Possible involvement of CD81 in acrosome reaction of sperm in mice

Tetraspanin CD81 is closely homologous in amino acid sequence with CD9. CD9 is well known to be involved in sperm-egg fusion, and CD81 has also been reported to be involved in membrane fusion events. However, the function of CD81 as well as that of CD9 in membrane fusion remains unclear. Here, we report that disruption of the mouse CD81 gene led to a reduction in the fecundity of female mice, and CD81-/- eggs had impaired ability to fuse with sperm. Furthermore, we demonstrated that when CD81-/- eggs were incubated with sperm, some of the sperm that penetrated into the perivitelline space of CD81-/- eggs had not yet undergone the acrosome reaction, indicating that the impaired fusibility of CD81-/- eggs may be in part caused by failure of the acrosome reaction of sperm. In addition, we showed that CD81 was highly expressed in granulosa cells, somatic cells that surround oocytes. Our observations suggest that there is an interaction between sperm and CD81 on somatic cells surrounding eggs before the direct interaction of sperm and eggs. Our results may provide new clues for clarifying the cellular mechanism of the acrosome reaction, which is required for sperm-egg fusion.

Allorecognition in urochordates: identification of a highly variable complement receptor-like protein expressed in follicle cells of Ciona

The evolutionary origin of allorecognition in vertebrates is unknown. Urochordates, being the closest living relatives of vertebrates [Delsuc F, Brinkmann H, Chourrout D, Philippe H]. Tunicates and not cephalochordates are the closest living relatives of vertebrates. Nature 2006; 439: 965-8], have efficient mechanisms to prevent both allogeneic fusion and self fertilization. To shed light on allorecognition in urochordates and on the molecules involved in preventing self fertilization, we compared gonadal cDNAs of three genetically unrelated Ciona intestinalis individuals by suppression subtractive hybridisation (SSH). Here, we report the discovery and characterization of a highly polymorphic gene coding for a transmembrane protein with several short consensus repeat domains (SCR/CCP). The protein, termed variable complement receptor-like 1 (vCRL1), is structurally similar to vertebrate complement receptors. However, in contrast to vertebrate complement receptors, vCRL1 shows an unprecedented high degree of amino acid variations among Ciona individuals and is expressed in follicle cells as well as in hemocytes. Based on our data we propose that in the absence of MHC Ciona uses variable components of the complement system as individuality markers.

Immunolocalization of the hepatocyte growth factor (HGF) system in the rat ovary and the anti-apoptotic effect of HGF in rat ovarian granulosa cells in vitro

Hepatocyte growth factor (HGF) regulates granulosa cell (GC) steroidogenesis and suppresses apoptosis in non-ovarian cells. The hypothesis was thus developed that intraovarian HGF supports folliculogenesis by mediating steroidogenesis and suppressing apoptosis. To investigate the latter, the anti-apoptotic actions of HGF were tested in GCs and follicles isolated from immature rats. Results showed that HGF suppressed apoptosis in GC and follicle cultures as visualized using apoptosis indicator dye, YO-PRO-1. Immunohistochemistry was used to investigate the distribution of HGF, c-met, and HGF activator (HGFA) protein during folliculogenesis in equine chorionic gonadotropin (eCG)-primed rats. Immunoreactive HGF content was the greatest in GCs within preantral follicles. Following eCG, large antral follicles showed elevated HGF staining in theca and interstitial cells when compared with GCs. Intense c-met staining was observed in GCs within non-primed small preantral follicles; following eCG, the level of c-met was diminished in GCs, but increased within theca and interstitial cells. Theca, interstitium, and GCs in non-primed and primed ovaries contained HGFA. Following eCG, HGFA was more apparent in theca cells and the interstitium when compared to that in GCs within large antral follicles. The presence of HGF, c-met, and HGFA in preantral follicles would potentially enable the anti-apoptotic effects of HGF that were observed in vitro to occur in vivo. Advanced folliculogenesis led to a change in the cellular distribution of the HGF, c-met, and HGFA, suggesting that the ovarian HGF system is hormonally regulated in vivo.

Microscopic characterization of follicular structures in letrozole-induced polycystic ovarian syndrome in the rat

BACKGROUND

Our objective was to characterize the tissular distribution of relevant cytoskeletal proteins, cellular adhesion molecules and proliferation markers and conduct a histomorphometrical study of the follicular wall of letrozole-induced polycystic ovaries.

