Combined apoptosis and autophagy, the process that eliminates the oocytes of atretic follicles in immature rats

We studied the alterations of dying oocytes in 1-28 days old rats using TUNEL method, immunolocalizations of active caspase 3, lamp1, localization of acid phosphatase, and DAPI staining. All procedures were performed in adjacent sections of each oocyte. In most dying oocytes exist simultaneously features of apoptosis as active caspase 3 and DNA breaks, and a large increase of lamp1 and acid phosphatase characteristic of autophagy. Large clumps of compact chromatin and membrane blebbing were absent. Electron microscope observations demonstrated the presence of small clear vesicles and autophagolysosomes. All these features indicate that a large number of oocytes are eliminated by a process sharing features of apoptosis and autophagy. In dying oocytes of new born rats the markers of apoptosis predominate over those of autophagy. However, fragmentation and apoptotic bodies were not found. These features suggest that in different cytophysiological conditions the processes of cell death may be differently modulated.

Morphologic, ultrastructural, and biochemical identification of apoptosis in vitrified-warmed mouse ovarian tissue

OBJECTIVE

To evaluate the incidence of apoptosis after vitrification warming of mouse ovaries.

DESIGN

Experimental study.

SETTING

University-based research laboratory.

ANIMAL(S)

Twelve- to 14-day-old National Medical Research Institute female mice.

INTERVENTION(S)

Vitrification of mouse ovaries using ethylene glycol.

MAIN OUTCOME MEASURE(S)

Follicle viability assessment by trypan blue testing, morphologic examination by hematoxylin-eosin staining and transmission electron microscopy, apoptosis assessment using the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling method and DNA laddering technique.

RESULT(S)

No statistically significant difference in follicle viability was observed between vitrified and nonvitrified ovaries. On transmission electron microscopy, vitrified ovaries showed a well-preserved ultrastructure. No sign of apoptosis was observed morphologically or by transferase-mediated deoxyuridine triphosphate nick end-labeling technique in either fresh or vitrified-warmed mouse ovaries. Despite the presence of a laddering pattern of DNA in control induced thymic tissue, no similar pattern was observed in fresh or vitrified-warmed ovaries.

CONCLUSION(S)

The data suggest that the vitrification technique does not induce apoptosis in mouse ovarian tissue investigated just after warming.

Cryopreservation and xenotransplantation of human ovarian tissue: an ultrastructural study

OBJECTIVE

To analyze the ultrastructure of human ovarian follicles after cryopreservation and short-term xenografting.

DESIGN

Prospective experimental study.

SETTING

Academic gynecology and anatomy research units.

PATIENT(S)

Ovarian cortical biopsy specimens were obtained from 13 patients.

INTERVENTION(S)

Each ovarian biopsy specimen was dissected into pieces of 1 mm(3) and divided into three groups: [1] fresh tissue, [2] frozen-thawed tissue, and [3] frozen-thawed tissue xenografted onto the peritoneum of nude mice for 3 weeks.

MAIN OUTCOME MEASURE(S)

Follicular ultrastructure was assessed by light and transmission electron microscopy in [1] fresh, [2] frozen, and [3] frozen-grafted tissue.

RESULT(S)

Thirty-five ovarian follicles were analyzed by light and transmission electron microscopy. Twenty-five primordial and primary ovarian follicles were found. Most of them exhibited ultrastructurally well preserved features (fresh [N = 8/10], frozen [N = 7/10], and frozen-grafted [N = 4/5] tissue). Ten secondary follicles were present in xenografts. By transmission electron microscopy, all the healthy-looking secondary follicles (70%) were shown to contain intact oocytes, with features typical of earlier developmental stages, surrounded by several layers of follicular cells.

CONCLUSION(S)

The present study demonstrates, for the first time, that cryopreservation and xenotransplantation do not appear to greatly affect human primordial/primary follicle ultrastructure. Interestingly, in frozen-thawed xenografts, secondary human ovarian follicles presented a well preserved ultrastructure, but asynchrony between oocyte and granulosa cell development was detected. The possible causes for this asynchrony are discussed.

