Ultrasound image attributes of the bovine corpus luteum: structural and functional correlates

Inter-software reliability and agreement for follicular and luteal morphometric and echotextural ultrasonographic parameters in beef cattle

This study aimed to compare the inter-software and inter-observer reliability and agreement for the assessment of follicular and luteal morphometry and echotexture parameters in beef crossbreed females (3/8 Bos taurus indicus and 5/8 Bos taurus taurus). B-mode and color Doppler ultrasonographic ovarian images were obtained at specific time points of estradiol-progesterone-based protocols for timed artificial insemination (TAI). Sonograms were analyzed by two observers using a licensed (IASP1) and an open access (IASP2) software package. A total of 292 snap-shot sonograms were analyzed for morphometric parameters and 504 for echotexture parameters. inter-software reliability was judged moderate to excellent (ICC or CCC=0.73-0.98), whereas inter-observer reliability for morphometric parameters was deemed good to excellent (ICC or CCC=0.82-0.98). A small percentage (up to 10.95 %) of measured parameters fell outside the limits of inter-software and inter-observer agreement. For echotexture parameters, inter-software reliability varied widely (ICC or CCC=0.16-0.95) based on the size of regions of interest (ROI), while inter-observer reliability ranged from moderate to excellent (ICC or CCC= 0.71-0.97). The highest inter-software reliability for pixel value and heterogeneity value was observed for the corpus luteum (ICCs=0.81-0.95; P>0.05), followed by the peripheral follicular antrum (ICCs=0.75-0.78; P<0.05). However, lower reliability was determined for the follicular wall (ICCs=0.08-0.33; P<0.0001) and perifollicular stroma (ICCs=0.16-0.46; P<0.05). In conclusion, both software packages showed high reproducibility for morphometric measurements, while echotexture measurements were more challenging to replicate based on ROI sizes. Caution is advised when selecting ROI sizes for echotexture measurements in bovine ovaries.

Association of genomic prediction for twin pregnancies with the incidence of double ovulation in primiparous dairy cows

Twin pregnancies compromise the health and well-being of dairy cattle. A recent genomic prediction model for twin pregnancies has been developed based on twin calving or abortion. However, the incidence of double ovulation is significantly higher than that of twin births. This study aimed to evaluate whether genomic prediction values for twin pregnancies are associated with the incidence of double ovulation in primiparous dairy cows. Factors influencing the double ovulation rate were analysed using binary logistic regression on 676 cows: 475 (70.3%) inseminated at spontaneous estrus and 201 following one of two different estrus synchronization protocols for fixed-time artificial insemination (FTAI). The odds ratio for double ovulations was 0.92 (p = .002) per unit increase in prediction value and 2 (p = .01) for cows subjected to an FTAI protocol. Our findings suggest that genomic prediction values for twin pregnancies can effectively identify the risk of double ovulation at the herd level.

Negative photoperiod induces an increase in the number of ovulations in dairy cattle

This study sought to examine the impact of negative photoperiod on the incidence of multiple ovulations and pregnancies in dairy cattle. The study population consisted of 5,373 pregnant cows in their third or greater lactation that experienced their first post-partum pregnancy after spontaneous estrus. The positive photoperiod (increasing day-length) extends from December 22 to June 21, whereas the negative photoperiod (decreasing day-length) extends from June 22 to December 21. The odds ratios (ORs) for multiple ovulations and pregnancies in cows that became pregnant during the negative photoperiod and the remaining cows that became pregnant during the positive photoperiod were 1.4 and 1.3 (P < 0.0001), respectively. The ORs for cows that became pregnant ≥ 90 days in milk and the remaining cows that became pregnant < 90 days in milk were 4.3 and 4.1 (P < 0.0001), respectively. No significant differences were detected in the monthly rates of multiple ovulations or pregnancies during positive and negative photoperiods. Thus, the present study demonstrates that the ovarian function in cows is related to changes in day-length, with decreasing day-length being associated with greater multiple ovulation and pregnancy rates. The present study also shows that positive and negative photoperiods exhibit different trends. The results of this study are consistent with a growing body of work demonstrating the effects of photoperiod patterns on the reproductive physiology of cows, with clear implications for twin pregnancy prevention.

[Sonographic studies on the significance of follicle size and corpus luteum morphology in dairy cows after insemination]

OBJECTIVE

In dairy cattle, numerous factors determine the success of an insemination. The aim of the present study was to generate findings concerning the association between the preovulatory follicles, the corpora lutea with or without cavities and pregnancy in dairy cows under field conditions.

MATERIAL AND METHODS

Data was obtained from 176 dairy cows scheduled for artificial insemination. The cows were gynecologically examined using sonography at the time of insemination, 24 hours later, on day 9, on day 34 and after day 42 after insemination. Additionally, blood samples were collected from the coccygeal vein at the time of insemination and on day 9 in order to determine blood progesterone level.

RESULTS

Depending on the result of the pregnancy test, no difference was detected between the dimensions of the follicles, corpora lutea as well as their cavities and progesterone levels 9 days after insemination in the dairy cows with spontaneous ovulations. In contrast to the corpus luteum without cavity, the surface area of the corpus luteum with cavity remained constant during the study period, while at the same time the cavity decreased in size to a significant degree. In addition, breed differences in corpus luteum sizes were detected on day 34.

CONCLUSION

No cause was detected for the formation of cavities in corpora lutea and there was no link to the follicle from which the corpus luteum developed.

CLINICAL RELEVANCE

Both the changes in corpus luteum sizes over time and their breed-related differences could have an impact on insemination outcome.

Morphologic, Steroidogenic, and Transcriptomic Assessment of the Corpus Luteum in Holstein Cows after Spontaneous or Hormone-Induced Ovulation

There is evidence that replacing the gonadotropin-releasing hormone (GnRH) with porcine luteinizing hormone (pLH) to synchronize ovulation prior to artificial insemination (AI) increased pregnancy per AI in dairy cows without affecting blood progesterone (P₄) concentrations. Whether morphologic, steroidogenic, and transcriptomic differences exist among corpora lutea (CL) formed after ovulation induced by GnRH and pLH is unclear. Our main objective, therefore, was to compare CL characteristics between GnRH- and pLH-induced CL. In 24 non-lactating Holstein cows, ovulations were spontaneous (Spont-Ov) or induced with 100 µg GnRH, 25 mg pLH, or 1 mg estradiol benzoate (EB), with CL excised 12 d after ovulation. In pLH- versus GnRH-treated cows, the duration of elevated LH (above baseline) was prolonged (10 versus 6 h, respectively, p < 0.01), but CL dimensions, pixel intensity of CL images, proportions of steroidogenic and non-steroidogenic luteal cells, and mean plasma LH did not significantly differ. Post-ovulation mean plasma P₄ (ng/mL) did not differ among Spont-Ov (3.0) pLH (3.1) or GnRH (3.0) cows but were lower in EB cows (2.0). In vitro P₄ concentration was greater in luteal explants of pLH-treated cows than in all other groups (combined means, 16.0 vs. 12.3 µg/mL, p < 0.02). Relative abundance of mRNA for oxytocin receptor (OXTR) was 2-fold higher (p < 0.01) in CL of pLH vs. GnRH cows and highest in Spont-Ov CL. In summary, pLH-treated cows had a longer LH peak, and greatest luteal tissue concentrations and in vitro production of P₄. We inferred that increased P₄ concentrations at the ovarian-uterine level in pLH-treated cows could have promoted embryo development and increased pregnancy per AI.

