Internet: A loose confederation of computer communication networks around the world. The networks that make up the Internet are connected through several backbone networks. The Internet grew out of the US Government ARPAnet project and was designed to facilitate information exchange.Germ Cells: The reproductive cells in multicellular organisms at various stages during GAMETOGENESIS.User-Computer Interface: The portion of an interactive computer program that issues messages to and receives commands from a user.Software: Sequential operating programs and data which instruct the functioning of a digital computer.Computer Graphics: The process of pictorial communication, between human and computers, in which the computer input and output have the form of charts, drawings, or other appropriate pictorial representation.Web Browser: Software application for retrieving, presenting and traversing information resources on the World Wide Web.Neoplasms, Germ Cell and Embryonal: Neoplasms composed of primordial GERM CELLS of embryonic GONADS or of elements of the germ layers of the EMBRYO, MAMMALIAN. The concept does not refer to neoplasms located in the gonads or present in an embryo or FETUS.Wheelchairs: Chairs mounted on wheels and designed to be propelled by the occupant.Anniversaries and Special Events: Occasions to commemorate an event or occasions designated for a specific purpose.Stem Cells: Relatively undifferentiated cells that retain the ability to divide and proliferate throughout postnatal life to provide progenitor cells that can differentiate into specialized cells.History, 20th Century: Time period from 1901 through 2000 of the common era.History, 21st Century: Time period from 2001 through 2100 of the common era.History, 19th Century: Time period from 1801 through 1900 of the common era.Sanitation: The development and establishment of environmental conditions favorable to the health of the public.Mediastinal Neoplasms: Tumors or cancer of the MEDIASTINUM.Endodermal Sinus Tumor: An unusual and aggressive tumor of germ-cell origin that reproduces the extraembryonic structures of the early embryo. It is the most common malignant germ cell tumor found in children. It is characterized by a labyrinthine glandular pattern of flat epithelial cells and rounded papillary processes with a central capillary (Schiller-Duval body). The tumor is rarely bilateral. Before the use of combination chemotherapy, the tumor was almost invariably fatal. (From DeVita Jr et al., Cancer: Principles & Practice of Oncology, 3d ed, p1189)Germinoma: A malignant neoplasm of the germinal tissue of the GONADS; MEDIASTINUM; or pineal region. Germinomas are uniform in appearance, consisting of large, round cells with vesicular nuclei and clear or finely granular eosinophilic-staining cytoplasm. (Stedman, 265th ed; from DeVita Jr et al., Cancer: Principles & Practice of Oncology, 3d ed, pp1642-3)Testicular Neoplasms: Tumors or cancer of the TESTIS. Germ cell tumors (GERMINOMA) of the testis constitute 95% of all testicular neoplasms.Seminoma: A radiosensitive, malignant neoplasm of the testis, thought to be derived from primordial germ cells of the sexually undifferentiated embryonic gonad. There are three variants: classical (typical), the most common type; anaplastic; and spermatocytic. The classical seminoma is composed of fairly well differentiated sheets or cords of uniform polygonal or round cells (seminoma cells), each cell having abundant clear cytoplasm, distinct cell membranes, a centrally placed round nucleus, and one or more nucleoli. In the female, a grossly and histologically identical neoplasm, known as dysgerminoma, occurs. (Dorland, 27th ed)Carcinoma, Embryonal: A highly malignant, primitive form of carcinoma, probably of germinal cell or teratomatous derivation, usually arising in a gonad and rarely in other sites. It is rare in the female ovary, but in the male it accounts for 20% of all testicular tumors. (From Dorland, 27th ed & Holland et al., Cancer Medicine, 3d ed, p1595)Marijuana Smoking: Inhaling and exhaling the smoke from CANNABIS.

The Caenorhabditis elegans sex determination gene mog-1 encodes a member of the DEAH-Box protein family. (1/2975)

In the Caenorhabditis elegans hermaphrodite germ line, the sex-determining gene fem-3 is repressed posttranscriptionally to arrest spermatogenesis and permit oogenesis. This repression requires a cis-acting regulatory element in the fem-3 3' untranslated region; the FBF protein, which binds to this element; and at least six mog genes. In this paper, we report the molecular characterization of mog-1 as well as additional phenotypic characterization of this gene. The mog-1 gene encodes a member of the DEAH-box family. Three mog-1 alleles possess premature stop codons and are likely to be null alleles, and one is a missense mutation and is likely to retain residual activity. mog-1 mRNA is expressed in both germ line and somatic tissues and appears to be ubiquitous. The MOG-1 DEAH-box protein is most closely related to proteins essential for splicing in the yeast Saccharomyces cerevisiae, but splicing appears to occur normally in a mog-1-null mutant. In addition to its involvement in the sperm-oocyte switch and control of fem-3, zygotic mog-1 is required for robust germ line proliferation and for normal growth during development. We suggest that mog-1 plays a broader role in RNA regulation than previously considered.  (+info)