Reproductive tissue regression: Involvement of caspases, inducible nitric oxide synthase and nitric oxide during moulting in White Leghorn hens

Moulting is a natural physiological process where the reproductive system of birds undergoes complete remodeling in preparation for the next laying cycle. In domestic chickens, moulting is artificially induced by feed withdrawal to recycle the old laying flock for best profit margins. This has received severe criticism from animal welfare organizations, forcing several countries to stop this practice. Several alternative methods to feed withdrawal methods were developed but were found to produce inconsistent results. Understanding the actual mechanism of moulting would help in designing a new animal welfare friendly method. The present investigation attempted to study the molecular mechanism of moulting in White Leghorn hens. Eighty-four layers (75 weeks) were divided into two groups. The birds in the first group were subjected to moulting by feed withdrawal (FW) while the other group received high dietary Zn (ZnF) treatment for 10 days. Six birds from each group were sacrificed on 0, 1-4, 6 and 10 days of moulting and mRNA expression of caspases-1, -2 and iNOS, along with the apoptotic ladder pattern and nitric oxide (NO) in the ovary and oviduct, was investigated. The mRNA expression of iNOS was upregulated with a corresponding increase in NO levels. Caspases-1 and -2 were differentially upregulated in the ovary and oviduct of moulted birds. A constant decline in serum estradiol and progesterone levels was also observed. It can be concluded that the pattern of reproductive regression during moulting by the two methods is different, as the expression of genes studied in the present investigation is different.

Effects of gonadotrophins, growth hormone, and activin A on enzymatically isolated follicle growth, oocyte chromatin organization, and steroid secretion

So far, standard follicle culture systems can produce blastocyst from less than 40% of the in vitro matured oocytes compared to over 70% in the in vivo counterpart. Because the capacity for embryonic development is strictly associated with the terminal stage of oocyte growth, the nuclear maturity status of the in vitro grown oocyte was the subject of this study. Mouse early preantral follicles (100-130 microm) and early antral follicles (170-200 microm) isolated enzymatically were cultured for 12 and 4 days, respectively, in a collagen-free dish. The serum-based media were supplemented with either 100 mIU/ml FSH (FSH only); 100 mIU/ml FSH + 10 mIU/ml LH (FSH-LH); 100 mIU/ml FSH + 1 mIU/ml GH (FSH-GH) or 100 mIU/ml FSH + 100 ng/ml activin A (FSH-AA). Follicle survival was highest in follicle stimulating hormone (FSH)-AA group in both cultured preantral (91.8%) and antral follicles (82.7%). Survival rates in the other groups ranged between 48% (FSH only, preantral follicle culture) and 78.7% (FSH only, antral follicle culture). Estradiol and progesterone were undetectable in medium lacking gonadotrophins while AA supplementation in synergy with FSH caused increased estradiol secretion and a simultaneously lowered progesterone secretion. Chromatin configuration of oocytes from surviving follicles at the end of culture revealed that there were twice more developmentally incompetent non-surrounded nucleolus (NSN) oocytes (>65%) than the competent surrounded nucleolus (SN) oocytes (<34%). We conclude that the present standard follicle culture system does not produce optimum proportion of developmentally competent oocytes.

The effect of leptin on maturation of the ovarian compartments of albino rats: an ultrastructural and histological study

BACKGROUND

Leptin serves as a signal to the central nervous system with information on the critical amount of adipose tissue stores that is necessary for activation of the hypothalamic-pituitary-ovarian axis.

OBJECTIVES

To document the histological and ultrastructural changes that occur in the ovarian follicles of immature albino rats treated with leptin when compared with controls. Furthermore, the endometrial histological and immunohistochemical, and vaginal cytological changes suggestive of ovulation were assessed.

ANIMALS AND METHODS

The study was carried out on 50 immature female albino rats aged 22 days; 24 of them were injected with 5 microg leptin daily and 26 rats were taken as controls. Vaginal smears were taken daily, three animals were sacrificed every 2-4 days from each group, ovaries and uteri were dissected and specimens were prepared for electron microscopic, histological and/or immunohistochemical assessment. The research project was approved by The Histology Department Committee of Alexandria Medical School, which is licensed for animal care and use.

RESULTS

Electron microscopic and histological examination confirmed the occurrence of maturational changes in various ovarian components from 26 days of age in leptin-treated rats, with ovulation occurring from the age of 30 days. The granulosa, theca and stroma cells showed signs of steroidogenesis, with increased mitosis within granulosa cells. The ooplasm showed an increased number of organelles, and annulate lamellae were demonstrated. The zona pellucida revealed microvilli, adhering junctions and gap junctions. Similarly, the endometrial histological and vaginal cytological maturational changes were detected in leptin-treated rats from 26 days of age. Furthermore, there was high expression of estrogen receptor-alpha in almost all columnar and stroma cells of the endometrium. However, the control rats ovulated around the normal age of maturation, i.e. 42 days.

