Elimination of apoptotic granulosa cells by intact granulosa cells and macrophages in atretic mature follicles of the guinea pig ovary

Phagocytic cells disposing of dying granulosa cells in the atretic ovarian follicles were morphologically studied in guinea pig ovaries at various stages of estrous cycle. Epon embedded semithin sections stained with toluidine blue were observed with a light microscope, and ultrathin sections were examined under a transmission electron microscope. Frozen sections were processed for acid phosphatase histochemistry and MR-1 (a monoclonal antibody against guinea pig macrophages) immunohistochemistry. In animals during the estrus period (days 1 and 2) as well as the second half of the estrous cycle (days 11 and 16), there were numerous mature follicles in which massive groups of granulosa cells were undergoing apoptosis. Two kinds of phagocytic cells were identified in these follicles of the initial stage of atresia: one was intact granulosa cells ingesting neighboring dead granulosa cells, and the other was large round cells identified as macrophages due to their strong acid phosphatase activity and MR-1 immunoreactivity. Mature follicles of the advanced stage of atresia were frequently recognized during the metestrus period (days 4 and 5). Small stellate cells were regarded as surviving granulosa cells, while large round cells showing intense reactions for acid phosphatase and MR-1 were identified as macrophages. This study demonstrates that both intact granulosa cells and macrophages participate in the elimination of apoptotic granulosa cells in atretic mature follicles of the guinea pig ovary, and remain even in the advanced stages of atresia.

Predicting optimal cervical mucus for infertility diagnosis

OBJECTIVE

We studied the relationship between cervical mucus evaluations and daily fertility examinations in order to find monitoring techniques that can predict optimal mucus one day before it occurs.

METHODS

Twenty-three healthy young female volunteers were followed during one spontaneous cycle with serial measurements of serum estradiol, progesterone, LH and FSH, urinary LH, and transvaginal ultrasound measurements of endometrial thickness and follicles. Data were related to cervical mucus scores.

RESULTS

All cycles were ovulatory with optimal mucus, but in 14 optimal mucus was present for only one day. Echographic measurement of the leading follicle (mean diameter > or = 18 mm) could predict the day of optimal mucus in 78% and estradiol (> 700 pmol/l) in 83% of the cases. These two measurements combined predicted optimal mucus in 100% of the investigated women one day in advance.

CONCLUSION

Optimal cervical mucus parameters can be predicted one day in advance by serial measurements of serum estradiol and follicular diameters.

The polycystic ovarian (PCO) condition: apoptosis and epithelialization of the ovarian antral follicles are aspects of cystogenesis in the dehydroepiandrosterone (DHEA)-treated rat model

This investigation was designed to study apoptosis and epithelialization during cystogenesis of the dehydroepiandrosterone rat model. Using in situ DNA 3'- end-labeling with non-radioactive digoxigenindidesoxy-UTP (dig-ddUTP), apoptosis is initially seen in cumulus granulosa cells and other granulosa cells facing the antrum. During cystogenesis, apoptosis systematically progresses from the cumulus towards the mural granulosa layer. In contrast, granulosa cells of atretic follicles undergo apoptosis in a random manner. The outer layer of mural granulosa cells during cystogenesis escapes apoptosis. Granulosa cells contain vimentin. However, the outer mural granulosa cell layer that lines the cyst acquires keratin. In addition to being associated with each other via gap junctions, the outer layer of granulosa cells acquire tight junctions. With the characterization of the transformation of the outer mural granulosa cells into a characteristic epithelium and the orderly progression of apoptosis, we further the understanding of the multifaceted process of cystogenesis of the ovarian antral follicle.

Ultrastructural localization of intracellular calcium stores in Xenopus ovarian follicles as revealed by cytochemistry and X-ray microanalysis

The ultrastructural localization of calcium in full-grown ovarian follicles of Xenopus laevis was demonstrated after fixation in the presence of fluoride ions and by means of energy dispersive X-ray microanalysis. In hormonally untreated follicles (prophase I-arrested oocytes), two calcium sites were detected: follicle cells and oocyte pigment granules. In follicle cells, calcium containing deposits were preferentially associated with macrovilli, which ended by gap junctions. In human chorionic gonadotropin treated follicles (meiotically reinitiated oocytes), deposits were only seen in follicle cells. This is the first report of the cytochemical detection of intracellular Ca2+ in follicle cells of amphibians. The possible involvements of these Ca2+ stores in mediating the hormonal control of meiotic maturation are discussed.

