color-Doppler Signals Of Blood Flow Research Articles

Angiocoupling between the dominant follicle and corpus luteum during waves 1 and 2 in Bos taurus heifers

The local two-way effect of the future and established dominant follicle (DF) and corpus luteum (CL) on color-Doppler signals of blood flow on each other (angiocoupling) was studied from ovulation to 16 days after ovulation during wave 1 and for the first time in wave 2 in Bos taurus heifers (N = 24). Identity of follicles greater than 4 mm was maintained from day to day. Blood-flow signals in the follicle wall and in the CL were estimated after scanning the entire structure. Ovarian patterns were defined based on the presence of a DF and CL: DF−CL pattern (DF and CL in the same ovary), DF pattern or CL pattern (DF and CL in opposite ovaries), and devoid pattern (neither DF nor CL). Comparisons were made of blood flow in each structure when in the same ovary vs opposite ovaries. Data were normalized to expected diameter deviation (DF closest to 8.5 mm). Blood-flow signals were detected in most growing follicles when they attained 6 mm (6.0–6.9 mm). Combined for waves 1 and 2, the percentage of all 6-mm growing follicles that displayed blood-flow signals was greater (P < 0.0001) for the DF−CL pattern (21/26, 81%) than for the patterns of DF alone, CL alone, or neither DF nor CL (total for the three patterns (17/42, 40.5%); there was no effect of left vs right ovaries. For each wave, the percentage of DF wall and percentage of CL tissue with blood-flow signals were greater for the DF−CL pattern vs the DF pattern or CL pattern. Percentage of DF wall with blood-flow signals for the DF−CL vs DF patterns was 30.0 ± 1.5% vs 19.5 ± 1.1% (P < 0.02) in wave 1 and 30.8 ± 1.3% vs 20.2 ± 1.1% (P < 0.0001) in wave 2. Percentage of CL tissue with blood-flow signals for the DF−CL vs CL patterns was 61.7 ± 2.4% vs 56.9 ± 1.7% (P < 0.03) in wave 1 and 78.8 ± 1.3% vs 74.0 ± 0.9% (P < 0.03) in wave 2. During wave 1, the percentage of CL tissue with blood-flow signals was greater (P < 0.002) when the DF and CL were in close proximity (distance between structures, < 2 mm; 66.9 ± 3.0%) than when separated (≥2 mm; 53.8 ± 3.5%). Normalization to the maximal DF diameter in wave 1 resulted in the novel finding that the percentage of blood-flow signals in the DF wall began to decrease 1 day before maximal diameter. Results supported the hypotheses that (1) percentage of DF wall and CL tissue with blood-flow signals in wave 2 is greater in the DF−CL pattern than in the DF or CL patterns and (2) percentage of DF wall with blood-flow signals in wave 1 decreases before the beginning of a decrease in diameter.

Role of luteal biosynthesis of prostaglandin F2α on function and structure of the corpus luteum during luteolysis in heifers

The role of endogenous prostaglandin F2α (PGF) in the induction of luteolysis by exogenous PGF was studied by simultaneous inhibition of endogenous PGF with flunixin meglumine (FM). Groups were controls (n = 8), PGF treated (n = 8), and FM + PGF treated (n = 9). Treatments were given 10 d postovulation at hours 0, 8, and 16. The protocol was based on (1) the assumption that luteolytic characteristics of exogenous PGF would be altered if the synthesis of endogenous PGF is simultaneously inhibited and (2) the reports that luteolysis involves a direct effect of uterine PGF on large luteal cells followed by an effect of the large cells on the small cells. At hour 48, progesterone concentration was greater in the controls (7.6 ± 0.8 ng/mL) than that in the FM + PGF group (3.0 ± 0.5 ng/mL) and lower in the PGF group (0.7 ± 0.3 ng/mL) than in the FM + PGF group (interaction, P < 0.0001). The effects of each of the 3 groups on percentage change in CL volume were similar to the effects on progesterone. At hour 48, the percentage of CL tissue with color-Doppler signals of blood flow was similar between the controls (56.2% ± 3.8%) and FM + PGF group (50.0% ± 6.4%) and lowest in the PGF group (15.6% ± 7.2%) (interaction, P < 0.0001). A resurgence in progesterone concentration began at hours 24 or 48 in 6 of 9 heifers in the FM + PGF group compared to 0 of 8 heifers in each of the other groups (P < 0.007). The progesterone resurgence in the FM + PGF group was associated with the maintenance of percentage of CL tissue with blood-flow signals. The experimental hypothesis that an inhibitor of endogenous PGF reduces the luteolytic response to exogenous PGF was supported.

