Mitotic activity of germ cells during normal development of Xenopus laevis tadpoles

Development ◽  
1975 ◽  
Vol 34 (3) ◽  
pp. 687-694
Author(s):  
Ken-Ichi Ijiri ◽  
Nobuo Egami
Keyword(s):  
Xenopus Laevis ◽  
Germ Cell ◽  
Mitotic Activity ◽  
Germ Cells ◽  
Regional Difference ◽  
Normal Development ◽  
Uniform Value ◽  
Interesting Conclusion ◽  
Spatio Temporal ◽  
Gland Development

Data on the spatio-temporal pattern of germ cell proliferation in Xenopus laevis tadpoles were obtained, tracing the germ cells from the cloacal position forward. This spatial pattern in germ cell distribution and its change during normal development clearly coincided with histological observations of germ gland development. By application of regression lines to the analysis of this complex pattern, an interesting conclusion about the mitotic activity of germ cells was suggested. While the mitotic activity of germ cells before sexual differentiation shows a regional difference along the germ-cell-containing ridge (GCCR), the doubling time of sexually differentiated gonia seems to show a uniform value over the whole GCCR

Events in the germ cell lineage after entry of the primordial germ cells into the genital ridges in normal and u.v.-irradiated Xenopus laevis

Development ◽  
1977 ◽  
Vol 41 (1) ◽  
pp. 33-46
Author(s):  
Brigitta Züst ◽  
K. E. Dixon
Keyword(s):  
Xenopus Laevis ◽  
Germ Cell ◽  
Germ Cells ◽  
Dorsal Root ◽  
Primordial Germ Cells ◽  
Cell Lineage ◽  
Cell Stage ◽  
Comparison Of The Results ◽  
New Generation

Approximately 20–25 primordial germ cells leave the endoderm between stages 38–41 and localize in the dorsal root of the mesentery by stage 43/44. At this time all the cells contain large quantities of yolk which is gradually resorbed. The cells begin dividing between stages 48–52. The number and size of the germ cells were measured in tadpoles between stages 48–54 of development. The results indicate that in females the germ cells divide more often than in males. In both sexes the mitoses are grossly unequal, leading to the formation of a new generation of germ cells which are considerably smaller (one-tenth to one-fifth) than the size of the primordial germ cells at stage 48. The germ cells in male tadpoles at stage 54 are larger than in female tadpoles at the same stage. In tadpoles which developed from eggs irradiated in the vegetal hemisphere with u.v. light at the 2- to 4-cell-stage, primordial germ cells migrate into the genital ridges much later (stage 46–48) than in unirradiated embryos. They also differ morphologically from germ cells in control animals at this stage in that they are approximately one-tenth the size, lacking yolk in the cytoplasm and have a more highly lobed nucleus. Comparison of the results in unirradiated and irradiated animals suggests that the germ cell lineage is composed of a series of ordered, predictable events, and serious disruption of one of the events deranges later events.

Relationship between the amount of the ‘germinal plasm’ and the number of primordial germ cells in Xenopus laevis

Development ◽  
1974 ◽  
Vol 31 (1) ◽  
pp. 89-98
Author(s):  
Kazuyuki Tanabe ◽  
Minoru Kotani
Keyword(s):  
Xenopus Laevis ◽  
Germ Cell ◽  
Germ Cells ◽  
Primordial Germ Cells ◽  
The Other ◽  
Direct Proportion ◽  
Sensitive Material ◽  
Cell Stage ◽  
Other Hand ◽  
Germinal Plasm

Tadpoles of Xenopus laevis completely lacking primordial germ cells were obtained by irradiating the vegetal hemisphere of early 2-cell eggs with u.v. (wavelength, 253·7 nm; dose, ca. 6000 ergs/mm2). An increasing number of primordial germ cells were observed as the stage at irradiation advanced from early 2-cell to early 4-cell stages. Furthermore, early 2-cell eggs irradiated with doses ranging from 750 to 6000 ergs/mm2 grew into tadpoles carrying a decreasing number of primordial germ cells in accord with the increase of the dose. On the other hand, tadpoles developed from eggs irradiated immediately after being centrifuged at 150 g for 1 min at early 2-cell stage to displace the ‘germinal plasm’ deeper into the cytoplasm, carried a considerable number of primordial germ cells. These facts were interpreted to suggest the presence of u.v.-sensitive germ cell determinant in the ‘germinal plasm’. It was revealed by varying the area of irradiation that the number of primordial germ cells decreased in direct proportion to the increase of the area irradiated. It was concluded that the amount of the u.v.-sensitive material(s) contained in the ‘germinal plasm’ determined the number of primordial germ cells in tadpoles.