Bmp4 is required for the generation of primordial germ cells in the mouse embryo. (2/2975)

In many organisms the allocation of primordial germ cells (PGCs) is determined by the inheritance of maternal factors deposited in the egg. However, in mammals, inductive cell interactions are required around gastrulation to establish the germ line. Here, we show that Bmp4 homozygous null embryos contain no PGCs. They also lack an allantois, an extraembryonic mesodermal tissue derived, like the PGCs, from precursors in the proximal epiblast. Heterozygotes have fewer PGCs than normal, due to a reduction in the size of the founding population and not to an effect on its subsequent expansion. Analysis of beta-galactosidase activity in Bmp4(lacZneo) embryos reveals that prior to gastrulation, Bmp4 is expressed in the extraembryonic ectoderm. Later, Bmp4 is expressed in the extraembryonic mesoderm, but not in PGCs. Chimera analysis indicates that it is the Bmp4 expression in the extraembryonic ectoderm that regulates the formation of allantois and primordial germ cell precursors, and the size of the founding population of PGCs. The initiation of the germ line in the mouse therefore depends on a secreted signal from the previously segregated, extraembryonic, trophectoderm lineage.  (+info)

Germ cell development in the XXY mouse: evidence that X chromosome reactivation is independent of sexual differentiation. (3/2975)

Prior to entry into meiosis, XX germ cells in the fetal ovary undergo X chromosome reactivation. The signal for reactivation is thought to emanate from the genital ridge, but it is unclear whether it is specific to the developing ovary. To determine whether the signals are present in the developing testis as well as the ovary, we examined the expression of X-linked genes in germ cells from XXY male mice. To facilitate this analysis, we generated XXY and XX fetuses carrying X chromosomes that were differentially marked and subject to nonrandom inactivation. This pattern of nonrandom inactivation was maintained in somatic cells but, in XX as well as XXY fetuses, both parental alleles were expressed in germ cell-enriched cell populations. Because testis differentiation is temporally and morphologically normal in the XXY testis and because all germ cells embark upon a male pathway of development, these results provide compelling evidence that X chromosome reactivation in fetal germ cells is independent of the somatic events of sexual differentiation. Proper X chromosome dosage is essential for the normal fertility of male mammals, and abnormalities in germ cell development are apparent in the XXY testis within several days of X reactivation. Studies of exceptional germ cells that survive in the postnatal XXY testis demonstrated that surviving germ cells are exclusively XY and result from rare nondisjunctional events that give rise to clones of XY cells.  (+info)

Ialpha exon-replacement mice synthesize a spliced HPRT-C(alpha) transcript which may explain their ability to switch to IgA. Inhibition of switching to IgG in these mice. (4/2975)

Antibody class switching is regulated by transcription of unrearranged C(H) genes to produce germline (GL) transcripts which direct the choice of isotype and are required for switching. However, their role is unknown. GL transcripts are initiated at the I exons located upstream of each switch region. Although deletion of the I exon by gene targeting prevents switch recombination to that CH gene, the Ialpha exon can be replaced by an entirely different DNA segment, a minigene driven by the phosphoglycerate kinase (PGK) promoter and encoding hypoxanthine phosphoribosyl transferase (HPRT), oriented in the sense direction, without reducing antibody class switching to IgA. To understand why HPRT substitution of the Ialpha exon does not disrupt switch recombination, we have analyzed the structure of the transcript from the targeted allele in these mice. We identify a spliced transcript in which the HPRT exons are spliced to the C(alpha) gene segments, resulting in a structure similar to normal GL transcripts. The abundance of this transcript is similar to that of the normal alpha GL RNA. We also demonstrate that switching to the four IgG subclasses in B cells from these mice is reduced in comparison to wild-type mice. We discuss the possibility that the strong PGK promoter inserted at the Ig alpha locus may interfere with interaction of the promoters for gamma GL transcripts with the 3' IgH enhancer.  (+info)

Production of donor-derived offspring by transfer of primordial germ cells in Japanese quail. (5/2975)

We transfused concentrated primordial germ cells (PGCs) of the black strain (D: homozygous for the autosomal incomplete dominant gene, D) of quail into the embryos of the wild-type plumage strain (WP: d+/d+) of quail. The recipient quail were raised until sexual maturity and a progeny test of the putative germline chimeras was performed to examine the donor gamete-derived offspring (D/d+). Thirty-one percent (36/115) of the transfused quail hatched and 21 (13 females and 8 males) of them reached maturity. Five females and 2 males were germline chimeras producing donor gamete-derived offspring. Transmission rates of the donor derived gametes in the chimeric females and males were 1.8-8.3% and 2.6-63.0%, respectively. Germline chimeric and the other putative chimeric males were also test-mated with females from the sex-linked imperfect albino strain (AL: d+/d+, al/W, where al indicates the sex-linked imperfect albino gene on the Z chromosome, and W indicates the W chromosome) for autosexing of W-bearing spermatozoa: No albino offspring were born.  (+info)