Color-Doppler signals of blood flow in the corpus luteum and vascular perfusion index for ovarian and uterine arteries during expansion of the allantochorion in Bos taurus heifers

Hemodynamics of the CL and each main uterine artery during expansion of the allantochorion from the ipsilateral side (CL side) to the contralateral side were studied in heifers (n = 8 nonbred, 9 pregnant). Progesterone concentration, vascular perfusion index for each uterine artery (by spectral ultrasonography), extent of blood flow in the CL (percentage of CL tissue with color-Doppler signals of blood flow), and intrauterine location of the expanding allantochorion (by gray-scale ultrasonic imaging) were determined daily from Days 14–60 (Day 0 = ovulation). In the pregnant group, but not in the nonbred group, the percentage of CL tissue with blood-flow signals increased (P < 0.003) from Days 16 (66.7 ± 4.2%) to 23 (79.4 ± 2.5) and then more slowly increased (P < 0.02) from Days 24 (76.7 ± 2.9%) to 50 (85.0 ± 2.0%). The volume of CL increased (P < 0.0001) progressively from Days 26 (6.1 ± 0.4 cm3) to 60 (7.3 ± 0.7 cm3). The vascular perfusion index in the ipsilateral uterine artery did not change in the nonbred group and progressively increased in the pregnant group beginning on Day 17 in approximate temporal association with the increase in luteal blood-flow signals. Functional increases in the CL during early pregnancy were attributed to the greater uterine arterial blood flow on the ipsilateral or CL side and the reported prominent anastomosis from a branch of the uterine artery to the ovarian artery that supplies the CL ovary. After an initial significant decrease in vascular perfusion index in each uterine artery in the pregnant group, the index began to increase on Day 17 in the ipsilateral artery and on Day 18 in the contralateral artery. The perfusion continued in the ipsilateral artery but discontinued in the contralateral artery on Day 21. Perfusion and diameter of the uterine artery were greater for the ipsilateral side until the vesicle entered the contralateral horn on Day 33 and increased for the contralateral horn between vesicle entry and filling of the horn on Day 44. During Days 35–60, the perfusion index (P < 0.04) and artery diameter (P < 0.001) were lower in the contralateral than in the ipsilateral artery. Results supported the hypotheses that (1) CL function increases during early pregnancy in temporal association with an increase in blood flow in the ipsilateral uterine artery and (2) blood flow in each of the ipsilateral and contralateral uterine arteries increases as the allantochorion expands in each uterine horn.

Effect of GnRH and hCG on progesterone concentration and ovarian and luteal blood flow in diestrous mares

The objective of the present study was to investigate the effect of reproductive hormones (GnRH, hCG, LH and progesterone) on the regulation of corpus luteum (CL) and ovarian blood flow. Diestrous mares received a single treatment of saline, 100μg gonadorelin (GnRH), or 1500IU hCG 10days after ovulation. Plasma LH and progesterone concentrations, resistance index (RI) for ovarian artery blood-flow, and percentage of corpus luteum (CL) with color-Doppler signals of blood flow were determined immediately before treatment (hour 0) and at hours 0.25, 0.5, 1, 1.5, 2, 3, 4, 5, and 6. In the GnRH group, LH increased (P<0.0001) between hours 0 and 0.25 and then progressively decreased; concentration of LH was not affected in the saline and hCG groups. Progesterone concentration was not different among groups. In the GnRH group, RI tended (P<0.07) to decrease between hours 0 and 1.5 and increased (P<0.01) between hours 1.5 and 4. In the hCG group, two transient RI decreases (P<0.05) occurred before hour 2. The percentage change from hour 0 in the percentage of CL with blood-flow signals was greater at hour 0.5 in the GnRH group than in the saline group and was intermediate in the hCG group. The similarity among groups in progesterone concentration indicated that changes in progesterone were not involved in the GnRH and hCG stimulation of ovarian vascular perfusion. Effects of treatment might have been mediated through LH; however, since hCG biological activity is primarily LH-like, the differences in timing and degree of ovarian and luteal blood flow changes after GnRH or hCG administration in the present study suggest that GnRH might have a direct effect on ovarian blood vessels and vascular control.