Effect of Genetic and Environmental Factors on Twin Pregnancy in Primiparous Dairy Cows

Twin pregnancies are highly undesirable in dairy cattle; they compromise the health and wellbeing of a cow and dramatically impair the farm economy. Recently, a genomic prediction for twin pregnancies has been developed. The objective of this study was to assess environmental and management risk factors affecting the incidence of twin pregnancies in high-producing dairy cows in their first lactation, with a special emphasis placed on the genomic prediction values of twin pregnancy. Our study population of primiparous cows proved valuable in identifying factors other than genomic predictive values that influence twin pregnancy rates. The odds ratio for twin pregnancies was 0.85 (p < 0.0001) for each unit of a prediction value increase, 3.5 (p = 0.023) for cows becoming pregnant during the negative photoperiod, and 0.33 (p = 0.016) for cows producing ≥42 kg of milk at AI, compared with the remaining cows who produced <42 kg of milk. As a general conclusion, the practical implication of our findings is that genomic prediction values can identify the risk of twin pregnancy at a herd level. Given the cumulative effect of genomic selection, selecting animals with a reduced genetic risk of twin pregnancies can contribute to reducing the incidence of twin pregnancies in dairy herds.

Prediction of the Spontaneous Estrus Expression Period Based on Large (≥10 mm) Follicle Numbers in Lactating Holstein Dairy Cows

The objectives of this study were (1) to investigate the distribution of large (≥10 mm) follicle numbers during the estrous cycle and (2) to compare the timing of the estrus expression period after the ovarian examination between cows with one large follicle (1F) and two or more large follicles (2F) with functional corpus luteum (CL) at the ovarian examination in lactating Holstein dairy cows. In experiment 1, we performed 393 ovarian examinations by ultrasonography, addressed the existence of CL (≥20 mm) and large follicle numbers, and classified cows into 1F (n = 229) and 2F (n = 164) groups. The 1F appearance rates were beyond 75% each day during 3 to 12 d after estrus. However, 2F appearance rates were beyond 75% each day during 15 to 24 d after estrus. In experiment 2, we performed 302 ovarian examinations by ultrasonography and classified cows into the 1F (n = 168) and 2F (n = 134) groups. Estrus detection was performed for 24 d after the ovarian examination in each cow. In the 2F group, 75% of estrus occurred within 9 d of the ovarian examination. However, 75% of estrus occurred 10 d after the ovarian examination in 1F. Days from the ovarian examination to estrus were significantly shorter in the 2F (6.0 d; median, 7.2 ± 4.0 d; mean ± SD) than in the 1F (13 d, 12.4 ± 4.3 d) group. In conclusion, focusing on ≥10 mm follicle numbers with CL could be useful for predicting the estrus expression period.

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.

Transfer of a single fresh in vitro-produced embryo may prevent twin pregnancy without compromising the fertility of the cow

This study examines whether the transfer of a fresh in vitro-produced (IVP) embryo can avoid the risk of twin pregnancy without reducing the fertility of a cow. The study population was comprised of 416 lactating dairy cows synchronized for oestrus: 294 were fixed-time inseminated (AI cows), and 122 were given GnRH treatment at the time of embryo transfer (ET) an IVP embryo (ET cows). Of the 416 cows, 167 (40.1%) became pregnant. Twin pregnancy was recorded in 20.8% of the AI pregnant cows (21/101), whereas no ET cows had twins (0/66). Significant interaction (p < .01) was observed between breeding technique and the period of the year for the likelihood of pregnancy. This meant that using AI cows during the warm period (May-September) as reference, the odds ratio for pregnancy in ET cows during the warm period was 3.4 (p = .001). In conclusion, transfer of a single fresh IVP embryo proved useful to prevent the risk of twin pregnancy without affecting fertility.

Ovarian response to prostaglandin F2α in lactating dairy cows: a clinical update

Prostaglandin F_2α (PGF_2α) and its analogs are used to induce luteolysis in estrus synchronization programs to terminate unwanted pregnancies or to promote ovulation in certain cow subpopulations. In the past few decades, the luteolytic dose of PGF_2α has remained unchanged. This review explores the clinical implications of increasing the standard dose for these applications in high-producing dairy cows. Ultrasonography may assist in selecting the most appropriate PGF_2α dose and improve the results. A reference has been used for PGF_2α for promoting ovulation in herds showing poor reproductive performance.

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.

Genomic profiling of bovine corpus luteum maturation

To unveil novel global changes associated with corpus luteum (CL) maturation, we analyzed transcriptome data for the bovine CL on days 4 and 11, representing the developing vs. mature gland. Our analyses revealed 681 differentially expressed genes (363 and 318 on day 4 and 11, respectively), with ≥2 fold change and FDR of <5%. Different gene ontology (GO) categories were represented prominently in transcriptome data at these stages (e.g. days 4: cell cycle, chromosome, DNA metabolic process and replication and on day 11: immune response; lipid metabolic process and complement activation). Based on bioinformatic analyses, select genes expression in day 4 and 11 CL was validated with quantitative real-time PCR. Cell specific expression was also determined in enriched luteal endothelial and steroidogenic cells. Genes related to the angiogenic process such as NOS3, which maintains dilated vessels and MMP9, matrix degrading enzyme, were higher on day 4. Importantly, our data suggests day 11 CL acquire mechanisms to prevent blood vessel sprouting and promote their maturation by expressing NOTCH4 and JAG1, greatly enriched in luteal endothelial cells. Another endothelial specific gene, CD300LG, was identified here in the CL for the first time. CD300LG is an adhesion molecule enabling lymphocyte migration, its higher levels at mid cycle are expected to support the transmigration of immune cells into the CL at this stage. Together with steroidogenic genes, most of the genes regulating de-novo cholesterol biosynthetic pathway (e.g HMGCS, HMGCR) and cholesterol uptake from plasma (LDLR, APOD and APOE) were upregulated in the mature CL. These findings provide new insight of the processes involved in CL maturation including blood vessel growth and stabilization, leucocyte transmigration as well as progesterone synthesis as the CL matures.