CONCLUSION

We documented ultrastructural, histological, immunohistochemical and cytological evidence that leptin accelerates the onset of puberty in female albino rats. The potential role of exogenous leptin, in cases of impaired reproductive function in humans, needs to be elucidated.

Ultrastructural changes of ovarian follicle and corpus luteum after experimental zearalenone mycotoxicosis in bitch

The aim of the study was to determine the influence of experimental zearalenone (ZEA) mycotoxicosis on the ultrastructure of ovaries in bitches receving zearalenone for 100 days per os in the anestrus phase. Experiment has been conducted on 9 sexually mature clinically healthy bitches. The sexually mature animals aged 1-3 years were in anestrus. The dogs have been divided into three groups: EI and EII, receiving ZEAper os in two dosages (25 microg/kg and 50 microg/kg b.w.) and control animals which received placebo per os. On the last day of experiment, ovariohysterectomy was performed in all the bitches and the uterine samples were submitted to ultrastructural analyses. The study has revealed that long lasting administration of higher dose of zearalenone causes ultrastructural changes in the granular layer of ovarian follicles, which showed due to their biological activity decrease. The changes in the granular layer, atrophy of intercellular connections and the appearance of intercellular spaces can stand for reduced activity of this layer. Changes in morphology of mitochondria, rough endoplasmic reticulum and Golgi apparatus sugest ZEA influence on cell metabolism and secretory processes. It seems therefore that in bitches and other monogastric animals, intoxications induced by this mycotoxin causes ultrastructural changes in granular cells of ovarian follicles.

[Nucleolus transformation in oocytes of mouse antral follicles. Revealing of coilin and RNA polymerase I complex components]

This study is the continuation of our previous investigation of the nucleolus transformation in growing oocytes from mouse multilayer follicles (Pochukalina, Parfenov, 2006). Here in the present research we have examined the features of organization and molecular composition of nucleolus like body, or postnucleolus, in two groups of oocytes with different chromatin configuration from mouse antral follicles. Using light and electron immunocytochemistry, we have defined the dynamics of ribosomal RNA synthesis and processing molecular component distribution in postnucleolus. Considerable changes in RNA polymerase I distribution and its colocalization with coilin at the periphery of postnucleolus were revealed. Putative role of coilin in formation of complexes with ribosomal RNA synthesis/processing components is discussed.

Ultrastructural alterations and occurrence of apoptosis in developing follicles exposed to low frequency electromagnetic field in rat ovary

Humans are continuously exposed to harmful environmental factors, including Electromagnetic Fields (EMF) produced by home appliances, diagnostic tools and industrial instruments. The present study investigates morphologically the effects of EMF on ovarian follicles. Female Wistar rats were exposed to 3 mili Tesla EMF for 4 h day(-1) for 4 months, the ovaries from both experimental and control groups were processed for Transmission Electron Microscopy (TEM) and TUNEL reaction technique. TEM revealed that in the oocytes from experimental group the nuclei were shrunken and zona pellucida appeared narrower than those in the control group. The number of microvilli were decreased significantly and in their cytoplasm there were several lipid droplets and organels were dispersed. Signs of apoptosis such as condensed nuclei, chromatin margination and nuclear membrane dilatation were common in granulosa and corona radiata cells from the EMF-exposed rats than those from the control group. Primary morphological changes in the granulosa cells from this group were retraction of granulosa cells, loss of microvilli and condensation or loss of mitochondrial cristae. The morphological changes in oocytes seem to indicate the cytotoxic effect of EMF and the changes occurred in granulosa cells coincide with initiation of apoptosis in granulosa cells. Present results suggest that EMF exposure may interfere with normal process of folliculogenesis.