Replacement of posterior by anterior endoderm reduces sterility in embryos from inverted eggs of Xenopus laevis

Development ◽  
1986 ◽  
Vol 94 (1) ◽  
pp. 83-93
Author(s):  
J. H. Cleine
Keyword(s):  
Cell Differentiation ◽  
Xenopus Laevis ◽  
Germ Cell ◽  
Germ Cells ◽  
Germ Plasm ◽  
Primordial Germ Cells ◽  
Inverted Position ◽  
Control Series ◽  
Germ Cell Differentiation ◽  
Tailbud Stage

The genital ridges of Xenopus laevis tadpoles reared from eggs kept in an inverted position contain less than 40 % of the number of primordial germ cells (PGCs) of controls (Cleine & Dixon, 1985). It has been suggested that this reduction is caused by the germ cells' ectopic position in the anterior endoderm of larvae from inverted eggs, from where they may be unable to migrate into the genital ridges (Cleine & Dixon, 1985). This hypothesis is tested here by interchanging anterior and posterior endodermal grafts between pairs of inverted embryos at the early tailbud stage. Replacement of anterior by posterior endoderm has no effect but replacement of posterior by anterior endoderm increases the number of PGCs in the genital ridges and significantly reduces the proportion of sterile embryos. In a control series, in which the same type of grafting was done with normal embryos, replacement of posterior by anterior endoderm reduced the number of germ cells to almost zero, but replacement of anterior by posterior endoderm nearly doubled it. These findings are explained in terms of the distribution of the germ cells in the endoderm at the time of grafting. The results firstly show that the position of the germ cells is crucial to successful migration and secondly they support the notion that germ plasm has a determinative role during early germ cell differentiation.

scholarly journals OBSERVATIONS ON EARLY GERM CELL DEVELOPMENT AND PREMEIOTIC RIBOSOMAL DNA AMPLIFICATION IN XENOPUS LAEVIS

1974 ◽  
Vol 62 (2) ◽  
pp. 460-472 ◽  
Author(s):  
Marvin R. Kalt ◽  
Joseph G. Gall
Keyword(s):  
Xenopus Laevis ◽  
Germ Cell ◽  
Ribosomal Dna ◽  
Germ Cells ◽  
Dna Hybridization ◽  
Meiotic Prophase ◽  
Germ Line ◽  
Tritiated Thymidine ◽  
Gradient Centrifugation ◽  
Dna Amplification

The origin of premeiotic ribosomal DNA (rDNA) amplification in germ-line cells of Xenopus laevis has been examined using in situ RNA-DNA hybridization on cytological preparations, tritiated thymidine autoradiography, and isopycnic density gradient centrifugation. Primordial germ cells (PGC), from the time they first become localized in the genital ridge at day no. 4 of development, until approximately day no. 22, remain in an extended interphase condition. During this time PGC do not incorporate tritiated thymidine, have near diploid levels of rDNA as demonstrated by cytological RNA-DNA hybridization, and possess only one or two nucleoli. Starting on day no. 22–24, mitosis, sexual differentiation, and rDNA gene amplification all begin in the germ cells. Multiple nucleoli also make their appearance at this stage. Ribosomal DNA amplification continues in gonial cells as long as they remain mitotically active. Amplified copies of rDNA are lost from germ cells at the onset of meiotic prophase. This loss is probably permanent in the male germ line, but variable and temporary in the female germ line. Early gonial cells in the ovary have been deduced to have an average cycle time for each mitotic division of between 3.8 and 4.3 days at a temperature of 21°C. Some oogonia appear to divide only four times before entering meiotic prophase, while the average during the initial wave of germ cell division is nine. Finally, a satellite DNA has been isolated from adult testes which has a density in neutral cesium chloride corresponding to the density of amplified oocyte rDNA. This satellite is not present in DNA isolated from somatic tissues of Xenopus.

