Secretion of progesterone during long and short days of the estrous cycle in goats that are continuous breeders

This study was conducted 1) to determine if the secretion of progesterone, as an index of ovarian activity, during the estrous cycle of nonseasonal Shiba goats is affected by seasonal changes, and 2) to learn if the pulsatile secretion of ovarian progesterone can be estimated from samples obtained by cannulation into the caudal vena cava via the femoral vein. Progesterone concentrations in jugular venous plasma during the estrous cycle in spring (May) were similar to those in autumn (November). Plasma progesterone concentrations in the jugular vein and caudal vena cava monitored for 10 h on Day 12 of the estrous cycle in spring were similar to those in autumn. The mean concentration (21.9 to 28.9 ng/ml) and the pulse frequency (6.2 to 7.4 pulses/10 h) of plasma progesterone in the caudal vena cava during both seasons were 3.1- to 4.7-fold and 1.7- to 2.4-fold those in the jugular vein, respectively. The degree of change in the peak magnitude and the base-line concentration of progesterone were higher in the caudal vena cava than in the jugular vein. These results indicate that progesterone secretion during the estrous cycle in nonseasonal goats is not affected by seasonal changes, and suggest that the pulsatile secretion of ovarian progesterone can be evaluated better from samples obtained from the caudal vena cava, near where progesterone is released, than from those obtained from the jugular vein.     

Secretion of progesterone, estradiol-17beta, PGE, PGF2alpha, and pregnancy-specific protein B by 90-day intact and ovariectomized pregnant ewes

Ninety-day pregnant ewes were either laparotomized, ovaries left in situ or bilaterally ovariectomized, and a jugular venous catheter and an inferior vena cava catheter via the saphenous vein were installed. Seven days later, placenta slices were collected and incubated in vitro for 4 h. Secretions of progesterone, PGE, estradiol-17beta and pregnancy-specific protein B (PSPB) in vitro by placenta from ovariectomized ewes were increased (P < or = 0.05) by 2.7-, 3.6-, 2.2-, and 2.4-fold, respectively, when compared to placenta slices from intact 90-day pregnant ewes. Secretion of PGF2alpha in vitro was unchanged (P > or = 0.05). Ovariectomy decreased (P < or = 0.05) jugular venous progesterone for 78 h followed by a quadratic increase (P < or = 0.05), whereas progesterone remained unchanged (P > or = 0.05) in intact ewes over the 162-h sampling period. Ovariectomy increased (P < or = 0.05) PGE in inferior vena cava plasma over the last half of the 162-h sampling period, whereas concentration of PGF2alpha did not change (P > or = 0.05). Increases in PGE occurred before the increase in progesterone. Concentrations of PSPB in inferior vena cava plasma of ovariectomized pregnant ewes increased (P < or = 0.05) during the last half of the 162-h sampling period, but not in intact ewes (P > or = 0.05). PSPB increased before PGE and progesterone. Concentrations of estradiol-17beta in jugular venous plasma of ovariectomized pregnant ewes increased (P < or = 0.05) during the last half of the sampling period, but not in intact ewes (P > or = 0.05). Increases in estradiol-17beta occurred before increases in PSPB. It is concluded that these data support the hypothesis that estradiol-17beta may control placental secretion of PSPB; PSPB may regulate placental secretion of PGE; and PGE may regulate placental secretion of progesterone.     

Evidence for the secretion of immunoreactive neurophysin I in addition to oxytocin from the ovary in cattle

In Exp. I, blood samples were collected simultaneously from the posterior vena cava and jugular vein or aorta from 7 heifers every 5-20 min for 2-5 h. Concomitant pulsatile secretion of oxytocin and immunoreactive neurophysin I was detected in the vena cava, but not in the jugular vein or aorta. Concentrations of oxytocin and immunoreactive neurophysin increased earlier and were higher in the vena cava than in the jugular vein or aorta after the injection of a luteolytic dose of prostaglandin F-2 alpha analogue during the mid-luteal phase of the oestrous cycle, demonstrating its ovarian but not pituitary origin. In Exp. II, blood samples were collected from the jugular vein every 12 h during 1 week after oestrus. Follicular growth had been stimulated during the preceding oestrous cycle with PMSG (10 heifers and cows) or with FSH (5 animals); 6 heifers served as controls. There was a high correlation between the number of follicles or CL and the increase in oxytocin and immunoreactive neurophysin I. Although PMSG had a greater luteotrophic effect than did FSH on progesterone secretion, a similar stimulation of oxytocin and immunoreactive neurophysin I was not observed. It is concluded that immunoreactive neurophysin I and oxytocin are secreted from the ovary in concentrations dependent upon the number of corpora lutea (and of follicles) present. During the mid-luteal period the secretion occurs in a concomitant pulsatile fashion.     

