Function analysis and molecular characterization of cyclin A in ovary development of oriental river prawn, Macrobrachium nipponense.

Macrobrachium nipponense has the characteristics of fast ovarian development cycle, which leads to the coexistence of multiple generations, the reduction of commodity specifications and the low economic benefit. Therefore, the study on the mechanism of ovarian development is of great significance to the development of industry. Cyclin A (CycA)is a key gene regulating ovarian development in vertebrates, but little information was available for its function in crustaceans. In this study, the full-length cDNA of Mn-CycA was obtained from the ovary. The full-length cDNA (2033 bp) with an open reading frame of 1368 bp, encoded a 456-amino acid protein. qRT-PCR revealed tissue-specific expression pattern of Mn-CycA, with abundant expression in the ovary. Results in different developmental stages of ovary indicated that Mn-CycA expression is positively correlated with ovarian maturation. qRT-PCR In different developmental stages, the expression of Mn-CycA mRNA gradually increased during the embryonic stage and decreased significantly on the first day of the hatching stage. At the 25th day of the metamorphosis stage, the expression level of Mn-CycAmRNA in female shrimp was 3.5 times higher than that in male shrimp, which may be related to the proliferation of oogonia and the formation of oocytes. In situ hybridization (ISH) of ovary showed Mn-CycA was examined in all stages and was mainly located in oogonia and oocytes. Compared with the control group, the obvious change of gonad somatic index (GSI) proved that injection of Mn-CycA dsRNA could delay the ovarian development cycle, which provided strong evidence for the involvement of Mn-CycA in ovarian maturation and oogenesis, and expanded a new perspective for studying the fast ovarian development cycle in M. nipponense.

Histological characterization of the maturation stages of the ovarian follicles of the goldfish Carassius auratus (Linnaeus, 1758).

The goldfish is a model organism showing great potential for research, particularly in comparative endocrinology concerning the neuroendocrine signalling and regulation of vertebrate reproduction. Furthermore, this teleost is increasingly stressed as a relevant alternative to more common fish model organisms, namely zebrafish. However, quality descriptions and illustrations of the complete goldfish gonadal histology are surprisingly scarce, but needed, to support research using this fish. Therefore, the main aim of this work is to describe in detail and adequately illustrate the goldfish oogenesis, from oogonia to late maturation, by applying routine stains (haematoxylin-eosin) and special procedures (periodic acid-Schiff and Goldner's trichrome). We hypothesized that the combined strategies would enable not only to observe the most general features but also to perceive some poorly described details of oocytes better. We describe the details of the following maturation stages: oogonia proliferation, chromatin-nucleolus, primary growth (one nucleolus step, multiple nucleoli step, perinucleolar step, cortical alveoli step) and secondary growth (early secondary growth step, late secondary growth step). Additionally, we report aspects of early and late follicular atresia. The study allowed comparisons with other species and showed that the Goldner's trichrome has the best discriminative power and should be the preferred stain, despite more time-consuming.

Oocyte growth, follicular complex formation and extracellular-matrix remodeling in ovarian maturation of the imperial zebra pleco fish Hypancistrus zebra.

This contribution describes the growth of oocytes, addressing the formation of structures that compose the follicular complex, as well as the remodeling of the extracellular matrix, specifically laminin, fibronectin and type IV collagen during gonadal maturation. Thirty-seven females of the Acari zebra fish, Hypancistrus zebra were captured and the ovaries were submitted to histological processing for light and electron microscopy and immunohistochemistry techniques. Oogonia and four stages (I - IV) of oocytes were distinguished, and structures such as the postovulatory follicle and atretic oocytes (initial and advanced atresia) were observed. The follicular complex consists of the mature oocyte, zona radiata (Zr1, Zr2 and Zr3), follicular cells, basement membrane and theca. During oocyte growth, proteins of the extracellular matrix showed different intensities of staining. Based on these observations, a model of oocyte growth is proposed to define specific characteristics of the oocyte and the remodeling of the extracellular matrix in the ovary of H. zebra. This model of oocyte growth can be extended to other species of ornamental fishes. This study contributes data for induced fertilization and eventual conservation of this species.

Impact of short-term temperature challenges on the larvicidal activities of the entomopathogenic watermold Leptolegnia chapmanii against Aedes aegypti, and development on infected dead larvae.

