Follicle vascularity coordinates corpus luteum blood flow and progesterone production

Ovarian and uterine arteries blood flow velocities waveform, hormones and nitric oxide in relation to ovulation in cows superstimulated with equine chorionic gonadotropin and luteolysis induction 10 and 17 days after ovulation

To investigate the ovarian responses, ovarian and uterine hemodynamics, circulating ovarian hormones, and nitric oxide (NO) with their relations in superstimulated cows. Eight Holstein Friesian dry cows previously synchronized with CIDR underwent rectal Doppler ultrasound scanning and blood sampling after administrating eCG (1500 I.U) on day 10 of the second ovulation (day -5). Cows were treated with 12.5 mg prostaglandin F2α (PGF2α) on days 10 and 17 after ovulation. Estradiol, progesterone, and NO were measured. Results showed that from ≥ 13 follicles, five follicles ovulated from both ovaries. The ovulated follicles increased antrum colored area and colored area % till day -1. The developed corpora lutea (CLs) attained similar diameter, area, colored area, and colored area % from day 2 till day 15. The peak point of velocity (PSV) of uterine arteries decreased while that of ovarian arteries increased from day -4 to day 0. Both ovarian arteries diameter, resistance index (RI), PSV, end velocity (EDV) and systolic/diastolic ratio (S/D) positively correlated (P < 0.0001), but their pulsatility index (PI) negatively correlated (P < 0.0001). The uterine arteries PI, RI, PSV, EDV, time average velocity (TAMV) and S/D negatively correlated (P < 0.0001) but their diameters positively correlated. Estradiol increased but progesterone decreased from day -5 till day 0. After ovulation, P4 reached maximum values on day 9 and started to decrease till day 19.NO showed one peak on day -3 and another one from day 3 to day 9. Conclusions: Blood flow of ovarian arteries is different from uterine arteries and depended on pre- or post-ovulation.

Comparison of the 7-day CO-Synch and 8-day estradiol-based protocols for estrus synchronization and timed artificial insemination in suckled Bos taurus cows

Two experiments were conducted to compare, follicle diameter (FD) on Day -1, corpus luteum (CL) area on Day 7, progesterone (P4) concentration on Day 7 and 18, pregnancy per timed artificial insemination (TAI) on Day 30, and pregnancy loss (PL) between Days 30 and 60 after TAI (TAI, Day 0) using two different synchronization protocols. In Experiment 1, Angus cows (n = 1148) were randomly assigned to either 7-d progesterone CO-Synch (7-d CO-Synch) or 8-d progesterone + estradiol (8-d P + ES) synchronization protocols for TAI. On Day -10, cows in the 7-d CO-Synch treatment group (n = 574) received a progesterone-releasing intravaginal device (PIVD; 0.5 g P4) and GnRH (0.105 mg), on Day -3 the PIVD was removed and cows received cloprostenol (0.150 mg), then, on Day 0 (64 h after PIVD removal), cows received GnRH (0.105 mg) and were TAI. On Day -10, cows in the 8-d P + ES treatment group (n = 574) received a PIVD (0.5 g P4) and estradiol benzoate (2.0 mg), on Day -2 the PIVD was removed, and cows received cloprostenol (0.150 mg) and estradiol cypionate (0.5 mg), then, on Day 0 (48 h after PIVD removal), cows were TAI. Pregnancy per TAI was determined on Days 30 and 60. In a subset of cows (7-d CO-Synch, n = 41; 8-d P + ES, n = 40), serum P4 concentration was evaluated on Day 18. In Experiment 2, anestrus (n = 34) and cyclic (n = 34) suckled beef cows were selected and submitted at random on Day -10, to either 7-d CO-Synch or 8-d P + ES treatment groups. Follicle diameter on Day -1, CL area, and serum P4 concentration on Day 7 were determined. In Experiment 1, pregnancy per TAI on Day 30 did not differ (7-d CO-Synch = 48.9%; 8-d P + ES = 45.6%) between treatments but it was greater for cows with BCS ≥5 (P < 0.01). Pregnancy loss between Days 30 and 60 did not differ between treatment groups but tended to be greater in cows with BCS <5.0 (P < 0.1). In a subset of cows, serum P4 concentration on Day 18 did not differ between treatment groups but tended to be lower (P < 0.1) in cows that had PL between Days 30 and 60 compared to cows that had no PL. In Experiment 2, FD tended to be greater (P < 0.1) and CL area was greater (P = 0.05) in anestrus cows from 7-d CO-Synch treatment. In cyclic cows, the treatment did not affect the FD or CL area. In conclusion, there was no difference in pregnancy per TAI on Day 30 and PL between Days 30 and 60 between cows using 7-d CO-Synch + PIVD or 8-d estradiol-based + PIVD protocols for estrus synchronization and TAI.

