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Female Embryos (female + embryo)
Selected AbstractsHuman and pig SRY 5, flanking sequences can direct reporter transgene expression to the genital ridge and to migrating neural crest cellsDEVELOPMENTAL DYNAMICS, Issue 3 2006Alexandre Boyer Abstract Mechanisms for sex determination vary greatly between animal groups, and include chromosome dosage and haploid,diploid mechanisms as seen in insects, temperature and environmental cues as seen in fish and reptiles, and gene-based mechanisms as seen in birds and mammals. In eutherian mammals, sex determination is genetic, and SRY is the Y chromosome located gene representing the dominant testes determining factor. How SRY took over this function from ancestral mechanisms is not known, nor is it known what those ancestral mechanisms were. What is known is that SRY is haploid and thus poorly protected from mutations, and consequently is poorly conserved between mammalian species. To functionally compare SRY promoter sequences, we have generated transgenic mice with fluorescent reporter genes under the control of various lengths of human and pig SRY 5, flanking sequences. Human SRY 5, flanking sequences (5 Kb) supported reporter transgene expression within the genital ridge of male embryos at the time of sex determination and also supported expression within migrating truncal neural crest cells of both male and female embryos. The 4.6 Kb of pig SRY 5, flanking sequences supported reporter transgene expression within the male genital ridge but not within the neural crest; however, 2.6 Kb and 1.6 Kb of pig SRY 5, flanking sequences retained male genital ridge expression and now supported extensive expression within cells of the neural crest in embryos of both sexes. When 2 Kb of mouse SRY 5, flanking sequences (,3 to ,1 Kb) were placed in front of the 1.6 Kb of pig SRY 5, flanking sequences and this transgene was introduced into mice, reporter transgene expression within the male genital ridge was retained but neural crest expression was lost. These observations suggest that SRY 5, flanking sequences from at least two mammalian species contain elements that can support transgene expression within cells of the migrating neural crest and that additional SRY 5, flanking sequences can extinguish this expression. Developmental Dynamics 235:623,632, 2006. © 2006 Wiley-Liss, Inc. [source] Gonadal morphogenesis and sex differentiation in intraovarian embryos of the viviparous fish Zoarces viviparus (Teleostei, Perciformes, Zoarcidae): A histological and ultrastructural studyJOURNAL OF MORPHOLOGY, Issue 9 2006Tina H. Rasmussen Abstract It is essential to know the timing and process of normal gonadal differentiation and development in the specific species being investigated in order to evaluate the effect of exposure to endocrine-disrupting chemicals on these processes. In the present study gonadal sex differentiation and development were investigated in embryos of a viviparous species of marine fish, the eelpout, Zoarces viviparus, during their intraovarian development (early September to January) using light and electron microscopy. In both sexes of the embryos at the time of hatching (September 20) the initially undifferentiated paired bilobed gonad contains primordial germ cells. In the female embryos, ovarian differentiation, initiated 14 days posthatch (dph), is characterized by the initial formation of the endoovarian cavity of the single ovary as well as by the presence of some early meiotic oocytes in a chromatin-nucleolus stage. By 30 dph, the endoovarian cavity has formed. By 44 dph and onward, the ovary and the oocytes grow in size and at 134 dph, just prior to birth, the majority of the oocytes are at the perinucleolar stage of primary growth and definitive follicles have formed. In the presumptive bilobed testis of the male embryos, the germ cells (spermatogonia), in contrast to the germ cells of the ovary, remain quiescent and do not enter meiosis during intraovarian development. However, other structural (somatic) changes, such as the initial formation of the sperm duct (30 dph), the presence of blood vessels in the stromal areas of the testis (30 dph), and the appearance of developing testicular lobules (102 dph), indicate testicular differentiation. Ultrastructually, the features of the primordial germ cells, oogonia, and spermatogonia are similar, including nuage, mitochondria, endoplasmic reticulum, and Golgi complexes. J. Morphol. © 2006 Wiley-Liss, Inc. [source] Altered mRNA expression patterns in bovine blastocysts after fertilisation in vitro using flow-cytometrically sex-sorted spermMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 8 2007K.M. Morton Abstract Sperm-sexing has been used to produce embryos and offspring of a pre-determined sex in a number of species. However, the fertility of sex-sorted sperm is reduced and the full effects of sperm-sexing remain to be elucidated. The purpose of the present study was to investigate the potential effects of sex-sorted sperm on mRNA expression patterns of developmentally important genes employing in vitro produced bovine embryos. Bovine embryos were produced in vitro with unsorted and sex-sorted sperm and mRNA expression