Ovarian follicle development in wapiti (Cervus elaphus) during the anovulatory season

The ovaries of 12 mature wapiti hinds were studied by transrectal ultrasonography during the anovulatory season to characterize follicular dynamics and to test the hypothesis that follicle development occurs in a wave-like fashion. The hinds were examined daily, standing without sedation. Follicle size and numbers were recorded, and individual follicles were identified serially. Follicle development was considered wave-like if periodic changes in follicle numbers could be associated temporally with the development of a dominant follicle. There were non-random changes (P<0.01) in the number of follicles > or =4 mm in diameter detected per day. Each peak in follicle numbers was associated with the development of a single dominant follicle. The dominant follicle of the cohort was larger (P<0.05) than the other follicles 1 day after its emergence. Intervals between successive peaks (6.8 +/- 0.4 day) and troughs (6.8 +/- 0.4 day) in follicle numbers, and emergence of sequential dominant follicles (7.1 +/- 0.5 day) were not different (P=0.86). Results confirmed the hypothesis that ovarian follicles develop in a wave-like fashion in wapiti during the anovulatory season.     

The structure of the spiny mouse (Acomys cahirinus) ovary during development

The study presents the structure of the ovaries of the spiny mouse (Acomys cahirinus) during the first months of life. The ovaries in neonate females exhibit a large number of primordial and primary follicles, sometimes clustered in nests. The growing follicles were also observed within the ovary at that period. The first, early antral follicles appeared in the ovary during the second week of life. In the group of 60-day old females, the structure of the ovaries was characterized by a significant increase in the connective tissue elements. Moreover, ovarian follicles at various stages of development were observed, except for the antral ones with cumulus oophorus. The first mature follicles were identified in 3-month old females. In the ovarian follicles, apoptosis occurs at all stages of follicle development, especially in the early antral follicles. In the atretic follicles, apoptotic cells were identified in the layer of granulosa cells.     

Ultrasonographic study of the effects of the corpus luteum on antral follicular development in unilaterally ovulating western white-faced ewes

The objective of this study was to examine the local effects of the corpus luteum (CL) on ovarian antral follicle development by looking at follicle populations and dynamics in ovaries with or without CL, in unilaterally ovulating ewes, using a retrospective analysis of daily ultrasonographic records. The present report summarises the data from the first luteal phase of the breeding season (August-October; n = 4), a luteal phase in the mid-breeding season (November-December; n = 5), the last luteal phase of the breeding season (January-March; n = 5), and the luteal phase after GnRH-induced ovulations in mid-anoestrus (May-June; n = 4) of western white-faced ewes. Mean daily numbers of 3mm follicles that did not grow any larger were significantly reduced in the CL-containing ovaries of ewes at all periods of study except for the transition to anoestrus. With all scanning periods combined, daily numbers of 3mm follicles not growing further increased (P<0.05) between day 6 and 15 after ovulation in the CL-containing ovaries. Based on mean data for the whole periods of observation, the non-CL-bearing ovaries of ewes in the transition to anoestrus had fewer (P<0.05) follicles growing from 3 to > or =5mm in size before regression compared with the mid-breeding season and mid-anoestrus. The lifespan of follicles reaching > or =5mm in diameter was shorter (P < 0.05) in the CL- compared with non-CL-containing ovaries of anoestrous ewes induced to ovulate with GnRH ((6.5+/- 1.3) and (9.0+/- 1.0) days, respectively). Circulating concentrations of progesterone were lower during both transitional periods (into and out of anoestrus) and mid-anoestrus than during the mid-breeding season (P < 0.001), and were less during anoestrus than during both transitional periods (P < 0.05). It was concluded that CL/luteal structures locally suppressed the growth of ovarian antral follicles to the 3mm size-range except during the transition to anoestrus, but that there was no inhibitory effect of the CL on the growth of ovarian follicles to larger diameters. The presence of CL/luteal structures did not affect the length of the lifespan of follicles reaching > or =5mm in diameter nor the number of ovulations per ovary in cyclic ewes, but shortened large follicle lifespan in anoestrous ewes. Variations in peripheral concentrations of progesterone across the breeding season and between the breeding season and anoestrus did not alter the lifespan of large antral follicles. In the transition to anoestrus and during mid-anoestrus, the presence of the CL in an ovary appeared to maintain follicle development to ovulatory sizes and to increase the rate of turnover of large antral follicles, respectively.     