Effects of two protocols of ovulation synchronization on corpus luteum size and blood flow, progesterone concentration, and pregnancy rate in beef heifers

The objective of this study was to evaluate the effect of 7-day estradiol-progesterone-based [Treat_(C)] and 5-day Co-Synch plus progesterone [Treat_(Co-Sy)] protocols on ovulation time, pre-ovulatory follicle diameter, corpus luteum (CL) size and blood flow, progesterone (P4) concentration and pregnancy rate (PR) in beef heifers. In Experiment 1, a crossover design was applied (n = 9). For Treat_(C), a progesterone intravaginal (PI) device was inserted, plus 2 mg of estradiol benzoate (day 0). On day 7, 500 µg of cloprostenol plus 0.5 mg of estradiol cypionate were administered, and PI was removed. For Treat_(Co-Sy), on day 0, a PI was inserted plus 100 µg gonadotropin-releasing hormone (GnRH). On day 5, PI was removed, plus 500 µg of cloprostenol and 100 µg of GnRH were administered at 69-70 h later. From day one to ovulation day, dominant follicle was evaluated by ultrasonography. On days 4 and 8 post-ovulation, CL was evaluated by color Doppler, and P4 concentration was determined by chemiluminescence. In Experiment 2, a split-plot experimental design was used. Protocols followed were the same as in Experiment 1 [Treat_(C); n = 310 and Treat_(Co-Sy); n = 314]. Heifers were fixed-time artificially inseminated. Pregnancy was determined on day 41. In Experiment 1, the interval between PI removal and ovulation time was different between protocols (P < 0.01). In addition, P4 concentration was related to the CL size (P < 0.001), CL blood flow (P < 0.01) and protocols (P < 0.03). In Experiment 2, PR did not differ between protocols.

Effect of increased serum progesterone on luteal morphology and function, pregnancy, and gestational loss in Nelore cows

The aim of the present study was to determine the impact of different strategies for increasing the level of serum progesterone (P4) on luteal morphology and function in bovine females. The effects of increasing P4 on pregnancy rate and gestational loss (GL) in Nelore cows subjected to timed artificial insemination (TAI) were also evaluated. A total of 939 cows were divided into three groups: P4LA (n = 305), 150 mg of long-acting injectable P4 7 days after TAI; GnRH (n = 306), 10 μg of buserelin acetate 7 days after TAI; and control (n = 328), no hormone treatment after TAI. Doppler ultrasound assessments and P4 measurements were performed on days 7 and 16 after TAI. The pregnancy rate and GL as a function of treatment were compared using the SAS GLIMMIX procedure. Corpus luteum (CL) vascular perfusion, volume, and plasma P4 concentration were analysed using the SAS PROC MIXED procedure. No significant difference was found among the treatments in terms of volume, number of pixels, and CL intensity or in the serum P4 concentration at 7 days after ovulation. The CL blood flow at 16 days after ovulation was lower in the P4LA and GnRH groups than that in the control group (p < .01). Serum concentrations of P4 at 16 days after ovulation were higher in the P4LA and GnRH groups than those in the control group (p = .04). A difference in the pregnancy rate (p = .003) and a trend in GL (p = .07) as a function of treatment were found. Overall, long-acting injectable P4 supplementation on day 7 after TAI or GnRH administration affected CL vascularization and increased the serum concentrations of P4 16 days after ovulation, promoting better pregnancy rates than the control.