Oocyte ultrastructure in bovine primordial to early tertiary follicles

The aim of the present study was to describe in detail the changes occurring in the cytoplasmic ultrastructure of the bovine oocyte from the onset of growth in the primordial follicle until the completion of growth in the tertiary follicle. Bovine oocytes from primordial, primary, secondary and early to mid-antral follicles were processed and analysed by light and transmission electron microscopy. The primordial follicular oocyte was characterized by numerous coated pits on the oolemma and the accumulation of free and organelle-related smooth (SER) and rough (RER) endoplasmic reticulum, round mitochondria and Golgi complexes around the nucleus, which was located slightly off centre. Up to the secondary follicular stage the oocyte displayed an increase in the number of microvilli, elongated mitochondria and Golgi complexes. During the secondary follicular stage, formation of the zona pellucida, development of gap junctions between the oocyte and the granulosa cells, formation of the cortical granules in the oocyte and reduction in the number of coated pits on the oolemma were seen. In the tertiary follicular oocyte up to 100 microm in diameter, the number of Golgi complexes and lipid droplets increased and the organelles were dislocated to the deep cortical region. During the final growth of the oocyte up to >120 microm, the organelles were dislocated further to the peripheral region, the extent of the free SER and RER compartments were reduced, the number of individual cortical granules increased, hooded mitochondria became abundant and the perivitelline space developed. In conclusion, the growth of the bovine oocyte is associated with the relocation and modulation of a number of cytoplasmic organelles as well as the development of oocyte specific structures such as the zona pellucida and cortical granules.

Isolation and characterization of primordial follicles from fresh and cryopreserved human ovarian tissue

OBJECTIVE

To develop an efficient isolation technique for human primordial follicles.

DESIGN

Prospective, experimental study of ovarian biopsies collected from healthy women undergoing elective cesarean section. Ovarian blocks either were fixed for histology and follicle counting or partially disaggregated with type 1A collagenase before or after cryopreservation. After partial disaggregation, follicles were isolated by microdissection.

SETTING

Leeds General Infirmary.

MAIN OUTCOME MEASURE(S)

Follicle viability was assessed with live-dead stains using 5-(and 6-) carboxyfluorescein diacetate, succinimidyl ester and propidium iodide, respectively, and using electron microscopy. The numbers recovered were expressed as a percentage of the numbers of primordial follicles in comparable blocks of tissue and the viability of the whole follicle and oocyte were scored separately.

RESULT(S)

On average, 18.0 +/- 3.8 and 15.9 +/- 2.2 (mean +/- SEM) follicles per block were recovered from fresh and cryopreserved ovarian tissue, respectively, corresponding to recovery rates of 57.9% +/- 8.8% and 56.2% +/- 16.7%. In the fresh group, the percent viability of whole follicles and oocytes were 71.6% +/- 2.4% and 91.3% +/- 2% compared with 71.5% +/- 4.7% and 95% +/- 4.3% in the frozen-thawed group. Electron microscopy confirmed that the majority of the cells lacked ultrastructural signs of damage after isolation and cryopreservation.

CONCLUSION(S)

Primordial follicles can be isolated from fresh and cryopreserved human ovarian tissue with similar high efficiency and viability rates.

Female infertility in mice lacking connexin 37

The signals regulating ovarian follicle development and the mechanisms by which they are communicated are largely undefined. At birth, the ovary contains primordial follicles consisting of meiotically arrested oocytes surrounded by a single layer of supporting (granulosa) cells. Periodically, subsets of primordial follicles undergo further development during which the oocyte increases in size and the granulosa cells proliferate, stratify and develop a fluid-filled antrum. After ovulation, oocytes resume meiosis and granulosa cells retained in the follicle differentiate into steroidogenic cells, forming the corpus luteum. It has been proposed that intercellular signalling through gap junction channels may influence aspects of follicular development. Gap junctions are aggregations of intercellular channels composed of connexins, a family of at least 13 related proteins that directly connect adjacent cells allowing the diffusional movement of ions, metabolites, and other potential signalling molecules. Here we show that connexin 37 is present in gap junctions between oocyte and granulosa cells and that connexin 37-deficient mice lack mature (Graafian) follicles, fail to ovulate and develop numerous inappropriate corpora lutea. In addition, oocyte development arrests before meiotic competence is achieved. Thus, cell-cell signalling through intercellular channels critically regulates the highly coordinated set of cellular interactions required for successful oogenesis and ovulation.