Differential response to gonadotropins and prostaglandin E2 in ovarian tissue during prenatal and postnatal development in cattle.

In cattle, growing follicles are present in fetal ovaries during the last part of gestation. This study examines the extent of changes in basal and hormone-stimulated adenylyl cyclase (AC) activity in ovaries of the bovine fetus when the first follicles begin to grow. The first growing follicles appeared in fetal ovaries around Day 180 and consisted mainly of primary and secondary follicles; few antral follicles were present before Day 220 of gestation. Basal AC activity in ovarian membranes increased simultaneously with the beginning of follicle growth in the fetus (5.8 +/- 0.9 vs. 9.3 +/- 1.3 pmol cAMP/mg protein/min at 130-180 and 180-210 days of gestation, respectively p less than 0.05). During the same time period, there was a significant increase in both the absolute (16.1 +/- 1.2 to 39.9 +/- 1.4 pmol cAMP/mg protein/min) and the relative (2.8 +/- 0.1 to 4.3 +/- 0.3 times the basal level, p less than 0.05) effects of guanosine triphosphate (GTP). After birth, basal and GTP-stimulated AC activities (pmol cAMP/mg protein/min) increased markedly in ovarian membranes of 1-wk-old calves and then decreased with age; the lowest levels were measured in mature cyclic cows. However, the relative effect of GTP (times the basal level) did not show this age-related variation. Prostaglandin E2 (PGE2) stimulation of AC in ovarian membranes from fetuses was high even on Day 120 (2.1 +/- 0.3 times the control level).(ABSTRACT TRUNCATED AT 250 WORDS)     

Fibrillins in Adult Human Ovary and Polycystic Ovary Syndrome: Is Fibrillin-3 Affected in PCOS?

Polycystic ovary syndrome (PCOS) is a common endocrinopathy in women of reproductive age. Although genetic linkage analyses have demonstrated a susceptibility locus for PCOS mapping to the fibrillin-3 gene, the presence of fibrillin proteins in normal and polycystic ovaries has not been characterized. This study compared and contrasted fibrillin-1, -2, and -3 localization in normal and polycystic ovaries. Immunohistochemical stainings of ovaries from 21 controls and 9 patients with PCOS were performed. Fibrillin-1 was ubiquitous in ovarian connective tissue. Fibrillin-2 localized around antral follicles and in areas of folliculolysis. Fibrillin-3 was present in a restricted distribution within the specialized perifollicular stroma of follicles in morphological transition from primordial to primary type [transitional follicles (TFs)]. Fibrillin-1 and -2 stainings of PCOS ovaries were similar to those of the controls. However, in eight of the nine PCOS ovaries, there was a decrease in the number of TFs associated with fibrillin-3, including no staining in five PCOS samples; decreased number of fibrillin-3-associated TFs/mm² was confirmed by quantitative analysis. Our findings support a role for fibrillin-3 in the pathogenesis of PCOS and suggest fibrillin-3 may function in primordial to primary follicle transition. We propose that loss of fibrillin-3 during folliculogenesis may be an important factor in PCOS pathogenesis. (J Histochem Cytochem 58:903–915, 2010)     

Suitability of antral follicle counts and computer-assisted analysis of ultrasonographic and magnetic resonance images for estimating follicular reserve in porcine,ovine and bovine ovaries ex situ

This study was conducted to determine if correlations exist between the numbers of microscopic follicles comprising ovarian follicular reserve (OFR) and antral follicle counts (AFCs), and to assess the usefulness of computerized analyses of ovarian ultrasonograms and magnetic resonance (MR) images for estimating OFR in excised porcine, ovine and bovine ovaries. As a pre-requisite to these analyses, we characterized and compared ovarian cortical histomorhpology and follicle populations in the three species varying in prolificacy and overall reproductive longevity, and hence the total number of microscopic and antral follicles. Ultrasonographic and MR images were obtained at the scanner settings optimized to provide opposing contrasts between antral follicles and the ovarian stroma. Commercially available ImageProPlus® analytical software was used to calculate numerical pixel values (NPVs) and pixel heterogeneity (standard deviation of the pixel values) along the computer-generated lines (4–6) placed in the area corresponding to the ovarian cortex. The numbers of primordial (r = 0.38, P < 0.01) and intermediate follicles (r = 0.37, P < 0.01) were correlated with the numbers of antral follicles in bovine ovarian sections. The numbers of primordial (r = 0.28, P < 0.05), intermediate (r = 0.31, P < 0.01) and primary follicles (r = 0.27, P < 0.05) correlated directly with mean NPVs of the ultrasonographic ovarian images in cattle. There was a negative correlation between primary follicle numbers and NPVs of MR images (3D FAST-SPOILED GRADIENT ECHO) of the porcine ovarian cortex (r = −0.31, P < 0.05). To summarize, the numbers of primordial and intermediate follicles could only be estimated from AFCs in cows. Using ultrasound NPVs, the numbers of primordial, intermediate and primary follicles could be directly estimated in bovine ovaries and the quantitative image attributes of MR images were useful for quantifying porcine primary follicles. The bovine ovarian model is compatible with human situation and hence future studies should be undertaken to ascertain the usefulness of AFCs and ultrasonographic image analyses for estimating OFR in women.     