Mitigation of low pregnancy rate in excitable Nellore cows by administration of GnRH or P4

This research aimed to determine the effect of temperament on reproductive parameters including cortisol and progesterone (P4) in Nellore cows. Additionally, two methods for increasing plasma progesterone (P4) levels in excitable animals to enhance pregnancy rate (P/AI) and reduce pregnancy loss were investigated. In total, 939 cows were subjected to timed artificial insemination (TAI) and divided into three groups: (P4LA; n = 305) 150 mg of injectable long-acting progestogen 7 days after TAI; (GnRH; n = 306), 10 μg of buserelin acetate on day 7 after TAI; control group (CG; n = 328) without hormonal treatment. In 213 cows, randomly chosen from each group, ultrasound evaluations of the preovulatory follicle (Mode B) were performed on the day of insemination and of the corpus luteum (Color Doppler) 7 and 16 days after TAI. Blood samples were obtained from 20% of the 939 animals, randomly chosen from each group, on the day of insemination and after 7 and 16 days to measure cortisol and progesterone, respectively. At the time of insemination, subjective temperament evaluations were performed with the animals being classified as excitable (EXC) or adequate (ADQ). The SAS GLIMMIX procedure was used to compare the pregnancy rate (P/AI) and gestational loss within each temperament for the three experimental groups. Continuous variables were analyzed utilizing SAS PROC MIXED procedure. Cortisol concentration was higher and POF (preovulatory follicle) and CL (corpus luteum) volumes at the time of insemination and 7 days after AI, respectively, were lower in EXC animals than in ADQ. No significant difference was observed between the number of pixels, CL intensity, and plasma concentration of P4, 7 days after TAI. However, 16 days post-insemination, among the animals classified as EXC, higher concentrations of P4 were observed in the GnRH and P4LA groups than in the control. Regarding P4 concentrations, there was a tendency to be lower in animals classified as EXC than in ADQ within the control group (P = 0.06), while rate of blood flow from the CL was lower in EXC animals than in ADQ animals (P = 0.04). Among the ADQ animals, the GnRH and P4LA groups showed a lower CL flow rate than that observed in the control (P = 0.04), 16 days after the TAI. Among EXC animals, a higher pregnancy rate was observed in the GnRH and P4LA groups than in the control group (P = 0.01). In the control group, the pregnancy rate (P/AI) of the ADQ animals was higher than that of the EXC animals (P = 0.05). No statistically significant differences were observed between gestational losses when the treatments or temperaments were compared. In conclusion, the use of GnRH or P4LA, 7 days after insemination, improves pregnancy rates in excitable animals and is a viable alternative to minimize the negative impact of stress and improve reproductive efficiency in beef cattle.

Applied Use of Doppler Ultrasonography in Bovine Reproduction

The use of Doppler ultrasonography to quantify blood vascularization in reproductive organs has increased over the past decade. Doppler technology has predominantly been explored in research settings to evaluate uterine blood flow and to assess follicular and luteal blood perfusion. Recent research has also explored the use of Doppler technology in applied reproductive management for both the beef and dairy industries and has focused on the use of luteal color Doppler ultrasonography to evaluate embryo transfer recipients and perform early pregnancy diagnosis. Although significant progress has been made and current literature indicates a strong potential for the applied use of Doppler ultrasonography to increase reproductive efficiency in the cattle industry, uptake of this technology is still currently limited. This review summarizes the recent developments in the applied use of color Doppler ultrasonography for reproductive management in both beef and dairy cattle herds.