Specificity of the requirement for Foxo3 in primordial follicle activation

Primordial follicles are long-lived structures assembled early in life. The mechanisms that control the balance between the conservation and the activation of primordial follicles are critically important for fertility and dictate the onset of menopause. The forkhead transcription factor Foxo3 serves an essential role in these processes by suppressing the growth of primordial follicles, thereby preserving them until later in life. While other factors regulating primordial follicle growth have been described, most serve multiple functions at several stages of female germ cell or follicle development, and corresponding mouse mutants exhibit pleiotropic phenotypes with disruption of multiple stages of follicle assembly, development, or survival. To investigate the possibility that Foxo3 also functions in other aspects of ovarian development beyond its known role in primordial follicle activation (PFA), we performed detailed analyses of mouse ovaries including electron microscopy to study primordial follicle structure, assembly, and early growth. These analyses revealed that the timing of primordial follicle assembly, early oocyte survival, and the expression of early germ line markers were unaffected in early Foxo3 ovaries. Taken together, these studies demonstrate that the phenotype associated with Foxo3 deficiency is remarkably specific for PFA and further support the placement of Foxo3 in a unique phenotypic class among mammalian female sterile mutants. Lastly, we discuss the implications of the specificity of this mutant phenotype with regard to the hypothesis that oocyte regeneration may occur in adults and serves as a means to replenish oocytes lost via natural physiological processes.

Nuclear morphology, diameter and meiotic competence of buffalo oocytes relative to follicle size

The nuclear morphology, diameter and in vitro meiotic competence of buffalo oocytes was compared relative to follicle size. Cumulus-oocyte complexes (COCs) were collected from 1-<2, 2-<3, 3-<4, 4-<6 and 6-<8 mm follicles from abattoir ovaries. Cumulus cells were removed using 3 mg mL(-1) hyaluronidase in saline and repeated pipetting. Denuded oocytes were measured, fixed in 3% glutaraldehyde, stained with 4,6-diamidoino-2-phenylindole and evaluated for nuclear morphology, namely the stage of germinal vesicle (GV) development before in vitro maturation (IVM). The COCs from >2-mm follicles were matured in vitro in their respective size groups for 24 h in Medium 199 supplemented with 10 microg mL(-1) follicle-stimulating hormone, 10 microg mL(-1) luteinizing hormone, 1.5 microg mL(-1) oestradiol, 75 microg mL(-1) streptomycin, 100 IU mL(-1) penicillin, 10 mM HEPES and 10% fetal bovine serum. Matured oocytes were fixed, stained and evaluated for GV status and meiotic development. The number of oocytes collected from follicles 1-<8 mm in diameter averaged 1.82 per ovary. Oocytes from follicles 1-<2 mm (107.7 +/- 1.6 microm), 2-<3 mm (108 +/- 1.1 microm) and 3-<4 mm (114.6 +/- 1.3 microm) in diameter were smaller in diameter (P < 0.05) than oocytes from follicles 4-<6 mm (124.4 +/- 1.3 microm) and 6-<8 mm (131.9 +/- 1.4 microm) in diameter. A majority of oocytes (P< 0.05) from <4-mm follicles was at the initial stages of GV development (GV-I, II and III), whereas oocytes from 4-<6- and 6-<8-mm follicles were at the final stages of GV-IV (35.0 and 21.6% respectively) and GV-V (49.1 and 67.5% respectively). Poor IVM rates of 32.0% and 32.7% to metaphase (M)-II were observed for oocytes isolated from 2-<3- and 3-<4-mm follicles, respectively, whereas significantly (P< 0.05) more oocytes from 4-<6- and 6-<8-mm follicles reached M-II (67.1% and 79.1% respectively). In conclusion, buffalo oocytes displayed a size-dependent ability to undergo meiotic maturation and we suggest that oocytes from >4-mm follicles should be considered in buffalo in vitro fertilization systems for better results.

Genomewide discovery and classification of candidate ovarian fertility genes in the mouse

Female infertility syndromes are among the most prevalent chronic health disorders in women, but their genetic basis remains unknown because of uncertainty regarding the number and identity of ovarian factors controlling the assembly, preservation, and maturation of ovarian follicles. To systematically discover ovarian fertility genes en masse, we employed a mouse model (Foxo3) in which follicles are assembled normally but then undergo synchronous activation. We developed a microarray-based approach for the systematic discovery of tissue-specific genes and, by applying it to Foxo3 ovaries and other samples, defined a surprisingly large set of ovarian factors (n = 348, approximately 1% of the mouse genome). This set included the vast majority of known ovarian factors, 44% of which when mutated produce female sterility phenotypes, but most were novel. Comparative profiling of other tissues, including microdissected oocytes and somatic cells, revealed distinct gene classes and provided new insights into oogenesis and ovarian function, demonstrating the utility of our approach for tissue-specific gene discovery. This study will thus facilitate comprehensive analyses of follicle development, ovarian function, and female infertility.

