1,720,996 research outputs found
Morphological classification of bovine ovarian follicles
No full textCopyright © 2010 Society for Reproduction and FertilityFollicle classification is an important aid to the understanding of follicular development and atresia. Some bovine primordial follicles have the classical primordial shape, but ellipsoidal shaped follicles with some cuboidal granulosa cells at the poles are far more common. Preantral follicles have one of two basal lamina phenotypes, either a single aligned layer or one with additional layers. In antral follicles 5 mm, only aligned/rounded phenotypes are present. Dominant and subordinate follicles can be identified by ultrasound and/or histological examination of pairs of ovaries. Atretic follicles 5 mm, only antral atresia is observed. The concentrations of follicular fluid steroid hormones can be used to classify atresia and distinguish some of the different types of atresia; however, this method is unlikely to identify follicles early in atresia, and hence misclassify them as healthy. Other biochemical and histological methods can be used, but since cell death is a part of normal homoeostatis, deciding when a follicle has entered atresia remains somewhat subjective.R. J. Rodgers and H. F. Irving-Rodger
Extracellular matrix of the developing ovarian follicle
No full textThere are many different types of extracellular matrices in the different follicle compartments. These have different roles in follicle development and atresia, and they change in composition during these processes. This review focuses on basal lamina matrix in particular, and considers follicular fluid, the newly identified focimatrix, and thecal matrices. When follicles commence growing, the follicular basal lamina changes in its composition from containing all six alpha chains of type IV collagen to only alpha1 and alpha2. Perlecan and nidogen-1 and -2 subsequently become components of the follicular basal lamina, and there is an increase in the amount of laminin chains alpha1, beta2, and gamma1, in the bovine at least. Late in follicular development and on atresia some follicles contain laminin alpha2. On atresia the follicular basal lamina is not degraded, as occurs in ovulation, but can be breached by cells from the thecal layer when it is not aligned by granulosa cells. A novel type of basal lamina-like matrix, called focimatrix (abbreviated from focal intraepithelial matrix), develops between the cells of the membrana granulosa as aggregates of basal lamina material. It does not envelop cells and so cannot perform functions of basal lamina as currently understood. It is hypothesized that focimatrix assists or initiates depolarization of the membrana granulosa necessary for the transformation into luteal cells. The largest osmotically active molecules in follicular fluid are hyaluronan and chondroitin sulfate proteoglycans, including versican and inter-alpha trypsin inhibitor. It has been suggested that these might be responsible for the formation of follicular fluid by creating an osmotic gradient across the follicular wall. The formation, development, and then either ovulation or regression of follicles requires considerable tissue remodeling, cellular replication, and specialization. The expectation of researchers is that extracellular matrix will be intimately involved in many of these processes. Much research has focused in identifying the components of extracellular matrix and associated developmental changes. We review the components of extracellular matrix associated with follicular development, including the basal lamina, focimatrix, follicular fluid, and matrix of the thecal layers.Helen F. Irving-Rodgers, Raymond J. Rodger
Formation of the ovarian follicular antrum and follicular fluid
No full textThe formation of the follicular antrum and follicular fluid has received scant attention from researchers, yet both are important processes in follicular development. The central hypothesis on follicular fluid formation suggests that production by granulosa cells of hyaluronan and the chondroitin sulphate proteoglycan versican generates an osmotic gradient. This gradient draws in fluid derived from the thecal vasculature. Inter-alpha-trypsin inhibitor is also present in follicular fluid at least in species with large follicles, and inter-alpha-trypsin inhibitor and versican could additionally bind or cross-link with hyaluronan, resulting in the retention of these molecules within the follicular antrum. Barriers to the movement of fluid across the membrana granulosa are apparently minimal, as even relatively large serum proteins are present in follicular fluid. Despite the relative permeability of the follicular wall, aquaporins are present in granulosa cells and could be actively involved in the transport of water into the follicle. The formation of an antrum also requires movement of granulosa cells relative to each other to allow the fluid to accumulate. This presumably involves remodeling of cell-cell junctions and in species with small follicles may involve death of centrally located granulose cells. Remodeling of the stroma and thecal layers also accompanies growth and expansion of the antrum and presumably involves similar processes that accompany growth of other glands.Raymond J. Rodgers and Helen F. Irving-Rodger
Extracellular matrix in ovarian follicular development and disease