Stable reference genes in granulosa cells of bovine dominant follicles during follicular growth, FSH stimulation and maternal aging

The aim of the present study was to determine a set of reference genes in granulosa cells of dominant follicles that are suitable for relative gene expression analyses during maternal and follicular aging. Granulosa cells of growing and preovulatory dominant follicles were collected from aged and young cows (maternal aging study) and from FSH-stimulated follicles developing under different durations of FSH treatment (follicular aging study). The mRNA levels of the two commonly used reference genes (GAPDH, ACTB) and four novel genes (UBE2D2, EIF2B2, SF3A1, RNF20) were analysed using cycle threshold values. Results revealed that mRNA levels of GAPDH, ACTB, EIF2B2, RNF20, SF3A1 and UBE2D2 were similar (P>0.05) between dominant follicle type, age and among follicles obtained after FSH-stimulation, but differed (P=0.005) due to mRNA processing (i.e. with versus without amplification). The stability of reference genes was analysed using GeNorm, DeltaCT and NormFinder programs and comprehensive ranking order was determined using RefFinder. The mRNA levels of GAPDH and ACTB were less stable than those of UBE2D2 and EIF2B2. The geometric mean of multiple genes (UBE2D2, EIF2B2, GAPDH and SF3A1) is a more appropriate reference control than the use of a single reference gene to compare relative gene expression among dominant and FSH-stimulated follicles during maternal and/or follicular aging studies.

Isolation of luteal endothelial cells and functional interactions with T lymphocytes

The objectives of this study were to optimize the isolation of luteal endothelial cells (LEC) and examine their functional interactions with autologous T lymphocytes. Analysis by flow cytometry showed that the purity of LEC isolated by filtration was nearly 90% as indicated by Bandeiraea simplicifolia (BS)-1 lectin binding. LEC expressed mRNA for progesterone receptor (PGR), prostaglandin receptors (PTGFR, PTGER2 and 4, and PTGIR), tumor necrosis factor receptors (TNFRSF1A&B) and interleukin (IL) 1B receptors (IL1R1&2). LEC were pretreated with either vehicle, progesterone (P₄; 0-20 µM), prostaglandin (PG) E₂ or PGF_2α (0-0.2 µM), and further treated with or without TNF and IL1B (50 ng/mL each). LEC were then incubated with autologous T lymphocytes in an adhesion assay. Fewer lymphocytes adhered to LEC after exposure to high compared to low P₄ concentrations (cubic response; P < 0.05). In contrast, 0.2 µM PGE₂ and PGF_2α each increased T lymphocyte adhesion in the absence of cytokines (P < 0.05). LEC induced IL2 receptor alpha (CD25) expression and proliferation of T lymphocytes. In conclusion, filtration is an effective way of isolating large numbers of viable LEC. It is proposed that PGs and P₄ modulate the ability of endothelial cells to bind T lymphocytes, potentially regulating extravasation, and that LEC activate T lymphocytes migrating into or resident in the CL.

Endometrial echotexture variables in postpartum cows with subclinical endometritis

The aim of this study was to evaluate endometrial echotexture changes on ultrasonographic digital images during subclinical endometritis using a computer-assisted image analysis program. Endometrial samples were collected from 140 Brown Swiss cows (days in milk = 35 ± 3) using a cytobrush method and classified as having a non-inflamed uterus (n = 66) and uterus with acute (n = 42), subacute (n = 21), and chronic (n = 11) inflammations. The mean cellular infiltration density was 0%, 31 ± 5%, 37 ± 6%, and 16 ± 8% for cows with non-inflamed uterus and cows with acute, subacute, and chronic uterine inflammations (P < 0.0001). As the cell infiltration density increased, both cervical diameter and mean gray level did not change. There were a liner decrease in homogeneity and a linear increase in contrast in response to increased cellular infiltration density. The sensitivity and specificity were 79.73% and 46.97% for the homogeneity value and 59.46% and 69.70% for the contrast value, respectively. In conclusion, monitoring endometrial echotexture alterations, especially homogeneity and contrast, changed depending on the cellular density and inflammation status and may be potential diagnostic markers for subclinical endometritis in cows.

Evaluation of endometrial echotexture and cervical cytology in cows during and after treatment of endometritis

OBJECTIVE

The aim of this study was to evaluate changes in the endometrium by using echotexture parameters during and after treatment of endometritis with intrauterine administration of an intrauterine antiseptic solution (Lotagen®, 3% metacresolsulphonic acid and formaldehyde) in cows which became pregnant after treatment.

MATERIAL AND METHODS

According to the severity of endometritis 21 cows were divided into three groups: E1 (slight, n = 7), E2 (moderate, n = 8), E3 (severe, n = 6). The control group (C, n = 11) consisted of cows without endometritis that did not receive an intrauterine medication. A software (Bs200 Pro®) was used to evaluate echotexture parameters Contrast (CON), Gradient (GR), Homogeneity (HOM), Mean Gray Level (MGL) of images taken during the examinations at hours (h) 0, 1 and 6 and days (d) 2, 3, 5 and 10.

RESULTS

At 0 h, GR was significantly lower in group E2 than in groups E1 and C (p < 0.05). There was an increase in GR values between 0 h and 10 d in group E2 and E3, but a decrease during the same time interval in group C (p < 0.05). In contrast, CON values of group E2 were lower (p < 0.05) at 0 h compared to other timepoints of examination and lower than in group C. HOM values were lower (p < 0.05) in groups E1, E2 and E3 than in group C on d 5 and d 10. HOM values were higher at 1 h compared to 6 h, d 2 and d 10 in group E3 (p < 0.05). By contrast to GR values, HOM values were higher in group C at 6 h and d 10 than they were in group E3. MGL values of group E2 were higher (p < 0.05) than in group C until d 10 and higher (p < 0.05) in group E3 than in group C at 6 h after treatment. In group E2 an increase of MGL values until d 2 was followed by a decrease (p < 0.05).

CONCLUSION

Echotexture parameters determined by the evaluation of sonographic B-mode images reflect changes in the endometrium and could be used for the evaluation of the recovery period after treatment of endometritis.

Accurate ultrasonographic prediction of progesterone concentrations greater than 1 ng/ml in Holstein lactating dairy cows

To develop an ultrasonographic assay for determining plasma progesterone concentration (P4 ) as < 1 ng/ml or ≥ 1 ng/ml, the corpus luteum (CL) area and P4 were measured in 1094 multiparous Holstein cows. The area-measuring function and frozen images were used to outline and measure CL imaged via ultrasonography, and CL area was estimated as a polygon of a continuation straight line. A significant correlation was found between CL area and P4 (p < 0.001), and this analysis resulted in the following correlation equation: y = -0.35 + 1.02x (r = 0.81). According to the correlation equation, a CL area of 1.3 cm(2) indicated a P4 of 1 ng/ml. Based on this relationship, each animal was categorized into one of six groups, groups differed based on CL area, and the area ranges were as follows: < 1.3 cm(2) (Group A), 1.3-2.2 cm(2) (Group B), 2.3-3.2 cm(2) (Group C), 3.3-4.2 cm(2) (Group D), 4.3-5.2 cm(2) (Group E) and > 5.2 cm(2) (Group F). For each group, the proportion of cows whose P4 was 1 ng/ml or more was 1.5% in Group A, 83.3% in Group B, 76.6% in Group C, 96.6% in Group D, 99.2% in Group E and 100% in Group F. There was a significant difference between Group A and the other five groups, and between Groups B or C and Groups D, E or F (p < 0.005). These results indicate that a functional CL does not exist when the CL area is less than 1.3 cm(2) and that it exists when the CL area is 3.3 cm(2) or more.