Influence of elevated ambient temperature after breeding on plasma corticoids, estradiol and progesterone in gilts

Thirty Yorkshire gilts were used to determine the influence of elevated ambient temperature during days 8 to 16 after breeding on concentrations of progesterone, corticoids and estradiol in plasma. Gilts were mated to a boar between 0800 and 1000 hr of the first day (day 0) and each subsequent day of estrus. On day 5 or 6, 22 gilts were anesthetized and a cannula was placed in the anterior vena cava. Gilts were randomly allotted to either control (23+/-1 C) or hot (35+/-1 C for 12 hr and 32+/-1 C for 12 hr daily) environmental chambers on day 8. Gilts were bled twice daily (0800 and 2000 hr) on days 9 through 16, then once daily until day 28. A third group of noncannulated gilts was bred and assigned to the control chamber. All cannulated gilts were injected intravenously with 25 IU of ACTH on day 16, and frequent blood samples were collected. Concentrations of progesterone in plasma were similar for heat-stressed and control gilts that were pregant. However, progesterone in plasma was reduced during days 13 to 19 in nonpregnant heat-stressed gilts compared to the pregnant and nonpregnant control gilts. Concentrations of estradiol in plasma were greater in nonpregnant heat-stressed gilts than in nonpregnant control and all pregnant gilts on days 10, 11 and 12 after estrus. Concentrations of corticoids and progesterone in plasma after infusion of ACTH on day 16 after breeding were reduced in heat-stressed nonpregnant gilts compared to heat-stressed pregnant, control pregnant and control nonpregnant gilts. These data indicate that reduced reproductive performance which occurs after exposure of gilts to increased ambient temperature during days 8 to 16 after breeding may be related to altered endocrine function.     

Effect of vascular cannulation on serum concentrations of LH, FSH, prolactin and cortisol in prepubertal gilts

Two experiments were conducted to determine whether cannulation of the jugular vein in gilts alters serum concentrations of LH, FSH, prolactin (PRL) or cortisol (C). In Experiment 1, 12 crossbred prepubertal gilts weighing 95 +/- 1.3 kg were immobilized by snaring, and tygon tubing was threaded into the anterior vena cava through a 12-gauge needle inserted into the jugular vein. Five hours later, blood samples were drawn at 20-min intervals for 4 h (Day 0). Samples were also drawn at 20-min intervals for 4-h periods 24 h (Day 1) and 48 h (Day 2) after cannulation. Serum concentrations of LH were similar (P=0.26) among Day 0 (0.40 ng/ml), Day 1 (0.39 ng/ml) and Day 2 (0.34 ng/ml). Serum PRL was similar (P=0.07) among Day 0 (4.10 ng/ml), Day 1 (3.87 ng/ml) and Day 2 (3.43 ng/ml). Serum concentrations of C were greater (P < 0.001) on Day 0 (8.32 ng/ml) than Day 1 (4.48 ng/ml) or Day 2 (3.54 ng/ml). In Experiment 2, cannulas were placed in 29 prepubertal gilts. Two days after initial cannulation, six blood samples were drawn at 20-min intervals. Gilts were then immobilized by snaring, and a second cannulae was inserted into the contralateral vein. Five blood samples were taken at 2-min intervals during the second cannulation and then six samples were drawn at 20-min intervals. Serum LH and FSH were not altered by cannulation or elevated during the subsequent 2-h sampling period (P>0.05). In contrast, serum concentrations of PRL rose slowly (P<0.05) during cannulation and remained elevated for 60 min before returning to baseline. Serum concentrations of C rose within 6 min of cannulation, remained elevated for 30 min, and then declined over the next 90 min. From these two experiments, it appears that secretory patterns of LH and FSH can be accurately assessed immediately after cannulation in prepubertal gilts. Measurements of serum PRL and C that reflect nonstressed conditions, however, cannot be obtained until at least 2 h or 1 d after cannulation, respectively.     

Acute stimulatory effects of prostaglandin F2 alpha on serum progesterone concentrations in pregnant and pseudopregnant pigs.