Disruption of periovulatory FSH and LH surges during induced anovulation by an inhibitor of prostaglandin synthesis in mares

The role of passage of follicular fluid into the peritoneal cavity during ovulation in the transient disruption in the periovulatory FSH and LH surges was studied in ovulatory mares ( n = 7) and in mares with blockage of ovulation by treatment with an inhibitor of prostaglandin synthesis ( n = 8). Mares were pretreated with hCG when the largest follicle was ≥32 mm (Hour 0). Ultrasonic scanning was done at Hours 24 and 30 and every 2 h thereafter until ovulation or ultrasonic signs of anovulation. Blood samples were collected at Hours 24, 30, 32, 34, 36, 38, 48, and 60. Ovulation in the ovulatory group occurred at Hours 38 (five mares), 40, and 44. Until Hour 36, diameter of the follicle and concentrations of FSH, LH, and estradiol-17β (estradiol) were similar between groups. Between Hours 34 and 36, a novel transient increase in estradiol occurred in each group, and color-Doppler signals of blood flow in the follicular wall decreased in the ovulatory group and increased in the anovulatory group. In each group, FSH and LH periovulatory surges were disrupted by a decrease or plateau between Hours 38 and 48 and an increase between Hours 48 and 60. The discharge of hormone-laden follicular fluid into the peritoneal cavity at ovulation was not an adequate sole explanation for the temporally associated transient depression in FSH and LH. Other routes from follicle to circulation for gonadotropin inhibitors played a role, based on similar depression in the ovulatory and anovulatory groups.

Short-term feed restriction decreases the systemic and intrafollicular concentrations of leptin and increases the vascularity of the preovulatory follicle in mares

The objective of this study was to evaluate the effect of short-term feed restriction on characteristics of the preovulatory follicle and on concentrations of systemic hormones (leptin, follicle-stimulating hormone [FSH], luteinizing hormone [LH]) and follicular fluid hormones and growth factors (leptin, estradiol, inhibin-A, activin-A, free insulin-like growth factor-1 [IGF1], insulin-like growth factor binding protein 2 [IGFBP2], vascular endothelial growth factor [VEGF]). Mares were submitted to a short-term (48 h) feed restriction when the expected ovulatory follicle was ≥27mm (Hour 0) or served as controls (n=8/group). No effect of short-term feed restriction was detected for systemic concentrations of FSH and LH and for intrafollicular concentrations of estradiol, activin-A, free IGF1, and IGFBP2. Restricted mares had decreased systemic concentrations of leptin at Hour 24 (approached significance) and at Hours 36 and 48 (P<0.04). Follicular fluid of restricted mares at Hour 48 had lower (P<0.02) concentration of leptin and a tendency (P<0.1) for greater concentrations of inhibin-A and VEGF. The percentage of wall of the preovulatory follicle with color-Doppler signals of blood flow at Hour 48 was greater (P<0.04) in the restricted group. Intrafollicular concentration of leptin (combined groups) was positively correlated with score for body condition (r=+0.60; P<0.002) and negatively correlated with the percentage of the follicle wall with blood-flow signals (r=−0.60; P<0.02). Our favored interpretation is that the preovulatory follicle seems to compensate for a nutritional deficiency by increasing the blood flow in the follicle wall.

Concentrations of circulating hormones normalized to pulses of a prostaglandin F 2α metabolite during spontaneous luteolysis in mares

The temporal relationships between a pulse of 13,14-dihydro-15-keto-PGF 2α (PGFM) and the concentrations of circulating hormones during the luteolytic period were studied for 11 pulses in 11 mares (Equus caballus) using samples collected hourly. Mean PGFM pulses encompassed 4 h before to 4 h after the peak, and hormone data were normalized to the PGFM peak (Hour 0). Concentration of progesterone decreased (P < 0.05) between Hours –4 and –3 and continued to decrease linearly throughout the PGFM pulse. The concentrations of cortisol and prolactin increased (P < 0.004) during Hours –4 to 0 and decreased (P < 0.002) during Hours 0 to 4. Estradiol concentration increased (P < 0.02) during Hours –4 to 0 but did not change significantly after Hour 0. Concentrations of follicle-stimulating hormone and luteinizing hormone did not change significantly during the PGFM pulse, and the oxytocin results were equivocal. Percentage of corpus luteum area with color-Doppler signals of blood flow did not change significantly between Hours –4 and 0 and first began to decrease (P < 0.004) between Hours 0 and 2. Results demonstrated that concentrations of progesterone decreased linearly during a PGFM pulse, and cortisol, prolactin, and estradiol increased during the ascending portion of the pulse. The progesterone and gonadotropin results supported the hypothesis that the initial progesterone and gonadotropin increases that have been reported to occur in response to a single bolus luteolytic treatment with prostaglandin F 2α do not occur in response to the natural secretion of prostaglandin F 2α.