Ovarian dysfunction in mice following chromium (VI) exposure

Chromium (VI) was given through drinking water in two sets of adult Swiss albino female mice in three doses; 250 ppm, 500 ppm and 750 ppm for 20 days in set 1 and 0.05 ppm, 0.5 ppm and 5.0 ppm in set II for 90 days. At the termination of the treatment, the animals of both the sets were euthanized for histopathology, follicle counting, counting of the superovulated ova, duration of estrus cycle and for ultrastructural studies. Ovaries of the highest dose group (750 ppm) showed large numbers of atretic follicles and congestion in stromal tissue compared to the rest of the treated groups. Also, there was a dose-dependent reduction in the number of follicles at different stages of their maturation. The number of ova recovered from superovulated chromium (VI)-treated animals showed significant decreases in the 500 and 750 ppm dosed groups compared to lower dosed (250 ppm) and control groups. The duration of estrus cycle increased in highest dosed (750 ppm) group. A dose-dependent increase in blood chromium level was also seen in treated mice. Ultrastructural observations revealed disintegrated cell membranes of two layered follicular cells and altered villiform mitochondria in thecal cells of 5 ppm dosed group. From the study it was concluded that ovarian physiology and rate of ovulation might be altered if females are exposed to sufficiently high chromium through oral route.

A morphological and functional study of the effect of slow freezing followed by complete in-vitro maturation of primary mouse ovarian follicles

Mechanically isolated intact early preantral follicles (100-130 microns diameter) from 14 day old mice were cryopreserved by a slow freezing protocol with dimethyl sulphoxide and then matured in vitro for 12 days after rapid thawing. Minor freeze damage observed after 1 day of in-vitro culture included ablation of the theca cell layer and granulosa cell dehydration, resulting in disruption of intercellular contacts with the oocyte and between granulosa cells. Of the follicles, 24% were irreversibly damaged and had a collapsed oocyte. The remaining majority of the follicles had an intact oocyte as evaluated by ultrastructural analysis. Follicles with an intact oocyte were cultured in vitro and, after an initial retarded development, the final number of fully grown oocytes ovulated in vitro was not different from that of unfrozen controls. Cryopreserved early preantral follicles matured in vitro responded to stimulus with human chorionic gonadotrophin in a similar way to controls, with mucification of the oocyte-cumulus complex, germinal vesicle breakdown and extrusion of the first polar body of the oocyte. These cryopreserved, in-vitro matured oocytes had the potential to fertilize and develop to hatched blastocysts.

Morphological characterization of bovine primordial follicles and their environment in vivo

Classically, primordial follicles have flattened pre-granulosa cells that become cuboidal and divide during follicular activation. This change in shape is thus an index of activation. To examine this and follicular morphology in cattle, ovaries were processed for light and electron microscopy (n = 21). In single sections (5 microns thick), primordial follicles had a mean ratio of maximum to minimum diameters of 1.33 +/- 0.18 (mean +/- SD; n = 317, randomly selected), indicating that they had a prolate rather than a spherical shape. The prolate shape was attributable to clustering of granulosa cells at two opposite poles on the long axis of each follicle; and in each histological section, 82.5% of primordial follicles (n = 317) had at least one cuboidal granulosa cell. More accurate measurements of primordial follicles indicated that they had three dimensions measured as length (45.4 +/- 2.4 microns), breadth (26.8 +/- 1.5 microns), and depth (< 30.4 +/- 1.4 microns) (mean +/- SEM; n = 12, constructed from serial sections); a surface area of 0.0032 mm2; and 24 +/- 2 granulosa cells. The ultrastructural morphology of the cells of the bovine primordial follicle (n = 31 examined by electron microscopy) was similar to that of other species. The ovarian cortex was composed of discrete zones. The zones containing primordial follicles were substantially avascular, as observed by localizing von Willebrand factor, and rich in collagen fibrils. In conclusion, since primordial follicles of bovine ovaries contain some cuboidal pre-granulosa cells, changes in shape cannot be used with certainty as a marker of activation of bovine follicles.

The extracellular matrices and vascularization of the developing corpus luteum in rats

The extracellular matrices and vascularization of the developing corpus luteum of adult female rats were studied with immunohistochemistry for laminin, type I, III and IV collagen and with electron microscopy. Ovaries were removed from Wistar-Imamichi rats that had a regular 4-day estrous cycle, 6 and 2 h before ovulation, immediately after ovulation, 6, 16 and 24 h after ovulation and at maturity of the corpus luteum and examined. The basement membrane of the follicles and capillaries of the theca interna started to break down around the entire circumference of the Graafian follicle 2 h before ovulation. More than 6 h after ovulation, dot-pattern positive reactions for type IV collagen and laminin were detected in the granulosa layer, and thin basement membrane structures appeared in association with the luteinizing granulosa cells. More than 16 h after ovulation, vascularization with the formation of capillary basement membrane was observed in the granulosa layer, and luteal mesenchymal cells with adjacent interstitial collagen components always appeared in close association with the newly formed capillaries. Our chronological observations revealed that both luteinizing cells and luteal mesenchymal cells are involved in the destruction and reconstruction of the follicular ECM, and that the luteal mesenchymal cells play an essential role in the neovascularization of the developing corpus luteum.