The objective of this study was to investigate whether PGF2 alpha, administered to pregnant and pseudopregnant gilts in vivo, would cause an acute increase in serum progesterone concentrations prior to luteolysis. Pregnant (n = 9) and pseudopregnant (n = 4) gilts were fitted with a jugular vein cannula on day 40, were treated with 3 ml vehicle (control) i.m. on day 42 and with 15 mg PGF2 alpha on day 45. Blood samples were collected at frequent (5 and 15 min) intervals from 1 h before until 1 h after control and PGF2 alpha injections, at 15 min intervals for 4 h, and then at 5, 6, 9, 21, 33, 45 and 57 h post injection. Progesterone was measured by radioimmunoassay (RIA) in all samples. Porcine LH was measured by RIA in samples collected frequently in the 1 h pre- and 1 h post-injection periods. Serum progesterone concentrations were unchanged in both pregnant and pseudopregnant animals in response to control injection on day 42. However, in both pregnant and pseudopregnant gilts, PGF2 alpha injection on day 45 resulted in an acute increase (approximately 75-80% above pre-treatment levels; p less than 0.05) in serum progesterone lasting approximately 1 h, followed by a return to pre-treatment levels by 2 h, and then a decline to 1 ng/ml or less by 45-57 h (pregnant) or 21-57 h (pseudopregnant), associated with luteolysis. Serum LH concentrations were unchanged between 1 h pre- and post-treatment periods in response to either control or PGF2 alpha-treatment, in both pregnant and pseuodpregnant gilts. These results indicate that PGF2 alpha-injection produces a rapid and transient increase in serum progesterone concentrations which may result from a rapid and direct stimulatory action of PGF2 alpha on porcine luteal cell progesterone synthesis/secretion in vivo.     

Contractility of the ovarian vascular bed during the oestrous cycle and early pregnancy in gilts

The vasoconstrictor activity of the ovarian vascular bed in vitro was investigated during the oestrous cycle and early pregnancy. Gilts were killed during the follicular phase (Days 20 to +1; N = 5) or luteal phase (Days 11 to 13; N = 4) of the oestrous cycle, or on Day 13 of pregnancy (N = 5). Immediately before death, a sample of vena cava blood was obtained for determination of progesterone and oestrogen (oestrone and oestradiol-17 beta) concentrations. One ovary was removed, cannulated, perfused in vitro, and subjected to 10-min infusions of saline (vehicle control) and noradrenaline. Vasoconstriction was provoked by electrical stimulation at the end of each infusion. Ovaries from luteal-phase gilts exhibited greater (P less than 0.01) vasoconstriction than did ovaries from follicular-phase and pregnant gilts at the end of saline and noradrenaline infusions. The oestrogen to progesterone ratio was less (P less than 0.01) for luteal-phase and pregnant than for follicular-phase gilts. Vasoconstriction was negatively correlated (r = -0.99, P less than 0.01) with the oestrogen to progesterone ratio in systemic blood of gilts during the oestrous cycle but not during early pregnancy (r = +0.39, P greater than 0.10), possibly due to an effect of the conceptuses.     

Ultrasound-guided cannulation of the caudal vena cava in the bovine for selective sampling of ovarian effluent

The accuracy of real-time, B-mode ultrasonography was assessed in the visualization and placement of the cannula tip, cranial to the entrance of the ovarian veins as they enter the caudal vena cava of the bovine. A cannula containing a wire guide was introduced into the coccygeal vein via a 14-gauge needle, and was then directed cranially into the caudal vena cava. Once the caudal vena cava was successfully cannulated (7 of 14 cows), ultrasonography allowed for the visualization of the cannula in 7 out of 7 cows. The tip of the cannula was successfully placed cranial to the entrance of the ovarian effuent into the vena cava in 6 of these 7 animals using ultrasound guidance. This was confirmed using progesterone or prostaglandin F(2alpha) radioimmunoassay (RIA). The primary limitation to this technique was the initial catherization of the coccygeal vein which was not achieved in 7 of 14 cows attempted in this study. Successful cannulation was limited to large framed Holstein cows that had at least one calf. Results from this study indicate that real-time, B-mode, ultrasonography is an effective tool for the visualization and accurate placement of the cannula tip within the caudal vena cava. This finding could have implications for research in ovarian hormonal physiology in the cyclic, postpartum or anestrous cow.     