Follicular-phase concentrations of progesterone, estradiol-17β, LH, FSH, and a PGF2α metabolite and daily clustering of prolactin pulses, based on hourly blood sampling and hourly detection of ovulation in heifers

Circulating concentrations of hormones were determined each hour in 13 heifers from the end of the luteolytic period to ovulation (follicular phase, 3.5 days). Diameter of the preovulatory follicle was determined every 8 hours, and the time of ovulation was determined hourly. The diameter of the preovulatory follicle decreased 0.8 ± 0.1 mm/h in heifers when there was 1 to 3 hours between the last two diameter measurements before ovulation. The concentration of progesterone (P4) after the end of the luteolytic period (P4 < 1 ng/mL) changed (P < 0.0001), as shown by a continued decrease until Hour -57 (Hour 0 = ovulation), then was maintained at approximately 0.2 ng/mL until 2 hours before the peak of the LH surge at Hour -26, and then a decrease to 0.1 ng/mL along with a decrease in estradiol-17β. Concentrations of LH gradually increased (P < 0.007) and concentrations of FSH gradually decreased (P < 0.0001) after the end of luteolysis until the beginning nadirs of the respective preovulatory surges. A cluster of prolactin (PRL) pulses occurred (P < 0.0001) each day with approximately 24 hours between the maximum value of successive clusters. Hourly concentrations of a PGF2α metabolite decreased (P < 0.007) until Hour -40, but did not differ among hours thereafter. Novel observations included the gradual increase in LH and decrease in FSH until the beginning of the preovulatory surges and follicle diameter decrease a few hours before ovulation. Results supported the following hypotheses: (1) change in the low circulating P4 concentrations during the follicular phase are temporally associated with change in LH concentrations; and (2) PRL pulses occur in a cluster each day during the follicular phase of the estrous cycle.

Automatic detection and segmentation of bovine corpora lutea in ultrasonographic ovarian images using genetic programming and rotation invariant local binary patterns

In this study, we propose a fully automatic algorithm to detect and segment corpora lutea (CL) using genetic programming and rotationally invariant local binary patterns. Detection and segmentation experiments were conducted and evaluated on 30 images containing a CL and 30 images with no CL. The detection algorithm correctly determined the presence or absence of a CL in 93.33 % of the images. The segmentation algorithm achieved a mean (±standard deviation) sensitivity and specificity of 0.8693 ± 0.1371 and 0.9136 ± 0.0503, respectively, over the 30 CL images. The mean root mean squared distance of the segmented boundary from the true boundary was 1.12 ± 0.463 mm and the mean maximum deviation (Hausdorff distance) was 3.39 ± 2.00 mm. The success of these algorithms demonstrates that similar algorithms designed for the analysis of in vivo human ovaries are likely viable.

Correlations between ultrasonographic characteristics of corpora lutea and systemic concentrations of progesterone during the discrete stages of corpora lutea lifespan and secretory activity in cyclic ewes

Associations between physical characteristics and functionality of corpora lutea (CL) have previously been reported in monovulatory species, albeit several studies in cattle and humans have refuted the existence of temporal relationships between CL size, echotexture and serum progesterone (P(4)) concentrations. The main objective of the present study was to examine whether or not there were correlations between ultrasonographic image attributes of CL and systemic concentrations of P(4) during the discrete stages of the luteal phase in two breeds of sheep differing in ovulation rates (non-prolific Western White Face [WWF] ewes and prolific Finn [F] sheep). Transrectal ovarian ultrasonography utilized a 7.5-MHz linear-array transducer connected to a portable scanner (Aloka SSD-500) and the images were analyzed using commercially available image analytical software (Image ProPlus(®)) validated for the present application in sheep. The correlations were assessed using the Pearson's Product Moment (PPM) analysis and also, to increase the accuracy of statistical tests, the analysis of covariance (ANCOVA), with the number of CL as a co-factor. In WWF ewes, serum concentrations of P(4) correlated significantly with the total luteal area (TLA) during the CL growth phase (days 3-6; day 0 = ovulation) and functional luteolysis (days 12-15), and with numerical pixel values (NPVs--pixel intensity) during luteolysis; the results obtained by using two different statistical methods were generally similar. In prolific F ewes, serum P(4) concentrations were directly correlated with TLA during CL growth (days 3-6; ANCOVA), functional luteolysis (days 13-14; PPM), and structural CL regression (days 11-14; PPM and ANCOVA), and with NPVs during functional luteolysis (PPM and ANCOVA). We concluded that systemic P(4) concentrations could only be accurately predicted from the changes in luteal area during CL growth and regression, and from NPVs during luteolysis, in both prolific and non-prolific ewes, but the changes in size and echotexture of the luteal glands at mid-cycle were not indicative of serum P(4) concentrations in sheep.

Inhibition of prostaglandin biosynthesis during postluteolysis and effects on CL regression, prolactin, and ovulation in heifers

The beginning of postluteolysis (progesterone, <1 ng mL(-1)) in heifers was targeted by using 8 h after ultrasonic detection of a 25% decrease in CL area (cm2) and was designated Hour 0. Flunixin meglumine (FM; n=10) to inhibit PGF2α secretion or vehicle (n=9) were given intramuscularly at Hours 0, 4, 8, 16, 24, 32, and 40. The dose of FM was 2.5 mg/kg at each treatment. Blood sampling and measurement of the CL and dominant follicle were done every 8 h beginning 14 days postovulation in each group. Blood samples for detection of pulses of PRL and pulses of a metabolite of PGF2α (PGFM) were obtained every hour for 24 h beginning at Hour 0. Pulse concentrations of both PGFM and PRL were lower in the FM group than in the vehicle group. Concentration of PRL was greatest at the peak of a PGFM pulse. Neither CL area (cm2) nor progesterone concentration differed between groups during Hours 0 to 48 (postluteolysis). Ovulation occurred in nine of nine heifers in the vehicle group and in three of 10 heifers in the FM group. The anovulatory follicles in the FM group grew to 36.2±2.9 mm, and the wall became thickened from apparent luteinization. The hypothesis that PGF2α was involved in the continued P4 decrease and structural CL regression during postluteolysis was not supported. However, the hypotheses that pulses of PGFM and PRL were temporally related and that systemic FM treatment induced an anovulatory follicle were supported.

