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Results for “Embryonic division”

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PubMedDate not supplied

Development of an in vivo model to study testicular morphogenesis.

We have developed an in vivo model to examine testicular cord formation by isolated Sertoli and myoid cells when implanted under the kidney capsule of severe combined immunodeficient (SCID) mice. Neonatal porcine Sertoli (92.5% +/- 3.5%) and myoid (2.2% +/- 0.7%) cellular aggregates were transplanted underneath the kidney capsule of SCID mice. Grafts were removed between 0 and 60 days posttransplantation and examined histologically for the progressive development of structures resembling testicular cords. Aggregates began to reorganize by day 3, and cord structures were present at day 7 posttransplantation. These structures became larger and more defined as the time progressed after implantation. To localize Sertoli and peritubular myoid cells, grafts were immunostained for the Sertoli cell proteins, vimentin, DNA transcription factor GATA-4, and Müllerian inhibiting substance (MIS), as well as for a myoid cell protein, smooth muscle alpha-actin. In the "seminiferous" epithelial layer, the Sertoli cells were arranged with their nuclei along the basal edge adjacent to the peritubular myoid cells that were surrounding the tubules. Moreover, the expression of MIS mimicked that during porcine testicular development, suggesting the Sertoli cells were developing normally. In addition, proliferating cell nuclear antigen (PCNA) was detected in the Sertoli cells at all time points, indicating the proliferation of Sertoli cells in the grafts, which is consistent with Sertoli cell proliferation prior to puberty in the native porcine testis. These results suggest that the specific factors required for cord formation and prepubertal development are inherent in the transplanted cells. Moreover, we have developed a novel in vivo transplantation model to study seminiferous cord formation and prepubertal development.

Animals↗
PubMed1992

Eclipse of the identifiable myoblast.

During development of the limb musculature there is an eclipse of the myoblasts from the time first formed until the limb musculature begins to develop. The formation of the muscles of the limb is from cells of somite origin that migrate into the forming limb bud. While it is possible to identify myogenic cells in the somite prior to when migration occurs, and to determine the time frame during which migration occurs, there is a hiatus of about 34 hours during which it is difficult to identify or culture myogenic cells from the limb. In part this is because it is difficult to distinguish myogenic cells that migrate from those that do not. There are no markers that distinguish the myogenic cells of the somite that form the axial muscles and therefore stay in place, and from the myogenic cells that migrate to form the peripheral muscles of the body. Thus it unclear if the cell commitment to different myogenic fates occurs during somite formation, or during their sojourn to the limb bud.

Animals↗
PubMed2005

[Expression of PAX2 and PAX8 genes in conventional type of renal carcinoma and their role in the tumor prognosis].

BACKGROUND: Sporadic renal cell carcinoma is one of the most common kidney malignancies in adults (85%). According to the IARC (The International Agency of Research on Cancer) Czech Republic has the first world position in the incidence and mortality for RCC. The prognosis of RCC is very poor because of high mortality around 70 to 50% and unpredictable progression after tumor removal. More precise molecular prognostic markers are required. Genes PAX2 and PAX8 control cell division during embryonic development and plays crucial role in tumor development because of stimulation of cell proliferation and/or inhibition of apoptotic program. METHODS AND RESULTS: Our RCC sample collection contains 64 tumor samples and 10 "normal" renal samples extracted from the affected kidney. mRNA was isolated from all samples and converted into cDNA. Expression of PAX genes was analyzed by using relative quantification real-time PCR with TaqMan labelled probe and GAPDH gene as an endogenous control. CONCLUSIONS: Expression of PAX2 gene was found in 97% and expression of PAX8 gene was found in 89% of analyzed tumor samples. The expression of both target genes was found in all "normal" renal samples. The level of expression of both PAX genes was very variable with the range from hundred times lower to forty times higher in comparison with the expression of chosen endogenous control. There were found no correlations between the expression of target genes and clinical-histological markers. These results do not have prognostic value yet because of short duration of patient observation. Follow-up clinical data are essential for completion of this research.

Biomarkers, Tumor↗
PubMed1991

Pulling the string: cell cycle regulation during Drosophila development.

The extensive cell proliferation which accompanies the development of multicellular organisms is co-ordinated with other developmental events. Cell cycle progression during embryogenesis is therefore controlled according to developmental stage and developmental fate. In Drosophila, entry into S phase is a constitutive, unregulated event until late in development. Entry into mitosis, however, is the first control point used for differential regulation, and the transcriptionally controlled expression of string (the Drosophila homologue of Schizosaccharomyces pombe cdc25+) directs the precise patterns of the embryonic cell divisions after the onset of morphogenesis. In contrast to string, cyclin proteins are produced in excess and their rate of accumulation does not regulate the time of mitosis.

Animals↗
PubMed1990

[Origin of islets of Langerhans by mitotic division of duct epithelium in the human early fetal period].

The investigations are carried out in 29 human fetal pancreases between the 10th and 19th week of age. Mitosis restricted to the duct epithelium in the 10th to 13th week. In the 14th week start the mitotic activity in the islet parenchyma. The mitotic activity decreased from the 10th to the 13th week, increased to the 15th week and decreased once more to the 19th week.

Cell Division↗
PubMed1987

Immunocytochemical evidence for transferrin-dependent proliferation during renal tubulogenesis.

The role of the transferrin receptor and of cell proliferation during human renal embryogenesis has been studied by using immunocytochemical techniques. Tissue sections of human fetal kidneys have been stained using monoclonal antibodies to the cell surface transferrin receptor (HB21) and the nuclear proliferation antigen (Ki67). Both antigens appear during nephron induction, are strongly expressed during the early stages of renal tubulogenesis, but are lost with progressive maturation. Simultaneous changes in the intermediate filament phenotype at this developmental stage have also been demonstrated by the use of monoclonal antibodies to vimentin and low molecular weight cytokeratin. This study provides immunocytochemical evidence that in the human kidney, as in in vitro development of the mouse kidney, one of the early events in tubule induction involves transferrin-dependent proliferation.

Cell Division↗
PubMed1985

Maturation and polarization of the endocytotic system in outside blastomeres during mouse preimplantation development.

The maturation and distribution of the endocytotic apparatus in outside cells of cleavage-stage mouse embryos have been studied to determine the nature and sequence of changes associated with the differentiation of the polarized trophectoderm epithelium of the blastocyst. Various quantitative and qualitative techniques used at the light and electron microscopic levels have revealed an incremental pattern of endocytotic maturation and polarization. Oocytes, eggs and blastomeres within embryos up to the early 8-cell stage contain clusters of prelysosomal endocytotic vesicles (endosomes) distributed randomly in the cortical cytoplasm. During the 8-cell stage and continuing into the early 16-cell stage, endosomes become progressively localized in the apical cytoplasm beneath the microvillous pole. Endosome polarization is initiated prior to overt polarization of the surface membrane. Concomitant with endosome polarization, pinocytotic activity at the cell surface, revealed by horseradish peroxidase labelling, becomes segregated preferentially to the apical rather than the basolateral membrane. The final maturation phase occurs at the late 16-cell stage when secondary lysosomes, characterized by trimetaphosphatase reactivity, form and polarize in the basal cytoplasm.

Animals↗