Clinical parameters influencing human zona pellucida thickness

OBJECTIVES

To assess which clinical parameters influence human oocyte zona pellucida (ZP) thickness.

PATIENTS

Sixty-five couples undergoing 75 IVF-ET cycles.

MAIN OUTCOME MEASURE

Zona pellucida thickness of 827 oocytes measured 16 to 20 hours after in vitro insemination under inverted light microscope.

RESULTS

Zona pellucida thickness was 18.9 +/- 3.8 microns (mean +/- SD) for unfertilized, 16.4 +/- 3.1 microns for fertilized, and 15.1 +/- 2.4 microns for polyspermic oocytes (significantly different). Among our patients, a few underwent two (or even three) IVF-ET cycles, and the mean ZP thickness was, in most cases, not significantly different from one cycle to the other(s). Regression analyses were calculated between ZP thickness and available clinical parameters, i.e., the age of the women, the duration of stimulation, the cumulus maturity, the number of retrieved oocytes, the number of hMG doses, the maximum E2 level, and the follicular volume. A significant linear decreasing relationship exists between the mean ZP thickness of each patient and the maximum E2 level and an increasing one with the hMG dose. Relationships with the other parameters appeared to be nonsignificant.

CONCLUSION

The ZP thickness is basically an individual feature that influences the fertilization rate. Nevertheless, it may be influenced slightly by the hormonal treatment during stimulation.

Pattern of vitellogenesis and follicle maturational competence during the ovarian follicular cycle of Fundulus heteroclitus

The patterns of vitellogenesis and follicle maturational competence were examined across the semilunar spawning cycle of Fundulus heteroclitus. Daily egg collection showed spawning cyclicity in six experimental groups, with a mean period between spawnings of 14.9 +/- 0.3 days, indicated by the nonlinear regression sine-curve matching analysis. Each cycle was then dated from Day -7 to Day 7, with Day 0 as the peak egg-collection day. Females from each group were sampled on selected days during two to three consecutive spawning cycles, and these days were each chronologically given a temporal relation to Day 0 to pool the data into a composite. The analysis of the size-frequency distribution of ovarian follicles > or = 0.5-mm diameter across the composite revealed a constant recruitment of small follicles (0.5- to 0.7-mm diameter) into vitellogenesis, which was supported by the continuous presence of vitellogenin (Vtg) I mRNA in the liver of the females. The plasma levels of Vtg were also essentially constant across the cycle, except for a progressive decrease from Day -7 through Day 3 that could be related to a more active Vtg uptake by a dominant population of follicles up to 1.7 mm in diameter. A second and more selective recruitment of full-grown follicles (1.3- to 1.4-mm diameter) toward maturation was noted at Days -5, -4, which appeared associated with high plasma levels of estradiol-17 beta. However, the responsiveness of those follicles undergoing oocyte maturation in vitro after gonadotropin and maturation-inducing steroid (MIS), 17, 20 beta-dihydroxy-4-pregnen-3-one, stimulation dramatically declined from Days -1, 0, 1 to Days 4, 5, concomitantly with an increase of the population of the largest follicles (1.8- to 2.1-mm diameter) in the ovary. These findings extend previous observations on the process of follicular recruitment in F. heteroclitus and indicate that full-grown follicles may be recruited into maturation by a mechanism that modulates the oocyte sensitivity to the MIS.

Follicular atresia as an apoptotic process: atresia-associated increase in the ovarian expression of the putative apoptotic marker sulfated glycoprotein-2

OBJECTIVE

To evaluate the possibility that morphologically confirmed/hypophysectomy-induced ovarian follicular atresia, a putative apoptotic process, is coupled to alterations in the steady-state levels of ovarian sulfated glycoprotein-2 (SGP-2) transcripts.

METHODS

Hypophysectomy-induced follicular atresia in immature rats, morphologically confirmed at the light and electron microscopic levels, was correlated with alterations in the steady-state levels of ovarian SGP-2 transcripts as assessed by a solution hybridization/RNase protection assay. Cellular localization was accomplished by in situ hybridization technology.