The oomycete Leptolegnia chapmanii is among the most promising entomopathogens for biological control of Aedes aegypti. This mosquito vector breeds in small water collections, where this aquatic watermold pathogen can face short-term scenarios of challenging high or low temperatures during changing ambient conditions, but it is yet not well understood how extreme temperatures might affect the virulence and recycling capacities of this pathogen. We tested the effect of short-term exposure of encysted L. chapmanii zoospores (cysts) on A. aegypti larvae killed after infection by this pathogen to stressful low or high temperatures on virulence and production of cysts and oogonia, respectively. Cysts were exposed to temperature regimes between -12 °C and 40 °C for 4, 6 or 8 h, and then their infectivity was tested against third instar larvae (L3) at 25 °C; in addition, production of cysts and oogonia on L3 killed by infection exposed to the same temperature regimes as well as their larvicidal activity were monitored. Virulence of cysts to larvae and the degree of zoosporogenesis on dead larvae under laboratory conditions were highest at 25 °C but were hampered or even blocked after 4 up to 8 h exposure of cysts or dead larvae at both the highest (35 °C and 40 °C) and the lowest (-12 °C) temperatures followed by subsequent incubation at 25 °C. The virulence of cysts was less affected by accelerated than by slow thawing from the frozen state. The production of oogonia on dead larvae was stimulated by short-term exposure to freezing temperatures (-12 °C and 0 °C) or cool temperatures (5 °C and 10 °C) but was not detected at higher temperatures (25 °C-40 °C). These findings emphasize the susceptibility of L. chapmanii to short-term temperature stresses and underscore its interest as an agent for biocontrol of mosquitoes in the tropics and subtropics, especially A. aegypti, that breed preferentially in small volumes of water that are generally protected from direct sunlight.

Female germ cell renewal during the annual reproductive cycle in Ostariophysians fish.

The objective was to characterize female germ cell renewal during the annual reproductive cycle in two species of ostariophysian fish with distinct reproductive strategies: a siluriform, Pimelodus maculatus, in which oocyte development is group synchronous and the annual reproductive period is short; and a characiform, Serrasalmus maculatus, with asynchronous oocyte development and a prolonged reproductive period. These reproductive strategies result in fish determinate and indeterminate fecundity, respectively. Annual reproductive phases were determined by biometric and histologic analysis of gonads and interpreted according to new proposals for phase classification and stages of oocyte development (with special attention to germinal epithelium activity). Histologically, there were two types of oogonia in the germinal epithelium: single oogonia and those in mitotic proliferation. Oogonial proliferation and their entry into meiosis resulted in formation of cell nests (clusters of cells in the ovarian lamellae). Morphometric analysis was used to estimate germ cell renewal. Based on numbers of single oogonia in the lamellar epithelium, and nests with proliferating oogonia or early prophase oocytes throughout the annual reproductive cycle, oogonial proliferation and entrance into meiosis were more intense during the regenerating phase and developing phase, but decreased sharply (P < 0.05) during the spawning-capable phase. Oogonial proliferation gradually recovered during the regressing phase. We concluded that, independent of species or features of the reproductive cycle, germ cell renewal occurred during the regenerating phase, ensuring availability of eggs for the spawning event.

Ovarian folliculogenesis in the smallnose fanskate sympterygia bonapartii (Müller & Henle, 1841) (Chondrichthyes, Rajidae) / Foliculogénesis ovárica en la raya marmorada, sympterygia bonapartii (Müller & Henle, 1841) (Chondrichthyes, Rajidae)

Chondrichthyes have become an important economic resource in the last decades, with Argentina as one of the countries that exploits more sharks and skates, even at levels that exceed de limits of many species. However, there is a scarce knowledge of the reproductive biology of this group, particularly from species inhabiting the Southern hemisphere. This work shows the most relevant facts during folliculogenesis in Sympterygia bonapartii. Results show that germinal cells are present in immature and maturing females. The most important facts that vary along de follicular development are the number of types and layers of follicular cells, the establishment of thin projections from the follicular cells and the degree of development of the thecae. Follicular cells are, at least, of two different types and both of them emit projections that break through the zona pellucida. The outer theca shows signs of synthetic activity. Atretic follicles of different sizes are present in exemplars of all the reproductive stages. These results are discussed in a physiological and adaptive context.