Endocrine secretion of prostaglandin F2alpha in cyclic gilts is decreased by intrauterine administration of exogenous oxytocin

When administered systemically, oxytocin (OT) stimulates secretion of uterine prostaglandin F2alpha (PGF2alpha) in swine, but the role of endometrially-derived OT in control of PGF2alpha release is not clear. This study determined the effect of exogenous OT, administered into the uterine lumen of intact cyclic gilts, on PGF2alpha secretion during late diestrus. Intrauterine infusion of 40USP units OT (in 30 ml 0.9% saline) was performed for 30 min (1 ml/min) into each uterine horn between 7:00 and 9:00 h on days 10, 12, 14 and 16 after estrus. Beginning 20 min before infusion, samples of jugular venous blood were drawn at 5-10-min intervals for 140 min for quantification of 13,14-dihydro-15-keto-PGF2alpha (PGFM), the major stable metabolite of PGF2alpha. Progesterone was analyzed in samples collected 0, 60 and 120 min after initiation of OT infusion. Treatment with OT did not alter plasma concentrations of PGFM on days 10 or 12 but decreased (P<0.001) PGFM concentrations for 40 min after onset of infusion on day 16. Concentrations of PGFM also were reduced in the pre-treatment samples on day 14 (P=0.05) and day 16 (P<0.001) in OT-infused gilts. Plasma progesterone declined (P<0.01) between days 10 and 16 in control-infused gilts but did not decline until after day 14 (P<0.001) in gilts infused with OT. These results indicate that when OT is administered into the uterine lumen of pigs during late diestrus, it has an anti-luteolytic effect to reduce endocrine secretion of PGF2alpha and delay the decline in progesterone that occurs during luteolysis.     

Effect of the aromatase inhibitor CGS-16949A on pregnancy and secretion of progesterone, estradiol-17beta, prostaglandins E and F2alpha (PGE; PGF2alpha) and pregnancy specific protein B (PSPB) in 90-day ovariectomized pregnant ewes

The aromatase inhibitor CGS-16949A was used to determine whether CGS-16949A altered secretion of progesterone, estradiol-17beta, PGE (PGE1 + PGE2), PGF2alpha and PSPB. Ninety day pregnant ewes were ovariectomized and received vehicle, PGF2alpha, CGS-16949A or PGF2alpha+CGS-16949A. None of the ewes treated with PGF2alpha, CGS-16949A or PGF2alpha+CGS-16949A aborted (P > or = 0.05) during the 108-h experimental period. Treatment with CGS-16949A lowered (P < or = 0.05) progesterone in jugular venous plasma but concentrations of progesterone were not affected (P > or = 0.05) by treatment with PGF2alpha. Concentrations of estradiol-17beta and PSPB in jugular venous plasma and PGE in inferior vena cava plasma were decreased (P < or = 0.05) by treatment with CGS-16949A. Concentrations of PGF2alpha in inferior vena cava plasma were not affected (P > or = 0.05) by treatment with CGS-16949A. Decreases in estradiol-17beta occurred before decreases in PSPB, which was then followed by decreases in PGE (P < or = 0.05). It is concluded that these data support the hypothesis that estradiol-17beta regulates placental secretion of PSPB; PSPB regulates placental secretion of PGE; and PGE regulates placental secretion of progesterone during mid-pregnancy in ewes.     

Mechanism whereby nitric oxide (NO) infused chronically intrauterine in ewes is antiluteolytic rather than being luteolytic

Nitric oxide (NO) has been reported to be luteolytic in vitro and in vivo in cows. However, an NO donor reversed PGF2alpha-induced inhibition of rat luteal progesterone secretion in vitro and an NO donor or endothelin-1 stimulated bovine luteal tissue secretion of prostaglandins E (PGE; PGE1, PGE2) in vitro without affecting progesterone or PGF2alpha secretion. In addition, chronic infusion of an NO donor into the interstitial tissue of the ovarian vascular pedicle adjacent the luteal-containing ovary prevented the decline in circulating progesterone, while a nitric oxide synthase (NOS) inhibitor did not affect luteolysis. The objective of this experiment was to determine whether an NO donor or NOS inhibitor infused chronically intrauterine adjacent to the luteal-containing ovary during the ovine estrous cycle was luteolytic or antiluteolytic. Ewes were treated either with vehicle (N=5), diethylenetriamine (DETA-control for DETANONOate; N=5), (Z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (DETANONOate-long acting NO donor; N=6), l-arginine (N=5), l-nitro-arginine methyl ester (l-NAME-NOS inhibitor; N=6), or NG-monomethyl-l-arginine acetate (l-NMMA; NOS inhibitor; N=5) every 6h from 2400h (0h) on day 8 through 1800h on day 18 of the estrous cycle. Jugular venous blood and inferior vena cava plasma via a saphenous vein cathether 5cm anterior to the juncture of the ovarian vein and inferior vena cava were collected every 6h for analysis for progesterone and PGF2alpha and PGE, respectively, by RIA. Corpora lutea were collected at 1800h on day 18 and weighed. Weights of corpora lutea were heavier (P< or =0.05) in DETANONOate-treated ewes when compared to vehicle, DETA, l-arginine, l-NAME, or l-NMMA-treated ewes, l-arginine luteal weights were heavier than vehicle, DETA, l-arginine, l-NAME, or l-NMMA-treated ewes, and luteal weights of vehicle, DETA, l-NAME, or l-NMMA-treated ewes did not differ amongst each other (P> or =0.05). Profiles of progesterone in jugular venous blood on days 8-18 differed (P< or =0.05) in DETANONOate-treated ewes when compared to vehicle, DETA, l-arginine, l-NMMA or l-NAME-treated ewes, which did not differ (P> or =0.05) amongst each other. The PGE:PGF2alpha ratio profile in inferior vena cava plasma of DETANONOate-treated ewes was increased (P< or =0.05) when compared to all other treatment groups. In a second experiment, conversion of [3H PGE2] to [3H PGF2alpha] by day 15 ovine caruncular endometrium in vitro was determined in vehicle, DETA, or DETANONOate-treatment groups. Conversion of [3H PGE2] to [3H PGF2alpha] was decreased (P< or =0.05) only by DETANONOate. It is concluded that NO is not luteolytic during the ovine estrous cycle, but may instead be antiluteolytic and prevent luteolysis by altering the PGE:PGF2alpha ratio secreted by the uterus.     