In utero and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin and 2,3,4,7,8-pentachlorodibenzofuran reduces growth and disrupts reproductive parameters in female rats

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 2,3,4,7,8-pentachlorodibenzofuran (PCDF) are widespread environmental pollutants. TCDD is well known for its adverse effects on female reproduction when administered acutely to immature or adult rats. It is also known that fetal/neonatal exposure to this compound alters reproductive parameters. It is unknown whether exposure to PCDF causes similar adverse effects in offspring. The objectives of the study were to investigate the effects of in utero and lactational (IUL) exposure to TCDD and PCDF on subsequent growth, estrous cycles, and ovulation. Additionally a gonadotropin-primed immature rat model was used to investigate possible direct effects on the ovary after IUL exposure to TCDD (2.5 microg/kg) by evaluating 1) ovarian morphometrics and 2) serum estradiol concentrations. Body weights were reduced in animals with IUL exposure to TCDD and PCDF relative to those in controls at 10 days of age (P < 0.05 for each), and this difference was maintained until termination of the experiment at 125-165 days of age (P < 0.05). Exposure to TCDD or PCDF also disrupted regular estrous cycles and inhibited ovulation rate. On Day 23 (before eCG stimulation), ovaries from animals exposed to TCDD contained the same number of primordial, primary, secondary, preantral, and antral follicles as ovaries from control animals. On Day 25 (48 h after eCG stimulation), ovaries from TCDD-exposed rats had significantly fewer large preovulatory follicles when compared with ovaries from controls. The numbers of smaller follicles (both antral and small antral) were not different. Serum estradiol was significantly lower in TCDD-exposed animals 48 h after eCG stimulation.     

Changes in follicle-stimulating hormone and follicle populations during the ovarian cycle of the common marmoset

The common marmoset (Callithrix jacchus) belongs to the family Callitrichidae, the only anthropoid primates with a high and variable number of ovulations (one to four). An understanding of folliculogenesis in this species may provide some insight into factors regulating multiple follicular growth in primates. The aims of this study were to characterize in detail changes in the antral follicle population at different stages of the ovarian cycle, to characterize the marmoset FSH profile, and to relate cyclic changes in FSH to changes in follicle sizes and circulating estradiol concentrations. Fifty-five pairs of ovaries were collected (32 of which were at five distinct stages of the cycle) from adult marmosets, and antral follicles were manually excised and separated into four size groups. Daily urinary FSH and plasma estradiol and progesterone concentrations from Day 0 of the follicular phase to 2 days postovulation were measured in 22 marmosets using enzyme immunoassays. The FSH profile revealed two distinct peaks, on Days 2 and 6, during the 10-day follicular phase, with a marginal periovulatory increase on Days 9 and 10. Estradiol levels rose significantly (P: < 0.05) above baseline (Days 1-4) on Day 5 and continuously increased to a peak on the day preceding ovulation (Days 8 and 9). Follicle dissection revealed a high (mean = 68) and variable (range, 14-158) total number of antral follicles >0.6 mm. The number of antral follicles significantly declined (P: < 0.001) with age. The number of preovulatory follicles (>2 mm) was positively correlated with the number of antral follicles (P: < 0. 001) and tended to be negatively related to age (P: = 0.06). The number of antral follicles did not vary significantly with stage of the ovarian cycle, although the follicle size distribution was cycle-stage dependent (P: < 0.05). Follicles >1.0 mm appeared only in the follicular phase, and preovulatory follicles (>2.0 mm) appeared only at the end of the follicular phase (Days 7-9). The Day 2 FSH peak corresponded to emergence of a population of medium-size antral follicles, and the Day 6 peak was consistent with rising estradiol levels and appearance of the preovulatory follicles. These results suggest that some aspects of marmoset folliculogenesis are comparable to those in Old World primates, including the absence of multiple follicular waves and the appearance of an identifiable dominant follicle in the midfollicular phase. However, the midphase FSH peak, multiple dominant follicles, and abundance of nonovulatory antral follicles differ strongly from the pattern in Old World primates and humans. The findings are discussed in relation to the regulation of growth of multiple ovulatory follicles and provide the basis for further studies on factors influencing the dynamics of follicular growth and development in this species.     

