Plasma endotoxin and concentrations of stable metabolites of prostacyclin, thromboxane A2, and prostaglandin E2 in postpartum dairy cows

The presence of endotoxin in plasma and patterns of stable metabolites of prostacyclin (PC), thromboxane A2 (TXA2) and prostaglandin E2 (PGE2) were determined during the first postpartum estrous cycles in sixteen dairy cows. These included 8 cows with uterine infections which exhibited shortened luteal phases (SC) and 8 cows which had normal luteal phases (NC) after the first post partum ovulations. Endotoxin was consistently detected in all SC cows during the abbreviated estrous cycles while plasma samples of NC cows were free of endotoxin. Plasma concentrations of TXA2 metabolite was higher in SC cows (p less than 0.05) (1785-3452 pg/ml) compared to NC cows (723-1240 pg/ml). Similarly, plasma concentrations of PC metabolite was higher in SC cows (p less than 0.07) (423-1847 pg/ml) compared to NC cows (159-325 pg/ml). In contrast, plasma concentrations of PGE2 metabolite was higher in NC cows (p less than 0.05) (850-2219 pg/ml) compared to SC cows (455-628 pg/ml). The results of this study suggest that postpartum uterine infections mediate the release of prostaglandins from the uteri by means of the endotoxin and endotoxin appears to stimulate selectively the production of PC and TXA2 favoring early demise of corpora lutea formed after first postpartum ovulations in dairy cows.     

Spontaneous uterine infections are associated with elevated prostaglandin F(2)alpha metabolite concentrations in postpartum dairy cows

Postpartum Holstein (n=21) and Jersey (n=4) cows were used to determine if uterine infections are associated with elevated plasma concentrations of 13,14-dihydro-15-keto-prostaglandin F(2)alpha (PGFM). Based upon clinical examinations and bacterial content of intrauterine fluid samples, cows detected with uterine infections between 21 and 28 d post partum were used (infected; n=14). These cows were matched with herdmates that were free of infection (control; n=11). Beginning on the day the cows were assigned to the experiment (Day 1), blood samples were collected on alternate days for the next 14 to 15 d. Plasma samples were stored at -20 degrees C until assayed. From Day 1 until the end of the experiment, uterine fluid samples were collected transcervically twice weekly for aerobic bacterial culture. Endometrial biopsies were collected between Days 6 and 8 and Days 13 and 15. Control cows did not show signs of uterine infection throughout the trial, and bacterial cultures indicated that there were no significant bacterial populations in the uteri of the control cows. The uteri of infected cows harbored numerous microbes. Actinomyces pyogenes was most prominent. Various species of Streptococcus and Pasteurella were also prevalent in the infected cows. Escherichia coli was present in the uterus of both infected and control cows. Biopsies showed that infected cows had more (P<0.05) neutrophils, plasma cells and lymphocytes in the endometrium than did the control cows. As determined by plasma progesterone concentrations, 83% of the control and 50% of the infected cows had functional luteal tissue during the 2-wk sampling period. Plasma PGFM profiles were linear (P<0.03) and did not differ between treatment groups (P>0.01). However, average plasma PGFM concentrations were greater (P<0.0001) in infected than in control cows. These data indicate that plasma PGFM concentrations are greater in postpartum cows with spontaneous uterine infections then in herdmates free of infection.     

Relationship between endogenous progesterone and follicular dynamics in lactating dairy cows with ovarian follicular cysts