Episodic secretion of gonadotrophins and ovarian steroids in jugular and utero-ovarian vein plasma during the follicular phase of the oestrous cycle in gilts

Blood samples were collected simultaneously from the jugular and utero-ovarian veins of 13 gilts from Days 11 through 16 of the oestrous cycle. A luteolytic dose (10 mg) of PGF-2 alpha was given on Day 12 to facilitate the natural occurrence of luteolysis and standardize the associated decrease in concentrations of progesterone. The mean interval from PGF to oestrus was 5.5 +/- 0.7 days (mean oestrous cycle length = 17.5 +/- 0.7 days). Mean concentrations, pulse amplitudes and pulse frequencies of oestradiol and progesterone were greater (P less than 0.05) in the utero-ovarian than jugular vein. Secretory profiles of LH and FSH were similar (P greater than 0.05) in plasma collected simultaneously from both veins. Based on these data, temporal relationships among hormonal patterns of FSH and LH in the jugular vein and oestradiol and progesterone in the utero-ovarian vein were examined. Concentrations of progesterone declined (P less than 0.05) between Days 12 and 14, while all secretory variables for oestradiol increased (P less than 0.05) from Day 12 through 16 of the oestrous cycle. The pulsatile secretion of FSH remained relatively constant during the experiment. However, both pulse amplitude and mean concentration tended (P less than 0.2) to be lower on Day 16 compared with Day 12. The episodic secretion of LH shifted from a pattern characterized by high-amplitude, low-frequency pulses to one dominated by numerous pulses of diminishing magnitude between Days 13 and 14. From Days 14 to 16 of the oestrous cycle, 91% of all oestradiol pulses were temporally associated with gonadotrophin pulses composed of both FSH and LH episodes. However, pulses of oestradiol (52%) not associated with an episode of LH and/or FSH were observed on Days 12 and 13. These data demonstrate that during the follicular phase of the pig oestrous cycle substantial oestradiol production occurred coincident with luteolysis and before the shift in the episodic secretion of LH. The pool of follicles which ovulated was probably the source of this early increase in the secretion of oestradiol. Therefore, we propose that factors in addition to FSH and LH are involved in the initial selection of follicles destined to ovulate during the early stages of the follicular phase of the pig oestrous cycle. In contrast, high-frequency, low-amplitude pulses composed of LH and FSH were the predominant endocrine signal associated with oestradiol secretion during the second half of the oestrous cycle.(ABSTRACT TRUNCATED AT 400 WORDS)     

Prolongation of the luteal phase by prostaglandin E(2) during the estrous cycle in the cow. A preliminary report

An experiment was conducted to determine the effects of prostaglandin E(2) (PGE(2)) on ovarian progesterone secretion during the estrous cycle in the cow. Intraluminal uterine catheters were implanted in three beef cows (2 treated, 1 control), and 1.3 mg of PGE(2) were infused into the uterus every 4 hours from days 9 through 21 post-estrus. Blood samples were collected from the jugular vein at 2-hour intervals from days 9 to 21 and twice daily from day 22 to 28 post-estrus. Progesterone was measured by applying a specific, direct plasma radioimmunoassay in all samples without extraction. Intrauterine infusion with PGE(2) resulted in maintenance of luteal-phase progesterone secretion until day 21 post-estrus, 4 days after luteal regression occurred in the vehicle-treated cow. In this study, we demonstrated that PGE(2) can prolong the presence of luteal phase plasma progesterone concentrations by possibly stimulating in vivo steroidogenesis by the corpus luteum during the estrous cycle in the cow.     