Induction of PGFM pulses and luteolysis by sequential estradiol-17β treatments in heifers

The effects of sequential induction of PGFM pulses by estradiol-17β (E2) on prominence of PGFM pulses and progesterone (P4) concentration were studied in heifers. Three treatments of vehicle (n = 12) or E2 (n = 12) at doses of 0.05 or 0.1 mg were given at 12-h intervals beginning on Day 15 postovulation. Blood samples were collected every 12 h from Days 13-24 and hourly for 12 h after the first and third treatments. On Day 15, all heifers were in preluteolysis and on Day 16 were in preluteolysis in the vehicle-treated heifers (n = 11) and either preluteolysis (n = 4) or luteolysis (n = 8) in the E2-treated heifers. Peak concentration of induced PGFM pulses during preluteolysis on Day 15 was greater (P < 0.04) than for pulses during preluteolysis on Day 16. The interval from ovulation to the beginning of luteolysis was shorter (P < 0.04) in the E2-treated heifers than in the vehicle-treated heifers. An E2-induced PGFM pulse was less prominent (P < 0.008) in heifers in temporal association with a transient resurgence in P4 than in heifers with a progressive P4 decrease. The hypothesis that repeated E2 exposure stimulates increasing prominence of PGFM pulses was not supported. Instead, repeated exposure reduced the prominence of PGFM pulses, in contrast to the stimulation from the first E2 treatment. Reduced prominence of a PGF(2α) pulse during luteolysis can lead to a transient resurgence in P4 concentration.

Pregnancy rates and corpus luteum-related factors affecting pregnancy establishment in bovine recipients synchronized for fixed-time embryo transfer

The objective was to investigate the influence of corpora lutea physical and functional characteristics on pregnancy rates in bovine recipients synchronized for fixed-time embryo transfer (FTET). Crossbred (Bos taurus taurus x Bos taurus indicus) nonlactating cows and heifers (n=259) were treated with the following protocol: 2mg estradiol benzoate (EB) plus an intravaginal progesterone device (CIDR 1.9g progesterone; Day 0); 400 IU equine chorionic gonadotropin (eCG; Day 5); prostaglandin F(2alpha) (PGF(2alpha)) and CIDR withdrawal (Day 8); and 1mg EB (Day 9). Ovarian ultrasonography and blood sample collections were performed on Day 17. Of the 259 cattle initially treated, 197 (76.1%) were suitable recipients; they received a single, fresh, quality grade 1 or 2 in vivo-derived (n=90) or in vitro-produced (n=87) embryo on Day 17. Pregnancy rates (23 d after embryo transfer) were higher for in vivo-derived embryos than for in vitro-produced embryos (58.8% vs. 31.0%, respectively; P<0.001). Mean (+/-SD) plasma progesterone (P(4)) concentration was higher in cattle that became pregnant than that in nonpregnant cattle (5.2+/-5.0 vs. 3.8+/-2.4 ng/mL; P=0.02). Mean pixel values (71.8+/-1.3 vs. 71.2+/-1.1) and pixel heterogeneity (14.8+/-0.3 vs. 14.5+/-0.5) were similar between pregnant and nonpregnant recipients (P>0.10). No significant relationship was detected between pregnancy outcome and plasma P(4), corpus luteum area, or corpus luteum echotexture. Embryo type, however, affected the odds of pregnancy. In conclusion, corpus luteum-related traits were poor predictors of pregnancy in recipients. The type of embryo, however, was a major factor affecting pregnancy outcome.

Level set segmentation of bovine corpora lutea in ex situ ovarian ultrasound images

BACKGROUND

The objective of this study was to investigate the viability of level set image segmentation methods for the detection of corpora lutea (corpus luteum, CL) boundaries in ultrasonographic ovarian images. It was hypothesized that bovine CL boundaries could be located within 1-2 mm by a level set image segmentation methodology.

METHODS

Level set methods embed a 2D contour in a 3D surface and evolve that surface over time according to an image-dependent speed function. A speed function suitable for segmentation of CL's in ovarian ultrasound images was developed. An initial contour was manually placed and contour evolution was allowed to proceed until the rate of change of the area was sufficiently small. The method was tested on ovarian ultrasonographic images (n = 8) obtained ex situ. A expert in ovarian ultrasound interpretation delineated CL boundaries manually to serve as a "ground truth". Accuracy of the level set segmentation algorithm was determined by comparing semi-automatically determined contours with ground truth contours using the mean absolute difference (MAD), root mean squared difference (RMSD), Hausdorff distance (HD), sensitivity, and specificity metrics.

RESULTS AND DISCUSSION

The mean MAD was 0.87 mm (sigma = 0.36 mm), RMSD was 1.1 mm (sigma = 0.47 mm), and HD was 3.4 mm (sigma = 2.0 mm) indicating that, on average, boundaries were accurate within 1-2 mm, however, deviations in excess of 3 mm from the ground truth were observed indicating under- or over-expansion of the contour. Mean sensitivity and specificity were 0.814 (sigma = 0.171) and 0.990 (sigma = 0.00786), respectively, indicating that CLs were consistently undersegmented but rarely did the contour interior include pixels that were judged by the human expert not to be part of the CL. It was observed that in localities where gradient magnitudes within the CL were strong due to high contrast speckle, contour expansion stopped too early.

CONCLUSION

The hypothesis that level set segmentation can be accurate to within 1-2 mm on average was supported, although there can be some greater deviation. The method was robust to boundary leakage as evidenced by the high specificity. It was concluded that the technique is promising and that a suitable data set of human ovarian images should be obtained to conduct further studies.

Examination of cyclic changes in bovine luteal echotexture using computer-assisted statistical pattern recognition techniques

B-mode sonography is a well-established diagnostic tool for determination of cycle stage in gynaecology. The aim of this study was to determine whether computer-assisted texture analysis of B- mode sonographic images of bovine luteal glands provides further information about the animal's plasma progesterone concentration and cycle stage. Four Simmenthal cows were examined during two consecutive estrous cycles with an ultrasound device equipped with a 7.5MHz microconvex probe. During each examination three B-mode images of the corpus luteum (CL) were digitized and analyzed off-line using a computer-assisted texture analysis program. Size, echogeneity, and echotexture of the CL were characterized by the following texture parameters: area of cross-sectional planes of the CL (A), mean gray level (MGL), correlation (CORR), run percentage (RPERC), and long-run emphasis (LREM). Plasma progesterone levels (P4) were also determined. All parameters showed characteristic changes during the estrous cycle (P<0.05). Variance component estimates for the effect of Day of estrous cycle on A, MGL, CORR, RPERC, and LREM were 56.6%, 64.6%, 77.6%, 89.9%, and 86.0%, respectively, and 20.6%, 24.5%, 7.2%, 0.0%, and 14.0% for the influence of the individual cow. The factor estrous cycle within cows was responsible for 22.8%, 10.9%, 15.2%, 10.1%, and 0.0% of the variability of A, MGL, CORR, RPERC and LREM values, respectively. Cyclic changes were similar in A and P4. In contrast to P4, which decreased already between Days -5 and -3 (Day 0=ovulation), A stayed at constant high values until Day -3. Mean MGL values were higher (P<0.05) on Days 7, 9, and 13 compared to Days 3 and -3. Mean CORR values were constantly high (P>0.05) during the first days after ovulation and decreased continuously (P<0.05) between Days 5 and 13. Thereafter, mean CORR values remained low (P<0.05) until the next ovulation, except on Day -3 (P<0.05). Mean RPERC rose between Days 1 and 9 from low to high values (P<0.0001) remained at these high values (P>0.05) between Days 9 and 15, and decreased (P<0.05) afterwards to baseline values on Day -1. Mean LREM inclined steeply (P<0.0001) from minimum to maximum between Days 1 and 5. From Days 7 to -3, mean LREM remained (P>0.05) at a constant level close below the maximum value, and decreased to baseline values on Day -1. The results of this study show that statistical pattern recognition techniques provide new information about the luteal glands, thus facilitating a more accurate differentiation between different cycle stages in cows.