METHODS

Twenty rats were divided into two groups: a control group (C) of ten rats that received vehicle only (0.9% NaCl solution) once daily p.o. and a treatment group (T) of ten animals administered letrozole at a concentration of 1 mg/kg p.o. dissolved in 0.9% NaCl solution once daily during 21 days. Twenty four h after the last administration, all animals were sacrificed. Control animals were sacrificed in proestrous (n = 5) and diestrous (n = 5). Serum hormone levels, histomorphometrical changes and immunoexpression of intermediate filaments (vimentin, cytokeratins and desmin), cadherins and proliferation cellular nuclear antigen were examined.

RESULTS

The granulosa cell layer of cystic follicles had a greater significant immunostaining for vimentin and cytokeratins. Immunohistochemical localization of desmin was restricted to the theca externa. Positive immunoreactivity for cadherins rises gradually and significantly, together with the follicular development, and immunoreactivity was comparatively stronger in follicular cysts. A significantly higher immunostaining for PCNA cells was observed in secondary and tertiary follicles as compared with atretic and cystic follicles. An increase in the LH, FSH and testosterone serum concentrations was observed in letrozole-treated rats. Estradiol and progesterone showed a considerable reduction.

CONCLUSIONS

The changes observed are probably due to structural and functional alterations that occur during the process of cystogenesis and may be associated with important modifications in the expression of cytoskeletal proteins, cellular adhesion molecules and proliferation markers that may be essential for proper cellular functioning.

Confocal laser scanning microscopy of whole mouse ovaries: excellent morphology, apoptosis detection, and spectroscopy

BACKGROUND

Ovaries consist of numerous follicles, oocytes, and granulosa cells in different stages of development. Many of these follicles will undergo an apoptotic process during the lifetime of the animal. By using proper tissue preparation methods, the events within the whole ovary can be observed by using 3D confocal microscopy.

METHODS

Whole ovaries were stained with LysoTracker Red (LT), fixed with 4% paraformaldehyde (PF) and 1% glutaraldehyde (Glut), dehydrated with methanol (MEOH), and cleared with benzyl alcohol and benzyl benzoate (BABB). Using this tissue preparation technique, the ovary becomes relatively transparent, allowing its morphology to be observed with confocal microscopes. A spectral imaging system (PARISS) located on a conventional microscope was used to interpret the LT dye spectra and fixation products in the tissues with different excitation wavelengths.

RESULTS

Apoptosis in the follicle was detected as clusters of intensely stained granulosa cells located in close proximity to the oocytes. The fixation with Glut and PF preserved morphological details, increased tissue fluorescence, thus increased the signal to noise of the background image.

CONCLUSIONS

Thick tissues can be imaged after they are properly stained, aldehyde fixed, and BABB cleared. LT intensely stained single cells or clusters of apoptotic cells in the follicles and the nucleolus. Spectral differences between LT as an indicator of apoptosis and Glut-PF fixation was used to visualize ovarian morphology and apoptosis. The PARISS spectrophotometer revealed spectral peaks for LT at 609.6 nm and for Glut-PF at 471.3 nm. The proper use of the spectra from these fluorescence molecules is the foundation for high quality morphological images of apoptosis. By sequentially imaging the two probes with a 488 nm laser and a 543/568 nm laser, there was a reduction in fluorescent cross talk and an increase in image quality.

Characterization and expression of different pituitary adenylate cyclase-activating polypeptide/vasoactive intestinal polypeptide receptors in rat ovarian follicles

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a bioactive peptide transiently expressed in preovulatory follicles. PACAP acts by interacting with three types of PACAP receptors. PACAP type I receptor (PAC(1)-R), which binds specifically to both PACAPs and vasoactive intestinal polypeptide (VIP), although with lower affinity, and two VIP receptors, VPAC(1)-R and VPAC(2)-R, which bind to PACAP and VIP with equal affinity. In the present study, we showed the expression of all three receptors in whole ovaries obtained from juvenile and gonadotropin-treated immature rats. A more detailed analysis on cells from preovulatory follicles showed that PAC(1)-R and VPAC(2)-R were expressed in granulosa cells, whereas only VIP receptors were expressed in theca/interstitial (TI) cells and fully grown oocytes presented only PAC(1)-R. The distribution of the VIP receptors was confirmed by immunofluorescence. HCG treatment induced stimulation of PAC(1)-R in granulosa cells and VPAC(2)-R in TI cells. The presence of functional PACAP/VIP receptors was also supported by metabolic studies. We further evaluated the presence of PACAP and VIP receptors by testing the effect of these peptides on apoptosis in granulosa cells cultured, isolated or in whole follicles. Treatment of follicles with PACAP and VIP dose-dependently inhibited apoptosis, while only PACAP significantly inhibited isolated granulosa cells. These results demonstrate a different expression of PACAP/VIP receptors in the various follicle compartments and suggest a possible role for PACAP and VIP on granulosa and TI cells, both during follicle development and ovulation.