RESULTS

Hypophysectomy of the 24-day-old immature rat, an established precipitant of follicular atresia, led (3 days later) to a significant (P < .05) increase (up to 3.3-fold) in the relative abundance of densitometrically quantified ovarian SGP-2 transcripts compared with age-matched intact controls. Detailed time-course analysis after hypophysectomy revealed significantly (P < .05) increased ovarian SGP-2 mRNA expression as early as 2 days after hypophysectomy; no further increments were noted on days 4 or 8. Light microscopic analysis of comparable ovarian material 4 days after hypophysectomy revealed increased numbers of atretic follicles displaying large numbers of degenerating granulosa cells. Electron microscopic analysis of the degenerating cells of atretic follicles (from hypophysectomized rats) disclosed nuclear condensation and cytoplasmic shrinkage as well as apoptotic bodies at all levels of the granulosa cell layer. In situ hybridization established the granulosa cell of the intact untreated rat as the somatic cell concerned with SGP-2 gene expression. In turn, hypophysectomy led to an increase in SGP-2 expression at the level of the theca-interstitial cell, an effect prevented by the concurrent provision of pregnant mare serum gonadotropin (PMSG). The hypophysectomy-induced increase in ovarian SGP-2 transcripts was similarly reversed (54% inhibition by day 27) by the concomitant provision of FSH, an established antiatretic principle. The delayed administration (day 26) of a single dose of PMSG to rats hypophysectomized on day 24 eliminated the hypophysectomy-induced increase in ovarian SGP-2 transcripts as assessed on day 28. Qualitatively similar but quantitatively more pronounced increments in ovarian SGP-2 gene expression were obtained when atresia was induced by hypophysectomy of PMSG-primed immature rats.

CONCLUSIONS

These observations establish the immature rat ovary as a site of SGP-2 gene expression and reveal hypophysectomy-induced follicular atresia to result in the up-regulation of ovarian (specifically, theca-interstitial) SGP-2 gene expression, an effect prevented by the concurrent provision of FSH or PMSG. To the extent that SGP-2 is an acceptable apoptotic marker, the present findings support the hypothesis that ovarian follicular atresia may be an apoptotic process.

Microtubular dynamics in granulosa cells of periovulatory follicles and granulosa-derived (large) lutein cells of sheep: relationships to the steroidogenic folliculo-luteal shift and functional luteolysis

Indirect immunofluorescence light microscopy was used to monitor temporal perturbations in the microtubular (tubulin) system of granulosa/lutein cells in paraffin-embedded sections of periovulatory follicles and corpora lutea of sheep. Estrogen-active granulosa cells of preovulatory follicles not yet exposed to the gonadotropin surge immunostained intensely for tubulin. Immunostaining of the microtubular matrix diminished after the onset of the surge and coincident with an abrupt fall in follicular estradiol production. A transient period of microtubular retraction was characterized by low-level steroid hormone output. Microtubules reappeared with the approach of ovulation and increase in follicular progesterone biosynthesis (luteinization). Treatment of animals during the preovulatory period with colchicine, a drug that binds specifically with tubulin and interferes with microtubular assembly, obstructed the follicular shift toward progesterone. Microtubular dynamics (polymerization<->depolymerization) evidently underpin fundamental mechanisms of follicular steroidogenesis. Finally, corpora lutea were isolated from ewes on Day 10 of the estrous cycle before (0 h) and after administration of prostaglandin (PG) F2 alpha. There was a small augmentation in luteal concentrations of progesterone at 2 h, followed by a sharp decrease from 4 to 16 h. Luteal weights were reduced (structural regression) at 24 h. Sections of large (PG-sensitive) steroidogenic cells of control corpora lutea typically displayed a radiating microtubular network. After administration of PGF2 alpha, tubular matrices of large cells were scant; mitochondrial clustering was evident in transmission electron micrographs. Affixed disassembly of the cytoskeleton of large luteal cells may be a heretofore unrecognized event in the biomechanics of functional luteolysis--perhaps uncoupling cholesterol translocation to mitochondrial cytochrome P450 side-chain cleavage.

Immunolocalization of tissue inhibitor of metalloproteinases-1 within ovine periovulatory follicular and luteal tissues

In previous studies, tissue inhibitor of metalloproteinases (TIMP)-1 mRNA increased in follicular tissue after the preovulatory gonadotropin surge and was expressed in luteal tissue. However, the localization of TIMP-1 protein within ovine periovulatory follicular and luteal tissues is unknown. The objectives of the present study were to 1) localize TIMP-1 within follicles collected before and after a preovulatory gonadotropin surge and within Day 3 and Day 10 corpora lutea (CL), 2) determine whether TIMP-1 was colocalized to Day 10 luteal cells with oxytocin or TIMP-2, and 3) determine whether TIMP-1 was present within secretory granules of large luteal cells. Ovaries were removed from ewes before (presurge; n = 4) or 12-14 h after (postsurge; n = 5) an LHRH-induced gonadotropin surge (36 h following PGF2 alpha-induced luteolysis; objective 1). Additionally, ovaries containing CL were collected on Days 3 (n = 5; objective 1) and 10 (n = 4, 3, and 2 for objectives 1, 2, and 3, respectively). TIMP-1 immunoreactivity was observed within the granulosa cells of postsurge but not presurge follicles. On Days 3 and 10, TIMP-1 was localized within luteal tissue in a cell-specific manner. On Day 10, many of the cells that were immunopositive for TIMP-1 were judged to be large luteal cells on the basis of morphology (diameter > 22 microns; round nucleus) and colocalization with oxytocin and TIMP-2. Electron microscopy demonstrated that TIMP-1 was localized to secretory granules undergoing exocytosis from Day 10 large luteal cells. These data indicate that TIMP-1 is produced by granulosa cells following a gonadotropin surge and is packaged in secretory granules by large steroidogenic cells of the ovine CL.