Relationships between ultrasonographic image attributes, histomorphology and proliferating cell nuclear antigen expression of bovine antral follicles and corpora lutea ex situ

The aim of this study was to examine the relationships between quantitative ultrasonographic image characteristics, histological attributes and cell proliferating ability of bovine antral follicles and corpora lutea (CL) ex situ. Bovine ovaries (n = 30) from animals at various reproductive states (metoestrus-early dioestrus, n = 8; mid-dioestrus, n = 12; oestrous phase of peripubertal heifers, n = 6; and pregnancy, n = 4) were collected at the slaughterhouse. High-resolution ultrasonographic images of the ovaries were obtained in the water bath, digitized and subjected to computerized image analyses. The analyses utilized line and spot techniques designed to determine pixel values of the follicular wall (the largest follicles >2 mm in diameter in each ovary) and CL, respectively. Individual ovarian structures were dissected and processed for histology and immunohistochemical detection of proliferating cell nuclear antigen (PCNA). The mean follicular diameter was negatively correlated with total cell density (r = -0.45, p < 0.05), granulosa layer thickness (r = -0.67, p < 0.001) and the percentage of PCNA-positive cells (r = -0.57, p < 0.001). Numerical pixel values and heterogeneity of the follicular wall were positively correlated with total cell density (r = 0.42, p < 0.05 and r = 0.62, p < 0.05; respectively), granulosa layer thickness (both r = 0.39, p < 0.05), and the percentage of PCNA-positive cells (r = 0.54, p < 0.01 and r = 0.69, p < 0.001, respectively). Estimates of cell density and proliferating cell index were not correlated with the ultrasonographic image attributes of CL. We conclude that follicular size and echotextural variables, as determined by computer-assisted image analysis of ovaries ex situ, are reliable markers of the histophysiological properties of bovine antral follicles, but the ultrasonographic characteristics are not indicative of cell density and proliferation in the bovine CL.

Ultrasonographic characteristics of ovulatory follicles and associated endocrine changes in cyclic ewes treated with medroxyprogesterone acetate (MAP)-releasing intravaginal sponges and equine chorionic gonadotropin (eCG)

The aim of this study was to assess the ultrasonographic characteristics of ovulatory follicles in cyclic Western White Face ewes (December) that had received intravaginal sponges containing medroxyprogesterone acetate (MAP; 60 mg) for 12 days, with or without an injection of 500 IU of equine chorionic gonadotropin (eCG) at sponge removal. We hypothesized that quantitative echotextural attributes of the follicles in ewes treated only with MAP would differ from those in MAP/eCG-treated ewes, reflecting the increased antral follicular growth and secretory function under eCG influence. Digital images of ovulatory follicles obtained at 0 and 24 h after MAP sponge removal and at 24 h before ovulation in the eCG-treated (five ewes, 13 follicles) and control (six ewes, 9 follicles) animals, were subjected to computerized analyses. The mean diameter of ovulatory follicles increased (p < 0.001) 24 h after eCG treatment. The mean pixel intensity and heterogeneity of the follicular antrum (p < 0.001), as well as mean pixel intensity of the follicular wall and perifollicular ovarian stroma (p < 0.05), were greater in eCG-treated animals compared with control ewes 24 h after sponge removal and at 24 h before ovulation. Mean serum concentrations of oestradiol-17beta tended to increase (p = 0.06) 24 h after eCG treatment and the eCG-treated ewes exceeded (p < 0.05) control animals in progesterone concentrations from days 9-15 after ovulation. Our results support the hypothesis that large antral follicles in eCG-treated ewes exhibit distinctive echotextural characteristics. Follicular image attributes in eCG-treated ewes appear to be indicative of the changes in follicular morphology and secretory activity caused by the administration of the exogenous gonadotropin, which has both FSH- and LH-like activities.

Enhancing ultrasound texture differences for developing an in vivo 'virtual histology' approach to bovine ovarian imaging

A ‘virtual histology’ can be thought of as the ‘staining’ of a digital ultrasound image via image processing techniques in order to enhance the visualisation of differences in the echotexture of different types of tissues. Several candidate image-processing algorithms for virtual histology using ultrasound images of the bovine ovary were studied. The candidate algorithms were evaluated qualitatively for the ability to enhance the visual differences in intra-ovarian structures and quantitatively, using standard texture description features, for the ability to increase statistical differences in the echotexture of different ovarian tissues. Certain algorithms were found to create textures that were representative of ovarian micro-anatomical structures that one would observe in actual histology. Quantitative analysis using standard texture description features showed that our algorithms increased the statistical differences in the echotexture of stroma regions and corpus luteum regions. This work represents a first step toward both a general algorithm for the virtual histology of ultrasound images and understanding dynamic changes in form and function of the ovary at the microscopic level in a safe, repeatable and non-invasive way.

Computer assisted image analyses of corpora lutea in relation to peripheral concentrations of progesterone: A comparison between breeds of sheep with different ovulation rates

Transrectal ovarian ultrasonography is a non-invasive technique that permits the real-time serial visualization of ovarian structures. Previous studies have reported correlations between serum progesterone concentrations and physical characteristics of the corpus luteum (CL) in different species. The aim of the present study was to investigate whether or not there were correlations between ultrasound image attributes of the CL and changing progesterone concentrations over time, in prolific and non-prolific ewes. Ultrasonographic images of CL were taken, once daily, from 12 Western White Face ewes and 7 Finn ewes for the duration of one luteal phase. Blood samples were collected daily prior to each scanning session and assayed to determine mean serum concentrations of progesterone. Analysis of ultrasound images was performed using a series of custom-developed computer algorithms optimized for ultrasonography on a computer graphics workstation. Both total luteal area and mean pixel values were correlated with the pattern of serum concentrations of progesterone from days 3 to 15 after ovulation in Western White Face ewes and from days 3 to 14 in Finn ewes. There was no significant correlation between progesterone concentrations and spot pixel heterogeneity for either Western White Face ewes or Finn ewes. We concluded that pixel heterogeneity is a poor indicator of progesterone secretory ability of the CL when compared to mean pixel values. However, luteal area and mean spot pixel values are better but not strong indicators of the functional status of the CL in cyclic ewes.