Two experiments were conducted to examine circulating concentrations of progesterone (P4) in cows with ovarian follicular cysts (OFCs) and to relate differing levels of P4 to subsequent follicular events. In experiment 1, peripheral concentrations of P4 were determined in cows diagnosed with OFCs. Nonpregnant, lactating Holstein and Jersey cows (n = 32) were diagnosed as having OFCs by rectal palpation. Ovarian follicular cysts were then examined by transrectal ultrasonography to confirm the presence of OFCs (follicle diameter, >/=17 mm; absence of luteal tissue). At confirmation, a blood sample was collected for quantification of P4. The concentration of P4 at confirmation was classified as low (<0.1 ng/ml), intermediate (0.1-1.0 ng/ml), or high (1.0-2.0 ng/ml). More OFCs were associated with intermediate (66%) than with either low (28%) or high (6%) concentrations of P4. In experiment 2, the fate of follicles (diameter, >/=10 mm) that formed in the presence of an OFC was determined and related to circulating concentrations of P4 during follicular development. Follicles (n = 59) that formed in the presence of an OFC ovulated (n = 19), formed a cyst (n = 30), or underwent normal growth and regression (NGR; n = 10). Endogenous P4 in the 7-day period during follicular development was classified as low (if P4 dropped to <0.1 ng/ml for 1 day or longer), intermediate (if P4 averaged between 0.1 and 1.0 ng/ml and never dropped to <0.1 ng/ml), or high (if P4 averaged >1.0 ng/ml and never dropped to <0.1 ng/ml). In the presence of intermediate P4, 75% of observed follicles formed cysts, compared with 10% that ovulated and 15% that experienced NGR. In the presence of low P4, 53%, 41%, and 6% of follicles ovulated, formed a follicular cyst, or experienced NGR, respectively. Thus, an association between intermediate P4 and the formation of OFCs was established.     

Inflammatory cytokine concentrations in uterine flush and serum samples from dairy cows with clinical or subclinical endometritis

The objective of this study was to compare the concentrations of inflammatory cytokines in uterine flush and serum from healthy postpartum dairy cows and cows with clinical or subclinical endometritis. Clinical endometritis was diagnosed by observation of vaginal discharges (>50% pus) and subclinical endometritis was diagnosed by evaluation of uterine cytology (neutrophils >18%) at 4 weeks postpartum. Uterine flush was obtained from 48 cows at 4, 6, and 8 weeks postpartum for evaluation of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6, IL-8, and IL-10 concentrations. Serum samples were obtained from 34 cows just after calving and at 1, 2, 4, 6, and 8 weeks postpartum for evaluation of TNF-α, IL-1β, and IL-6 concentrations. Concentrations of TNF-α, IL-6, and IL-10 were greater (P < 0.05) in cows with clinical endometritis than in cows with subclinical endometritis and healthy controls, whereas concentrations of IL-8 in both cows with clinical and subclinical endometritis were greater (P < 0.005) than in controls. Overall, IL-6 and IL-10 concentrations decreased during the postpartum period. IL-1β concentrations in cows with clinical endometritis decreased (P < 0.0005) during the postpartum, whereas concentrations in cows with subclinical endometritis and controls did not change significantly with time; at 4 weeks postpartum, concentrations were greater (P < 0.0001) in cows with clinical endometritis. There were no significant effects of group, sampling time, or interaction on serum cytokine concentrations. In conclusion, cows with endometritis have greater inflammatory cytokine concentrations in uterine flush than healthy cows, but no differences were observed in serum.     

Activity of alkaline phosphatase in uterine flushings of dairy cows affected with ovarian cysts or endometritis

Both uterine horns of 14 dairy cows with ovarian follicular cysts, and four animals affected with purulent endometritis were flushed via catheter using 30 ml phosphate buffered saline, following evisceration at a local abattori. Activity in the flushing media of alkaline phosphatase (ALP) and aspartate aminotransferase (GOT) were examined. Ovaries were prepared for light microscopy. Amount and morphological integrity of luteinized tissue found on the ovaries were reflected by correspondent levels in ALP activity, which was higher in the media taken from the ipsilateral to the luteal tissue situated uterine horns (651 +/- 228 vs 244 +/- 62 u/l, n = 3). Only cows having relatively large amounts of luteal tissue on the cystic ovaries (as in luteinized follicular cysts) exhibited very high ALP activity in uterine flushings (2693 +/- 1348 u/l, n = 2). Results suggest the existence of local relationships between luteal tissue in the ovary and the ipsilateral uterine horn in cows with ovarian follicular cysts.     