patterns were determined for glucose-3 transporter (Glut-3), glucose-6-phosphate dehydrogenase (G6PD), X-inactive specific transcript (X-ist) and Heat shock protein 70.1 (Hsp) using semi-quantitative endpoint reverse transcriptase-PCR in male and female, day-7 and 8 embryos. The relative abundance (RA) of Glut-3 was higher for day-7 male than female embryos, and day-7 embryos derived from unsorted compared with sex-sorted sperm. The RA of G6PD was higher for embryos derived from unsorted than sex-sorted sperm, and for day-8 female compared with male embryos. The RA of Xist was higher for female than male embryos, and for day-7 female embryos derived from unsorted than sex-sorted sperm. Hsp RA was higher for female compared with male embryos, was similar for day-7 and 8 embryos, and unsorted and sex-sorted sperm derived embryos. These results demonstrate differential expression of developmentally important genes between male and female embryos, and embryos derived from unsorted and sex-sorted sperm. Mol. Reprod. Dev. 74: 931,940, 2007. © 2007 Wiley-Liss, Inc. [source] The Biology of the Development of the Genital Organs.ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 2005A Multimedia Teaching Program In my presentation, I review the sexual differentiation from the genetic sex until the appearance of the external genitalia and the developmental anomalies to use an animated cartoon. The first critical stage of sexual differentiation occurs at the moment of fertilization, when the genetic sex of the zygote is determined by the nature of the sex chromosome contributed by the sperm. Although an XY zygote is destined to become a male, no distinctive differences between the early development of male and female embryos have been noted. This is accomplished after migration of the primordial germ cell into the early gonad. Because of the early commonality of genital structures, anomalies are the result of abnormal retention or loss of appropriate genital structures. Therefore, most genital anomalies are some form of intersex. During the early differentiation of the gonads, while the mesonephros is still the dominant excretory organ, the gonads arise as ridge like thickenings (gonadal ridge) on its ventromedial face. Differentiation of the indifferent gonads into ovaries or testes occurs after the arrival of the primordial germ cells. The primordial germ cells arise from the endodermal cells of the yolk. The principal function of the Y chromosome is to direct the differentiation of the presented indifferent gonad into a testis from the sixth week, while two X chromosome are presented the ovaries start to develop, from the 12th week. The next and most obvious phase in sexual differentiation of the embryo is the differentiation of the somatic sex. The early embryo develops a dual set of potential genital ducts, one is the original mesonephric (Wolff ) ducts, which persists after degeneration of the mesonephros as an excretory organ, and the another is newly formed pair of ducts called the paramesonephric (Müllerian) ducts. Under the influence of testosterone secreted by the testes, the mesonephric ducts develop into the duct system through which the spermatozoa are conveyed from the testes to the urethra. The potentially female paramesonephric ducts regress under the influence of another product of the embryonic testes, the Müllerian inhibitory factor, a glycoprotein secreted by the Sertoli cells. In genetically female embryos, neither testosterone nor Müllerian inhibitory factor are secreted by the gonads. In the absence of testosterone the mesonephric ducts regress and lack of Müllerian inhibitory factor permits the paramesonephric ducts to develop into oviducts, the uterus and part of the vagina. The next stage is the development of the external genitalia. In very young embryos, a vaguely outlined elevation known as the genital eminence can be seen in the midline, just cephalic to the proctodeal depression. This is soon differentiated into a central prominence (genital tubercle) closely flanked by a pair of folds (genital folds) extending toward the proctodeum. Somewhat farther to either side are rounded elevation known as the genital swellings. From this common starting point the external genitalia of both sex differentiate. If the individual is to develop into a male the genital tubercle, under the influence of dihydrotestosterone, becomes greatly elongated to form the penis and the genital swellings become enlarged to form the scrotal pouches. During the growth of the penis a groove develops along the entire length of its caudal face and is continuous with the slit-like opening of the urogenital sinus. This groove later becomes closed over by a ventral fusion of the genital folds, establishing the penile portion of the urethra. The portion of the urogenital sinus between the neck of the bladder and the original opening of the urogenital sinus becomes the prostetic urethra. In the female, the genital tubercle becomes the clitoris, the genital folds become the labia minora, and the genital swellings become the labia majora. The urethra in the female is derived from the urogenital sinus, being homologous with the prostatic portion of the male urethra. [source] | ||||||||||