Mechanisms of programmed cell death during oogenesis in Drosophila virilis

We describe the features of programmed cell death occurring in the egg chambers of Drosophila virilis during mid-oogenesis and late oogenesis. During mid-oogenesis, the spontaneously degenerating egg chambers exhibit typical characteristics of apoptotic cell death. As revealed by propidium iodide, rhodamine-conjugated phalloidin staining, and the TUNEL assay, respectively, the nurse cells contain condensed chromatin, altered actin cytoskeleton, and fragmented DNA. In vitro caspase activity assays and immunostaining procedures demonstrate that the atretic egg chambers possess high levels of caspase activity. Features of autophagic cell death are also observed during D. virilis mid-oogenesis, as shown by monodansylcadaverine staining, together with an ultrastructural examination by transmission electron microscopy. During the late stages of oogenesis in D. virilis, once again, the two mechanisms, viz., nurse cell cluster apoptosis and autophagy, operate together, manifesting features of cell death similar to those detailed above. Moreover, an altered form of cytochrome c seems to be released from the mitochondria in the nurse cells proximal to the oocyte. We propose that apoptosis and autophagy function synergistically during oogenesis in D. virilis in order to achieve a more efficient elimination of the degenerated nurse cells and abnormal egg chambers.

Serum anti-Müllerian hormone expression in women with premature ovarian failure

BACKGROUND

Premature ovarian failure (POF) is generally irreversible. However, developing follicles up to the antral stage are reported in POF and anti-Müllerian hormone (AMH) might be a good indicator of follicular presence. This study analysed serum AMH, ovarian histology and AMH immunoexpression in POF patients.

METHODS

A cross-sectional study of 48 POF patients in an Endocrinology Department setting. Patients had an ovarian biopsy simultaneously with serum AMH sampling and/or ovarian AMH immunostaining.

RESULTS

Mean serum AMH was 1.04 +/- 1.66 ng/ml. Serum AMH was significantly higher in women with 15 or more follicles at ovarian histology (P = 0.001). Comparison of ovarian AMH immunostaining from POF patients and 10 normal controls revealed a normal AMH expression in POF pre-antral follicles, but a decreased expression at the early antral stages. Serum AMH was undetectable in 77% of the patients with 0-5 AMH immunopositive follicles and detectable in 100% of the patients with more than 15 AMH immunopositive follicles.

CONCLUSIONS

AMH levels in POF patients could identify women with persistent follicles. The decrease of AMH immunoexpression in POF antral follicles could suggest a defect of antral development.

Human chorionic gonadotropin-dependent up-regulation of genes responsible for estrogen sulfoconjugation and export in granulosa cells of luteinizing preovulatory follicles

Estrogen sulfotransferase (EST) is responsible for the sulfoconjugation of estrogens, thereby changing their physical properties and preventing their action via the estrogen receptors. These sulfoconjugated steroids no longer diffuse freely across the lipid bilayer; instead, they are exported by members of the ATP-binding cassette family, such as ABCC1. The objective of this study was to investigate the regulation of EST and ABCC1 during human chorionic gonadotropin (hCG)-induced ovulation/luteinization. The transcripts for EST and ABCC1 were cloned by RT-PCR, and the regulation of their mRNAs was studied in preovulatory follicles obtained during estrus at 0, 12, 24, 30, 33, 36, and 39 h after hCG. Results obtained from RT-PCR/Southern blot analyses showed significant changes in steady-state levels of both EST and ABCC1 mRNA after hCG treatment (P < 0.05). In granulosa cells, a significant increase in EST transcript was observed 30-39 h after hCG. Similarly, ABCC1 transcript levels were induced in granulosa cells 12-39 h after hCG. In contrast, no significant changes in either EST or ABCC1 were detected in theca interna samples after hCG. The increase in EST and ABCC1 transcripts observed in granulosa cells was reflected in preparations of intact follicle walls, suggesting that the granulosa cell layer contributes the majority of EST and ABCC1 expression in preovulatory follicles. The present study demonstrates that follicular luteinization is accompanied not only by a decrease in 17 beta-estradiol biosynthesis but also by an increase in expression of genes responsible for estrogen inactivation and elimination from granulosa cells, such as EST and ABCC1, respectively.