Use of plasma concentrations of 13,14-dihydro,15-keto-PGF2 alpha (PGFM) in the diagnosis of sub-clinical endometritis and its relationship to fertility in the postpartum dairy cow

The objective of this study was to determine the value of using plasma concentrations of PGFM to diagnose subclinical endometritis in the dairy cow, and its relationship to subsequent fertility. A total of 274 cows between 24 to 29 d post partum was divided into 4 groups on the basis of clinical features of the uterus and ovary. Cows in Group 1 (n = 74) had a normal, involuting uterus and a CL on the ovary; cows in Group 2 (n = 51) had a normal, involuting uterus but no CL on the ovary; cows in Group 3 (n = 83) did not have a normal, involuting uterus but had a CL on the ovary; and cows in Group 4 (n = 66) did not have a normal, involuting uterus or a CL on the ovary. A blood sample was obtained from each cow on the day they were placed on the study, and plasma concentrations of PGFM and P4 were determined using RIA. Cows were artificially inseminated (AI) at the first observed estrus after Day 60 post partum, and pregnancy was determined by palpation of the uterus per rectum between 45 and 50 d postAI. Reproductive responses evaluated were conception rate to first service, days open, and percentage of cows pregnant by 90, 120, 150 and 180 d post partum. Data were analyzed using GLM procedures of SAS and a 2 x 2 factorial with contrast procedures. Polynomial regression analysis was used to determine the shape of the PGFM, P4 and fertility curves. There was no difference among mean PGFM concentrations of cows in each group. The rate of decline of plasma PGFM concentrations was lower in cows with an abnormal uterus and a CL on the ovary compared with those without a CL. A lower percentage of cows with abnormal uteri was pregnant by 90 d post partum compared with cows with normal uteri. From the results of this study, it was concluded that plasma PGFM concentrations between Days 24 to 29 post partum were not effective in identifying cows with subclinical endometritis.     

Relationship between intra-uterine bacterial contamination, endotoxin levels and the development of endometritis in postpartum cows with dystocia or retained placenta

A study was conducted to investigate the relationship between intra-uterine bacterial contamination, endotoxin levels and the development of endometritis in cows that experienced a dystocia or retained their placenta. Fifteen healthy cows, 31 cows with retained placenta (RP) and 13 cows that had dystocia were clinically examined 1 or 2 days after parturition when a uterine swab for bacteriological examination was taken. In addition, plasma and uterine lochia samples were collected to determine lipopolysaccharide (LPS) and the plasma IgG anti-LPS concentrations. Subsequently, 15 RP and 6 dystocia cows were initially left untreated and another uterine swab was collected at 2 and 4 wk postpartum. Immediately after calving, RP cows had significantly higher LPS levels in uterine lochia (average of 2.24 x 10(4) Endotoxin Units (EU)/mL) as compared to dystocia and healthy postpartum cows (average of 0.10 and 0.26 EU/mL, respectively). However, plasma LPS levels were below the detection limit (<0.036 EU/mL platelet-rich plasma) in all groups of cows. IgG anti-LPS levels in plasma were not significantly different between the 3 groups immediately postpartum (average of 26, 16 and 44 Median Units (MU)/mL) for healthy, dystocia and RP cows, respectively), but they were significantly lower when compared to plasma IgG anti-LPS levels of healthy cows at more than 2 months postpartum (mean 83 MU/mL). High LPS levels in lochia at 1 or 2 days postpartum were significantly related to abnormal cervical discharge, the presence of Escherichia coli, black pigmented gram-negative anaerobes and Clostridium spp. shortly after calving, and Arcanobacterium pyogenes and gram-negative anaerobes in the uterus at 14 days postpartum. These results suggest that the presence of E. coli and LPS (endotoxins) in lochia early postpartum favor the development of uterine infections by A. pyogenes and gram-negative anaerobes later postpartum. LPS were not observed in plasma, suggesting that either they are not absorbed into the blood, or they are efficiently detoxified by IgG anti-LPS or other detoxification mechanisms.     

Plasma progesterone and gonadotrophin concentrations and ovarian activity in post-partum dairy cows