Ovarian and endocrine responses to prostaglandin F2α (PGF2α) given at the expected time of the endogenous FSH peak at mid-cycle in ewes

In the ewe, a rise in circulating concentrations of FSH preceding follicular wave emergence begins in the presence of growing follicles from a previous wave. We hypothesized that prostaglandin F(2alpha) (PGF(2alpha)) given at the time of an endogenous FSH peak in cyclic ewes would result in synchronous ovulation of follicles from two consecutive waves, increasing ovulation rate. Twelve Western White Face (WWF) ewes received a single i.m. injection of PGF(2alpha) (15 mg/ewe) at the expected time of a peak in FSH secretion, from Days 9 to 12 after ovulation. The mean ovulation rate after PGF(2alpha) treatment (2.3+/-0.3) did not differ (P>0.05) from the pre-treatment ovulation rate (1.7+/-0.1). Five ewes ovulated follicles from follicular waves emerging before and after PGF(2alpha) injection (3.0+/-0.6 ovulations/ewe) and seven ewes ovulated follicles only from a wave(s) emerging before PGF(2alpha) treatment (2.0+/-0.3 ovulations/ewe; P>0.05). The mean interval from PGF(2alpha) to emergence of the next follicular wave (1.0+/-0.4 and 4.0+/-0.0 d, respectively; P<0.001) and the interval from PGF(2alpha) treatment to the next FSH peak (0 and 3.5+/-0.4d, respectively; P<0.05) differed between the two groups. Six ewes ovulated after the onset of behavioral estrus, with a mean ovulation rate of 1.7+/-0.2, and six ewes ovulated both before and after the onset of estrus (3.0+/-0.5 ovulations/ewe; P<0.05). None of the ovulations that occurred before estrus resulted in corpora lutea (CL) with a full life span. At 24h before ovulation, follicles ovulating before or after the onset of estrus differed in size (4.1+/-0.3 or 5.5+/-0.4mm, respectively; P<0.05) and had distinctive echotextural characteristics. In conclusion, the administration of PGF(2alpha) at the expected time of an FSH peak at mid-cycle in ewes may alter the endogenous rhythm of FSH secretion and was not consistently followed by ovulation of follicles from two follicular waves. In non-prolific WWF ewes, PGF(2alpha)-induced luteolysis disrupted the normal distribution of the source of ovulatory follicles and may be associated with untimely follicular rupture and luteal inadequacy.

Nuclear magnetic resonance spectroscopy of bovine ovarian follicular fluid at four selected times of the oestrous cycle

The objective of the study was to determine if nuclear magnetic resonance (NMR) spectral features of ovarian follicular fluid were correlated with the physiological status of follicles so that we could assess the feasibility of using NMR spectroscopy during assisted reproduction therapy. Thirty-five sexually mature, nullparious heifers were monitored by transrectal ultrasonography to assess their follicle wave status during the oestrous cycle. Ovariectomies were performed on Day 3 of wave 1 (D3W1, n = 10), Day 6 of wave 1 (D6W1, n = 9), Day 1 of wave 2 (D1W2, n = 9), or in the immediate preovulatory period of at least 17 days after ovulation (D≥17, n = 9). Follicle status was determined to be dominant or subordinate. Follicular fluid was extracted from the follicles and NMR spectra were collected. Principal components were extracted from ratios of line amplitudes and tested for effects of follicle status (dominant v. subordinate) and cycle time point (D1W3, D1W6, D1W2 and D≥17) using multivariate analysis of variance. For most line ratio combinations, main effects of status, time point and their interaction were found (P < 0.05). We concluded that NMR spectra may be used for the determination of ovarian follicle physiological status.

Form and function of the corpus luteum during the human menstrual cycle

OBJECTIVE

To characterize the growth and regression of the corpus luteum (CL) during an interovulatory interval (IOI) using serial transvaginal ultrasonography.

METHODS

Fifty healthy women of reproductive age with a history of regular menstrual cycles underwent daily transvaginal ultrasonography for one IOI. Measurements of luteal area and luteal numerical pixel value (NPV) were recorded each day after ovulation until the CL could no longer be detected. Blood was drawn every third day during the IOI to measure serum concentrations of progesterone and estradiol-17beta.

RESULTS

Corpora lutea were of two morphological types: those with a central fluid-filled cavity (CFFC) (78%) and those without (22%). Eighty-eight percent of women exhibited a CL containing a CFFC 2 days after ovulation, followed by 34% 13 days after ovulation and 2% 27 days after ovulation. Luteal area, progesterone concentration and estradiol concentration increased for approximately the first 6 days following ovulation followed by a subsequent decline. Luteal NPV decreased from days 1 to 11 and increased during days 11-16. Changes in luteal area, NPV, progesterone and estradiol concentrations did not differ in women with two versus three waves of follicular development.

CONCLUSIONS

Peak luteal function, as determined by maximum luteal area, progesterone concentration and estradiol concentration, is observed 6 days following ovulation. Luteal NPV is reflective of morphological and endocrinological changes in the CL. The development of a CFFC during luteinization is a normal physiological phenomenon. The CL can be detected, but is not functional, during the follicular phase of the menstrual cycle.

Ultrasound image attributes of human ovarian dominant follicles during natural and oral contraceptive cycles

BACKGROUND

Computer-assisted analyses were used to examine ultrasound image attributes of human dominant ovarian follicles that developed during natural and oral contraceptive (OC) cycles. We hypothesized that image attributes of natural cycle follicles would quantitatively differ from those in OC cycles and that OC cycle follicles would possess image attributes indicative of atresia.

METHODS

Dominant ovarian follicles of 18 clinically normal women were compared using transvaginal ultrasonography for the 7 days before ovulation during a natural cycle (n = 9) or the 7 days before peak estradiol in women using OC (n = 11). Follicles were analyzed using region and line techniques designed to compare the image attributes numerical pixel value (NPV), pixel heterogeneity (PH) and area under the curve (AUC).

RESULTS

NPV was higher in OC cycle follicles with region analysis and tended to be higher with line analysis (p = 0.005 and p = 0.06, respectively). No differences were observed in two other image attributes (AUC and PH), measured with either technique, between natural and OC cycle follicles.

CONCLUSION

The increased NPV value of OC cycle follicles and lack of differences in PH and AUC values between natural cycle and OC cycle follicles did not support the hypothesis that OC cycle follicles would show ultrasonographically detectable signs of atresia. Image attributes observed in OC cycle follicles were not clearly indicative of atresia nor were they large enough to preclude preovulatory physiologic status in OC cycle follicles.

Intraovarian blood flow measured with color doppler ultrasonography inversely correlates with vascular density in the human corpus luteum of the menstrual cycle

OBJECTIVE

To evaluate the morphologic characteristics underlying the ultrasonographic appearance and blood flow dynamics in the human corpus luteum (CL) of the menstrual cycle.

DESIGN

Cross-sectional study.

SETTING

Umeå University Hospital, Umeå, Sweden.

PATIENT(S)

Twenty-six otherwise healthy women with proven fertility and a history of regular menstrual cycles, scheduled for elective hysterectomy or tubal sterilization.

INTERVENTION(S)

An ovulatory LH rise in urine was established and the CL age was determined according to the day after the LH rise. Before surgery, a standardized ultrasonographic examination of the CL, including B-mode and color Doppler ultrasonography measurements, was performed. Upon commencing the minilaparotomy, the CL was excised and measured using a digital slide-caliper. The volume density (percentage of CL volume occupied by blood vessels) of factor VIII-related antigen immunostained endothelial cells was determined.