New strategy for in vitro activation of primordial follicles with mTOR and PI3K stimulators

It had been known for decades that primordial follicles in mammalian ovaries are assembled with definite numbers and represent the ovarian reserve throughout the reproductive life. Intra-oocyte PI3K/mTOR pathways have been indicated to play a central role on the activation of primordial follicles. Genetic modified mouse models with chronic activation of PI3K/mTOR signals in primordial oocytes showed premature activation of all primordial follicles and eventually their exhaustion. On the other hand, this may suggest that, unlike chronic activation of PI3K/mTOR, its acute activation in infertility would activate primordial follicles, permitting fertility during the treatment. Previously, PI3K stimulators were reported as a temporary measure to accelerate primordial follicle activation and follicular development in both mouse and human, and were applied in the treatment of infertility in premature ovarian failure (POF) patients. To address whether mTOR stimulators could play similar role in the process, we transiently treated neonatal and aged mouse ovaries with mTOR stimulators-phosphatidic acid (PA) and propranolol. Our results demonstrated the stimulators increased activation of primordial follicles and the production of progeny. Human ovarian cortex cubes were also treated with mTOR or/and PI3K stimulators in vitro. When they were used separately, both of them showed similar promotive effects on primordial follicles. Surprisingly, after joint-treatment with the 2 kinds of stimulators together, synergistic effects on follicular development were observed. Based on increased efficiency of follicular activation in humans, here we propose in vitro transient treatment with mTOR and PI3K stimulators as an optimized protocol for the application in different clinical conditions with limited follicle reserve.     

Early primary--rather than primordial follicles constitute the main follicular reserve in the African elephant (Loxodonta africana)

Information on the ovarian follicle reserve in the African elephant (Loxodonta africana) is lacking. This study set out to determine the ratios of early preantral follicles and their relative dimensions in the ovaries of 16 African elephant aged 10-34 years. The ovaries were sectioned histologically. Follicles were counted and classified according to expansion of the pre-granulosa cells. Early primary follicles were the most common (75.8%±11.8%), followed by true primary follicles (23.8%±11.8%), whereas primordial follicles were the most rare (<2%). Measurements made on at least 100 early preantral follicles from each animal (n=1464) indicate that growth in oocyte and nuclear diameters started with transition to the true primary stage P<0.01. This, together with the observed ratios between the three types of early preantral follicles suggest that both classical primordial and early primary follicles contribute to the ovarian reserve in the African elephant.     

Smad 3 may regulate follicular growth in the mouse ovary

Although Smad 3 is known to serve as a signaling intermediate for the transforming growth factor beta (TGFbeta) family in nonreproductive tissues, its role in the ovary is unknown. Thus, we used a recently generated Smad 3-deficient (Smad 3-/-) mouse model to test the hypothesis that Smad 3 alters female fertility and regulates the growth of ovarian follicles from the primordial stage to the antral stage. In addition, we tested whether Smad 3 affects the levels of proteins that control apoptosis, survival, and proliferation in the ovarian follicle. To test this hypothesis, breeding studies were conducted using Smad 3-/- and wild-type mice. In addition, ovaries were collected from Smad 3-/- and wild-type mice on Postnatal Days 2-90. One ovary from each animal was used to estimate the total number of primordial, primary, and antral follicles. The other ovary was used for immunohistochemical analysis of selected members of the B-cell lymphoma/leukemia-2 family of protooncogenes (Bax, Bcl-2, Bcl-x), proliferating cell nuclear antigen (PCNA), and cyclin-dependent kinase 2 (Cdk-2). The results indicate that Smad 3-/- mice have reduced fertility compared with wild type mice. The results also indicate that Smad 3 may not affect the size of the primordial follicle pool at birth, but it may regulate growth of primordial follicles to the antral stage. Further, the results indicate that Smad 3 may regulate the expression of Bax and Bcl-2, but not Bcl-x, Cdk-2, and PCNA. Collectively, these data suggest that Smad 3 may play an important role in the regulation of ovarian follicle growth and female fertility.     