Naturally suppressed apoptosis prevents follicular atresia and oocyte reserve decline in the adult ovary of Lagostomus maximus (Rodentia, Caviomorpha)

It has been widely accepted that mammalian females are born with a non-renewing, finite pool of oocytes that will be continuously cleared by atresia, with only a small proportion of them reaching ovulation. Apoptosis regulates this mass germ cell death, especially through the balance between pro- and anti-apoptotic proteins encoded by the BCL-2 gene family. The caviomorph rodent Lagostomus maximus, the South American plains viscacha, displays the highest ovulation rate known for a mammal releasing 400–800 eggs per cycle. We tested the hypothesis that in L. maximus massive polyovulation is a consequence of reduced apoptosis resulting in suppressed follicular atresia. We found that anti-apoptotic BCL-2 gene is markedly expressed in all kind of follicles from primordial to fully mature antral stages in the adult ovary of L. maximus. On the other hand, pro-apoptotic BAX gene showed weak signals or was undetectable by immunohistochemical examination. Western blot against both proteins confirmed immunohistochemical results. Screening for DNA fragmentation by TUNEL assay was conspicuously negative in ovaries from both pregnant and non-pregnant females. In addition, α-oestrogen receptor also showed an enhanced expression from primordial stage to fully mature antral follicles. Our results show that natural preferential expression of BCL-2 and restricted BAX expression greatly suppresses apoptosis in the ovary of L. maximus. This prevents the decline of the oocyte reserve by abolishing follicular atresia and enables the highest ovulation rate known for a mammal, 400–800 or more eggs per cycle.

Molecular Evidence That Growth of Dominant Follicles Involves a Reduction in Follicle-Stimulating Hormone Dependence and an Increase in Luteinizing Hormone Dependence in Cattle1

The bovine dominant follicle (DF) model was used to identify molecular mechanisms potentially involved in initial growth of DF during the low FSH milieu of ovarian follicular waves. Follicular fluid and RNA from granulosa and theca cells were harvested from 10 individual DF obtained between 2 and 5.5 days after emergence of the first follicular wave of the estrous cycle. Follicular fluid was subjected to RIA to determine estradiol (E) and progesterone (P) concentrations and RNA to cDNA microarray analysis and (or) quantitative real-time PCR. Results showed that DF growth was associated with a decrease in intrafollicular E:P ratio and in mRNA for the FSH receptor, estrogen receptor 2 (ER beta), inhibin alpha, activin A receptor type I, and a proliferation (cyclin D2) and two proapoptotic factors (apoptosis regulatory protein Siva, Fas [TNFRSF6]-associated via death domain) in granulosa cells. In contrast, mRNAs for the LH receptor in granulosa cells and for two antiapoptotic factors (TGFB1-induced antiapoptotic factor 1, LAG1 longevity assurance homolog 4 [Saccharomyces cerevisiae]) and one proapoptotic factor (tumor necrosis factor [ligand] superfamily, member 8) were increased in theca cells. We conclude that the bovine DF provides a unique model to identify novel genes potentially involved in survival and apoptosis of follicular cells and, importantly, to determine the FSH-, estradiol-, and LH-target genes regulating its growth and function. Results provide new molecular evidence for the hypothesis that DF experience a reduction in FSH dependence but acquire increased LH dependence as they grow during the low FSH milieu of follicular waves.

Tyrosine kinase B receptor and its activated neurotrophins in ovaries from human fetuses and adults

The signals initiating the growth of primordial follicles are unknown. Growth factors such as neurotrophin 4/5 (NT-4/5) and brain-derived neurotrophic factor (BDNF) may play a role in this process. To investigate the expression of NT-4/5 and BDNF and their receptor tyrosine kinase B (TrkB) in the early developing follicles, we fixed and froze 12 ovarian samples from adolescents/adults and 31 ovaries from human fetuses. The fixed samples were prepared for immunohistochemical staining for NT-4/5, BDNF and the TrkB receptor. Total RNA was extracted from the frozen ovarian samples, and the expression of NT-4/5, BDNF and the TrkB receptor (full length and two truncated isoforms) was investigated by RT-PCR. Products were resolved by 1% agarose gel electrophoresis and image analysis. Immunohistochemical staining revealed the expression of NT-4/5 and BDNF mainly in oocytes and, in a minority of samples, also in the granulosa cells (GCs); TrkB receptor was identified in oocytes and GCs. Transcripts of NT-4/5, BDNF and all forms of TrkB receptor were identified in the samples. To elucidate whether indeed NT-4/5 and BDNF are involved in growth initiation of human primordial follicles, they should be added to the culture medium.

Immunocytochemical evidence for the presence and location of the neurotrophin-Trk receptor family in adult human preovulatory ovarian follicles

OBJECTIVE

This study was undertaken to evaluate the presence or absence of neurotrophins and their respective receptors within adult human preovulatory follicles.