Ultrastructural changes in the follicular epithelium ofCeratophrys cranwelliprevitellogenic oocytes

In this work we carried out ultrastructural, autoradiographic and biochemical analyses of the follicular epithelium duringC. cranwelliprevitellogenesis. This study revealed that the follicular epithelium in early previtellogenesis is constituted of a single layer of squamous homogeneous cells. During mid-previtellogenesis two types of cells develop: dark cells and clear cells. The follicular dark cells are actively involved in the synthesis of RNA, which is transferred to the oocyte through the interface. In late previtellogenesis the dark cells show apoptotic characteristics such as chromatin condensation, DNA fragmentation and cytoplasm shrinkage. This process forms apoptotic bodies that seem to be engulfed by the oocyte. Our results show evidence that, during mid- and lateC. cranwelliprevitellogenesis, the follicular epithelium undergoes remodelling processes interacting with the oocyte.

Assembly of ovarian follicles in the caecilians Ichthyophis tricolor and Gegeneophis ramaswamii: light and transmission electron microscopic study

Though much is known about various aspects of reproductive biology of amphibia, there is little information on the cellular and mechanistic basis of assembly of ovarian follicles in this group. This is especially true of the caecilians. Therefore, taking advantage of the abundant distribution of caecilians in the Western Ghats of India, two species of caecilians, Ichthyophis tricolor and Gegeneophis ramaswamii, were subjected to light and transmission electron microscopic analysis to trace the sequential changes during the assembly of ovarian follicles. The paired ovaries of these caecilians are elongated sac-like structures each including numerous vitellogenic follicles. The follicles are connected by a connective tissue stroma. This stroma contains nests of oogonia, primary oocytes and pregranulosa cells as spatially separated nests. During assembly of follicles the oocytes increase in size and enter the meiotic prophase when the number of nucleoli in the nucleus increases. The mitochondrial cloud or Balbiani vitelline body, initially localized at one pole of the nucleus, disperses through out the cytoplasm subsequently. Synaptonemal complexes are prominent in the pachytene stage oocytes. The pregranulosa cells migrate through the connective tissue fibrils of the stroma and arrive at the vicinity of the meiotic prophase oocytes. On contacting the oocyte, the pregranulosa cells become cuboidal in shape, wrap the diplotene stage oocyte as a discontinuous layer and increase the content of cytoplasmic organelles and inclusions. The oocytes increase in size and are arrested in diplotene when the granulosa cells become flat and form a continuous layer. Soon a perivitelline space appears between the oolemma and granulosa cells, completing the process of assembly of follicles. Thus, the events in the establishment of follicles in the caecilian ovary are described.

Insulin signaling in mouse oocytes

Continuous exposure of follicles/oocytes to elevated levels of insulin compromises embryonic developmental competence, although the underlying cellular mechanisms are unknown. The objectives of the present study were to determine whether mouse oocytes have insulin receptors and a functional insulin signaling cascade, and whether insulin exposure during oocyte growth or maturation influences meiotic progression and chromatin remodeling. Immunoblot and immunocytochemical analyses of germinal vesicle-intact (GVI) oocytes demonstrated the presence of insulin receptor-beta. Insulin receptor expression in oocytes was increased by gonadotropin stimulation, and remained elevated throughout meiotic maturation. Fully grown GVI oocytes contained 3-phosphoinositide-dependent protein kinase-1 (PDPK1), thymoma viral proto-oncogene 1 (AKT1), and glycogen synthase kinase 3 (GSK3). In vitro maturation of GVI oocytes in 5 microg/ml insulin had no influence on meiotic progression or the incidence of normal metaphase II (MII) chromosome condensation. Treatment of oocytes during maturation had no effect on GSK3A/B protein expression or phosphorylation of S21/9. However, the culturing of preantral follicles for 10 days with 5 microg/ml insulin increased the phosphorylation of oocyte GSK3B, indicating GSK3 inactivation. The rates of development to metaphase I (MI) were similar for oocytes obtained from insulin-treated follicles and controls, whereas the incidence of abnormal MI chromatin condensation was significantly higher in oocytes obtained from follicles cultured with insulin compared to those cultured without insulin. These results demonstrate that oocytes contain a functional insulin signaling pathway, and that insulin exposure during oocyte growth results in chromatin remodeling aberrations. These findings begin to elucidate the mechanisms by which chronic elevated insulin influences oocyte meiosis, chromatin remodeling, and embryonic developmental competence.