Effects of pulsatile infusion of luteinizing hormone-releasing hormone on luteinizing hormone secretion and ovarian function in hypophysial stalk-transected beef heifers

Hypothalamic regulation of luteinizing hormone (LH) secretion and ovarian function were investigated in beef heifers by infusing LH-releasing hormone (LHRH) in a pulsatile manner (1 microgram/ml; 1 ml during 1 min every h) into the external jugular vein of 10 hypophysial stalk-transected (HST) animals. The heifers were HST approximately 30 mo earlier. All heifers had increased ovarian size during the LHRH infusion. The maximum ovarian size (16 +/- 2.7 cm3) was greater (P less than 0.01) than the initial ovarian size (8 +/- 1.4 cm3). Ovarian follicular growth occurred in 4 of 10 HST heifers in response to pulsatile LHRH infusion. In 2 heifers, an ovarian follicle developed to preovulatory size, but ovulation occurred in only 1 animal after the frequency of LHRH was increased (1 microgram every 20 min during 8 h). In blood samples obtained at 20-min intervals every 5th day, LH concentrations in peripheral serum remained consistently low (0.9 ng/ml) and nonepisodic in the 10 HST heifers during infusion of vehicle on the day before beginning LHRH. In 7 of 10 HST animals, episodic LH secretion occurred in response to pulsatile infusion of LHRH. In 3 of these long-term HST heifers, however, serum LH remained at basal levels and the isolated pituitary seemingly was unresponsive to pulsatile infusion of LHRH as indicated by sequential patterns of gonadotropin secretion obtained at 5-day intervals. These results indicate that pulsatile infusion of LHRH induces LH release in HST beef heifers.     

Growth hormone and prolactin secretion after hypothalamic deafferentation in pigs

Control of growth hormone (GH) and prolactin (PRL) secretion was investigated in ovariectomized, prepuberal Yorkshire gilts by comparing the effects of anterior (AHD), complete (CHD), and posterior (PHD) hypothalamic deafferentation with sham-operated controls (SOC). Blood samples were collected sequentially via an indwelling jugular catheter at 20-min intervals during surgery and recovery from anesthesia (Day 0) and Days 1 and 2 after cranial surgery. Mean serum concentrations of GH after AHD, CHD, and PHD were reduced (P less than 0.01) when compared with SOC gilts. Furthermore, episodic GH release evident in SOC animals was obliterated after hypothalamic deafferentation. PRL concentrations in peripheral serum of hypothalamic deafferentated gilts remained similar (P greater than 0.05) to those of SOC animals. These results indicate that anterior and posterior hypothalamic neural pathways play a minor role in the control of PRL secretion in the pig in as much as PRL levels remained unchanged after hypothalamic deafferentation. These findings may be interpreted to suggest that the hypothalamus by itself seems able to maintain tonic inhibition of PRL release. In contrast, the maintenance of episodic GH secretion depends upon its neural connections traversing the anterior and posterior aspects of the hypothalamus in the pig.     

Schistosoma mansoni: mechanism of attrition and routes of migration from lungs to hepatic portal system in the laboratory mouse

The number of schistosomula in the axillary lymph nodes of mice was determined by compressed tissue autoradiography at 13 intervals from 0.5 to 28 days after exposure of abdominal skin to 75Se-labeled cercariae of S. mansoni. Significant accumulations were observed between days 3 and 6 and peaked on day 4 at which time 9.4 +/- 1.1% of the schistosomula present in the whole body were found in the axillary lymph nodes. The total number and distribution of schistosomula in all tissues of mice were likewise determined at 12 intervals from 3 to 24 days following exposure. The frequent appearance of small numbers of schistosomula in trachea and esophagus suggested that normal attrition resulted at least in part from physical expulsion of schistosomula from the body by way of the tracheobronchial tree and gastrointestinal tract. The distribution of schistosomula observed in heart chambers, caudal vena cava, hepatic portal vein, aorta, intestinal wall, thoracic cavity rinses, and diaphragm supported all 3 standing hypotheses regarding route of migration from lungs to hepatic portal system, i.e., that schistosomula migrate via (1) the pulmonary artery, right heart, caudal vena cava, and hepatic veins, (2) the pulmonary vein, left heart, aorta, and cranial mesenteric artery, and (3) the thoracic cavity and diaphragm.     