No full textThe original publication is available at www.springerlink.comThe ovarian follicle contains several different cell types and separate compartments and undergoes substantial development during its growth and maturation. Extracellular matrix (ECM) could be expected to play a major role in these processes. Most research on ECM in follicles has focused on the follicular basal lamina and its changing composition during folliculogenesis and on the specialised matrix formed at ovulation by the cumulus cells surrounding the oocyte and the zona pellucida. We review these aspects. Few naturally occurring gene mutations have identified unique roles for ECM molecules in follicular function. Presumably, any mutations leading to reduced fertility are eliminated quickly by natural selection and, when mutations are not eliminated, considerable redundancy occurs to ensure successful reproduction. In mice, in which the genome can be easily manipulated, the modification of matrix components associated with cumulus and oocytes has often resulted in partial infertility, suggesting redundancy. We provide an update of basal lamina components focusing on newer discoveries. In addition, we review matrix associated with the occyte and cumulus cells (excluding the zona pellucida) and other components of ECM. Where possible, we examine evidence for the role of the ECM in follicular development and diseases.Helen F. Irving-Rodgers and Raymond J. Rodger
Studies of Polycystic Ovary Syndrome Candidate Genes and the Developing Fetal Ovary
No full textThe cause of polycystic ovary syndrome (PCOS) is not well understood and hence there are no syndrome-specific treatments nor prevention strategies. PCOS appears to have both genetic and fetal origins. The polycystic ovary is fibrous with expanded amounts of stroma and it is not known why and if this represents a fibrosis later in life or merely altered stroma formation and growth during fetal ovary development. The work in this thesis attempts to link these facts to begin to understand the aetiology of PCOS. Previously our group had identified the origin and examined the growth of ovarian stroma in the fetal ovary. They had also identified a second somatic cell type, the gonadal ridge epithelial-like (GREL) cells that are likely progenitors of granulosa cells and surface epithelial cells. No one had previously isolated these GREL cells and cultured them. A procedure for purifying bovine GREL cells and fetal ovarian fibroblasts was established. The optimised procedure includes culture of fetal ovarian cells on collagen type I-coated surfaces in the presence of EGF and clonal expansion of pure GREL cell or fibroblast clones. The cells exhibited different morphologies. We examined gene expression in these cells and in their adult cell counterparts that include adult ovary fibroblasts, granulosa cells and surface epithelial cells. We discovered that the GREL cells differ in expression of a number of genes to fetal fibroblasts and that both cells are also different to their adult counterparts. Thus, clearly the fetal somatic cells are of two lineages. We examined the expression of PCOS candidate genes that were in loci identified previously by GWAS and microsatellite mapping. We looked in control and PCOS ovaries from adults and across gestation in bovine and human fetal ovaries. By far the most exciting data were in the fetal ovaries with genes expressed either early, late or continuously across gestation. In the former two groups the expression levels of genes were highly correlated with each other. However, there were very few differences in expression between GREL cells and fetal ovarian stromal cells. Finally, we cultured fetal fibroblasts with a range of growth factors. Importantly, TGFβ1 regulated a number of the PCOS candidate genes inhibiting the expression of 7 of the 25 PCOS candidate genes as well as of AR, and stimulating expression of the AR co-activator TGFB1I1. TGFβ is a master regulator of stromal fibroblasts stimulating in the adult collagen deposition, cell replication and fibrosis. In summary, these studies provide further understanding of the cells involved in fetal ovarian development and the development of a predisposition to PCOS. Importantly, they suggest that alterations in TGFβ signalling during fetal ovary development are a likely candidate to be involved in the aetiology of PCOS.Thesis (Ph.D.) -- University of Adelaide, Adelaide Medical School, 202
The Development of Bovine Fetal Ovary and Its Relationship with Reproductive Disease
Full text linkThe development of fetal ovary is a complex process involving the communication between primordial germ cells (PGCs), Gonadal Ridge Epithelial-Like (GREL) cells and stroma. Many studies in ovarian development have focused on follicles, making other features, such as stroma and ovarian surface the least studied. Additionally, perturbation of ovarian development has been suggested to lead to many reproductive diseases, such as Polycystic Ovary Syndrome (PCOS) and ovarian cancer. Studies have shown that prenatally androgenised female mammals had ovaries with PCOS features, such as small follicles and increased ovarian stromal volume. Similarly, ovarian cancer has been suggested to be able to arise from non-ovarian tissue, such as fallopian tubes and endometrium. This thesis discussed the changes of ovarian stroma (chapter II) and linked the changes to PCOS (chapter III). Furthermore, this thesis quantitated changes of non-stromal areas containing GREL cells and follicles (chapter IV) as well as identified the changes in ovarian surface during fetal development (chapter V). Early in ovarian development, the surface epithelium of the mesonephros differentiates into GREL cells and proliferates, forming the ovarian primordium into which PGCs migrate. The stroma from the mesonephros penetrates the developing ovary and then branches. At this time, a true surface epithelium is located only at the base of the developing ovary. When the stroma reaches just underneath the surface of the developing ovary, it spreads laterally. The branching and spreading of the stroma encloses some GREL cells and PGCs into ovigerous cords. At this point, the ovigerous cords are still open to the ovarian surface. The stroma keeps on spreading, dividing the ovigerous cords into smaller units and eventually into primordial follicles. GREL cells located on the ovarian surface then start to differentiate into surface epithelium. At the last stage of development, a single layer of surface epithelium is formed and the stroma underneath the surface epithelium changes its phenotype into tunica albuginea, a collagen rich layer. In this thesis, I analysed the stromal and non-stromal areas morphometrically and linked ovarian development with expression of a number of