Early Embryonic Cell Differentiation Research Articles

A Rapid Bioassay Test for Assessing Environmental Contamination Using the Marine Sedentary Polychaete Hydroides elegans

To investigate the impact of environmental contaminants on the early life stages of the marine polychaetae Hydroides elegans, a toxicity test was designed. In our previous study, we reported gametes and embryos of H. elegans were sensitive to heavy metal pollution and effluents. In continuation of this, we used H. elegans gametes to assess the water quality of samples taken along the southeast coast of India. The samples were collected from five different locations of the Chennai coast (Muttu Kadu, Neelangarai, Marina, Royapuram, and Ennore), and two different bioassay toxicity tests were performed. Sperm and eggs were pre-exposed to water samples taken from different locations to assess the water quality. Water samples collected from Ennore station and the Royapuram fish landing center were found to be more polluted than those collected from other locations. Sperm were shown to be more sensitive than eggs. The different morphological effects produced by water samples reflected the defects in the early differentiation of embryonic cells. Since fertilization can be inhibited in the presence of any xenobiotic, both fertilization and early development could be used as a biological indicator for a rapid bioassay to monitor marine pollution. The percentage of successful fertilization and early development was comparatively higher at the reference site (Neelangarai) and in the seawater samples collected from Marina. The physicochemical characteristics of the seawater from these sampling stations corroborated the findings of this investigation. Our results showed that H. elegans gametes were highly sensitive to any contaminant present in the seawater, and confirmed previous findings that this polychaetae can be routinely used as a test organism for ecotoxicological bioassays in tropical and subtropical regions.

Effluent Toxicity Test Using Developmental Stages of the Marine Polychaete Hydroides elegans

The US Environmental Protection Agency (USEPA) has established a suite of methods that use coastal invertebrate species as bioassay organisms to test industrial and domestic effluent as well as coastal waters for potential toxicity. Although these methods are used globally, the potential of such toxicity tests has not been adequately explored for Asian coastal waters. This study describes bioassay utilizing the gametes of Hydroides elegans to monitor coastal water quality and is based on the sensitivity of H. elegans embryo and larva to different concentrations of effluents and water samples collected from different regions of east coast of India. Among the water samples collected from different regions, seawater from Ennore station showed decrease in percentage of development, and 25% effluent concentration led to development arrest of H. elegans embryos. The different morphological effects produced by effluents clearly reflect the defect in early differentiation of embryonic cells. Since fertilization can be inhibited in the presence of any xenobiotic, both fertilization and early development can be used as a biological indicator for a rapid bioassay to monitor pollution. Toxicity tests utilizing early life stages of H. elegans are suitable for the assessment of effects produced by low levels of pollutants due to their high sensitivity to various contaminants relative to other marine species and also due to the relative simplicity of the bioassay.

Differential expression of glucose transporter isoforms during embryonic stem cell differentiation

In mouse blastocysts six facilitative glucose transporter isoforms (GLUT)1–4, 8 and 9 are expressed. We have used the mouse embryonic stem (ES) cell line D3 and spontaneously differentiating embryoid bodies (EB) to investigate GLUT expression and the influence of glucose during differentiation of early embryonic cells. Both ES cells and EBs (2d–20d) expressed GLUT1, 3, and 8, whereas the isoforms 2 and 4 were detectable exclusively in EBs. Differentiation-associated expression of GLUT was analyzed by double staining with stage-specific embryonic antigen (SSEA-1), cytokeratins (CK18, 19), nestin, and desmin. Similar to trophoblast cells in mouse blastocysts the outer cell layer of endoderm-like cells showed a high GLUT3 expression in early EBs. In 20-day-old EBs no GLUT3 protein and only minor GLUT3 mRNA amounts could be detected. A minimal glucose concentration of 5 mM applied during 2 and 8 days of EB culture resulted in up-regulated GLUT4, Oct-4 and SSEA-1 levels and a delay in EB differentiation. We conclude that GLUT expression depends on cellular differentiation and that the expression is modulated by glucose concentration. The developmental and glucose-dependent regulation of GLUT strongly suggests a functional role of glucose and glucose transporters in ES cell differentiation and embryonic development.