Plasma progesterone concentrations in jugular vein blood samples collected every other day after calving from 13 Friesian dairy cows indicated that ovarian cyclic activity was initiated by 16.6 +/- 1.1 (s.e.m.) days post partum, except for 1 cow which did not resume cyclic activity until Day 98 post partum. Rectal palpation of the ovaries indicated that a developing follicle was recognizable at a mean time of 15.7 +/- 2.0 days after calving. During the first oestrous cycle after parturition there was a significantly shorter period when plasma progesterone levels were elevated than during the next 2 cycles. Concentrations of progesterone, LH, FSH and prolactin were determined for 4 cows, in blood samples taken every 6 h from 2 to 36 days post partum. Tonic LH release was lower during the first 10 days than subsequently, but the lack of change in pattern for FSH suggests dissimilar control mechanisms for these hormones during this time. Three cows showed evidence of a resumption of ovarian cyclicity during the sampling period: in 2 there was an initial LH surge of a magnitude which would normally give rise to ovulation, followed 4 days later by an increase in plasma progesterone lasting only 5 and 9 days. This progesterone was considered to be of follicular origin. A second LH surge was followed by the presence of a corpus luteum.     

Plasma endotoxin and concentrations of stable metabolites of prostacyclin, thromboxane A2, and prostaglandin E2 in postpartum dairy cows

The presence of endotoxin in plasma and patterns of stable metabolites of prostacyclin (PC), thromoxane A₂ (TXA₂) and prostaglandin E₂ (PGE₂) were determined during the first postpartum estrous cycles in sixteen dairy cows. These included 8 cows with uterine infections which exhibited shortened luteal phases (SC) and 8 cows which had normal luteal phases (NC) after the first post partum ovulations. Endotoxin was consistently detected in all SC cows during the abbreviated estrous cycles while plasma samples of NC cows were free of endotoxin. Plasma concentrations of TXA₂ metabolite was higher in SC cows (p<0.05) (1785–3452 pg/ml) compared to NC cows (723–1240 pg/ml). Similarly, plasma concentrations of PC metabolite was higher in SC cows (p<0.07) (423–1847 pg/ml) compared to NC cows (159–325 pg/ml). In contrast, plasma concentrations of PGE₂ metabolite was higher in NC cows (p<0.05) (850–2219 pg/ml) compared to SC cows (455–628 pg/ml). The results of this study suggest that postpartum uterine infections mediate the release of prostaglandins from the uteri by means of the endotoxin and endotoxin appears to stimulate selectively the production of PC and TXA₂ favoring early demise of corpora lutea formed after first postpartum ovulations in dairy cows.     

Incidence and treatment of abnormal postpartum ovarian function in dairy cows

The objectives of this study were to determine 1) the incidence of abnormal postpartum ovarian function in a large dairy herd in North Central Florida and 2) the effectiveness of gonadotrophin releasing hormone (GnRH) in treating this condition. The study was conducted from April 1988 to June 1989. The internal genitalia of the cows were initially examined per rectum (Day 0) between 19 and 29 (23 +/- 0.25) d after calving and again 14 d later (Day 14) for evidence of uterine involution and ovarian activity. The presence of a palpable corpus luteum (CL) and retrospective determination of plasma progesterone (P4) concentrations > 1 ng/ml were the criteria used to assess ovarian activity. Cows possessing a palpable CL and P4 concentrations > 1 ng/ml on Day 0 were determined to be cycling normally. A total of 1356 cows was used in this study. On Day 0, two groups were formed: Group 1 consisted of normal, cyclic cows, Group 2 of noncyclic cows. On Day 0, alternate cows in Group 2 were treated with GnRH (100ug i.m). On Day 14, the previously nontreated cows in Group 2 were further divided into two groups, forming Group 3, nontreated cows and Group 4, cows treated with GnRH at this time. Group 5 was comprised of cows from Group 2 that did not respond to treatment with GnRH on Day 0; these cows were treated on Day 14 with GnRH (100ug i.m). Group 6 was comprised of nontreated cows from Group 2 that responded spontaneously (presence of a CL) by Day 14. Reproductive parameters evaluated were the percentage of cows pregnant within 180 d after calving and at the end of the study, the number of days open and the number of services per conception. Data were statistically analyzed using Chisquare and survival analysis. The results of this study indicate that the incidence of abnormal postpartum ovarian function in this herd was 30.2% and that the nontreated cows experienced more days open and required more services per conception than the treated cows, those that were cycling normally on the initial examination, and those that responded spontaneously by Day 14.     