Prostaglandins F in uterine and ovarian venous plasma from nonpregnant and pregnant ewes collected by cannulation.

Periodic collections of uterine venous blood were obtained from three nonmated, three pregnant and two mated but nonpregnant ewes in which uterine veins were cannulated with polyvinyl tubing on day 11 postestrus. Frequent sampling was achieved in three of these ewes with additional cannulae in the ovarian veins. Blood samples were collected at 3-hr intervals from 0600 on day 12 to 1800 on day 13 and then 6-hr intervals through day 15. On day 13, three additional samples at 30-min intervals were collected between 1400 and 1530. Prostaglandins F (PGF) in plasma were quantified by radioimmunoassay. On day 12, one ewe in each group had at least one measurement which suggested an increased rate of release of PGF into the uterine vein. Seven of eight ewes on day 13 appeared to have increased rates of release of PGF from the uterus between 0900 and 1500. The highest level measured in each ewe during this period ranged from 2.7 to 11 ng per milliliter. Concentrations of PGF in ovarian venous plasma in two of three ewes were positively correlated (P less than .05) with concentrations of PGF in uterine venous plasma (r equals .64 in each ewe). No evidence was obtained that pregnant and nonpregnant ewes differ in rate or pattern of release of PGF from the uterus into the uterine vein on days 12 and 13. Comparisons could not be made with confidence concerning PGF either in uterine veins on days 14 and 15 or in ovarian veins on all days due to limited number of observations.     

Influence of synthetic lamprey GnRH-III on gonadotropin release and steroid hormone levels in gilts

Based on the supposition that lamprey GnRH-III (lGnRH-III) elicits FSH releasing activity in swine, synthetic lGnRH-III (peforelin, Maprelin® XP10) was used in puberal estrus synchronized gilts. The secretion of reproductive hormones FSH, LH, estradiol and progesterone was analyzed, and follicle growth and ovulation recorded. Altogether, 24 German Landrace gilts were treated after an 18-day long synchronization of the estrus cycle with Regumate® as follows: 48 h after the last Regumate® feeding they received im either 150 μg Maprelin® XP10 (lGnRH-III, group Maprelin, n = 6), 50 μg Gonavet Veyx® (GnRH-I agonist, group GnRH, n = 6), 850 IE Pregmagon® (eCG, group eCG, n = 6) or saline (group Control, n = 6). Additionally, in eight gilts the concentrations of FSH and LH were analyzed after treatment with 150 μg Maprelin® XP10 (n = 3), 50 μg Gonavet Veyx® (n = 3) or saline (n = 2) at mid-cycle (day 10 of the estrus cycle). Blood samples were collected via implanted jugular vein catheters. Ovarian features were judged endoscopically at the end of the Regumate® feeding and on days 5 and 6 after treatment. Maprelin® XP10 had no effect on FSH release in gilts; neither at the pre-ovulatory period or at mid-cycle. Furthermore, LH levels were unaffected. In contrast, GnRH-I agonist stimulates FSH release, however less compared to LH secretion. LH secretion was induced by GnRH-I both during the follicular phase and at mid-cycle. Equine CG did not stimulate the release of pituitary hormones FSH and LH due to its direct action on the ovary. Increased estradiol concentrations during days 2 to 5 after Regumate® in all treatment groups indicated pre-ovulatory follicle growth in gilts. Equine CG stimulated a higher (P < 0.01) number of ovulatory follicles compared to the other treatment groups. All together, 83 to 100 % of gilts ovulated by day 6 post treatment. In summary, results of our study on reproductive hormone secretion do not provide evidence that synthetic lGnRH-III (Maprelin® XP10) selectively releases FSH in estrus synchronized gilts.     

Effect of PGF2alpha, indomethacin, tamoxifen, or estradiol-17beta on incidence of abortion, progesterone, and pregnancy-specific protein B (PSPB) secretion in 88- to 90-day pregnant sheep