STUDY DESIGN

Prospective study of neurotrophins and their receptors in follicular cells and unfertilized oocytes from women undergoing aspiration for in vitro fertilization/intracytoplasmic sperm injection. Cells (mural and cumulus granulosa cells, unfertilized oocytes) were examined for immunocytochemical staining of neurotrophin and receptor proteins.

RESULTS

Mural and cumulus granulosa cells were positive for BDNF, NT-4/5, NT-3, and NGF, as well as for Trk B, Trk C, and Trk A receptors. Unfertilized oocytes were positive for Trk B, Trk C, and Trk A receptors.

CONCLUSION

Neurotrophins and their respective receptor proteins are present within the mural and cumulus granulosa cells of adult human preovulatory follicles. Neurotrophin receptors are present in human unfertilized oocytes. The location of the neurotrophins and their receptors suggest both an autocrine and paracrine function within the adult human ovarian follicle.

Role of nitric oxide in ovarian follicular development and egg production in Japanese quail (Coturnix coturnix japonica)

Role of nitric oxide (NO) in regulating the reproductive functions at hypothalamo-hypophysealovarian axis in Japanese quail was studied. In first experiment, metabolites of NO, i.e. nitrite and nitrate (NO2 and NO3) were estimated together in hypothalamus, serum and ovarian follicles of good and poor layers. In the second experiment, different NO modulators such as L-arginine (L-Arg), sodium nitroprusside (SNP) and N(G)-nitro-L-arginine methyl ester, HCl (L-NAME) were administered to the birds. In the first experiment, significantly higher (P < 0.01) NO2 and NO3 levels in serum, hypothalamus and largest (F1) ovarian follicles were observed in good layers as compared to poor layers. Higher (P < 0.05) NO2 and NO3 concentration was observed in F1 follicles than smaller follicles (F2) only in good layers. The NO2 and NO3 concentration was significantly reduced (P < 0.05) in post ovulatory follicles (POFs) in comparison to F1 and F2 follicles. In the second experiment, the serum NO2 and NO3 concentrations were higher (P < 0.05) in the SNP, lower (P < 0.05) in the L-Name group and unchanged in the L-Arg treated group in comparison to control group. compared to control, L-Arg and SNP increased (P < 0.05) the hypothalamic NO2 and NO3 concentration where as L-NAME reduced (P < 0.05) these levels. The NO2 and NO3 concentration was increased (P < 0.05) as the follicle size increased and it was significantly reduced (P < 0.05) in POFs. The higher (P < 0.05) follicular NO2 and NO3 concentration was observed in L-Arg group in comparison to control group. Egg production was also found to be higher (P < 0.05) in L-Arg group whereas it was not different (P > 0.05) in SNP and L-NAME treated groups. The yolk weight and yolk to albumin ratio was reduced (P < 0.05) in L-NAME group in comparison to control group. It may be concluded from the present study that NO plays a key role in regulating follicular development, ovulatory mechanisms and egg production in Japanese quail.

In vitro effect of vitellogenin on steroid production by ovarian follicles of greenback flounder Rhombosolea tapirina

Ovarian follicles from vitellogenic greenback flounder (Rhombosolea tapirina) were incubated in L15 medium alone, or containing human chorionic gonadotropin (hCG), dibutyryl cyclic AMP (dbcAMP) or the steroid precursors testosterone (T), 17-hydroxyprogesterone (17P) and androstenedione (A) in the presence of vitellogenin (Vtg) at 0.1-5.0mg mL(-)(1). Medium concentrations of 17beta-estradiol (E(2)) and T were measured by radioimmunoassay. HCG generally stimulated follicular E(2) but not T production, whereas 17P, A and T stimulated production of E(2), T, and E(2) respectively. Treatment of follicles with dbcAMP inhibited follicular E(2) production, but increased follicular T production at high doses. The effect of low concentrations of Vtg on follicular steroid production was variable; however, higher doses of Vtg significantly suppressed basal, hCG-, dbcAMP- and steroid precursor-stimulated follicular E(2) and T production. The results of this study show that high concentrations of Vtg may suppress follicular steroid production by interfering in the steroidogenic pathway. This suggests that Vtg may regulate its own production by limiting the ovarian production of E(2).