The effects of ovarian function on estrus synchronization with PGF in dairy cows

Milk progesterone concentration (P4), milk yield, milk composition, ovarian structures and pregnancy status were studied in 108 cows treated with two doses of PGF 14 days apart and inseminated at fixed time (TAI) 80-82 h later. The synchronization protocol was started at 70+/-1.4 days after parturition. Milk P4 profiles revealed that anestrus, failure of luteolysis following treatment with PGF and failure to ovulate following luteolysis were the main reasons for low pregnancy rate with TAI. Anestrous cows had a higher percentage of milk fat (P<0.05) and higher fat to protein ratio (P<0.01), and cows that did not undergo luteolysis had higher milk yield (P<0.05) and lower percentage of milk protein (P<0.05) than cows that responded to PGF treatment. Cows that did not undergo luteolysis and cows that did not ovulate following luteolysis had lower milk P4 during the luteal phase preceding the second PGF injection (P<0.01 and P<0.05, respectively). Pregnancy rates 24 and 47 days after TAI in cows that responded as expected to the synchronization treatment were 62% and 54%, respectively. Pregnancy was precluded in non-responsive cows. The largest follicle at the time of TAI in cows experiencing late embryonic mortality was smaller (P=0.02) than in cows that successfully maintained pregnancy. Results suggest that a primary reason for low pregnancy rate in dairy cows after administration of PGF and TAI is inappropriate ovarian function prior to, or following treatment.     

Endometrial expression of selected transcripts involved in prostaglandin synthesis in cows with endometritis

Several cytokines and prostaglandins play an important role in preparing the endometrium for implantation and mediating pro-inflammatory events. The aim of the present study was to examine mRNA expression of interleukin 1α (IL-1α), interleukin receptor antagonist (IL-1-RN), cytosolic prostaglandin E synthase (cPGES), microsomal PGES (mPGES-1 and mPGES-2) and lipocalin-type PGDS (L-PGDS) in the bovine endometrium. Endometrial epithelium samples were collected ex vivo from cows with different status of health at day 21-27 postpartum on a dairy farm. Three groups (n = 9 animals each) were defined: (1) healthy cows with no signs of endometritis (control group), (2) cows with subclinical endometritis, and (3) cows with signs of clinical endometritis. Oestrous cycle-dependent mRNA expression pattern was investigated using bovine endometrial epithelial cells from healthy uteri collected at the abattoir. These uteri were classified into post-ovulatory, early-to-mid luteal, late luteal or pre-ovulatory phase (n = 8 animals for each cycle phase). After collecting endometrial epithelium using the cytobrush-method, mRNA analysis was performed by real-time RT-PCR. L-PGDS, IL-1α and IL-1-RN mRNA were expressed significantly higher (P < 0.05) in the endometrium of cows with subclinical or clinical endometritis compared with healthy cows. A twofold lower cPGES mRNA expression (P < 0.05) was detected in cows with subclinical endometritis compared to healthy cows. L-PGDS and IL-1-RN mRNA expression was increased (P < 0.05) after ovulation compared with the pre-ovulatory or luteal phase, respectively. These results support the hypothesis that a dys-regulated cytokine and/or prostaglandin profile in the uterus could be induced by subclinical endometritis or clinical endometritis.     

Changes in prostaglandin production and ovarian function in gilts during endometritis induced by Escherichia coli infection

