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PubMed2005

Embryonic development of the human hematopoietic system.

Human hematopoiesis is initiated in the yolk sac during the third week of development. At the same time the capacity to produce blood cells also arises in the embryo, within the splanchnopleura, but this potential is not expressed before day 27, when clustered hematopoietic stem cells emerge from the ventral wall of the aorta and vitelline artery. Budding of hematopoietic cells from vessel walls reflects the re-differentiation of local endothelial cells, which are likely derived from angio-hematopoietic mesodermal ancestors emigrated from the splanchnopleura. Yolk sac-derived stem cells are limited to myelo-erythroid development, whereas those born in the embryo are, in addition, lymphopoietic and therefore represent the first multi-potent, adult-type blood progenitors that appear in human ontogeny, preceding shortly the onset of liver hematopoiesis. These results allowed the establishment of a novel hierarchy of blood-forming tissues in human development and induced an in depth reconsideration of the very origin of definitive human hematopoiesis. These results also fully corroborate the outcome of experiments performed in parallel in avian and mouse embryos and point to the conservation in all higher vertebrates of an ancestral route of blood cell production via embryonic vessel walls.

Cell Differentiation↗
PubMed1999

Restricted spatiotemporal expression of lactoferrin during murine embryonic development.

Lactoferrin is a member of the transferrin family of iron-binding glycoproteins. Lactoferrin is induced by estrogen in the mouse uterus during early pregnancy. However, the expression and function, if any, of lactoferrin in the preimplantation embryo during this developmental period has not been investigated. In the current study, the spatiotemporal expression of lactoferrin during murine embryogenesis was examined using in situ hybridization and immunohistochemical analyses. Lactoferrin expression was first detected in the 2-4 cell fertilized embryo and continued until the blastocyst stage of development. Interestingly, at the 16-cell stage, coinciding with the first major differentiation step in the embryo, lactoferrin messenger RNA (mRNA) is synthesized by the inner cells, whereas the protein is selectively taken up by the outside cells. This differential pattern of lactoferrin messenger RNA and protein localization continues until the blastocyst stage, with expression almost absent in the hatched blastocyst. Lactoferrin expression does not resume in the embryo until the latter half of gestation, where it is first detected in neutrophils of the fetal liver at embryonic day 11.5 and later in epithelial cells of the respiratory and digestive systems. Our results show that lactoferrin is expressed in a tightly regulated spatiotemporal manner during murine embryogenesis and suggest a novel paracrine role for this protein in the development of the trophoectodermal lineage during preimplantation development.

Animals↗
PubMed2002

Cell nucleus activity during post-embryonic development of Apis mellifera L. (Hymenoptera: Apidae). Intranuclear acid phosphatase.

We report nuclear acid phosphatase activity in the somatic (intra-ovariolar and stromatic) and germ cells of differentiating honey bee worker ovaries, as well as in the midgut cells of metamorphosing bees. There was heterogeneity in the intensity and distribution of electron dense deposits of lead phosphate, indicative of acid phosphatase activity in the nuclei of these tissues, during different phases of post-embryonic bee development. This heterogeneity was interpreted as a variation of the nuclear functional state, related to the cell functions in these tissues.

Acid Phosphatase↗
PubMed2005

[Effect of carbon disulfide exposure at different phases on the embryonic development in mid-pregnancy of female mice].

OBJECTIVE: To explore the sensitive point of embryotoxicity of carbon disulphide on female mice. METHODS: At the phases of follicle developing, implanting and post-implantation of blastocyst, female mice were injected intraperitoneally with carbon disulphide 631.4 mg/kg per day for three days while controls with plant oil. All indexes were detected at the fourteenth day of pregnancy. RESULTS: (1) In follicle developing CS(2) exposed group, the weight of embryos fossa [(1.23 +/- 0.36) g was 41% less than that in controls [(2.08 +/- 0.48) g, P = 0.000], and in implanting CS(2) exposed group the weight of embryo fossa, and embryos [(1.27 +/- 0.97) g, and (0.12 +/- 0.09) g respectively] were 39% and 37% less than those in controls [(2.08 +/- 0.48), (0.19 +/- 0.06) g, P = 0.068, P = 0.045]; (2) In both follicle developing and implanting CS(2) exposed group, the weights of uterus and placenta were also less than those in controls (P < 0.01). (3) In post-implantation CS(2) exposed group, the above parameters were not significantly different from those in controls. CONCLUSION: Follicle developing phase as well as implanting of blastocyst may be sensitive point for embryotoxicity induced by carbon disulphide.