Follicular Size Threshold for Ovulation Reassessed. Insights from Multiple Ovulating Dairy Cows

Simple Summary

The selection of a single ovarian follicle able to differentiate and ovulate is a phenomenon common to monovular species including humans. The selected follicle acquires the capacity to ovulate when it reaches a diameter of about 10 mm. In cows with a single follicle of ovulatory size, the probability of ovulation significantly increases with follicle diameter. However, two or more follicles of ovulatory size are often present at estrus. In cows with one follicle of ovulatory size and another follicle of 7–9 mm, the small follicle may, under certain circumstances, ovulate producing a pregnancy.

Abstract

In Bos. taurus cattle, follicular deviation to dominance begins when the selected ovulatory follicle reaches a mean diameter of 8.5 mm. The dominant follicle acquires the capacity to ovulate when it reaches a diameter of about 10 mm. In this study, data derived from 148 cows in estrus with one follicle of ovulatory size and another of 7–9 mm, reveal that the small follicle has the capacity to ovulate alone or with the dominant follicle; thus, giving rise to a single or twin pregnancy. This indicates that a follicle of deviation size may ovulate in the presence of a follicle of ovulatory size.

Evaluation of ovarian hemodynamics by color and spectral Doppler in cows stimulated with three sources of follicle-stimulating hormone

This study hypothesized that ovarian response for superovulation is better when using compounds containing luteinizing hormone (LH). To compare the ovarian responses and the ovarian blood flow using three gonadotropins, three equal groups of Holstein cows (N = 18) were treated with Pluset (P), Follitropin (F), and eCG (G). The ovarian response was evaluated from the day of starting treatments (Day -5) till Day 5 after ovulation using Doppler ultrasound. Results revealed that the ovarian arteries pulsatility index (PI), peak systolic velocity (PSV), and the blood flow volume (BFV) varied (P < 0.0001) between both ovarian arteries. Cows treated with P had low number of small and medium follicles and a high number of the large follicles on Day -1. Cows treated with F showed low (P = 0.0001) number and percentage of colored follicles and high % of ovulated follicles (P=0.0001) that obtained high colored areas (P = 0.043) and colored area % (P = 0.001). The G produced more (P = 0.001) colored follicles (Days -1, 0) of low area. Both P and G had the same higher (P = 0.0001) percentages of colored follicles (>80 %) on Day-1 than F (<60 %). F and P had higher ovulated colored follicles % than G. P obtained nearly the same ovulated follicles diameters and areas as F with higher antrum area (P = 0.029) but lower colored area (P = 0.043) and colored area % (P = 0.001). In conclusion, the number and the doses of gonadotropin injections and the side of the ovary influenced the ovarian response.

Uterine and Corpus Luteum Blood Flow Evaluation Prior to Uterine Flushing in Llama Embryo Donors

The aim of this study was to assess the uterine blood flow (UBF) and corpus luteum blood flow (CLBF) in llamas 8 days post-mating, using color-Doppler ultrasonography (CDU), to determine the possible relationship between vascularization and the presence of an embryo. Adult females (n = 25) were used to monitor ovarian dynamics by palpation and transrectal ultrasonography until detection of a ≥6 mm growing follicle. Females were randomly assigned to one of two groups: Group I (n = 19), were mated and ovulation was induced by a single dose of buserelin (GnRH analog) that same day (Day 0); and Group II (n = 6), only ovulation was induced (control). On Day 8, UBF and CLBF were evaluated transrectally in both groups. The color-flow images obtained were analyzed with Image J1.52a software to determine the vascularization area and the percentage of corpus luteum with blood flow emission (CLBF%) together with the percentage for each uterine horn (UBF%). Statistical analysis was performed using an ANOVA test. In Group I, uterine flushing was performed to obtain the embryos, thus dividing the females into Group I+ (n = 10), when an embryo was recovered and Group I- (n = 9), when no embryo was recovered. Embryo recovery rate was 52.63% (10/19). In Group I+, UBF% was significantly higher compared to Group I- and Group II (P <0.05). UBF appears to be a good predictor for embryo presence, with an area under the curve (AUC) of 0.9 and an optimal cut-off value of 9.37% (with a sensitivity of 90% and specificity of 88.9%). The CLBF% did not differ between groups (P > 0.05). In conclusion, it is possible to detect a local increase of UBF in the presence of an embryo on day 8 post-mating in llamas. This could be useful to achieve an early pregnancy diagnosis or to decide whether to carry out the uterine flushing in a llama embryo transfer program.