One objective of this experiment was to evaluate our hypotheses that estradiol-17beta regulates secretion of pregnancy specific protein B (PSPB) and that secretion of progesterone during pregnancy is regulated by a prostanoid by examining the effects of prostaglandin F2alpha (PGF2alpha), a luteolyic agent; indomethacin, a prostanoid synthesis inhibitor; tamoxifen, an estrogen receptor antagonist; estradiol 17-beta; and interaction of these factors on the incidence of abortion and progesterone and PSPB secretion. Another objective was to determine if there is a luteal source of PSPB. Weights of corpora lutea were decreased (P < or = 0.05) by PGF2alpha, indomethacin, PGF2alpha + tamoxifen, PGF2alpha + indomethacin, and PGF2alpha + estradiol-17beta but not (P > or = 0.05) by tamoxifen or estradiol-17beta alone. No ewe treated with PGF2alpha alone aborted (P > or = 0.05). Forty percent of ewes treated with PGF2alpha + estradiol-17beta aborted (P < or = 0.05), but ewes were not aborted by any other treatment within the 72-h sampling period. Profiles of progesterone in jugular venous blood differed (P < or = 0.05) among control, indomethacin-, tamoxifen-, and PGF2alpha + indomethacin-treated ewes. Progesterone in jugular venous blood of control ewes decreased (P < or = 0.05) by 24 h, followed by a quadratic increase (P < or = 0.05) from 24 to 62 h. Progesterone in jugular venous blood of indomethacin-, PGF2alpha-, PGF2alpha- + tamoxifen-, PGF2alpha + indomethacin-, PGF2alpha + estradiol-17beta-, and tamoxifen-treated ewes was reduced (P < or = 0.05) by 18 h and did not vary (P > or = 0.05) for the remainder of the 72-h sampling period. Progesterone in vena cava and in uterine venous blood was reduced (P < or = 0.05) at 72 h in PGF2alpha-, indomethacin-, tamoxifen-, PGF2alpha + indomethacin-, PGF2alpha + tamoxifen-, and PGF2alpha + estradiol-17beta-treated ewes. Weights of placentomes did not differ among treatment groups (P > or = 0.05). Profiles of PSPB in inferior vena cava blood differed (P < or = 0.05) among control, estradiol-17beta-, indomethacin-, tamoxifen-, PGF2alpha + indomethacin-, and PGF2alpha + tamoxifen-treated 88- to 90-day pregnant ewes. Concentrations of PSPB in inferior vena cava blood were increased (P < or = 0.05) in indomethacin-, estradiol-17beta-, tamoxifen-, PGF2alpha + tamoxifen-, and PGF2alpha + indomethacin-treated 88- to 90-day pregnant ewes within 6 h and did not vary (P > or = 0.05) for the remainder of the 72-h sampling period. Concentrations of PSPB in uterine venous blood of indomethacin-, tamoxifen-, PGF2alpha + tamoxifen-, and PGF2alpha + indomethacin-treated ewes were greater (P < or = 0.05) at 72 h than at 0 h. PSPB in ovarian venous blood did not differ (P > or = 0.05) adjacent or opposite to the ovary with the corpus luteum. It is concluded from these data that estrogen regulates placental secretion of PSPB and that a prostanoid, presumably prostaglandin E, regulates placental secretion of progesterone during 88-90 days of gestation in sheep and that there is no luteal source of PSPB.     

Effect of porcine conceptus secretory proteins on interestrous interval and uterine secretion of prostaglandins

Porcine conceptus secretory proteins (pCSP) were obtained from medium in which pig conceptuses, collected on Day 15 of pregnancy, were cultured for 30 h. Culture medium was pooled, dialyzed, and concentrated by Amicon ultrafiltration for intrauterine infusion. Serum proteins (SP) were obtained from blood collected from a Day 15 pregnant gilt and diluted for intrauterine infusion. Catheters were placed into both uterine horns and the inferior vena cava of cyclic (Day 8) gilts. Single blood samples were collected at 0800 h on Days 9, 10, and 11. On Day 11, all gilts received 1 mg estradiol-17 beta (E2) i.m. at 0800 h. Protein infusions commenced on Day 12 and continued through Day 15, twice daily at 0800 h and 2000 h. Protein infusions per uterine horn were (1) 4.0 mg pCSP + 4.0 mg SP (pCSP, 4 gilts) and (2) 8.0 mg SP (SP, 4 gilts). Blood samples were collected every 15 min on Days 12 through 17 between 0805 h and 1100 h. Single blood samples were collected at 0800 h after Day 17 until gilts exhibited estrus. Concentrations of prostaglandin (PG) E, 13,14-dihydro-15-keto-PGF2 alpha (PGFM), and progesterone (P4) were measured by specific radioimmunoassays. Interestrous intervals for pCSP-treated (18.2 days) and SP-treated (18.0 days) gilts were not different (SEM = 0.8 days) and temporal changes in concentrations of P4 in plasma did not differ between pCSP-treated (29.2 ng/ml) and SP-treated (31.2 ng/ml) gilts.(ABSTRACT TRUNCATED AT 250 WORDS)