Ultrastructural observations of previtellogenic ovarian follicles of the caecilians Ichthyophis tricolor and Gegeneophis ramaswamii

The ultrastructural organization of the previtellogenic follicles of the caecilians Ichthyophis tricolor and Gegeneophis ramaswamii, of the Western Ghats of India, were observed. Both species follow a similar seasonal reproductive pattern. The ovaries contain primordial follicles throughout the year with previtellogenic, vitellogenic, or postvitellogenic follicles, depending upon the reproductive status. The just-recruited primordial follicle includes an oocyte surrounded by a single layer of follicle and thecal cells. The differentiation of the theca into externa and interna layers, the follicle cells into dark and light variants, and the appearance of primordial yolk platelets and mitochondrial clouds in the ooplasm mark the transition of the primordial follicle into a previtellogenic follicle. During further development of the previtellogenic follicle the following changes occur: i) the theca loses distinction as externa and interna; ii) all the follicle cells become the dark variant and increase in the complexity of ultrastructural organization; iii) the nucleus of the oocyte transforms into the germinal vesicle and there is amplification of the nucleoli; iv) the primordial yolk platelets of the cortical cytoplasm of the oocyte increase in abundance; v) the mitochondrial clouds fragment and the mitochondria move away from the clouds, leaving behind the cementing matrix, which contains membrane-bound vesicles of various sizes, either empty or filled with a lipid material; vi) the perivitelline space appears first as troughs at the junctional points between the follicle cells and oocyte, which subsequently spread all around to become continuous; vii) macrovilli and microvilli develop from the follicle cells and oocyte, respectively; and viii) the precursor material of the vitelline envelop arrives at the perivitelline space. The sequential changes in the previtellogenic follicles of two species of caecilians are described.

Adherens junction remodeling by the Notch pathway in Drosophila melanogaster oogenesis

Identifying genes involved in the control of adherens junction (AJ) remodeling is essential to understanding epithelial morphogenesis. During follicular epithelium development in Drosophila melanogaster, the main body follicular cells (MBFCs) are displaced toward the oocyte and become columnar. Concomitantly, the stretched cells (StCs) become squamous and flatten around the nurse cells. By monitoring the expression of epithelial cadherin and Armadillo, I have discovered that the rate of AJ disassembly between the StCs is affected in follicles with somatic clones mutant for fringe or Delta and Serrate. This results in abnormal StC flattening and delayed MBFC displacement. Additionally, accumulation of the myosin II heavy chain Zipper is delayed at the AJs that require disassembly. Together, my results demonstrate that the Notch pathway controls AJ remodeling between the StCs and that this role is crucial for the timing of MBFC displacement and StC flattening. This provides new evidence that Notch, besides playing a key role in cell differentiation, also controls cell morphogenesis.

Mathematical modelling of oxygen transport-limited follicle growth

Mathematical modelling was used to investigate oxygen transport in the developing ovarian follicle. In contrast to previous findings, the results show that oxygen can reach the oocyte in large preantral follicles. This is largely due to the inclusion of fluid voidage in the model and improved estimates of oxygen diffusion coefficients through the granulosa. The results also demonstrate that preantral follicles will eventually reach a size beyond which further growth will result in the follicle becoming increasingly anoxic. The predicted size range at which this occurs is consistent with the size range at which antrum formation is observed in many mammals. This suggests that the antrum formation stage of follicular growth may be pivotal to the further development and ultimate fate of the follicle, and that antrum formation itself may represent a mechanism by which the follicle can overcome oxygen limitations. This was supported through extension of the model to the antral follicle, which showed that antrum formation can provide a way in which the follicle can continue to grow and yet avoid becoming hypoxic. The results of the model were consistent with observed follicle development.

Effects of fibroblast growth factor-2 on the in vitro culture of caprine preantral follicles