The aim of this study was to determine the prostaglandins (PGs) production and ovarian function in gilts after intrauterine infusions of 10(6) and 10(9) colony-forming units (cfu)/ml of Escherichia coli (E. coli). In Experiments 1 and 2, 30 ml of saline or 30 ml of E. coli suspension containing 10(6) or 10(9)cfu/ml, were infused once into each uterine horn in three groups of gilts on day 3 of the estrous cycle, respectively. In Experiment 1, 17 days after treatment it was revealed that inoculation of E. coli 10(9)cfu/ml induced severe acute or subacute endometritis while 10(6)cfu of E. coli evoked moderate acute endometritis or resulted in no inflammatory changes. In the gilts receiving 10(9)cfu/ml of E. coli, the concentration of 13,14-dihydro-15-keto-PGF(2)alpha in blood from the jugular vein was elevated (P<0.05-0.001) compared to concentration in the gilts inoculated with 10(6)cfu on days 8-17 after treatment. Both the E. coli-treated groups had a lower (P<0.05, P<0.01) progesterone plasma level from days 10 to 14 after administration than the control group. On day 17 of the study, infusion of E. coli 10(9)cfu/ml, in comparison to 10(6)cfu, resulted in the greater (P<0.001) content of PGE(2) in the myometrium. The content of both PGs in the endometrium as well as PGF(2alpha) in the myometrium of gilts-treated with 10(9)cfu/ml of E. coli was lower (P<0.001) than in gilts-treated with 10(6)cfu of bacteria. Newly formed corpora lutea were found in the gilts infused with 10(6), but not those infused with 10(9)cfu/ml of E. coli on day 17 after infusion. On day 8 of the study (Experiment 2), the blood from utero-ovarian vein of the gilts-treated with 10(9)cfu/ml of bacteria had a higher (P<0.05) PGF(2alpha) level and lower (P<0.001) PGE(2) level than following infusion of E. coli 10(6)cfu/ml. Also on day 8 of the study, the content of PGE(2) in the endometrium, both the PGs in the myometrium as well as cyclooxygenase-2 in the endometrium and myometrium was greater (P<0.01, P<0.001) after applying 10(9)cfu/ml than 10(6)cfu/ml of E. coli. These results indicate that intrauterine infusions of 10(6) or 10(9)cfu/ml of E. coli lead to the development of inflammatory states of different intensities which is connected with different PGF(2alpha) and PGE(2) production and function of ovaries.     

Relationships between ovarian blood flow and ovarian response to eCG-treatment of dairy cows

The goal of the present study was to investigate ovarian blood flow and ovarian response in cows undergoing a gonadotropin treatment to induce a superovulatory response, using transrectal colour Doppler sonography. Forty-two cows including 19 cross-bred, 14 German Holstein and 9 German Black Pied cows were examined sonographically before hormonal stimulation on Day 10 of the oestrous cycle, three days after administration of eCG (Day 13) and seven days after artificial insemination (Day 7(p.i.)). After each Doppler examination, blood was collected for determination of total oestrogens (E) and progesterone (P4) in peripheral plasma. The blood flow volume (BFV) and pulsatility index (PI), which is a measure for blood flow resistance, were determined in the ovarian artery, and B-mode sonography was used to count dominant follicles and corpora lutea. Important criteria to assess the ovarian response following the hormonal treatment were the number of follicles >5mm in diameter on Day 13 and the number of corpora lutea on Day 7(p.i.) per cow. The number of follicles ranged from 2 to 61 (mean+/-S.E.M.: 17.5+/-1.7) and corpora lutea from 0 to 50 (mean+/-S.E.M.: 17.0+/-1.6). The BFV increased from 28.4 to 45.0 ml/min between Days 10 and 13 and reached a maximum of 108.5 ml/min on Day 7(p.i.) The PI decreased from 6.25 on Day 10 to 4.70 on Day 13 and to 2.10 on Day 7(p.i.) The BFV and PI on Day 13 did not correlate with the number of follicles (P>0.05). However, on Day 7(p.i.) the number of corpora lutea correlated positively with the BFV (r=0.64; P<0.0001), and an inverse relationship was found for the PI (r=-0.51; P=0.0005). There were no correlations (P>0.05) between the BFV and PI on Day 10 and the number of follicles on Day 13 or the number of corpora lutea on Day 7(p.i.) Results of the present study show that in cows, a hormonal treatment to induce a superovulatory response yielded a marked increase in BFV and a marked decrease in PI in the ovarian artery. However, there was no correlation between BFV and PI in the ovarian arteries before hormonal stimulation and the number of follicles and corpora lutea that developed after stimulation. Thus BFV and PI measured in the ovarian arteries have limited diagnostic value to predict the outcome of a gonadotropin treatment.     