Ovarian follicles during infancy in Romanov and Ile-de-France ewe lambs

The ovaries of new born lambs (15 Ile-de-France and 19 Romanov, 34 ovaries) and of 4-week-old lambs (6 Ile-de-France and 12 Romanov, 18 ovaries) were examined histologically to compare ovarian follicular development in infant lambs of breeds differing in their prolificacy. Breed was the major factor affecting follicular population at birth. Ile-de-France lambs had a higher total number of growing follicles (P less than 0.001), and more preantral (P less than 0.001) and antral (P less than 0.005) follicles than did Romanov lambs. Furthermore, the size of the largest follicles was also reduced in Romanov compared to Ile-de-France lambs. At 4 weeks of age, most of the features of the ovarian follicular population except the mean size of the third largest follicle were similar between the two breeds. However, atresia of antral follicles had appeared only in Ile-de-France and not in Romanov lambs. When a challenge with exogenous gonadotrophins (1000 i.u. PMSG followed by 1500 i.u. hCG) was attempted, ovulation was triggered in 2/6 and 0/12 Ile-de-France and Romanov lambs respectively. Massive follicular development was noted in 3/6 Ile-de-France lambs but in none of 12 Romanov lambs. Retardation of follicular development together with retardation in the establishment of ovarian sensitivity to gonadotrophins are therefore features typical of the ovaries of Romanov lambs compared to Ile-de-France lambs during the post-natal period.     

Mouse oocytes derived from fetal germ cells are competent to support the development of embryos by in vitro fertilization

Mouse oocyte development in vitro has been studied in the past several years, but no evidence showed that the fertilizable oocytes could be obtained from the fetal mouse germ cells before the formation of the primordial follicles. In this study, an efficient and simple method has been established to obtain the mature oocytes from the fetal mouse germ cells at 16.5 days post-coitum (dpc). For the initial of follicular formation, fetal mouse 16.5 dpc ovaries were transplanted to the recipient under the kidney capsule, and the ovaries were recovered after 14 days. Subsequently, the growing preantral follicles in the ovarian grafts were isolated and cultured in vitro for 12 days. Practically, the mature oocytes ovulated from the antral follicles were able to be fertilized in vitro and support the embryonic development. The results demonstrate that the fetal mouse 16.5 dpc germ cells are able to form primordial follicles with the ovarian pregranulosa cells during the period of transplantation in the ectopic site, and the oocytes within the growing follicles are able to mature in vitro, then are able to support the embryonic development.     

Xenobiotic effects on ovarian preantral follicles

Women are born with a finite population of ovarian follicles, which are slowly depleted during their reproductive years until reproductive failure (menopause) occurs. The rate of loss of primordial follicles is determined by genetic and environmental influences, but certain toxic exposures can accelerate this process. Ionizing radiation reduces preantral follicle numbers in rodents and humans in a dose-dependent manner. Cigarette smoking is linked to menopause occurring 1-4 yr earlier than with nonsmokers, and components of smoke, polycyclic aromatic hydrocarbons, can cause follicle depletion in rodents or in ovaries in vitro. Chemotherapeutic agents, such as alkylating drugs and cisplatin, also cause loss of preantral ovarian follicles. Effects depend on dose, type, and reactivity of the drug, and the age of the individual. Evidence suggests DNA damage may underlie follicle loss induced by one common alkylating drug, cyclophosphamide. Occupational exposures have also been linked to ovarian damage. In an industrial setting, 2-bromopropane caused infertility in men and women, and it can induce ovarian follicle depletion in rats. Solvents, such as butadiene, 4-vinylcyclohexene, and their diepoxides, can also cause specific preantral follicle depletion. The mechanism(s) underlying effects of the latter compound may involve alterations in apoptosis, survival factors such as KIT/Kit Ligand, and/or the cellular signaling that maintains primordial follicle dormancy. Estrogenic endocrine disruptors may alter follicle formation/development and impair fertility or normal development of offspring. Thus, specific exposures are known or suspected of detrimentally impacting preantral ovarian follicles, leading to early ovarian failure.     