Histone ubiquitination and chromatin remodeling in mouse spermatogenesis. (6/2975)

Male infertility in HR6B knockout mice is associated with impairment of spermatogenesis. The HR6B gene is a mammalian, autosomal homolog of the Saccharomyces cerevisiae gene Rad6 encoding a ubiquitin-conjugating enzyme. In addition, X-chromosomal HR6A has been identified, in human and mouse. RAD6 in yeast is required for a variety of cellular functions, including sporulation, DNA repair, and mutagenesis. Since RAD6 and its mammalian homologs can ubiquitinate histones in vitro, we have investigated the pattern of histone ubiquitination in mouse testis. By immunoblot and immunohistochemical analysis of wild-type mouse testis, a high amount of ubiquitinated H2A (uH2A) was detected in pachytene spermatocytes. This signal became undetectable in round spermatids, but then increased again during a relatively short developmental period, in elongating spermatids. No other ubiquitinated histones were observed. In the HR6B knockout mice, we failed to detect an overt defect in the overall pattern of histone ubiquitination. For somatic cell types, it has been shown that histone ubiquitination is associated with destabilization of nucleosomes, in relation to active gene transcription. Unexpectedly, the most intense uH2A signal in pachytene spermatocytes was detected in the sex body, an inactive nuclear structure that contains the heterochromatic X and Y chromosomes. The postmeiotic uH2A immunoexpression in elongating spermatids indicates that nucleosome destabilization induced by histone ubiquitination may play a facilitating role during histone-to-protamine replacement.  (+info)

Activin and TGFbeta limit murine primordial germ cell proliferation. (7/2975)

Mammalian primordial germ cells (PGCs) proliferate as they migrate from their initial location in the extraembryonic mesoderm to the genital ridge, the gonadal anlage. Once in the genital ridge, PGCs cease dividing and differentiate according to their gender. To identify ligands that might limit PGC proliferation, we analyzed growth factor receptors encoded in RNA obtained from purified germ cells shortly after their arrival in the genital ridge. Receptors for two members of the TGFbeta superfamily were found, TGFbeta1 and activin. As the signal-transducing domains of both receptor systems are highly conserved, the effects of both TGFbeta1 and activin on PGCs would be expected to be similar. We found that both ligands limited the accumulation of germ cells in primary PGC cultures. BrdU incorporation assays demonstrated that either ligand inhibits PGC proliferation. These results suggest that these signal transduction pathways are important elements of the mechanism that determines germ cell endowment.  (+info)

A novel quantitative morphometry of germ cells for the histopathological evaluation of rat testicular toxicity. (8/2975)

A view that 14 stages of rat spermatogenic cycle could be arranged into 4 groups, viz., conventional stages I-VI, VII-VIII, IX-XI and XII-XIV, according to the features of elongated spermatids was previously presented. A novel morphometry of seminiferous epithelia based on these 4 groups was also proposed. In the present study, utility of the proposed morphometry in the histopathological evaluations of testicular toxicities was monitored in comparison with the conventional one. After administrating adriamycin, ethylene glycol monomethyl ether or 1,3-dinitrobenzene to rats, the viability of their germ cells was estimated by the proposed morphometry and the conventional one employed stages II-III, V, VII, X and XII. In every case, the evaluating results of the proposed morphometry were similar to those of the conventional one. Thus, it was verified that the proposed morphometry was identical with the conventional one in respect of reliable detection of the testicular toxicities. In addition, in situ terminal dUTP nick end labeling indicated that death of spermatogonia, pachytene spermatocytes or round spermatids induced by the above 3 toxic compounds was exclusively apoptotic death. In conclusion, the proposed morphometry would be useful as a practical tool in the evaluation of testicular toxicities.  (+info)