extracellular matrix genes. My results show that the volume of the ovarian cortex and medulla increased throughout gestation. The stromal proportion and total volume in the cortex were significantly increased (p>0.05), whereas the proliferation index and numerical density of proliferating cells in the stroma decreased significantly (p>0.05). There was no change in numerical density of stromal cells in the cortex. Twelve extracellular matrix genes were highly expressed later in the development and positively correlated with each other and with gestational age. The total volume of non-stromal areas in the ovarian cortex significantly increased and then levelled off. The proportion of non-stromal areas in the cortex decreased significantly. The proliferation index of the non-stromal area peaked in early gestation and then decreased significantly and then remained low. The numerical density of the stromal area remained constant throughout ovarian development. My morphometric data of the stromal area as well as the gene expression have been published in Reproduction Fertility and Development. The data of the non-stromal area have been combined with other data and published in PLoS ONE. Since many reproductive diseases might have a fetal origin, we studied the linkage between fetal ovarian development and PCOS. Recent studies have recognised 18 PCOS candidate genes identified by genome wide associated study (GWAS) analyses. Using qRTPCR, I analysed the expression of these genes, as well as three other genes (androgen receptor (AR), Transforming Growth Factor Beta 1 induced transcript 1 (TGFB1I1), fibrillin3 (FBN3)) in the bovine fetal ovaries across gestation. To assess the regulation of these genes in the bovine fetal ovary, I analysed the expression of these genes in bovine fetal fibroblasts which had been treated with cAMP regulators, growth factors and hormones in vitro (24 treatments in total) during a previous honour project. FBN3, GATA4, HMGA2, TOX3, DENND1A and LHCGR were highly expressed in the early development, whereas INSR, FSHR and LHCGR, including 3 PCOS-related genes (AMH, AR and TGFB1I1) were highly expressed in the late development. These eleven genes were strongly correlated to each other, although some of them expressed in different cell types. Treatment of fetal stromal cells with TGFβ induced the expression of INSR, AR, C8H9orf3 and RAD50 and inhibited expression of TGFB1I1. The data have been submitted to Scientific Reports. In the attempt of investigating the changes of ovarian surface, I analysed Scanning Electron Microscope (SEM) images and compared them with immunohistochemistry images, as well as determined the proportions of different types of cells in the ovarian surface epithelium. Early in development, the cells at the base of the developing ovary were cuboidal whereas the remaining surface appeared more irregular. Around 10 weeks of gestation until 5 months of gestation, the surface was covered by a stratified or simple epithelium of cuboidal cells. During mid-gestation clefts could be observed on the surface coinciding below with open ovigerous cords. Later in development, most of the ovary was covered by a simple surface epithelium. There appear to be two origins of ovarian surface epithelium – at the base/hilum originating from the mesonephros and on the remainder from the GREL cells.. The data have been submitted to Journal of Histology and Cytochemistry. Together, this work has shown the behavioural and structural changes of stroma and ovarian surface during fetal development. Since some of the PCOS candidate genes are expressed during fetal ovarian development, any potential disruption during ovarian development might have implications for the development of PCOS phenotype in the adult life.Thesis (Ph.D.) -- University of Adelaide, Adelaide Medical school, 201
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Expression and distribution of cytokeratin 8/18 intermediate filaments in bovine antral follicles and corpus luteum: An intrinsic mechanism of resistance to apoptosis?
Full text linkApoptosis is a mechanism of cell elimination during follicular atresia and luteal regression. Recent evidence suggests sensitivity to apoptosis in some cell types is partly dependent upon cytokeratin-containing intermediate filaments. Specifically, cytokeratin 8/18 (CK8/18) filaments are thought to impart resistance to apoptosis. Here, cytokeratin filament expression within bovine ovarian follicles and corpora lutea (CL) was characterized and the potential relationship between cell-specific CK8/18 expression and apoptosis explored. Immunoprecipitation and western blot analysis confirmed CK8 associates with CK18 to form CK8/18 heterodimeric filaments within bovine ovarian cells. Immunostaining revealed populations of CK18-positive (CK18+) cells in healthy growing follicles that increased in postovulatory follicles. Atretic follicles at all stages of atresia also contained some CK18+ cells. However, no CK18+ cells were detected in primordial or primary follicles. In CL, developing CL contained a higher proportion of CK18+ cells (similar to 35%, range 30-70%) than mature CL (similar to 16%) and regressing CL (similar to 5%; P<0.05, n = 3-5 CL/stage), suggesting CK8/18 filament expression diminishes over time, as luteal cells become more susceptible to apoptosis. Dual-fluorescence labeling for CK18 and a cell death marker (TUNEL labeling) confirmed this view, demonstrating less death of CK18+ than CK18-luteal cells throughout the estrous cycle (P<0.05). The results indicate differential expression of CK8/18 filaments occurs in cells of bovine ovarian follicles and CL throughout the estrous cycle. The prevalence and cell-specific pattern of cytokeratin expression in these structures is consistent with the concept these filaments might impart resistance to apoptosis in ovarian cells as is seen in other cell types.David H. Townson, Amanda N. Putnam, Brian T. Sullivan, Lankai Guo, Helen F. Irving-Rodger
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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