Ovarian follicular and luteal dynamics in wapiti during the estrous cycle

The reproductive tracts of 13 mature hinds were examined daily by transrectal ultrasonography and blood samples were taken daily from October to January to characterize follicular, luteal, and endocrine dynamics in wapiti during the estrous season. Follicle development occurred in waves characterized by regular, synchronous development of a group of follicles in temporal succession to a surge in serum FSH concentration. The mean interovulatory interval was 21.3 +/- 0.1 d, but was shorter in hinds exhibiting two follicular waves than in hinds exhibiting three and four waves (P < 0.05). The interwave interval was similar among waves in two-wave cycles and the first wave of three-wave cycles. All other interwave intervals in three- and four-wave cycles were shorter (P < 0.05). The maximum diameter of the dominant follicle of the first wave was similar among two-, three-, and four-wave cycles. For all other waves in three- and four-wave cycles, the maximum diameter was smaller (P < 0.05). Corpus luteum diameter and plasma progesterone concentrations were similar between two- and three-wave cycles, but the luteal phase was longer (P < 0.05) in four-wave cycles. The dominant follicle emerged at a diameter of 4 mm at 0.4 +/- 0.1 and 0.8 +/- 0.1 d before the largest and second largest subordinate follicles, respectively. The follicle destined to become dominant was larger (P < 0.05) than the largest subordinate follicle one day after emergence, which coincided with the first significant decrease in serum FSH concentration. We concluded that the estrous cycle in wapiti is characterized by two, three, or four waves of follicular development (each preceded by a surge in circulating FSH), that there is a positive relationship between the number of waves and the duration of the cycle, and an inverse relationship between the number of waves and the magnitude of follicular dominance (diameter and duration of the dominant follicle).     

Influences of prenatal and postnatal fraternity size on ovarian development in the mouse

An experiment was conducted to test effects of prenatal and postnatal fraternity size (size of litter in which an individual develops prenatally or is reared postnatally) on ovarian development in mice. Fraternity size treatments were created by standardizing sizes of prenatal and postnatal fraternities in which mice were gestated and reared. Prenatal fraternity size was standardized by surgery on Day 9 of gestation to 6, 10, and 14 fetuses. Postnatal fraternity size was standardized by randomly assigning pups to litters of 5, 10, or 15 pups within 24 h of birth. Female pups were killed at either 3 or 20 wk of age and right ovaries were prepared for histology. Follicles were classified by size and morphology, and numbers of follicles in each class were tabulated. Interaction of postnatal fraternity size and age was observed for number of antral follicles (p less than 0.05). Mice reared in small postnatal fraternities had more antral follicles at weaning (3 wk) and fewer antral follicles at maturity (20 wk of age) than mice reared in large postnatal fraternities. No effect of either prenatal or postnatal fraternity size on other follicle populations was observed (p greater than 0.20). Numbers of Type 2 (primordial), Type 3a, and Type 3b follicles changed with age (p less than 0.01); numbers of primordial follicles declined with age, but numbers of Type 3a and 3b follicles increased. A hypothesis of a negative association between postnatal fraternity size and number of antral follicles at 3 wk of age was supported, but a hypothesis of a positive association between fraternity size and number of primordial follicles was not supported.     

Origin of the preovulatory follicle in Mouflon sheep (Ovis gmelini musimon) and effect on growth of remaining follicles during the follicular phase of oestrous cycle

Daily transrectal ultrasonographies were conducted to study development of all follicles with antral diameters > or = 2mm during the follicular phase of oestrous cycle in Mouflon, a strictly monovular wild-sheep. A total of 14 follicular phases was studied after oestrus synchronization with two cloprostenol doses, 9 days apart, in five cyclic Mouflon ewes. In 13 cycles (92.8%), the ovulatory follicle arose from those antral follicles present in both ovaries when luteolysis was induced, being the largest one with a mean size of 4.4+/- 0.3mm at that moment in 10 cycles (76.9%). The remaining cycles had a larger follicle, but it was decreasing in size. Appearance of new follicles > or =2mm in size remained unaffected during the follicular phase (3.7+/- 0.2), but there was found a linear decrease in the number of those growing to > or =3mm (2.5+/- 0.4 to 1.1+/- 0.2, P < 0.05) and > or = 4mm (0.6+/- 0.2 to 0.1+/- 0.1, P < 0.005), detection of new follicles growing to > or = 5mm was negligible. Then, number of medium (4-5mm) growing follicles present in both ovaries decreased from 1.5+/- 0.3 at 0 h to 0.3+/- 0.1 at 72 h (P<0.005). In conclusion, the single ovulatory follicle is the largest growing follicle present in both ovaries at the moment of luteolysis. This follicle is selected to grow and ovulate while development of other follicles is inhibited.     