The aims of the present study were to evaluate the effects of fibroblast growth factor-2 (FGF-2) on survival, activation and growth of caprine early-staged (preantral) follicles using histological and ultrastructural studies. Fragments of caprine ovarian cortex were cultured for 1 or 5 days in an enriched minimum essential medium, supplemented or not with different concentrations of FGF-2 (10, 50 or 100 ng/ml). Fragments from non-cultured ovarian tissue (control) and from tissues cultured for 1 or 5 days in a specific medium were processed for transmission electron microscopy (TEM) or classical histology to evaluate the morphological quality of caprine preantral follicles and to calculate the percentages of normal follicles. Additionally, effects of FGF-2 on oocyte and follicle diameter of cultured preantral follicles were investigated. Our results showed that, although the percentages of histologically normal follicles were lower in cultured than in non-cultured ovarian tissue fragments, there were no differences in this regard among treatments, neither on day 1 nor on day 5 of culture. After 1 and 5 days of culture, a significantly higher percentage of growing follicles was observed in the medium supplemented with 50 ng/ml of FGF-2. This FGF-2 treatment furthermore resulted in an increase in diameter of both oocytes and follicles that were cultured for 5 days. TEM showed that the ultrastructural integrity of caprine preantral follicles was maintained during their 5-day culture in the presence of 50 ng/ml FGF-2. In conclusion, this study demonstrated that at a concentration of 50 ng/ml FGF-2 not only maintains the morphological integrity of caprine preantral follicles cultured for 5 days, but also stimulates the activation of primordial follicles and the growth of activated follicles.

Effects of atrazine on female Wistar rats: morphological alterations in ovarian follicles and immunocytochemical labeling of 90 kDa heat shock protein

Fertility in female mammals may be affected by a variety of endocrine disrupters present in the environment. Herbicide atrazine is an example of endocrine disrupter employed in agriculture, which disrupts estrous cyclicity in rats. Aiming to characterize morphologically the effect of low and sublethal doses of atrazine on the ovaries of Wistar rats, in an effort to determine the possible intrafollicular target site through which this herbicide acts adult females were submitted to both subacute and subchronic treatments. Additionally, immunocytochemical labeling of 90 kDa heat shock protein (HSP90) was performed in order to evaluate the role played by this protein in the ovary, under stressed conditions induced by herbicide exposure. The results indicated that atrazine induced impaired folliculogenesis, increased follicular atresia and HSP90 depletion in female rats submitted to subacute treatment, while the subchronic treatment with low dose of atrazine could compromise the reproductive capacity reflected by the presence of multioocytic follicle and stress-inducible HSP90.

Effects of storing pig ovaries at 4 or 20 degrees C for different periods of time on the morphology and viability of pre-antral follicles

The purpose of this study was to evaluate the effect of cooling ovarian tissue on pig pre-antral follicles. Ovaries were maintained in saline solution (0.9%) at 4 or 20 degrees C for 6, 12 or 18 h. After storage, pre-antral follicles were morphologically evaluated. While primordial follicles were not affected by the storage, the percentage of morphologically normal growing follicles was significantly reduced in ovarian tissue stored at 20 degrees C for 12 or 18 h. To test the viability of stored follicles, growing follicles isolated from ovaries stored at 4 degrees C for 18 h and at 20 degrees C for 6 h were cultured for 3 days. Follicles stored in either condition presented the same growth pattern in vitro as fresh follicles. We conclude that storage of pig ovaries at 4 degrees C for up to 18 h or at 20 degrees C for up to 6 h does not affect the morphology of growing follicles or their ability to grow in vitro.

Ultrastructural and morphometric characterization of buffalo (Bubalus bubalis) ovarian preantral follicles

The main objective of the present study was to characterize buffalo preantral ovarian follicles. Parts of ovarian cortex, collected from postpubertal buffalo females that were having estrous cycles at regular intervals, were selected under stereomicroscopy and processed for optic and transmission electron microscopy. Primordial follicles were characterized as an oocyte encircled by one layer of flattened cells. The buffalo primordial follicle has a mean diameter of 35 microm and the oocyte diameter is 24.9 microm. The oocyte nucleus is relatively large and eccentric; and in the cytoplasm a large amount of mitochondria, vesicles and endoplasmic reticulum cistern, mainly of the smooth type is observed. The primordial follicles cells are rich in plasma membrane invaginations, which are observed within the cell and between the cell and the oocyte. The primary follicles (mean diameter of 41.8 microm) consist of an oocyte, with a medium diameter of 26.9 microm, surrounded by one layer of cubical granulosa cells. At this follicular stage, the beginning of zona pellucida deposition can also be seen in areas between the oocyte and follicular cells. The secondary follicles, which are surrounded by more than one layer of cubical cells, have a diameter of 53.3 microm, and the oocyte has a mean diameter of 29.4 microm. The ultrastructural analysis showed a large amount of coalescent vesicles, more evident in the oocyte periphery. The zona pellucida (ZP) is thicker at this stage and contains a large quantity of glycoproteins. In general, the ultrastructure of buffalo preantral follicles was similar to that of other mammalian species, but some differences were observed, which indicate species specific characteristics. The main differences observed were cytoplasmic vesicles quantity, mitochondria shape and inner content, ZP deposition and granulosa cell-oocyte junctions. In conclusion, the morphological differences described in this paper, could be responsible for some functional differences observed in Bubalus bubalis in vitro embryo production and follicular dynamics, when compared with Bos taurus or Bos indicus species.