Animals↗
PubMed2005

Expression of mouse Coiled-coil-DIX1 (Ccd1), a positive regulator of Wnt signaling, during embryonic development.

Wnt signaling plays an important role in cell growth, differentiation, polarity formation, and neural development. We have recently identified the Coiled-coil-DIX1 (Ccd1) gene encoding a third type of a DIX domain-containing protein. Ccd1 forms homomeric and heteromeric complexes with Dishevelled and Axin, and positively regulates the Wnt/beta-catenin pathway. Here, we examined the spatiotemporal expression pattern of Ccd1 mRNA in mouse embryos from embryonic day 6.5 (E6.5) to E17.5 by in situ hybridization. Ccd1 expression was detected in the node region in gastrula embryos, in the cephalic mesenchyme and tail bud at E8.5, and in the branchial arch and forelimb bud at E9.5. In the central nervous system, Ccd1 expression began and persisted in the regions where the neurons differentiated, so that it was observed throughout the brain and spinal cord at E17.5. Ccd1 expression was also strong in the peripheral nervous system, including sensory cranial ganglia (trigeminal, facial, and vestibulocochlear ganglia), dorsal root ganglia, and autonomic ganglia (sympathetic ganglia, celiac ganglion, and hypogastric plexus). Ccd1 was detected in the sensory organs, such as the inner nuclear layer of the neural retina, saccule and cochlea of the inner ear, and nasal epithelium. Outside the nervous system, Ccd1 mRNA was observed in the cartilage, tongue, lung bud, stomach, and gonad at E12.5-E14.5, and in the tooth bud, bronchial epithelium, and kidney at E17.5. Taken together, these findings demonstrate that Ccd1 expression is observed in all the neurons in the nervous system, closely associated with neural crest-derived tissues, and largely overlapping with the regions where several Wnt genes are reported to play a role.

Animals↗
PubMed2005

Embryonic development within carotenoid-enriched eggs influences the post-hatch carotenoid status of the chicken.

Carotenoids in the diet of the laying hen are incorporated into the egg yolk and subsequently into the liver and other tissues of the chicken embryo. Since these pigments are known to provide a range of health benefits to a variety of animals, it is of interest to know whether the effects of maternally derived carotenoids are strictly limited to the embryonic period or if they persist in the progeny after hatching. The aim of this study is to compare the effectiveness of pre-hatch (from the hen's diet) with that of post-hatch (from the progeny's diet) supplementation with carotenoids on the carotenoid status of the chick during the first 4 weeks of post-hatch life. Hens were fed a control diet or a diet supplemented with a carotenoid-rich extract of alfalfa. Eggs from the supplemented hens contained up to 22 times more carotenoids than the controls. The concentration of carotenoids in the livers of chicks hatching from the enriched eggs was initially 29 times greater than in the control chicks. Hepatic carotenoid concentrations in chicks from enriched eggs maintained post-hatch on the control diet were sustained at higher values compared with chicks from control eggs that were fed post-hatch on the carotenoid-supplemented diet, for at least the first 7 days. However, by 14 days, the latter group had overtaken the former in terms of liver carotenoid levels. Thus, under these conditions, maternal effects predominate for at least the first week after hatching, whereas from 2 weeks onwards, the progeny's diet becomes the main determinant of its carotenoid status. Since the antioxidant and immunostimulatory roles of carotenoids are likely to be especially important during the immediate post-hatch period, maternal dietary intake of carotenoids may have important ramifications for the viability of the offspring.

