Search results for "Embryonic Structure"
showing 10 items of 624 documents
Fine Structure of the Tunic ofCiona intestinalisL. II. Tunic morphology, cell distribution and their functional importance
1981
Ciona intestinalis L. tunic architecture and cell distribution were investigated with the electron microscope. The observations showed that the ascidian covering is formed by a thin outer cuticle, a subcuticle of variable width and a large single layer of ground substance. “Large granule”, morula, phagocyte and granulocyte are the cellular types encountered; they appear mainly in highly vacuolated states and are distributed throughout the whole tunic. The “large granule” cells, however, are mainly seen in the cuticle layer and the morula cells appear mostly in the outer zone of the ground substance. The role of these cells in tunic construction, repair and regeneration as well as their scav…
Development of nucleoside phosphotransferase activity in the cerebral hemispheres of embryonal and adult chick.
1981
In the cerebral hemispheres of the chick embryo, the level of nucleoside phosphotransferase activity is much higher than that of thymidine kinase and it increases progressively during development up to the adult stage. Therefore nucleoside phosphotransferase is not coupled with DNA synthesis.
Funktion der Spermien in inkompatiblen Kreuzungen der StechmückeCulex pipiens L.
1972
After irradiating males of the incompatible crossC. pipiens ‘Hamburg’ ♀♀×C. pipiens ‘Paris’ ♂♂ with X-ray doses between 1 kR and 40 kR, it could be shown that in this cross the sperm has only the function of activating the egg. All the hybrid embryos develop from the haploid female pronucleus.
Bet-hedging in diapausing egg hatching of temporary rotifer populations - A review of models and new insights
2014
Habitat unpredictability is a local adaptation factor shaping life-history traits in rotifer populations. It may select for the evolution of bet-hedging through risk-spreading strategies in diapausing egg hatching. This means that a fraction of diapausing eggs in wild populations do not hatch even when the conditions are favorable for population growth. Thus, there is a remaining fraction of viable diapausing eggs standing in the sediments for longer periods. According to theory, it is expected that the incidence of bet-hedging strategies for diapausing egg hatching will be higher in more uncertain habitats. Here, we review the major predictions derived from theoretical models applied to th…
EctoparasiticArgulus coregoni(Crustacea: Branchiura) hedge their bets - studies on egg hatching dynamics
2004
Unpredictability in the temporal availability of susceptible hosts is likely to act as a selection pressure affecting the life history strategies of parasites. In highly variable environments the future of the lineage can be secured by spreading the risk, for example, by producing descendants that differ in their timing of emergence. Counter to this, in predictable environments a single “best-adapted” phenotype is expected. We asked whether ectoparasitic Argulus coregoni egg hatching pattern can be explained as a genetically canalized individual trait; an instance of phenotypic plasticity or bet-hedging. We collected egg clutches laid by individual A. coregoni females in early and late repr…
Dephosphorylation of Centrins by Protein Phosphatase 2C α and β.
2009
In the present study, we identified protein phosphatases dephosphorylating centrins previously phosphorylated by protein kinase CK2. The following phosphatases known to be present in the retina were tested: PP1, PP2A, PP2B, PP2C, PP5, and alkaline phosphatase. PP2C 𝛼 and 𝛽 were capable of dephosphorylating P-Thr138-centrin1 most efficiently. PP2C𝛿 was inactive and the other retinal phosphatases also had much less or no effect. Similar results were observed for centrins 2 and 4. Centrin3 was not a substrate for CK2. The results suggest PP2C 𝛼 and 𝛽 to play a significant role in regulating the phosphorylation status of centrins in vivo.
Effect of Gibberellin on Mature Euonymus europaeus L. Seeds
1992
The release from dormancy of Euonymus europaeus L. embryos by a brief treatment with GA 3 has been studied. During 48 h incubation of dormant embryos in GA-free medium, phospholipid levels increased at first, then declined sharply over the last 6 h. When the embryos were placed in GA, medium during this 6 h period levels of total phospholipids as well as of phosphatidylethanolamine increased whilst phosphatidylinositol and phosphatidylcholine declined slightly
Glutathione content of V79 cells in two- or three-dimensional culture
1997
The cellular glutathione (GSH) content of two- and three-dimensional cell cultures of V79 hamster lung cells has been studied. As previously described, cells in monolayer cultures show a decrease in GSH when they reach the confluent state. Three-dimensional cell cultures (multicell spheroids) allow a smoother transition from the initial proliferating to the nonproliferating status, and they show a central area of necrosis when a certain diameter is reached. Cellular GSH content in spheroids is variable throughout the culturing period: 1) GSH content (expressed per mg protein) is lower in spheroids with central necrotic areas than in smaller spheroids without necrosis, and 2) results expres…
The placenta: phenotypic and epigenetic modifications induced by Assisted Reproductive Technologies throughout pregnancy
2015
International audience; Today, there is growing interest in the potential epigenetic risk related to assisted reproductive technologies (ART). Much evidence in the literature supports the hypothesis that adverse pregnancy outcomes linked to ART are associated with abnormal trophoblastic invasion. The aim of this review is to investigate the relationship between epigenetic dysregulation caused by ART and subsequent placental response. The dialogue between the endometrium and the embryo is a crucial step to achieve successful trophoblastic invasion, thus ensuring a non-complicated pregnancy and healthy offspring. However, as described in this review, ART could impair both actors involved in t…
Prenatal Clinical Assessment of sFlt-1 (Soluble fms-like Tyrosine Kinase-1)/PlGF (Placental Growth Factor) Ratio as a Diagnostic Tool for Preeclampsi…
2013
Background: Aim of the study was a critical assessment of the clinical validity of the prenatal determination of sFlt-1/PlGF for preeclampsia (PE), pregnancy-induced hypertension (PIH), and proteinuria. Our analysis was based on a specificity of 95 % and a sensitivity of 82 % for the prediction of preeclampsia, as described by Elecsys (Roche). Methods: In this retrospective study the ratio of the prenatal antiangiogenic factor sFlt-1 (soluble fms-like tyrosine kinase-1) to the proangiogenic factor PIGF (placental growth factor) was analyzed using the electrochemiluminescence immunoassay of Elecsys (Roche Diagnostics, Mannheim, Germany) in 173 pregnant women. Sixty-three women with PE, 34 wo…