MAIN OUTCOME MEASURE(S)

Pulsatility index obtained from intraovarian blood vessels supplying the CL and volume density of blood vessels in CL tissue. The CL maximal and minimal outer and inner dimensions were measured in vivo by ultrasonography and ex vivo by a digital slide caliper.

RESULT(S)

A statistically significant decrease of blood vessel density and an increased resistance to blood flow, as indicated by pulsatility index, was established during the course of corpus luteum development. An inverse correlation between pulsatility index and volume density of blood vessels was found. A high degree of agreement between ultrasonographic and anatomic measurements of surgically removed CL was found.

CONCLUSION(S)

Transvaginal ultrasonography in combination with intraovarian color Doppler flow measurements is a simple and reliable method to evaluate the size and vascularization of the human CL.

Ultrasonographic evaluation of the pre-pubertal development of the reproductive tract in beef heifers

To study the development of the reproductive tract in heifers, the ovaries, uterus, cervix and vagina were examined by transrectal ultrasonography every 2 weeks, from 2 to 60 weeks after birth. First ovulation occurred at 63.7 +/- 1.1 weeks of age. Ovarian dimensions increased rapidly from 2 to 14 weeks of age, and increased again after 34 weeks of age (P<0.05). The size of the largest ovarian follicles increased from 8 to 14 weeks of age, from 38 to 42 weeks of age, and finally from 52 to 60 weeks of age (P<0.05). The number of follicles > or =3 mm in diameter tended to increase from 6 to 14 weeks of age (P<0.10) and increased significantly from 6 to 60 weeks of age (P<0.05). Mean numerical pixel values of the ovarian images decreased from 4 to 26 weeks of age, and then rose to 44 weeks of age (P<0.05). Diameter of the uterine body, cervix and vagina increased from 2 to 20-24 weeks of age, and again after 32 weeks of age (P<0.05). Mean numerical pixel values for the uterus and vagina decreased initially (uterus: 4-8 weeks and vagina: 6-22 weeks of age) and then increased (uterus: 14-42 weeks and vagina: 22-32 weeks of age; P<0.05). Pixel heterogeneity showed a consistent peak at 20-22 weeks of age for the uterus, cervix and vagina (P<0.05). In summary, in the heifer calf, the marked growth of the reproductive tract in the first few months of age, and prior to first ovulation, reflects phases of increased ovarian follicle (> or =3 mm in diameter) numbers and size. Ultrasonographic image analysis revealed patterns of numerical pixel values and heterogeneity that may be useful in determining important stages of growth and differentiation of the reproductive system.

Promise of new imaging technologies for assessing ovarian function

Advancements in imaging technologies over the last two decades have ushered a quiet revolution in research approaches to the study of ovarian structure and function. The most significant changes in our understanding of the ovary have resulted from the use of ultrasonography which has enabled sequential analyses in live animals. Computer-assisted image analysis and mathematical modeling of the dynamic changes within the ovary has permitted exciting new avenues of research with readily quantifiable endpoints. Spectral, color-flow and power Doppler imaging now facilitate physiologic interpretations of vascular dynamics over time. Similarly, magnetic resonance imaging (MRI) is emerging as a research tool in ovarian imaging. New technologies, such as three-dimensional ultrasonography and MRI, ultrasound-based biomicroscopy and synchrotron-based techniques each have the potential to enhance our real-time picture of ovarian function to the near-cellular level. Collectively, information available in ultrasonography, MRI, computer-assisted image analysis and mathematical modeling heralds a new era in our understanding of the basic processes of female and male reproduction.

Luteogenesis in cyclic ewes: echotextural, histological, and functional correlates

To date, it has not been possible to detect corpus luteum (CL) by ultrasonography, immediately following ovulation, in the ewe. Early CL detection is essential to be able to relate luteal outcome to the developmental pattern of the ovulated follicle and to confirm ovulation. Image analysis of the CL may be useful in providing a noninvasive picture of CL differentiation and function. The present study was designed to use high-resolution ultrasonography to monitor and to correlate the echotextural, histological, and functional attributes of the developing ovine CL from Days 1 to 3 after ovulation. Ten ewes underwent twice-daily transrectal ultrasonography and blood sampling from the day of synchronized estrus. Ewes were ovariectomized at 12-24, 36-48, and 60-72 h after ovulation. Ovaries collected were scanned in a water bath before processing for histology. Ultrasonographic images of CL were analyzed for echotexture. Histological sections were analyzed for the percentage area of the CL occupied by blood clot or luteal tissue. Serum samples were analyzed for progesterone concentration. Numerical pixel value, heterogeneity, and percentage of the CL occupied by blood clot declined (P<0.05) from 12-24 to 60-72 h after ovulation. Luteal area and serum progesterone concentration increased (P<0.05) from 12-24 to 60-72 h. The results indicated that it was possible to visualize developing CL as early as 12-24 h after ovulation in the ewe. Echotexture of the CL was closely associated with its morphological and functional characteristics; image analysis holds promise for noninvasive monitoring of CL differentiation and growth.

Ovarian dynamics and their associations with peripheral concentrations of gonadotropins, ovarian steroids, and inhibin during the estrous cycle in goats

Ovarian changes determined by daily transrectal ultrasound and its relationship with FSH, LH, estradiol-17beta, progesterone, and inhibin were investigated in six goats for three consecutive interovulatory intervals. Estrous cycles were synchronized using two injections of prostaglandin F2alpha analogue 11 days apart. All follicles 3 mm or greater in diameter and corpora lutea were measured daily. A follicular wave was defined as one or more follicles growing to 5 mm or greater in diameter. The day that the follicles reached 3 mm in diameter was defined as the day of wave emergence, and the first wave after ovulation was defined as wave 1. During the interovulatory interval (mean +/- SEM, 21.3 +/- 0.4 days; n = 18), follicular waves emerged at 0.3 +/- 0.5, 6.5 +/- 0.2, and 12.1 +/- 0.4 days for wave 1, wave 2, and wave 3, respectively, in goats with three waves of follicular development and at -0.6 +/- 0.3, 4.7 +/- 0.2, 9.4 +/- 0.5, and 13.4 +/- 0.5 days for wave 1, wave 2, wave 3, and wave 4, respectively, in goats with four waves of follicular development (Day 0 = the day of ovulation). The mean diameter of the largest follicle of the ovulatory wave was significantly larger than those of the largest follicles of the other waves. Corpora lutea could be identified ultrasonically at Day 3 postovulation and attained 12.1 +/- 0.3 mm in diameter on Day 8. Transient increases in plasma concentrations of FSH were detected around the day of follicular wave emergence. The level of FSH was negatively correlated with that of inhibin. These results demonstrated that follicular waves occurred in goats and that the predominant follicular wave pattern was four waves with ovulation from wave 4. These results also suggested that the emergence of follicular waves was closely associated with increased secretion of FSH.