Ovarian and uterine arteries blood flow waveform response in the first two cycles following superstimulation in cows

To investigate the ovarian and uterine blood flow responses, hemodynamic, circulating ovarian hormones and nitric oxide (NO) after end of treatment by Folltropin. Holstein Friesian (12) cows previously synchronized with CIDR underwent Doppler ultrasound after administrating of FSH daily for 4 days in eight injections started on day 10 of the second ovulation (day -5). Oestradiol (E2), progesterone (P4) and nitric oxide (NOMs) were measured. During the follicular phase, follicle area and antrum area of the second cycle reached maximum value on the day of ovulation compared with that in the first cycle, while during the luteal phase, both showed a pattern of increase and decrease. The luteal area and total coloured area increased till day 10 in the first and second cycle. The first cycle ipsilateral ovarian artery (Ov.A) had higher pulsatility (PI) (p = .001), resistance (RI) (p = .001), peak velocity (PSV) (p = .009) and lower end-diastolic velocity (EDV) (p = .003) compared with the second cycle. The increased ipsilateral Ov.A PSV (p = .009) was accompanied by lower EDV. The first cycle ipsilateral middle uterine artery (MUA) had higher PI (p = .001) and RI (p = .001), with lower PSV (p = .001) and EDV (p = .001). It was concluded that blood flow of ovarian and middle uterine arteries changed after the end of superstimulation as the increased ipsilateral Ov. A and MUA PSVs accompanied by lower EDV and both Doppler indices that reflect the amount of ovarian and uterine blood flow waveform.

Heterotopic ovarian allotransplantation in goats: Preantral follicle viability and tissue remodeling

An appropriate implantation site favors angiogenesis and avoids ovarian tissue damage after tissue grafting. The objective of this study was to evaluate the effects of intramuscular (IM) and subcutaneous (SC) sites for ovarian grafts in goats by evaluating follicular morphology and activation, preantral follicle and stromal cell densities, tissue DNA fragmentation, collagen types I and III depositions, and graft revascularizations. Ovarian cortical tissue was transplanted in IM or SC sites and recovered 7 or 15 days post-transplantation. There was a greater percentage of developing follicles and lesser follicular and stromal cell densities in all grafted tissues as compared to ovarian tissues of the control group. The stromal cell density and percentage of normal follicles were positively associated. At 15 days post-transplantation, tissues at the SC and IM sites had similar amounts of DNA fragmentation and type III collagen content. In contrast, tissues at the SC, as compared with IM site, had greater abundances of collagen type I. Furthermore, there was a positive association between collagen type I and percentage of morphologically normal follicles post-transplantation. In addition to a marked decrease in follicular density 15 days post-transplantation in ovarian grafts at the SC and IM sites, low percentages of normal follicles and follicular activation were observed similarly in both transplantation sites. There were also positive associations of stromal cell density and abundance of type I collagen fibers with the percentage of intact follicles in grafted ovarian tissues.

Deficiency in proliferative, angiogenic, and LH receptors in the follicle wall: implications of season toward the anovulatory condition