Interrelationships between progesterone, 13,14-dihydro-15-keto PGF-2 alpha (PGFM) and LH in cyclic and early pregnant cows

Plasma progesterone and LH secretion patterns were examined in 18 mature dairy cows during the oestrous cycle and after insemination. Blood samples were collected every 15 min for 8 h per day on Days 3, 5, 6, 7, 8, 9, 10, 12, 14, 16, 17, 18, 19, 20 and 21 of the oestrous cycle, then, in the same cows, at the same times during early pregnancy. PGF-2 alpha secretion rates (as determined by plasma PGFM concentrations) were also monitored on Days 14, 16 and the day of, or equivalent to, luteal regression. Mean daily plasma progesterone concentrations were similar until Day 16 in cyclic and pregnant cows, after which values in non-pregnant animals declined. Regression analysis indicated that progesterone concentrations were best described by a quadratic expression with fitted maximum values on Day 13 in non-pregnant animals but values increased linearly over the whole period to Day 21 in pregnant cows. The frequency, amplitude and area under the curve of LH episodes showed no significant differences between cyclic and pregnant animals. In pregnant cows, the amplitude and area under the curve of progesterone episodes increased linearly between Days 8 and 21, although no such increase occurred in cyclic cows. Low-level PGFM episodes were present in cyclic and pregnant cows on Days 14 and 16 after oestrus, and high amplitude episodes occurred in non-pregnant cows during luteal regression. Pregnant cows showed a significant depression of the amplitude, but not the frequency of episodes at the expected time of luteal regression. These results confirm that the corpus luteum of pregnancy secretes an increasing amount of progesterone per se and per unit of LH until at least Day 21 after mating. They further suggest that the corpus luteum of the cyclic cow may experience small episodes of PGF-2 alpha and be subjected to initial degenerative changes by Day 14 after oestrus, some time before the onset of definitive luteolysis.     

Decreased sensitivity of atopic mononuclear cells to prostaglandin E2 (PGE2) and prostaglandin D2 (PGD2)

The effect of PGE2 and PGD2 on several lymphocyte functions in vitro was evaluated in nonatopic and atopic subjects. Both PGE2 and PGD2 inhibited phytohemagglutinin-induced protein synthesis ([3H] leucine uptake) by nonatopic mononuclear cells and T cells in a dose-dependent manner (10(-6) to 10(-12) M). Protein synthesis by atopic mononuclear cells was not significantly suppressed by the above concentration of PGE2. Although PGD2 effectively suppressed protein synthesis by atopic mononuclear cells and T cells at 10(-6) M, lower concentrations were ineffective. Kinetic studies revealed significant differences in the suppressive effects of PGE2 and PGD2 on atopic and nonatopic mononuclear cells at 24 and 48 h, but not at 72 or 96 hr. Protein synthesis by T helper-enriched populations (suppressor cell depletion by anti-Leu-2b + complement) obtained from nonatopics was significantly reduced by PGE2 and PGD2, suggesting that these mediators may be directly inhibiting the responding population. By contrast, protein synthesis by T suppressor-enriched populations (helper cell depletion by OKT4 + complement) obtained from nonatopics was enhanced by PGE2 and PGD2, suggesting that the PG were activating these cells. Atopic T helper and T suppressor cells exhibited decreased responsiveness to PGE2 and PGD2 compared with nonatopic cells. PGE2 and PGD2 inhibited the phytohemagglutinin-stimulated proliferative response ([3H]thymidine uptake) by both atopic and nonatopic mononuclear cells in a dose-dependent manner and to the same extent. However, although PGE2 and PGD2 generated functional suppressor activity (when using a coculture technique) in nonatopic mononuclear cells, these mediators failed to activate atopic suppressor cells. These results suggest that reduced responses by atopic T cells to signals provided by PGE2 and PGD2 are not solely restricted to suppressor cell function, and could indicate an impaired ability to regulate immune and/or inflammatory reactions.     

Effects of prostaglandin E1 or E2 (PGE1; PGE2) on luteal function and binding of luteinizing hormone in nonpregnant ewes