Growth and development of the ovary and small follicle pool from mid fetal life to pre-puberty in the African elephant (Loxodonta africana)

ABSTRACT: BACKGROUND: Follicle numbers and developing ovarian morphology, particularly with reference to the presence of interstitial tissue, are intimately linked within the ovary of the African elephant during the period spanning mid-gestation to puberty. These have not been previously quantified in any studies. The collection of 7 sets of elephant fetal ovaries between 11.2 and 20.2 months of gestation, and 29 pairs of prepubertal calf ovaries between 2 months and 9 years of age during routine management off-takes of complete family groups in private conservancies in Zimbabwe provided an opportunity for a detailed study of this period. RESULTS: The changing morphology of the ovary is described as the presumptive cortex and medulla components of the fetal ovary settled into their adult form. Interstitial tissue dominated the ovary in late fetal life and these cells stained strongly for 3beta-hydroxysteroid dehydrogenase. This staining continued postnatally through to 4.5 years of age suggesting continued secretion of progestagens by the ovary during this period. The considerable growth of antral follicles peaked at 28% of ovarian volume at around 16.7 months of fetal age. The numbers of small follicles (primordial, early primary and true primary), counted in the cortex using stereological protocols, revealed fewer small follicles in the ovaries of animals aged 0 to 4.5 years of age than during either late fetal life or prepubertal life. CONCLUSIONS: The small follicle populations of the late-fetal and prepubertal ovaries of the African elephant were described along with the changing morphology of these organs. The changes noted represent a series of events that have been recorded only in the elephant and the giraffe species to date. The expansion of the interstitial tissue of the fetal ovary and its continued presence in early post natal life may well contribute to the control of follicle development in these early years. Further research is required to determine the reasons behind the variation of numbers of small follicles in the ovaries of prepubertal calves.     

Maturation of mouse primordial follicles by combination of grafting and in vitro culture

Cryopreservation of ovarian cortical tissue and subsequent transplantation or in vitro culture of follicles are technologies under development with the aim to safeguard fertility in patients with gonadal failure. In the present study, we investigated whether primordial follicles could be triggered to full maturation by a combination of in vivo transplantation and in vitro culture in a mouse model. In a first step, newborn mouse ovaries containing only primordial follicles were allotransplanted under the renal capsule of ovariectomized recipient mice. The second step was to mechanically isolate growing preantral follicles from the graft and culture these in vitro to maturity. In our experiment, one newborn mouse ovary was transplanted under the renal capsule of each 8- to 12-wk-old F1 (C57Bl/6j x CBA/Ca) female ovariectomized recipient (n = 26). Two weeks after transplantation, all 26 grafts were recovered. Four grafts were processed for histology and showed that developmental stages of follicles in 14-day-old ovarian grafts were comparable to those in 14-day-old mouse ovaries. The 22 remaining grafts were used for mechanical isolation of preantral follicles. As a control group, preantral follicles isolated from ovaries of 14-day-old mice were used. The mean preantral follicle yield per ovary was 11 in the transplant group versus 33 in the control group. Follicles were cultured individually in 20-microliter droplets of alpha-MEM supplemented with 100 mIU rFSH and 5% fetal bovine serum for 12 days under an atmosphere of 5% CO(2) in air at 37 degrees C. By Day 12 of culture, 66.5% of follicles retained their oocytes in the grafting group versus 97.5% in the control group (P < 0.001). Final oocyte maturation was induced by addition of 2.5 IU/ml hCG. At 14-16 h post-HCG, the percentages of oocytes showing germinal vesicle breakdown and polar body extrusion were significantly higher in the control group (90.6% and 82.8%) compared to the grafting group (60% and 45%). The mean diameter of the mature oocytes of the grafting group (69.9 +/- 4.45 micrometer) was similar to that of oocytes from the control group (70.5 +/- 2.35 micrometer). Our results suggest that maturation of mouse primordial follicles is feasible by combination of in vivo transplantation and in vitro culture. This two-step strategy may be an attractive model for promoting the growth and maturation of primordial follicles from other species.