  • Epigenetic reprogramming in mammalian germ cells, zygote and early embryos, plays a crucial role in regulating genome functions at critical stages of development. (hu-berlin.de)
  • To grow cultures of human ES cells, Thomson and his collaborators used 36 fresh or frozen embryos generated in IVF laboratories from couples undergoing treatment for infertility. (nih.gov)
  • From the 14 embryos that developed to the blastocyst stage, they established 5 human ES cell lines-H1, H7, H9, H13 and H14 [ 35 ]. (nih.gov)
  • DNA methylation and post-translational modifications (PTMs) of histones have been extensively characterised in cell types present in, or derived from, mouse embryos. (biomedcentral.com)
  • We are testing the possibility that certain Turner features result from reduced protein synthetic capacity in embryos with only one RPS4 gene per cell. (searlescholars.net)
  • The pluripotency of transgene-free iPSCs was confirmed by immunocytochemistry for pluripotency markers and by the ability of the iPSCs to differentiate spontaneously into 3 germ layers in vitro. (readbyqxmd.com)
  • Because these cells retain their developmental properties after being isolated and established in vitro from the inner cell mass of the blastocyst, they are the archetypal pluripotent cells. (biomedcentral.com)
  • Biology Open provides rapid publication for scientifically sound observations and valid conclusions in developmental, cell, experimental and translational biology. (biologists.org)
  • Functional germ cells are special because they do not contain a double set of chromosomes and are no longer capable of division," says Professor Christian R. Eckmann, a developmental geneticist and Heisenberg Professor at MLU. (idw-online.de)
  • These findings of the MLU research group on Developmental Genetics suggest that the same genetic program may operate in germ cells of other, more complex organisms as well - albeit in a timely less compressed form. (idw-online.de)
  • Signaling mechanisms in the fetal testis and ovary determine whether germ cells enter the male or female developmental pathway, respectively. (biomedcentral.com)
  • At the onset of testis or ovary development the germ cells can enter the male or female developmental pathway, regardless of whether they are genetically male (XY) or female (XX). (biomedcentral.com)
  • Complete understanding of the germline reprogramming processes is important not only in the light of genomic imprinting but also for resolving other mechanisms connected with restoring cellular totipotency, such as cloning and stem cell derivation. (hu-berlin.de)
  • J Stem Cell Res Ther 4:201. (omicsonline.org)
  • Further comparative transcriptomics illustrates similarities between GSCs and primordial germ cells and provides a molecular footprint of the stem cell state. (biologists.org)
  • All this enthusiasm for stem cells has been propelled by advances in stem cell biology, which have been fueled and complemented by research on model organisms ( Hunter, 2008 ). (biologists.org)
  • For a germ cell to develop out of a stem cell, two specific RNA-binding proteins need to be destroyed to reorganise the cell's genetic programme. (idw-online.de)
  • As cells divide and differentiate throughout the lifespan of an organism or cell line, the telomeres become progressively shortened and lose the ability to maintain their length. (nih.gov)
  • After entering the developing testes or ovary the germ cells differentiate down the spermatogenic or oogenic pathways in response to their respective environments [ 6 - 9 ]. (biomedcentral.com)
  • As a foundation to explore the role of these RNA-binding proteins in germ cells, we established a novel transgenic reporter strain that expresses NANOS3 fused with EGFP under the control of Nanos3 regulatory elements. (bioscientifica.com)
  • In the absence of AZF , spermatogenic output is diminished or extinguished, and in the more severe cases the testes contain no germ cells. (searlescholars.net)
  • Germ line epigenetic reprogramming assures erasure of all the imprinting marks and epi-mutations and establishment of new sex-specific gametic imprints. (hu-berlin.de)
  • Single-cell genome analyses reveal the amount of mutations a human brain cell will collect from its fetal beginnings until death. (the-scientist.com)
  • Neoplasms, Germ Cell and Embryonal" is a descriptor in the National Library of Medicine's controlled vocabulary thesaurus, MeSH (Medical Subject Headings) . (umassmed.edu)
  • This graph shows the total number of publications written about "Neoplasms, Germ Cell and Embryonal" by people in this website by year, and whether "Neoplasms, Germ Cell and Embryonal" was a major or minor topic of these publications. (umassmed.edu)
  • Below are the most recent publications written about "Neoplasms, Germ Cell and Embryonal" by people in Profiles. (umassmed.edu)
  • This is evidence for specification of germ cells by induction. (bionity.com)
  • A 62-year old Chinese Han Alzheimer's disease (AD) female patient with ApoE3/4 genetic background donated her Peripheral blood mononuclear cells (PBMC). (readbyqxmd.com)
  • Widely different programmes have to be sequenced in parallel to produce gametes: „On the one hand, the genetic material of the source cells must be halved in the cell division process. (idw-online.de)
  • In this study we have developed a small molecule screening protocol combined with flow cytometry to identify signaling pathways that direct male-specific development of germ cells. (biomedcentral.com)
  • Germ cells are the only type of cell that can transmit all genomic information to the next generation. (omicsonline.org)
  • In birds, which lack germline-competent stem cells , genomic modulation of germ cells might serve to generate genetically modified poultry for both commercial applications and basic research. (omicsonline.org)