This study aimed to gain insight on the effect of different seasons of the year on the expression pattern of growth factor and hormone receptors involved in follicle development. A novel follicle wall biopsy technique was used to collect in vivo follicle wall layers (ie, granulosa, theca interna, and theca externa) and follicular fluid samples from growing dominant follicles, simultaneously and repeatedly, using the same mares during the spring anovulatory (SAN), spring ovulatory (SOV), summer (SU), and fall ovulatory (FOV) seasons. The immunofluorescent expression patterns of epidermal growth factor receptor (EGFR), Ki-67, vascular endothelial growth factor receptor (VEGFR), and LH receptor (LHR) were evaluated in each follicle wall layer, in addition to intrafollicular estradiol and nitric oxide (NO). Proliferative proteins (EGFR and Ki-67) were highly (P < 0.05-P < 0.001) expressed during the SOV season compared with the SAN and FOV seasons. Lower (P < 0.05-P < 0.001) expression of both proteins was observed during SU compared with the SOV season. The expression of VEGFR was greater (P < 0.05-P < 0.01) in the theca interna of dominant follicles during the SOV season compared with the SAN and SU seasons. Similarly, in the overall quantification, the VEGFR expression was greater (P < 0.001) during the SOV season compared with the SU and FOV seasons. A higher (P < 0.05) LHR expression was detected in the theca interna during the SOV season than the SAN season. Furthermore, a higher (P < 0.05-P < 0.001) expression of LHR was observed in the granulosa, theca interna, and in the overall quantification during the SOV season compared with the SU and FOV seasons. Intrafollicular NO concentration did not differ (P > 0.05) among different seasons of the year. The intrafollicular estradiol concentration was higher (P < 0.05) during the SU compared with the SAN season and higher (P < 0.05) during the FOV season compared with the SAN and SOV seasons. In conclusion, the synergistic effect of lower expression of proliferative protein, angiogenic, and LH receptors in at least some of the layers of the follicle wall seems to trigger dominant follicles toward the anovulation process during the spring and fall transitional seasons.

The Role of Blood Flow in Corpus Luteum Measured by Transvaginal Two-Dimensional and Three-Dimensional Ultrasound in the Prediction of Early Intrauterine Pregnancy Outcomes

Objective: The purpose of this study was to explore the application of transvaginal two-dimensional and three-dimensional power Doppler ultrasound in pregnancy corpus luteum to predict the final outcome of early intrauterine pregnancy.

Methods: This is a prospective observational cohort study. Six hundred early intrauterine pregnant women in Shanghai Changning Maternity and Infant Health Hospital were selected as the research objects from January 2015 to December 2015. According to the follow-up of 12 weeks, these pregnant women were divided into the normal pregnancy group (group A, n = 512) and the terminational pregnancy group (group B, n = 88). They all underwent both transvaginal two-dimensional ultrasound and three-dimensional power Doppler ultrasound to obtain relevant parameters of corpus luteum, namely, the average diameter of the corpus luteum (D), resistance index (RI), pulsatility index (PI), corpus luteum volume (V), vascularization index (VI), blood flow index (FI), and vascularized blood flow index (VFI). Among them, V, VI, FI, and VFI were calculated with the virtual organ computer-aided analysis method. Receiver operator characteristic (ROC) curves were drawn. The corresponding diagnostic cut-off, sensitivity, and specificity were calculated and compared.

Results: Compared with group A, the D, V, VI, FI, and VFI of corpus luteum in group B were statistically significant lower while RI and PI were statistically significant higher (P < 0.05). The diagnostic cut-off values in the prediction of early intrauterine pregnancy outcomes were D: 14.48, RI: 0.56, PI: 0.81, V: 3.89, VI: 21.48, FI: 38.99, and VFI: 10.21 respectively, and the sensitivity and specificity were D (99.2%, 67.0%), RI (98.9%, 65.0%), PI (78.4%, 89.1%), V (95.1%, 78.4%), VI (74.%, 90.9%), FI (91.8%, 90.9%), and VFI (93.9%, 87.5%) respectively. The area under the ROC curve of the combined index (RI + FI) was 0.963, which was not significantly higher compared with any single index, and both the sensitivity and specificity were 94.3%.

Conclusion: Both transvaginal two-dimensional and three-dimensional ultrasonography are of high diagnostic value in predicting the early intrauterine pregnancy outcomes.