Chromatin diminution in the copepod Mesocyclops edax: diminution of tandemly repeated DNA families from somatic cells

Chromatin diminution, i.e., the loss of selected chromosomal regions during the differentiation of early embryonic cells into somatic cells, has been described in taxa as varied as ciliates, copepods, insects, nematodes, and hagfish. The nature of the eliminated DNA has been extensively studied in ciliate, nematode, and hagfish species. However, the small size of copepods, which makes it difficult to obtain enough DNA from early embryonic cells for cloning and sequencing, has limited such studies. Here, to identify the sequences eliminated from the somatic cells of a copepod species that undergoes chromatin diminution, we randomly amplified DNA fragments from germ line and somatic line cells of Mesocyclops edax, a freshwater cyclopoid copepod. Of 47 randomly amplified germ line clones, 45 (96%) contained short, tandemly repeated sequences composed of either 2 bp CA-repeats, 8 bp CAAATAGA-repeats, or 9 bp CAAATTAAA-repeats. In contrast, of 83 randomly amplified somatic line clones, only 47 (57%) contained such short, tandemly repeated sequences. As previously observed in some nematode species, our results therefore show that there is partial elimination of chromosomal regions containing (CAAATAGA and CAAATTAAA) repeated sequences during the chromatin diminution observed in the somatic cells of M. edax. We speculate that chromatin diminution might have evolved repeatedly by recruitment of RNAi-related mechanisms to eliminate nonfunctional tandemly repeated DNA sequences from the somatic genome of some species.

Cadmium-induced inhibition of proliferation and differentiation of embryonal carcinoma cells and mechanistic aspects of protection by zinc.

Murine embryonal carcinoma cells have been used in in vitro models to study the effects of cadmium chloride on proliferation and differentiation of early embryonic cells. This approach allows the various cell types within the early embryo as well as several developmental mechanisms to be dissected and studied in isolation using larger numbers of cells than would be readily available from the embryo itself. The present study shows that both embryonal carcinoma cell proliferation and differentiation into parietal endoderm are inhibited by cadmium chloride. The effects are counteracted by the additional presence of zinc chloride. The uptake of cadmium into the cells is inhibited in the presence of zinc chloride, suggesting that competition between these metals for passage into the cells contributes to the mechanism underlying the protective effect of zinc. In addition, metallothionein gene expression is enhanced more rapidly after simultaneous incubation with zinc chloride, indicating that the attenuating effect of zinc on cadmium toxicity is also partly attributable to detoxification by metallothioneins.

Myc products induce the expression of catecholaminergic traits in quail neural crest-derived cells.

The avian myelocytomatosis virus strain MC29 v-myc oncogene transforms a wide panel of avian cells in vitro and either blocks or maintains differentiation, depending on the cell type. In the present work, we have investigated the effect of this oncogene on the differentiation of early embryonic cells, neural crest cells, grown in vitro. We report that the MC29 v-myc gene product induces a strong cellular proliferation of 2-day quail neural crest with the appearance of catecholaminergic traits. Other v-myc as well as the c-myc gene products also trigger this phenotype. Retroviruses carrying some other oncogenes do not elicit this phenotypic expression, although they activate cell multiplication. Thus, our results indicate that myc gene products induce (directly or indirectly) a differentiated phenotype in a subpopulation of neural crest cells.

Localization of phosphatase activities on mouse teratocarcinoma embryoid bodies

Non-specific alkaline phosphatase and Mg 2+-dependent adenosine triphosphatase activities were ultracytochemically investigated on embryoid bodies of murine teratocarcinomas, in order to find markers of endodermal cell differentiation of early embryonic cells. The former was localized mainly on the cell surface of inner embryonal carcinoma cells, as already shown by other workers, and weakly on the bound surface of outer endodermal cells of embryoid bodies. The latter, however, was found only on the outer free surface of endodermal cells and never on the surface of embryonal carcinoma cells. It suggests that Mg 2+-dependent ATP activity might become the marker for early differentiation of embryonal carcinoma cells.