Expression of phospholipase A2 group IVA (PLA2G4A) is upregulated by human chorionic gonadotropin in bovine granulosa cells of ovulatory follicles

Prostaglandins are required for the ovulatory process, and their biosynthesis depends on the initial release of arachidonic acid from membrane phospholipids. We hypothesized that phospholipase A2 group IVA (PLA2G4A) expression is upregulated in granulosa cells (GC) at ovulation. We have characterized bovine PLA2G4A cDNA, and investigated its spatiotemporal regulation at the mRNA and protein levels in hCG-induced ovulatory follicles and in vitro, using forskolin-stimulated GC. Regulation of PLA2G4A mRNA expression was studied in GC obtained from bovine follicles collected at different developmental stages: small follicles (2-4 mm), dominant follicles at Day 5 (D5) of the estrous cycle, ovulatory follicles 24 h following injection of hCG, and corpus luteum at D5. PLA2G4A mRNA increased by 14-fold in GC of hCG-stimulated versus dominant follicles (P < 0.0001). Follicular walls obtained from ovulatory follicles recovered at 0, 6, 12, 18, and 24 h post-hCG injection showed an initial 16-fold increase in PLA2G4A transcript at 12 h that reached a 45-fold increase at 24 h, as compared to 0 h (P < 0.0001). Immunoblots of GC extracts showed an initial induction of the PLA2G4A protein at 18 h post-hCG, reaching a maximum at 24 h. Immunohistochemistry observations showed that PLA2G4A signal was mainly observed in mural GC compared to antral GC in hCG-stimulated follicles. Stimulation of cultured bovine GC with 10 microM of forskolin caused an increase in PLA2G4A mRNA and protein. Ovulation is associated with an LH/hCG-dependent induction of PLA2G4A in GC via the adenylyl cyclase/cAMP pathway.

Transient expression of SOX9 protein during follicular development in the adult mouse ovary

SOX9 is an essential activating transcription factor that plays a critical role in Sertoli cell differentiation and subsequent testis cord formation. Cytoplasmic SOX9 is present in both sexes during early gonadal embryogenesis. While in males the protein is later translocated into the nucleus of pre-Sertoli cells, its expression is rapidly turned off in females. In mammalian male gonads, SOX9 activates the expression of anti-Müllerian hormone (AMH), a male hormone that initiates Müllerian ducts regression and that is also expressed in postnatal ovarian follicles. Here, we confirm that the SOX9 protein is not present in the immature ovary but also show that SOX9 is transiently expressed in the mature ovary depending on the follicular cycle. Indeed, SOX9 protein was found in the nuclear compartment of the inner cells of the theca interna cell layer which surrounds the pre-antral/antral follicles. In contrast, no expression was detected in the AMH expressing granulosa cells. While these findings exclude the possibility that SOX9 regulates AMH expression in the ovary, they show that SOX9 could nevertheless play a role in the developing follicle.

Identification of a novel C2 domain factor in ovaries of orange-spotted grouper (Epinephelus coioides)

Follicle consists of an oocyte and a lot of surrounding follicular cells, and significant interactions exist between the oocyte and the somatic cells. In this study, a novel cDNA has been screened from a subtractive cDNA library between tail bud embryos and blastula embryos in the protogynous hermaphrodite orange-spotted grouper (Epinephelus coioides). Its full-length cDNA is 821 bp, and has an ORF of 414 bp for encoding a peptide of 137 aa, which shows 38%, 37%, 33%, and 33% homology with 4 putative proteins screened from zebrafish (Danio rerio). Conserved domain search in NCBI reveals a single C2 domain existing in the C2 domain superfamily proteins, and has only 7 beta strands in comparison with 8 beta strands of C2 domains in other C2 domain superfamily proteins. Artificial sex reversal, RT-PCR analysis and Western blot detection demonstrated ovary-specific expression of the C2 domain factor, and therefore the novel gene was designated as E. coioides ovary-specific C2 domain factor, EcOC2 factor. Moreover, predominant expression of EcOC2 factor was further revealed in grouper mature ovary, and its strong immunofluorescence signals were located between granulosa cells and oocyte zona radiata in grouper mature follicles. The data indicate that the novel EcOC2 factor might be a main component that associates between granulosa cells and the oocyte during oocyte maturation, and might play significant roles in regulating oocyte maturation and ovulation. Further studies on its developmental behaviour and physiological functions will elucidate the interactions between oocyte and the surrounding somatic cells and the underlying molecular mechanisms.

