change upon PGF2a injection. At 1200 h on Day 113, gilts were given an i.m. injection of 30 mg PGF2e,-trihy-droxymethylaminomethane (THAM) salt in PBS (6 ml) or an equal volume of PBS. Blood (10 ml) was collected in disposable borosilicate culture tubes (16 X 100 mm) containing 0.2 ml of heparin sodium salt (100 IU/ml; NBCO Biochemicals, Cleveland, OH) and was immediately centrifuged (1800 X g for 10 min). Plasma was decanted and stored at — 20°C until required for hormone assay. ventolin inhaler

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  • Prostaglandin F2a-Induced Luteolysis: MATERIALS AND METHODS(1)

    Dec 31, 2012 Author: Walter Mcneil | Filed under: Prostaglandin

    MATERIALS AND METHODS(1)

    Animals

    Sixteen purebred Yorkshire gilts, averaging 130 ± 10 kg BW (± SE), that had exhibited at least one normal estrous cycle averaging 21 ± 1 days were used in this experiment; the first day of estrus was designated Day 0. Unmated gilts were hysterectomized on Days 6-8 after estrus. After a 24-h period without feed, gilts were restrained by nasal snare on the day of surgery, and anesthesia was administered by ear vein injection of sodium thiopental (0.14 mg/kg BW, Pentothal; Abbott Laboratories, North Chicago, IL). birth control pills

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