Immunohistochemical analysis of the microanatomy of primate ovary

The ovary is a complex organ composed of cells of diverse lineages. Therefore, in this study we examined whether immunolocalization of various cytoskeletal, epithelial, immune-cell, and neural-associated proteins can differentiate various cells in the baboon and human ovaries. Surface epithelial cells exhibited immunoreactivity for cytokeratin and desmin, however, they did not immunostain for other epithelial markers such as carcinoembryonic antigen or epithelial membrane antigen. Smooth muscle actin was distributed apically whereas vimentin was localized basally in these cells. Ova exhibited strong immunoreactivity for S-100, Leu-M1, and neurofilament and did not show immunoreactivity for epithelial and cytoskeletal proteins. In antral follicles and theca cells, and after formation of corpus luteum, both granulosa and theca cells expressed immunoreactivity for vimentin. Cytokeratins were absent in the preantral and antral follicles. However, atresia and development of apoptosis was associated with expression of immunoreactive cytokeratins in atretic follicles. Development of corpus luteum led to major changes in the immunophenotype of follicular cells. The mere presence of immunoreactivity for cytokeratin and a strong immunoreactivity for desmin in the luteinized granulosa and not in the theca cells allowed discrimination of these cells from each other and from their ancestral cells. Proliferating cell nuclear antigen was present in various ovarian cells except for ovum. The distinct patterns of expression of cytoskeletal, epithelial, and neural-associated proteins in various cells of the ovary facilitates their identification and discrimination.

Analysis of atresia in bovine follicles using different methods: flow cytometry, enzyme-linked immunosorbent assay, and classic histology

This study was performed in order to validate flow cytometry as an acceptable method for analyzing follicular atresia in bovine granulosa cells by comparing it to two other techniques, histology and ELISA. Ovaries from 35 nontreated cows, all at different times of their estrous cycle, and 12 superovulated cows were collected. Superovulation treatments began between Days 9 and 12 (Day 0 = estrous), and animals were administered 8 doses of FSH-P (32 or 20 mg) at 12-h intervals over 4 days with or without the addition of 1 mg of prostaglandin s.c. on the third day. Animals were slaughtered after the last FSH-P injection. Granulosa cells from 133 follicles from non-treated cows and 85 follicles from superovulated cows were analyzed. Follicular diameters ranged from 2 to 20 and 2 to 16 mm, respectively. Because of the ample amounts of cells collected, it was possible to perform more than one technique for each follicle. Flow cytometry detected in most follicles a subpopulation of cells that possessed less DNA than normal, viable cells (referred to as -G1 cells). Histological classes used (established in previous work) were nonatretic (< or = 5% picnotic nuclei), slightly atretic (> 5 to < 15% picnotic nuclei), and atretic (> or = 15% picnotic nuclei). A strong linear correlation existed between the percentage of picnotic nuclei and the percentage of -G1 cells (R = 0.86; p < 0.001) with granulosa cells from follicles from nontreated cows. In some cases, flow cytometry detected a certain percentage of cells with reduced DNA content while histology revealed very few picnotic nuclei, indicating a higher sensitivity of flow cytometry. Superovulation decreased considerably the percentage of atretic cells seen with both techniques. The linear correlation was not as strong because follicles from superovulated animals represent a very homogenous population (R = 0.54; p < 0.001). The ELISA technique coincided with flow cytometry as seen in the strong correlation between the two techniques (R = 0.91; p < 0.001). Flow cytometry appeared to be very effective and rapid in evaluating the atretic states of follicles from nontreated and superovulated cows. Strong correlations existed between this method and histology and ELISA.