Expression pattern of glycoconjugates in the Bidderian and ovarian follicles of the Brazilian toad Bufo ictericus analyzed by lectin histochemistry

The Bidder's organ and ovary of the Brazilian toad Bufo ictericus were studied by light microscopy, using hematoxylin-eosin (HE) and periodic acid Schiff (PAS) staining. The expression and distribution of carbohydrate moieties was analyzed by lectin histochemistry, using 8 lectins with different carbohydrate specificities: Ulex europaeus (UEA I), Lens culinaris (LCA), Erythrina cristagalli (ECA), Arachis hypogaea (PNA), Ricinus communis (RCA I), Aleuria aurantia (AAA), Triticum vulgaris (WGA), and Glycine maximum (SBA). The results showed that the Bidderian zona pellucida presented alpha-mannose, alpha-L-fucose, beta-D-galactose, N-acetyl-D-glucosamine, and alpha/beta-N-acetyl-galactosamine residues. The Bidderian follicular cells showed the presence of beta-D-galactose and N-acetyl-D-glucosamine. In the extracellular matrix, alpha-mannose and alpha/beta-N-acetyl-galactosamine residues were detected. The ovarian zona pellucida showed alpha-L-fucose, N-acetyl-D-glucosamine, alpha/beta-N-acetyl-galactosamine residues, and alpha-mannose and N-acetyl-D-glucosamine residues were detected in the follicular cells. Thus, the zona pellucida in both organs contains N-acetyl-D-glucosamine, and alpha/beta-N-acetyl-galactosamine residues. alpha-L-fucose residues were detected in the zona pellucida of both organs, using different lectins. Considering that beta-D-galactose residue was absent from ovary but present in the Bidder's organ, this sugar residue may play an important role in follicle development, blocking the Bidderian follicles and preventing further development of the Bidder's organ into a functional ovary.

[The nucleolus in oocytes of multylayer mouse follicles: topography of fibrillarin, RNA polymerase I and coilin]

By electron microscopy, conventional fluorescence and confocal microscopy, some features of structural and molecular organization of the nucleolus in oocyte nucleus from mouse multilayer follicles were examined. The examined nucleolus lacks almost all characteristic nucleolar components, such as fibrillar centers, dense fibrillar and granular components. This nucleolus consists exclusively of a homogenous filamentous material and is penetrated by numerous interstices. Besides, a striking association of the nucleolus with coilin, a marker of Cajal bodies, was observed. We could map the coilin accumulation in three different areas: around, in the periphery, or inside the nucleolus. Additionally, we examined a topological relationship between coilin and two key proteins of nucleolar transcription-processing machinery, RNA polymerase I and fibrillarin. RNA polymerase I rather than fibrillarin was found to be colocalized with coilin. Finally, we propose that data on dynamics of coilin relation with the nucleolus may elucidate a possible role of coilin in functional relationship between the nucleolus and Cajal bodies.

Ultrastructural localisation of calcium deposits in pig ovarian follicles

Calcium intracellular signaling regulates many intracellular events including oocyte maturation. This signaling is strongly dependent on the influx of calcium ions from extracellular spaces and on the state of intracellular calcium stores. In this study, intracellular calcium deposits were detected in follicle-enclosed pig oocytes using the combined oxalate-pyroantimonate method. These deposits were observed in the nucleus, the mitochondria, the cytoplasm, and on the surface of lipid droplets. The amount of calcium deposits was expressed as a percentage of the area of the respective cellular compartment, which is covered with calcium deposits on ultrathin sections. The distribution of calcium deposits in oocytes changed during folliculogenesis. The amount of calcium deposits in nuclei (1.11% of the area of oocyte nuclei) and cytoplasm (1.02%) in oocytes from secondary and early antral follicles (0.90% nuclei; 0.99% cytoplasm) is significantly lower (P < 0.05) than the amount of calcium deposits in these compartments in oocytes from primary follicles (2.51% nuclei; 2.34% cytoplasm) or antral follicles with growing oocyte (2.91% nuclei; 2.21% cytoplasm). The amount of calcium deposits in mitochondria of oocytes from primary follicles (1.27%) or antral follicles with growing oocyte (1.14%) is significantly lower (P < 0.05) than in the nucleus (2.51% in oocytes from primary follicles; 2.91% in growing oocytes from antral follicles) or cytoplasm (2.34% in oocytes from primary follicles; 2.21% in growing oocytes from antral follicles). The amount of calcium deposits in the cytoplasm of fully-grown oocytes (1.46%) dropped to levels significantly lower (P < 0.05) than those observed in the oocyte nucleus (2.29%). On the basis of these data, we can conclude that the population of follicles on pig ovaries differs in the distribution and concentration of calcium deposits in oocytes, and these changes may be involved in the regulation of the meiotic competence of oocytes.