An objective volumetric method for assessment of ovarian follicular and luteal vascular flow using colour Doppler ultrasonography

Our goal was to develop an objective computer-assisted volumetric method of assessing vascular flow from colour Doppler ultrasound data of ovarian structures recorded by free-hand movement. We hypothesized that a vascularity index (ratio of the region of blood flood to the region of ovarian structure) obtained from the three-dimensional volumetric analysis would be more precise (less variable) than conventional two-dimensional analysis of single images in estimating the functional status of the preovulatory follicles and corpus luteum. Doppler ultrasound cineloops of water buffaloes (Bubalus bubalis; n = 22) ovaries were recorded daily from 12 h before GnRH treatment to four days after ovulation. Cineloops were processed using Fiji and Imaris software packages for segmenting the area (two-dimensional analysis) and the volume (three-dimensional analysis) occupied by the blood-flow and associated tissue to calculate the vascularity index. For volumetric measurement, all images in a cineloop were used (i.e., no a-priori selection of images) while for two-dimensional analysis, three images from the region with apparent maximum vascularity were selected. The volumetric method was verified with theoretical ellipsoidal volume of the follicle (r = 0.96 P < 0.01) or corpus luteum (r = 0.58 P = 0.02). The variability in the follicular vascularity index among animals was lower using the volumetric method than two-dimensional analysis (0.018 ± 0.002 vs 0.030 ± 0.005, P < 0.01), while the variability for CL vascularity was similar between methods (P = 0.23). An increase in the follicular vascularity index was detected at 12 h after GnRH treatment using both methods (two-dimensional: 0.030 ± 0.008, P < 0.01; three-dimensional: 0.016 ± 0.006, P < 0.02). Buffaloes that ovulated tended to have a greater increase in 3D vascularity index than non-responding buffaloes (P = 0.06); the two-dimensional method was not able to detect these changes. Using the three-dimensional method, a moderate positive correlation (r = 0.59; P = 0.02) was evident between the follicular vascularity index at 14-16 h after GnRH treatment and follicular diameter. In conclusion, an objective volumetric method for assessing relative ovarian blood flow changes was developed using Doppler ultrasound cineloops recorded by free-hand movement. The 3-dimensional method eliminates the need for a-priori selection of images and is more precise as a result of decreased technical variability.

Ultrasonography-accessed luteal size endpoint that most closely associates with circulating progesterone during the estrous cycle and early pregnancy in beef cows

The aim was to evaluate the associations between circulating P4 concentrations, corpus luteum (CL) size (diameter, area or volume) and blood perfusion (BP) in cows. In Experiment 1, Pearson's correlations (P < 0.05) with P4 concentrations were observed during CL development (D8) for total area (TA; r = 0.76), luteal area (ACL; r = 0.72), total and luteal diameter (TD and DCL respectively; r = 0.46). During mid-late diestrus, there was a positive correlation (P < 0.05) only at D15 with TA and ACL (r > 0.60), TD, total volume (TV) and luteal volume (VCL; r > 0.434). During luteal regression, the correlation was only observed at D18 for ACL (r = 0.478) and D20 with several variables. In Experiment 2, CL weight and ACL had the greatest correlation with P4 (r > 0.6). In Experiment 3, TA and ACL were the variables that were most closely correlated with serum P4 concentrations at D7 in recipient cows. Correlation coefficients were greater for luteal measurements when there were compact compared with cavitary CLs. In Experiment 4, there was no correlation (P > 0.05) between P4 and any of the variables measured on D4 and D7 in recipient cows detected in estrus. On D18 to D20, all CL characteristics were correlated (P < 0.05) with plasma P4, and luteal BP and BP area were more closely (P < 0.05) correlated than ACL. In conclusion, CL perimeter area measurements had the greatest association with luteal function during CL development; whereas for BP there was a greater correlation with P4 than luteal size during luteolysis.