Two studies were conducted to determine the effects of PGE1 or PGE2 on luteal function and binding of luteinizing hormone (LH) to luteal cell membranes in nonpregnant ewes. In Study I, ewes (n=5 per group) received an injection of vehicle (VEH) or 333 micrograms of PGE1 or PGE2 into the tissue surrounding the ovarian vascular pedicle (intrapedicle) on day 7 postestrus. Systemic progesterone concentrations of PGE1-treated ewes were greater (P less than 0.01) than those of VEH-treated ewes at 24 and 48 hr after injection. For PGE2-treated ewes, progesterone concentrations were greater (P less than 0.01) than for VEH-treated ewes only at 24 hr. Neither PGE1 nor PGE2 affected luteal weights or LH binding capacity at 48 hr. Treatment with PGE1, however, increased (P less than 0.10) endogenously bound LH at this time. In Study II, ewes (n=5 per group) received an intrapedicle injection of VEH, or 10 mg of PGE1 or PGE2 on day 8 postestrus. Systemic progesterone concentrations in PGE1-treated ewes were less (P less than 0.01) than for VEH-treated ewes at 24 hr, but by 72 hr were not different from those of VEH-treated ewes. For PGE2-treated ewes, systemic progesterone declined steadily to reach low values by 72 hr. Prostaglandin E2 had no effect on luteal binding of LH at 72 hr, whereas PGE1 increased (P less than 0.05) LH binding capacity and endogenously bound LH. Although PGE2 had no apparent affect on luteal binding of LH in these studies, PGE1 may enhance the function of ovine corpora lutea by stimulating an increase in their binding of LH and capacity to bind LH when the CL receives a luteolytic signal.     

Reduced prostaglandin E2 (PGE2) receptors on atopic T lymphocytes

We have recently demonstrated that atopic T lymphocytes have decreased sensitivity to prostaglandin E2 (PGE2). In order to determine whether this decreased sensitivity was reflected at the receptor level, we have employed a radioligand binding assay utilizing [3H]PGE2. We have demonstrated a single specific reversible binding site for [3H]PGE2 on normal T cells (N = 10) with a mean KD (+/-SD) of 32.2 (+/-25.0) nM, a binding capacity of 20.2 (+/-13.0) pM, and a mean of 1004 (+/-118) receptors per cell. Atopic T cells (N = 10) were also found to have a single specific binding site for [3H]PGE2 with a mean KD of 24.9 (+/-17.8) nM, a binding capacity of 7.1 (+/-10.1) pM, and a mean of 372 (+/-61) receptors per cell. These radioligand binding studies were correlated with functional studies in the same subjects. Phytohemagglutinin-stimulated protein synthesis ([3H]leucine uptake) was suppressed in a dose-dependent fashion by PGE2 (10(-6)-10(-12) M). The maximal effect of PGE2 on normal T cells was 10(-6) M PGE2 with an IC50 of 10(-12) M. Atopic T cells responded quantitatively less than normal T cells to PGE2. Further, the maximum suppression of protein synthesis by PGE2 occurred at 10(-6) M with an IC50 of 10(-10) to 10(-11) M. These studies suggest that part of the decreased sensitivity of atopic T cells to PGE2 may result from a reduction in PGE2 binding sites.     

Effects of intrauterine infusion of Escherichia coli endotoxin in normal cows and in cows with endometritis induced by experimental infection with Streptococcus agalactiae

Two experiments were carried out to describe the effects of intrauterine infusion of Escherichia coli endotoxin on some aspects of nonspecific uterine defense mechanisms in healthy cyclic cows (Experiment 1) and in cows with induced endometritis by experimental infection with Streptococcus agalactiae (Experiment 2). In Experiments 1 and 2, the mean log(e) total white cell counts (>95% neutrophils) in the uterine flushing fluid of the endotoxin-treated group were significantly increased (P<0.01 and P<0.05, respectively). Streptococcus agalactiae was detected by the Latex Agglutination Test (LAT) in 47% of the samples from uteri experimentally infected with this organism; 12.5% were positive on culture, and only 10% were positive on both tests. With one exception, all the samples with a positive culture were positive to the LAT, but not all samples submitted to the LAT had positive culture. There was a significant (P<0.05) association between endotoxin treatment and the presence of infection detected by the LAT but not with that detected by culture (P>0.05) at 3 to 12 days post infection. Similar results were found at 8 to 16 days post infection. The infection disappeared from the endotoxin-treated group but not from the non-treated group 12 days after the induction of infection. It is concluded that intrauterine E. coli endotoxin infusion might provide an alternative treatment for those cows with endometritis that is refractory to conventional antimicrobial and hormonal therapy. It is also concluded that the LAT is an easier, quicker and more reliable method than bacterial culture for the detection of endometritis caused by Strep. agalactiae , and, possibly, such immunodiagnostic tests may be useful for the detection of other uterine infections.