Los Condrictios se han convertido en un recurso económico importante en las últimas décadas, siendo Argentina uno de los países que más explota tiburones y rayas, incluso a niveles que exceden los límites de varias especies. A pesar de esto, es poco lo que se conoce sobre la biología reproductiva de este grupo, particularmente en especies del Hemisferio Sur. En este trabajo se estudian los estadios más relevantes de la foliculogénesis en Sympterygia bonapartii. Los resultados muestran que las ovogonias están presentes tanto en ejemplares inmaduros como subadultos. Las características más importantes que varían a lo largo del desarrollo folicular son el número de capas y tipos celulares que constituyen el epitelio folicular, el desarrollo de proyecciones de las células de la granulosa y el grado de desarrollo de las tecas. Las células foliculares son, al menos, de dos tipos y ambos emiten proyecciones que atraviesan la zona pelúcida. La teca externa presenta características compatibles con la actividad sintética. Folículos atrésicos de distintos tamaños están presentes en ejemplares de todos los estadios de madurez sexual. Estos resultados se discuten en un marco fisiológico y adaptativo.

Growth of primordial oocytes in neonatal and adult mammals.

Mammalian ovaries are endowed with a huge number of small oocytes (primordial oocytes) in primordial follicles. A small number of primordial oocytes start to grow, while others remain quiescent. Little is known about the mechanism regulating the activation of primordial oocytes. Recently, we found that primordial follicles in mature cows and prepubertal pigs took longer to initiate growth in xenografts compared with those in neonatal animals. We think that primordial oocytes in adult mammals are different from those in neonatal mammals. In this review, we summarize the results regarding the activation of primordial oocytes in neonatal and adult ovaries of different species and propose a model in which ovaries of neonatal mammals contain a mixed population of both quiescent and activated primordial oocytes, while almost all primordial oocytes are quiescent in adult females. The dormancy of primordial oocytes may be required to reserve the non-growing oocyte pool for the long reproductive life in mammals. FOXO3 is considered one of the molecules responsible for the dormancy of primordial oocytes in adult ovaries. These quiescent primordial oocytes are activated, perhaps by certain mechanisms involving the interaction between stimulatory and inhibitory factors, to enter the growth phase.

Production of oogonia and oospores of Leptolegnia chapmanii Seymour (Straminipila: Peronosporomycetes) in Aedes aegypti (L.) larvae at different temperatures.

The aquatic oomycete fungus Leptolegnia chapmanii Seymour is pathogenic to mosquito larvae, but it has been little studied since it was first isolated. Although studies have been performed on different biological isolates of L. chapmanii around the world, they were made on zoospores and a very little or even nothing is known about the sexual stage (oogonia and oospores), which allows L. chapmanii to remain in the environment when conditions are not favorable. The main objective of this study was to determine the relationship between temperature and time of onset of L. chapmanii oogonia and oospores in Ae. aegypti larvae. Leptolegnia chapmanii-infected IV instar Ae. aegypti larvae were incubated at different temperatures between 5 and 45 degrees C and photoperiod-controlled for 90 days. The number of oogonia and oospores was examined daily for each tested temperature. As was expected, low temperatures extended the times of oogonia formation, as much as seven times. Likewise, temperatures significantly affect the number of oogonia produced.

Oogenesis in pig ovaries during the prenatal period: ultrastructure and morphometry.

Oogenesis in fetal pig ovaries comprises the successive changes from the primordial germ cells to the dictyotene oocytes in primordial ovarian follicles. In this study the observations were carried out with an electron microscope and stereological analysis was performed. At the ultrastructural level there are no differences between the primordial germ cells and oogonia, but oogonia are connected with the intercellular bridges. The onset of the dictyotene phase was accompanied by the changes in the cytoplasm of oocytes. Near the nucleus, the yolk nucleus is formed containing numerous Golgi bodies, endoplasmic reticulum (ER), mitochondria and granules. ER proliferates in contact with the external leaflet of the nuclear envelope forming the narrow ER cisterns. Between the nuclear envelope and ER cisterns, the vesicles with grey content are visible. The proliferating ER forms numerous concentric cisterns around the nucleus. Next, the most external cisterns fragment, detach, and then form the cup-like structures. These structures separate the distinct areas of cytoplasm-compartments, which contain mitochondria, ribosomes and lipid droplets. The cells of cortical sex cords of the ovary, which encloses the oocyte, form the follicles. The volume of oocytes in forming follicle increases due to the increase in the number of the cell inclusions: lipid droplets, vacuoles and yolk globules. In the oocytes of primordial ovarian follicles, the compartments are transformed into the yolk globules, which are encountered by a sheath of ER cisterns and the grey vesicles; they contain the mitochondria, lipid droplets and light vacuoles. The role of the compartments and yolk globules as metabolic units is discussed in comparison with similar structures of the mature eggs of pigs and other mammal species.