Pre-ovulatory follicle affects corpus luteum diameter, blood flow, and progesterone production in mares

Color Doppler ultrasonography was used to study the temporal relationships between pre-ovulatory follicle (POF) and corpus luteum (CL) diameter and blood flow, with systemic progesterone (P4) concentration during two transitional ovulatory seasons in mares. Variables of POF and CL/P4 were evaluated for 6days before and 17days after ovulation, respectively. Evaluations were performed during two consecutive estrous cycles in spring and fall seasons, and during the last estrous cycle of the season. There were significant correlations among POF and CL variables, and P4 concentration that ranged from 0.24 to 0.95, and among the ratios of different variables that ranged from 0.39 to 0.92. There were linear regressions (P<0.01-0.001) for all comparisons among different variables. The POF diameter before the first ovulation of the season was larger (P<0.05), and POF vascularity was less (P<0.05), than in the last estrous cycle during the season. The CL blood flow was less (P<0.01) during the last compared with first pre-ovulatory period of the season. The POF diameters were positively correlated (r=0.67) during the two pre-ovulatory periods of spring and fall. Results provide evidence that the POF affects CL diameter and blood flow, and subsequently P4 production, and that POF diameter is repeatable within the same individual during different seasons.

Influence of two ovulation-inducing agents on the pituitary response and follicle blood flow in mares

The objective of the current study was to evaluate the effects of deslorelin and hCG, two ovulation-inducing therapies, on LH surge and follicle vascularity in mares. Thirty mares were either treated with 1.5 mg IM of deslorelin, 2,500 IU IV of hCG or 2 mL IM of NaCl 0.9% (GnRH, hCG and Saline groups, respectively). Power-flow Doppler examination and blood collection were performed every hour during the first 12 hours after treatment (H0) and every six hours between hours 12 (H12) and 30 (H30) after treatment. Moreover, endpoints were evaluated every hour through the last six hours before ovulation (OV-6 to OV-1). In GnRH group, plasma LH concentration progressively increased (P < 0.001) during the first 6 hours after treatment and remained high (P > 0.1) until OV-1. A significant increase in LH concentrations was first detected (P < 0.05) at 24 hours after treatment in hCG group, while no changes (P > 0.1) on LH levels were found during H0-H30 and between OV-6 and OV-1 in the Saline group. Independent of the treatment, significant variations on the percentage of the follicle wall with Doppler signals were not observed (P > 0.1) throughout the entire experiment. A weak correlation between the preovulatory follicle vascularity and the plasma LH concentration was found in GnRH, hCG and Saline groups (r = +0.29, +0.29 and -0.23, respectively; P ˂ 0.0001). These results described for the first time the immediate and continuous pituitary response to ovulation-inducing therapy with injectable deslorelin. Moreover, spontaneous and induced ovulations were not preceded by an increased follicle vascularity, which differs from previous reports in large animals.

Luteal angiogenesis and its control

Angiogenesis, the formation of new blood vessels from preexisting ones, is critical to luteal structure and function. In addition, it is a complex and tightly regulated process. Not only does rapid and extensive angiogenesis occur to provide the corpus luteum with an unusually high blood flow and support its high metabolic rate, but in the absence of pregnancy, the luteal vasculature must rapidly regress to enable the next cycle of ovarian activity. This review describes a number of key endogenous stimulatory and inhibitory factors, which act in a delicate balance to regulate luteal angiogenesis and ultimately luteal function. In vitro luteal angiogenesis cultures have demonstrated critical roles for fibroblast growth factor 2 (FGF2) in endothelial cell proliferation and sprouting, although other factors such as vascular endothelial growth factor A (VEGFA) and platelet-derived growth factor were important modulators in the control of luteal angiogenesis. Post-transcriptional regulation by small non-coding microRNAs is also likely to play a central role in the regulation of luteal angiogenesis. Appropriate luteal angiogenesis requires the coordinated activity of numerous factors expressed by several cell types at different times, and this review will also describe the role of perivascular pericytes and the importance of vascular maturation and stability. It is hoped that a better understanding of the critical processes underlying the transition from follicle to corpus luteum and subsequent luteal development will benefit the management of luteal function in the future.