Stereo-electron microscopy of the ovarian follicles of cat and mouse

Three dimensional structure of developing ovarian follicles in the cat and the mouse were examined to clarify the cellular and the extra cellular components during follicular maturation by scanning electron microscopy. Epithelial cells of the membrana granulosa (MG) and the cumulus oophorus (CO) show variable morphology, which depends on the location of the cells in the follicle. In the small antral follicle, there is no morphological difference between the surface structure of the MG and the CO lining cells. In the large antral follicle, however, the lumenal lining cells of the MG change their spherical shape to a rather flattened one showing numerous pseudopodial processes creeping over the surrounding lumenal cells. The CO cells remain rounded with fine cytoplasmic protrusions on their outer surfaces which seem to make a network. The outer surface view of the zona appears as composed of labyrinthine canals with relatively large pores of various sizes, however, the inner surface is rather compact with a number of small pores.

Oogenesis in four species ofPiscicola (Hirudinea, Rhynchobdellida)

Piscicola has a pair of elongated sac-shaped ovaries. Inside the ovaries are numerous small somatic cells and regularly spherical egg follicles. Each follicle is composed of three types of cells: many (average 30) germ cells (cystocytes) interconnected by intercellular bridges in clones (cysts), one intermediate cell, and three to five outer follicle cells (envelope cells). Each germ cell in a clone has one intercellular bridge connecting it to the central anucleate cytoplasmic mass, the cytophore. Each cluster of germ cells is completely embedded inside a single huge somatic follicle cell, the intermediate (interstitial) cell. The most spectacular feature of the intermediate cell is its development of a system of intracytoplasmic canals apparently formed of invaginations of its cell membrane. Initially the complex of germ cell cluster + intermediate cell is enclosed within an envelope composed of squamous cells. As oogenesis progresses the envelope cells gradually degenerate. All the germ cells that have terminated their mitotic divisions are of similar size and enter meiotic prophase, but one of the cystocytes promptly starts to grow faster and differentiates into the oocyte, whereas the remaining cystocytes withdraw from meiosis and become nurse cells (trophocytes). Numerous mitochondria, ER, and a vast amount of ribosomes are transferred from the trophocytes via the cytophore toward the oocyte. Eventually the oocyte ingests all the content of the cytophore, and the trophocytes degenerate. Little vitellogenesis takes place; the oocyte gathers nutrients in the form of small lipid droplets. At the end of oogenesis, an electron-dense fibrous vitelline envelope appears around the oocyte, among short microvilli. At the same time, electron-dense cortical granules occur in the oocyte cortical cytoplasm; at the end of oogenesis they are numerous, but after fertilization they disappear from the ooplasm. In the present article we point out many differences in the course of oogenesis in two related families of rhynchobdellids: piscicolids and glossiphoniids.

Follicle stimulating hormone and fibroblast growth factor-2 interact and promote goat primordial follicle development in vitro

The aims of the present study were to investigate the effects of the interaction between follicle stimulating hormone (FSH) and fibroblast growth factor-2 (FGF-2) on survival, follicular growth initiation and further growth of caprine preantral follicles. Pieces of caprine ovarian cortex were cultured for 1 or 7 days in minimum essential medium (MEM) supplemented with FSH, FGF-2 or FSH + FGF-2. Small fragments from non-cultured ovarian tissue and from those cultured for 1 or 7 days were processed for classical histology and transmission electron microscopy (TEM) to verify follicular morphology and growth. The results showed that, after 7 days culture, the highest percentages of normal follicles were observed in medium supplemented with FSH. After 7 days culture, the interaction between FSH and FGF-2 was most effective to promote the initiation of primordial follicles growth and oocyte growth. TEM showed ultrastructural integrity of follicles after 1 day of culture in MEM and after 7 days in all treatments, except in those follicles cultured for 7 days in MEM. In conclusion, this study demonstrated that the interaction between FSH and FGF-2 stimulates the initiation of primordial follicles growth and the subsequent growth of developing follicles. Furthermore, these data showed that FSH is important to maintain follicular integrity after 7 days culture.