Germ-cell transfer and sex ratio in Xenopus laevis

Development ◽  
1965 ◽  
Vol 13 (1) ◽  
pp. 51-61
Author(s):  
A. W. Blackler
Keyword(s):  
Xenopus Laevis ◽  
Germ Cell ◽  
South African ◽  
Germ Cells ◽  
Sexual Differentiation ◽  
Primordial Germ Cells ◽  
Primordial Germ Cell ◽  
Hormone Treatment ◽  
Sex Reversal ◽  
Cell Transfer

A Technique for the transfer of primordial germ cells between neurulae of the South African Clawed Toad Xenopus laevis has been described by Blackler & Fischberg (1961). This method was originally developed with the object in mind of eventually making a genetic analysis of abnormal embryos resulting from the transplantation of somatic nuclei. Such analysis involves two schemes which require the transfer of embryonic gonocytes from the defective transplant embryo to a normal recipient. Moreover, one of these two schemes requires that transferred germ cells be reversed in their sexual differentiation in the developing gonad of the host (see Fischberg, 1961; Fischberg & Blackler, 1963a, b). Since it has been known for some time, from experiments involving parabiosis, transplantation of the gonadal rudiment and hormone treatment (e.g. Burns, 1925, 1930; Witschi, 1937; Humphrey, 1929, 1933, 1948, 1957; Gallien, 1953, 1956), that the manifestation of the sex genotype of a primordial germ cell can be physiologically reversed by the hormonal characteristics of the gonad, there seemed no obstacle to obtaining sex-reversal of the transferred gonocytes in Xenopus.

GROWTH, CARCASS MEASUREMENTS AND SEXUAL DEVELOPMENT OF PARTIALLY AND COMPLETELY CASTRATED PIGS

1968 ◽  
Vol 48 (3) ◽  
pp. 353-359
Author(s):  
E. E. Swierstra ◽  
G. W. Rahnefeld
Keyword(s):  
Germ Cell ◽  
Histological Examination ◽  
Conventional Method ◽  
Germ Cells ◽  
Sexual Development ◽  
Cell Populations ◽  
Slaughter Weight ◽  
Significant Difference ◽  
Testis Volume ◽  
Gland Development

Rate of gain, carcass measurements and sexual development of 19 males, partially castrated by Baiburtcjan’s method, were compared with those of 39 littermates castrated by the conventional method. The partial castrates reached slaughter weight of about 89 kg at 130 days of age and the complete castrates at 132 days of age. There was no significant difference between the two castration methods with respect to age-at-slaughter, dressing percentage, ham weight, loin-eye area, average backfat thickness and carcass length. The regenerated testes of the partial castrates averaged 34.5 g. Histological examination of these testes revealed that the fraction of the testis volume occupied by intertubular space was about twice that found in normal mature testes. All testes contained all stages of the cycle of the seminiferous epithelium, indicating that sperm were being produced. This observation was substantiated by the presence of sperm in 28 of the 35 epididymides examined. In addition to tubules with normal germ cell populations, there were many tubules that lacked one or more generations of germ cells, or that lacked germ cells entirely. Accessory sex gland development was directly proportional to the weight of the paired testes. Forty-seven percent of the partial castrates were graded as ridglings (cryptorchids) and their average sale value was 19% less than that of the complete castrates.

The spatio-temporal framework of melanogenic induction in pigmented retinal cells of Xenopus laevis

Development ◽  
1980 ◽  
Vol 60 (1) ◽  
pp. 173-188
Author(s):  
Olga A. Hoperskaya ◽  
Olga N. Golubeva
Keyword(s):  
Xenopus Laevis ◽  
Normal Development ◽  
Rana Temporaria ◽  
Terminal Differentiation ◽  
Gastrula Stage ◽  
Cell Type ◽  
Retinal Cells ◽  
Spatio Temporal ◽  
Species Specific

Using methods involving transplantation of neuroectoderm and eye rudiments between aap/ap mutants and + / + embryos of Xenopus laevis, new aspects of melanogenic induction have been ascertained. The possibility of separate induction of a melanocyte cell type and of the product of terminal differentiation in it — melanosomes, has been demonstrated. Melanogenic induction starts at the late gastrula stage. It has an irreversible character which has been shown using the technique of double transplantation. Melanogenic factor (MgF) is produced only by the region of endomesoderm which is adjacent to eye rudiments in the course of normal development. Competence for melanogenic induction lasts till stage NF 30. Melanogenic induction appears to be species-specific; at least after transplantation of eye vesicles from ap/apXenopus laevis to Rana temporaria the melanoprotein synthesis cannot be switched on. L-Tyrosine, under the conditions of the experiments, is not a factor in the induction of melanogenesis.