Ultrastructure of bovine ovarian follicles induced to extended growth by perioestrous suprabasal progesterone levels

The present study was undertaken to determine if a short-term prolonged growth of the ovulatory follicle (12 to 18 h after expected time of ovulation), induced by progesterone implants, would cause ultrastructural changes in the follicular wall. Oestrous behaviour, follicular growth, follicular and blood plasma levels of oestradiol-17 beta, progesterone and plasma luteinizing hormone (LH) were monitored in heifers oophorectomized at 9 to 12 h (controls) or 36 h after the onset of oestrus, in order to sample the pre-ovulatory follicle present. The suprabasal plasma progesterone concentrations (approximately 1.2 nmol L-1) allowed expression of oestrus at the expected time, but ovulation was delayed owing to the absence of a LH-surge. The resulting prolongation of follicle growth was associated with mild degenerative changes in the follicle wall, i.e. both granulosa and thecal cells presented increased electron density, higher amounts of secondary lysosomes and lipid droplets, increased intercellular spaces with presence of debris. No signs of luteinization were seen.

Simple or repeated induction of superovulation: a study on ovulation rates and microvessel corrosion casts in ovaries of golden hamsters

Repeatedly stimulated ovaries are reported to decrease the ovulation rate. One cause among others might be that the microvascular bed has been insufficiently developed. Therefore, 30-day-old golden hamsters were superovulated either once or repeatedly. At the light microscopic level, the ovulation rate in serially sectioned ovaries was indirectly determined by the occurrence of corpora lutea and of abnormal follicle rupture with oocyte release into the cortical stroma (IOR). For the study with scanning electron microscopy (SEM), the microvascular bed of the ovaries was cast with a polyester resin, and the corrosion casts of mature follicles observed. The histological sections of once-stimulated ovaries showed a large number of corpora lutea and IOR follicles. This indicated hyperovulation. In corrosion casts of once-stimulated ovaries, large-sized antral follicles with two layers of a dense capillary meshwork were observed. Capillary sprouts were aligned around the antrum 0 to 12 h after administration of human chorionic gonadotrophin (hCG), and these radiated towards the center of the antrum after 12 to 36 h had elapsed. The ovulation site was recognized at the follicle apex by three similarly sized structures which were either a sinusoid, an oocyte replica, or an opening. Repeatedly stimulated ovaries produced a low number of corpora lutea and almost no IOR follicles. This was judged as hypoovulation. The microvessels of mature follicles were reduced in number and incompletely cast. Widespread resin leakages were conspicuous in the follicle wall 36 h after hCG injection, but the capillary sprouts radiated towards the center of the antrum. No ovulation site was detectable. It is concluded, that capillary sprouts are induced before luteinization. The ovulation site is indicated by particular changes in its microvascular bed. An insufficiently developed microvascular bed may be responsible for hypoovulation in repeatedly stimulated ovaries.

Ultrastructural changes in ovarian follicles of monkeys administered hexachlorobenzene

OBJECTIVE

To test hexachlorobenzene (HCB), an environmental pollutant, for its potential toxicity to the ovary.

DESIGN

Nonhuman primates were orally administered the pollutant at doses between 0.01 and 10 mg of HCB/kg of body weight to test viability of ovarian follicles. At the end of dosing period, the monkeys received a compound that contained follicle-stimulating and luteinizing hormones to stimulate development of follicles that would be examined by electron microscopy.

ANIMALS

Twenty, 6- to 13-year-old cynomolgus monkeys were randomly assigned to 5 groups.

PROCEDURE

The HCB, in concentrations of 0.01, 0.1, 1.0, and 10.0 mg/kg, was orally administered with glucose in gelatin capsules for 13 weeks. Monkeys receiving capsules containing glucose only served as controls. After the 13th week, monkeys were given a compound that contained follicle-stimulating and luteinizing hormones daily during days 2 to 7 from the start of menses. On day 8 of the menstrual cycle, 5,000 IU of human chorionic gonadotropin was administered, and 35 to 38 hours later, 1 ovary from each monkey was obtained during laparotomy. Approximately 1-mm cubes of tissue from each ovary were harvested, fixed by immersion in buffered 2% glutaraldehyde, and processed for transmission electron microscopy.

RESULTS

Ultrastructure of ovarian follicles was altered in the monkeys administered HCB. Lesions were observed in the follicles from monkeys given the lowest concentrations of HCB, and comprised condensed mitochondria in the developing ova and follicular cells that contained nuclei with deep indentations and abnormal accumulation of cytoplasmic lipid droplets. Alterations, such as herniation of the ooplasm, degeneration of the follicular cells, and appearance of abnormal spaces between follicular cells were observed in the follicles from monkeys of the 0.1 to 1.0 mg of HCB/kg dosage groups. The most relevant alterations were seen in the mitochondrion, an organelle that appeared to be most sensitive to the compound. Mitochondria were condensed, with abnormal intracristal spaces in the lower-dosage groups, and were markedly degenerated in the 10 mg/kg group. The effect of HCB were dose-related.