Lead concentrates in ovarian follicle compromises pregnancy

Following absorption, lead can concentrate in bodily compartments where it disrupts cellular processes and can result in detrimental health consequences. The concentration and impact of lead within follicular fluid has not been characterized and we used inductively coupled plasma mass spectroscopy (ICP-MS) to determine lead levels in blood and follicular fluid from nine patients undergoing in vitro fertilization (IVF) treatment. Lead levels within follicular fluid were found to be significantly higher in non-pregnant patients compared to pregnant patients suggesting that elevated concentrations of the environmental toxicant lead adversely affect female reproduction.

Cx37 and Cx43 localize to zona pellucida in mouse ovarian follicles

In the ovarian follicle, granulosa cells adjacent to the oocyte extend processes through the zona pellucida matrix, and these projections establish gap junctions both with the oocyte and with neighboring transzonal projections. The identity of connexins contributing to gap junctions between transzonal projections has not been extensively studied. Here, we examined the expression pattern of Cx37 and Cx43 in mouse zona pellucida using multiple connexin-specific antibodies. Immunofluorescence staining revealed abundant Cx37 and Cx43 puncta within the zona pellucida of both preantral and antral follicles. Cx37 persisted in the zona pellucida of mature follicles up to 5 h after an ovulatory stimulus whereas Cx43 was reduced in the zona pellucida by 3 h after an ovulatory stimulus. We suggest that in addition to its role in oocyte-granulosa cell communication, Cx37 could enable a distinct communication pathway between those granulosa cells that are in direct contact with the oocyte.

Oestrogen receptor α and β, androgen receptor and progesterone receptor mRNA and protein localisation within the developing ovary and in small growing follicles of sheep

A first step to elucidating the roles that steroids may play in the processes of ovarian development and early follicular growth is to identify the cell types that are likely to be receptive to steroids. Thus, cell types expressing receptors for oestrogen (α and β form; ERα and ERβ respectively), androgen (AR) and progesterone (PR) were determined by in situ hybridisation and immunohistochemistry in ovine ovarian tissues collected during ovarian development and follicular formation (days 26–75 of fetal life) as well as during the early stages of follicular growth. Expression of ERβ was observed early during ovarian development and continued to be expressed throughout follicular formation and also during the early stages of follicular growth. ERβ was identified in germ cells as well as in the granulosa cells. At the large preantral stage of follicular growth, expression of ERα was also consistently observed in granulosa cells. AR was first consistently observed at day 55 of fetal life in stroma cells throughout the ovary. Within the follicle, expression was observed in granulosa and thecal cells from the type-2 to -3 stage of follicular growth. PR mRNA did not appear to be expressed during ovarian development (days 26–75 of gestation). However, PR (mRNA and protein) was observed in the theca of type-3 (small preantral) and larger follicles, with mRNA – but not protein – observed in granulosa cells of some type-4 and 5 follicles. Expression of ERβ, ERα and AR, as well as PR, was also observed in the surface epithelium and ovarian stroma of the fetal, neonatal and adult ovary. Thus, in sheep, steroid hormones have the potential to regulate the function of a number of different ovarian cell types during development, follicular formation and early follicular growth.

Remodeling of extracellular matrix at ovulation of the bovine ovarian follicle

Using immunohistochemistry and RNA analyses we examined the fate of components of a newly identified matrix that develops between granulosa cells (focimatrix, abbreviated from focal intraepithelial matrix) and of the follicular basal lamina in ovulating bovine ovarian follicles. Pre- and postovulatory follicles were generated by treatment with estradiol (Day 1), progesterone (Days 1-10), and prostaglandin analogue (Day 9) with either no further treatment (Group 1, n = 6) and or with 25 mg porcine LH (Day 11, Group 2, n = 8 or Day 10, Group 3, n = 8) and ovariectomy on Day 12 (12-14 hr post LH in Group 2, 38-40.5 hr in Group 3). In the time frame examined no loss of follicular basal lamina laminin chains beta2 and gamma1 or nidogen 1 was observed. In the follicular basal lamina collagen type IV alpha1 and perlecan were present prior to ovulation; after ovulation collagen type IV alpha1 was discontinuously distributed and perlecan was absent. Versican in the theca interna adjacent to the follicular basal lamina in preovulatory follicles was not observed post ovulation, however, the granulosa cells then showed strong cytoplasmic staining for versican. Expression of versican isoforms V0, V1, and V3 was detected at all stages. Focimatrix was observed in preovulatory follicles. It contained collagen type IV alpha1, laminins beta2 and gamma1, nidogen 1 and perlecan and underwent changes in composition similar to that of the follicular basal lamina. In conclusion focimatrix and the follicular basal lamina are degraded at ovulation. Individual components are lost at different times.