Electron microscope study of the effects of radiation on insect fertility

1990 ◽  
Vol 48 (3) ◽  
pp. 72-73
Author(s):  
Judy Ju-Hu Chiang ◽  
Robert Kuo-Cheng Chen
Keyword(s):  
Electron Microscopy ◽  
Germ Cell ◽  
Germ Cells ◽  
Electron Microscope Study ◽  
Radiation Treatment ◽  
Light And Electron Microscopy ◽  
Stem Borer ◽  
Metabolic Energy ◽  
Rice Stem Borer ◽  
Effects Of Radiation

Germ cells from the rice stem borer Chilo suppresalis, were examined by light and electron microscopy. Damages to organelles within the germ cells were observed. The mitochondria, which provide the cell with metabolic energy, were seen to disintegrate within the germ cell. Lysosomes within the germ cell were also seen to disintegrate. The subsequent release of hydrolytic enzymesmay be responsible for the destruction of organelles within the germ cell. Insect spermatozoa were seen to lose the ability to move because of radiation treatment. Damage to the centrioles, one of which is in contact with the tail, may be involved in causing sperm immobility.

Examination of the dynamics of global DNA methylation pattern establishment during spermatogenesiss

2007 ◽  
Vol 30 (4) ◽  
pp. 90
Author(s):  
Kirsten Niles ◽  
Sophie La Salle ◽  
Christopher Oakes ◽  
Jacquetta Trasler
Keyword(s):  
Dna Methylation ◽  
Germ Cell ◽  
Germ Cells ◽  
Epigenetic Modification ◽  
Methylation Pattern ◽  
Chromosome 9 ◽  
Specific Gene ◽  
Global Methylation ◽  
Dna Methylation Pattern ◽  
Methylation Patterns

Background: DNA methylation is an epigenetic modification involved in gene expression, genome stability, and genomic imprinting. In the male, methylation patterns are initially erased in primordial germ cells (PGCs) as they enter the gonadal ridge; methylation patterns are then acquired on CpG dinucleotides during gametogenesis. Correct pattern establishment is essential for normal spermatogenesis. To date, the characterization and timing of methylation pattern acquisition in PGCs has been described using a limited number of specific gene loci. This study aimed to describe DNA methylation pattern establishment dynamics during male gametogenesis through global methylation profiling techniques in a mouse model. Methods: Using a chromosome based approach, primers were designed for 24 regions spanning chromosome 9; intergenic, non-repeat, non-CpG island sequences were chosen for study based on previous evidence that these types of sequences are targets for testis-specific methylation events. The percent methylation was determined in each region by quantitative analysis of DNA methylation using real-time PCR (qAMP). The germ cell-specific pattern was determined by comparing methylation between spermatozoa and liver. To examine methylation in developing germ cells, spermatogonia from 2 day- and 6 day-old Oct4-GFP (green fluorescent protein) mice were isolated using fluorescence activated cell sorting. Results: As compared to liver, four loci were hypomethylated and five loci were hypermethylated in spermatozoa, supporting previous results indicating a unique methylation pattern in male germ cells. Only one region was hypomethylated and no regions were hypermethylated in day 6 spermatogonia as compared to mature spermatozoa, signifying that the bulk of DNA methylation is established prior to type A spermatogonia. The methylation in day 2 spermatogonia, germ cells that are just commencing mitosis, revealed differences of 15-20% compared to day 6 spermatogonia at five regions indicating that the most crucial phase of DNA methylation acquisition occurs prenatally. Conclusion: Together, these studies provide further evidence that germ cell methylation patterns differ from those in somatic tissues and suggest that much of methylation at intergenic sites is acquired during prenatal germ cell development. (Supported by CIHR)

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