Age Factors↗
PubMed2005

Expression of ADP-ribosylation factor (ARF)-like protein 6 during mouse embryonic development.

ADP-ribosylation factor (ARF)-like protein 6 (ARL6) is a member of the ARF-like protein (ARL) subfamily of small GTPases (Moss, 1995; Chavrier, 1999). ARLs are highly conserved through evolution and most of them possess the consensus sequence required for GTP binding and hydrolysis (Pasquallato, 2002). Among ARLs, ARL6 which was initially isolated from a J2E erythroleukemic cell line is divergent in its consensus sequences and its expression has been shown to be limited to the brain and kidney in adult mouse (Ingley, 1999). Recently, it was reported that mutations of the ARL6 gene cause type 3 Bardet-Biedl syndrome in humans and that ARL6 is involved in ciliary transport in C. elegans (Chiang, 2004; Fan, 2004). Here, we investigated the expression pattern of ARL6 during early mouse development by whole-mount in situ hybridization and found that interestingly, ARL6 mRNA was localized around the node at 7.0-7.5 days post coitum (dpc) embryos, while weak expression was also found in the ectoderm. At the later stage (8.5 dpc) ARL6 was expressed in the neural plate and probably in the somites. Based on these results, a possible role of ARL6 in early development is discussed in relation to the findings in human and C. elegans (Chiang, 2004; Fan, 2004).

ADP-Ribosylation Factors↗
PubMed1998

Expression of neuronal nitric oxide synthase during embryonic development of the rat cerebral cortex.

The expression of neuronal nitric oxide synthase (nNOS) during the development of the rat cerebral cortex from embryonic day (E) 13 to postnatal day (P) 0 was analyzed by immunocytochemical procedures using a specific antibody against rat brain nNOS. Expression of nNOS was first seen on E14 in cells of Cajal-Retzius morphology located in the marginal zone. Neuronal NOS immunoreactivity persisted in this layer throughout the embryonic period and only began to decrease on E20, when neuronal migration is coming to an end. From E17 onwards, migrating neurons expressing nNOS were observed in the intermediate zone with their leading processes directed towards the cortical plate. At the same time, efferent nNOS-immunoreactive axons originating from cortical plate cells entered the intermediate zone. From E19 onwards, cells expressing nNOS and with the morphological characteristics of migrating cells were observed in and near the subventricular zone. Confocal analysis of double immunostaining for nNOS and glial fibrillary acidic protein or nestin showed no coexpression of nNOS and glial markers in these cells, suggesting that nNOS-positive cells leaving the subventricular zone were not glial cells. Commissural, callosal and fimbrial fibers were seen to express nNOS on E18 and E19. This expression decreased from E20 and was very weak on E21 and P0. The observations suggest that nitric oxide is synthesized during embryonic life in relation to maturational processes such as the organization of cerebral lamination, and is involved in controlling migrational processes and fiber ingrowth.

Animals↗
PubMedDate not supplied

Embryonic development in the blue fox.

Embryos from vixens at different stages of gestation were measured and photographed. Implantation was observed 16-18 days after breeding. Differentiation and the development of characteristic features were described and embryonic loss was studied in relation to number of corpora lutea.

Animals↗
PubMed2000

Temporal and spatial patterns of cbfal expression during embryonic development in the teleost, Oryzias latipes.

Cbfa1, a transcription factor of the runt family, was recently shown to be a key regulator in skeletal development in mammals. In the present study, we identified the cbfa1 gene from the medaka, Oryzias latipes. The amino acid sequence, including the runt domain, is highly conserved with that of mammalian cbfa1. Whole mount in situ hybridization showed that the medaka cbfa1 was expressed prominently in immature osteoblasts and chondrocytes of the developing skeletal structures during embryogenesis. The expression pattern suggests functional and evolutionary implications of the cbfa1 gene in chondrocyte differentiation between teleosts and mammals.

Amino Acid Sequence↗