[Microsatellite marker analysis of gynogenesis by artificial induction in Pseudosciaena crocea].

Gynogenesis was induced in two groups of Pseudosciaena crocea by the cool-shock and hydrostatic pressure method. The 24 fry in the gynogenetic families G1 and G2, 20 fry in their contrast groups and their parents were PCR amplified using 6 pairs of microsatellite marker primers LYC0002, LYC0003, LYC0013, LYC0012, LYC0004 and LYC0006 and analyzed. The results showed that the effect of cool-shock method, obtained a hatching rate of 35.3%, and a survival rate of 9.9% at 45 days, was obviously better than hydrostatic pressure method. Four pairs of primers could amplify clearly distinct parental bands. The results of primers LYC0012 and LYC0006 revealed no male gene in G1, suggesting they all derived from gynogenesis. Amplification using primers LYC0013 and LYC0004 in G2 revealed the presence of male genes in 3 individuals, suggesting they came from normal fertilization. The homozygosity ratio of the offspring from the two families was 87.5% and 76.2% and the average was 81.9%. They were 0 respectively in their contrast groups. The homozygous ratio of gene improved for 81.9% by gynogenesis. This study shows that gynogenesis is an effective method to promote gene purification In addition, microsatellite marker technique is an effective method of gynogenesis verification and genetic analysis.

Ovarian follicle development and transgenic mouse models.

Ovarian follicle development is a complex process that begins with the establishment of what is thought to be a finite pool of primordial follicles and culminates in either the atretic degradation of the follicle or the release of a mature oocyte for fertilization. This review highlights the many advances made in understanding these events using transgenic mouse models. Specifically, this review describes the ovarian phenotypes of mice with genetic mutations that affect ovarian differentiation, primordial follicle formation, follicular growth, atresia, ovulation and corpus luteum (CL) formation. In addition, this review describes the phenotypes of mice with mutations in a variety of genes, which affect the hormones that regulate folliculogenesis. Because studies using transgenic animals have revealed a variety of reproductive abnormalities that resemble many reproductive disorders in women, it is likely that studies using transgenic mouse models will impact our understanding of ovarian function and fertility in women.

The neuroendocrine mechanism responsible for sexual inversion of the gonad in the protandrous hermaphroditic mollusc, Crepidula fornicata L.

An in vitro investigation has clarified the neuroendocrine mechanism responsible for the differentiation of the female gonad in the protandrous hermaphrodite Crepidula fornicata. The male gonads were used as target organs; in some experiments they were brought to a uniform resting state by prior decerebration of donor animals. When isolated in culture, most of the male gonad degenerates, leaving only the stem cells lining the wall of the acini. No ovarian autodifferentiation has been observed. A masculinizing factor, released by the nervous ganglia during the male phase, controls spermatogonial mitosis and maintenance of male differentiation. A feminizing factor, secreted by the nervous ganglia during sex inversion and the female phase and present in the hemolymph, initiates oogonial mitosis and female differentiation in the male phase gonad.

[Oogonia degeneration in human pre- and perinatal oogenesis]. / Degeneratsiia oogoniev v pre- i perinatal'nom oogeneze cheloveka.

The number of the degenerating sex cells is extremely small in the period between the 6th and 12th-13th weeks of the intra-uterine development. The cells are represented by isolated oogonia at the interphase or mitosis and by oocytes. The number of the degenerating sex cells increases after the 13th week. Nearly all of them are represented by oocytes at all the stages of the meiosis prophase I. From the 26th week one may observe an intensive degeneration of the cells which is represented mostly by oocytes in diplo- and dictyotene.

Studies on the oogonial cycle in Puntius ticto (Ham.) III. Formation of degenerated follicles.

In Puntius ticto, the atresia has been observed both in mature and empty follicles. In empty follicles, theca becomes highly vascularized and the granulosa layer hypotrophied. The later invades into the lumen of the empty follicle and finally disappears. In yolk laden follicles, both theca and granulosa show hypertrophy in their cells. The granulosa becomes multilayered and finally starts digesting yolk globules after liquefying it.