CONCLUSION

The HCB is a reproductive system toxicant, and its damaging effects may be a result of augmentation of lipid peroxidation, especially in the primary follicle, which abnormally affects cellular membranes and thus, impairs their permeability.

FSH receptor gene expression during ovarian follicle development in sheep

A key question in elucidating the role of FSH in ovarian function is to determine when during follicular growth the FSH receptor first appears. The aim of this study was to examine the site and time of FSH receptor gene expression during early follicular growth. This study was carried out on ovaries of adult sheep during the luteal and prostaglandin-induced follicular phase of the oestrous cycle and also on ovaries of fetal sheep at 90, 100, 120 and 135 days of gestation (term = day 147). Using reverse transcription-PCR and a set of PCR primers spanning exons 8/9/10, two partial FSH receptor cDNAs (500 and 310 bp) were isolated from adult sheep ovary. It was shown by sequencing that exon 8 was deleted in the 310 bp cDNA, implying that this was part of an alternatively spliced FSH receptor transcript. Using RNA in situ hybridisation on ovaries of adult sheep, FSH receptor mRNA was observed in granulosa cells of early preantral follicles with one to two cell layers and it was seen that gene expression continued throughout folliculogenesis into advanced stages of atresia. Moreover, in the fetus, FSH receptor gene expression was detected in follicles with two or more layers of granulosa cells in ovaries taken at 100, 120 and 135 days of gestation. These results suggest that the FSH receptor gene is expressed after the granulosa cells of a follicle have begun to divide but not during the earliest stages of follicle growth, namely the transformation of a primordial follicle to a primary follicle.

Folliculocentesis: a novel research technique to investigate the intrafollicular endocrine microenvironment

During development of the dominant follicle, the avascular granulosa cells and oocyte are exposed to the follicular fluid endocrine microenvironment. An alteration in the endocrine characteristics of follicular fluid affects follicular steroidogenesis, oocyte maturation, ovulation and subsequent corpus luteum function. In-vitro studies on pooled follicular fluid from ovarian specimens lacked temporal precision between menstrual and follicular endocrine events. We have established a new technique, termed folliculocentesis (FC), to sample follicular fluid from the dominant ovarian follicle without compromising its growth or function during the mid- to late follicular phase. A total of 38 subjects with regular ovulatory cycles each underwent two identical cycles of hormone and follicle growth monitoring: one cycle served as the control, and FC was performed during the second cycle. During all cycles, plasma luteinizing hormone (LH), oestradiol and ultrasound monitoring of follicle growth were commenced on day 7 and continued until after ovulation. During FC cycles, 200 microliters of follicular fluid were aspirated from the dominant follicle using transvaginal ultrasound guidance when the follicle diameter reached > or = 10 mm. Six subjects were excluded from the study because of incomplete or invalid endocrine data. In all, 32 subjects completed both the FC and control cycles. The follicle growth pattern, maximum follicle diameter, plasma oestradiol, oestradiol peak, plasma LH, LH surge and follicular phase length were similar during FC and control cycles. A total of 50 valid follicular fluid samples were obtained when the dominant follicle was sampled once, twice or three times during the same cycle and from the same follicle in 15, 16 and one subjects respectively. The follicular fluid samples contained steroid concentrations consistent with those of the mid- to late follicular phase. We conclude that the FC procedure is safe, easy to perform and does not affect follicle growth or hormone dynamics. Analysis of the follicular fluid samples is expected to provide us with valuable in-vivo information about ovarian endocrinology.

Atretic changes of follicular wall caused by destruction of the germinal disc region of an immature preovulatory follicle in the chicken: an electron microscope study

The germinal disc of the female gamete and its overlying follicular wall (the germinal disc region) is hypothesized to play an important role in the regulation of follicular growth. The role of the germinal disc region in follicular growth in chickens was investigated by destroying the germinal disc region or an area opposite the germinal disc (control) of the second largest follicle 22-23 h before ovulation of the F1 follicle, by localized freezing with solid CO2. Structural changes of the follicular wall (non-frozen region) were observed by electron microscopy 10-20 h after the destruction of the germinal disc region. Development of the inner structure of mitochondria in granulosa cells and accumulation of lipid droplets in thecal cells were observed in follicles 15 h after destruction of the germinal disc region. Twenty hours after destruction of the germinal disc region, follicles showed early signs of atresia (bursting atresia). Degenerative changes in follicles, including hydrolysis by lysosomal enzymes, were present in thecal fibroblast-like cells. Control follicles, in which an area opposite the germinal disc region was frozen 20 h before examination, had no degenerative features. These results provide further evidence that the germinal disc region is required for follicular growth.