Age-related dynamics of follicles and hormones during an induced ovulatory follicular wave in mares

An ovulatory follicular wave was induced by ablation of follicles ≥6mm and treatment with prostaglandin F2α (PGF) on Day 10 (ovulation=Day 0). Follicle and hormone dynamics of the induced waves were compared among three age groups: young (5–6 y, n=14 waves), intermediate (10–14 y, n=16), and old (≥18 y, n=15). During the common-growth phase of the induced wave (Days 12–17), diameter of the future ovulatory follicle was not different among ages, but the young group had more (P<0.05) follicles that reached ≥10mm. The number was correlated (r=+0.7; P<0.0001) within mares between consecutive interovulatory intervals, indicating repeatability. Concentrations of LH increased in all age groups during Days 12–17, but were greatest (P<0.002) in the young group and continued to be greater (P<0.0001) throughout the ovulatory LH surge. During several days before Day −1, there were no age-related effects on systemic estradiol concentrations, diameter of the preovulatory follicle, or B-mode echo texture or color-Doppler signals of blood flow in the follicle wall. Interpretations were: (1) greater number of follicles in the young group reflected a greater follicle reserve, (2) greater LH concentrations throughout the ovulatory surge in the young group reflected a more positive response to an extraovarian/environmental influence after removal of the negative effect of progesterone, and (3) lower LH concentrations in the older groups were adequate for the preovulatory changes in the follicle.

Incidence, Endocrinology, Vascularity, and Morphology of Hemorrhagic Anovulatory Follicles in Mares

The incidence of hemorrhagic anovulatory follicles (HAFs) is approximately 5% and 20% of estrous cycles during the early and late ovulatory season, respectively. The structures are more common in old mares (eg, >20 years), tend to occur repeatedly in individuals, and occur most frequently during the late follicular phase. In a recent study, the day of ovulation in controls and the first day of HAF formation, as indicated by cloudiness of follicular fluid, were defined as day 0. On day -1, future ovulating and HAF groups did not differ in follicle diameter or in the frequency of discrete gray-scale ultrasonic indicators of impending ovulation; however, in future HAFs, a greater percentage of the circumference of the follicle exhibited color-Doppler signals of blood flow. No differences were found between the two groups in systemic concentrations of progesterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) on days -4 to 2, but estradiol was elevated in the HAF group on day -3. The wall of the HAFs developed well-vascularized luteal tissue as indicated by echotexture and color Doppler signals and by the production of near normal levels of progesterone. In conclusion, HAFs formed from viable preovulatory follicles that did not differ from ovulatory follicles in diameter or gray-scale echotexture. Estradiol concentrations were elevated a few days before the failure of ovulation, and the wall of the follicle was more extensively vascularized on day -1.

Effect of prostaglandin F2α on ovarian, adrenal, and pituitary hormones and on luteal blood flow in mares

The effect of a single injection of prostaglandin F2α (PGF) during mid-diestrus on systemic concentrations of progesterone, LH, FSH, estradiol, and cortisol and on blood flow to the corpus luteum was studied in 10 controls and 10 PGF-treated mares. Blood flow was assessed by estimating the percentage of corpus luteum with color-Doppler signals of blood flow during real-time scanning of the entire structure and by the diameter of the vascular pedicle near its attachment to the ovary. Treatment was done 8 days after ovulation and 0 h was immediately before the treatment. Examinations and collection of blood samples were done at 0 h, every 5 min until 1 h, and then at 1.5, 2, 4, 8, 12, 24, 48, and 72 h. The concentrations of estradiol did not change, but progesterone, LH, FSH, and cortisol increased significantly within 5 min. Concentrations of LH and FSH in the PGF group remained elevated until a temporarily lower concentration at 8 or 4 h, respectively, rebounded to 12 h, and then slowly decreased. Cortisol remained elevated, until a decrease between 1 and 4 h. Progesterone in the PGF group increased significantly until 10 min after 0 h and then decreased by 40 min to below the concentrations in controls. Within the PGF group, progesterone decreased significantly by 45 min to below the concentrations at 0 h. The values for each of the two indicators of blood flow did not differ significantly between the PGF and control groups until a decrease at 24 h in the PGF group. Results did not support the hypothesis that the immediate transient post-PGF increase in progesterone was associated with an increase in luteal blood flow. Luteolysis, as indicated by decreasing progesterone, began well before the beginning of a decrease in luteal blood flow.