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PubMed1999

Syntaxin 1A is transiently expressed in fetal lung mesenchymal cells: potential developmental roles.

Lung development is a complex process in which epithelial-mesenchymal interactions play a key role. A conserved secretory apparatus, the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex, is essential for exocytosis in many cell types. Syntaxins, located on the terminal plasma membrane (T-SNAREs), are a critical component of the secretosomal complex involved in vesicular docking, fusion, and exocytosis. We analyzed syntaxin 1A mRNA and protein in fetal rat lung ontogeny, demonstrating peak expression on about day 19 of embryonic development, immediately preceding type II pneumocyte differentiation. Syntaxin 1A is predominantly expressed by lipofibroblasts, which are required for bombesin-like peptide-induced surfactant phospholipid synthesis (choline uptake) by isolated type II cells. In organ cultures, anti-syntaxin 1A antibody HPC-1 blocks choline uptake both at baseline and when induced by bombesin-like peptide or dexamethasone. HPC-1 also promotes thymidine uptake in parallel in a dose-dependent fashion. These observations indicate a potential role for syntaxin 1A during fetal lung development, possibly through involvement in secretion of mesenchymal cell-derived factors that induce terminal type II cell differentiation.

Animals↗
PubMed1992

Temporal effects of taurine on mouse preimplantation development in vitro.

Previously it has been shown that significantly more 2-cell mouse embryos reach the blastocyst stage when cultured in medium supplemented with taurine. In this study, in-vitro fertilized zygotes from a hybrid mouse strain were used to examine the temporal effects of 10 mM taurine on embryonic development in vitro during the preimplantation period. Taurine exerted its beneficial effect exclusively during the first 2 days post-insemination. The effect of taurine on blastocyst formation appeared to be restricted mostly to the period 20-48 h after fertilization, during which time mouse embryos are at the two-cell stage. Although more blastocysts were found when embryos were cultured in taurine-containing medium from 5 to 20 h post-insemination, this difference was not significant compared to the number of blastocysts when embryos were cultured without taurine. Taurine did not appear to affect the two-cell block of mouse embryos from random-bred strains.

Animals↗
PubMed2001

Chemical waves in open flows of active media: their relevance to axial segmentation in biology.

The boundary forcing of open flows of active media can lead to a variety of spatiotemporal structures, depending on the local kinetics of the medium and on the characteristics of the forcing. Here, we demonstrate that regardless of the local kinetics, the combination of flow and boundary forcing is a powerful method for replacing intrinsic modes with extrinsic ones. This entrainment of dynamics has important implications for biological morphogenesis. During early embryonic development it is frequently observed that stripes of gene expression and segments arise one after the other along a growth-axis. We show that axial growth can be viewed as an open flow of cells away from a growth zone. Based on this realisation, we demonstrate using three generic reaction-diffusion-advection schemes how a space-periodic structure is induced, one "segment" at a time along the growth/flow axis, by a segmental clock that is synchronised within the growth zone. The schemes are investigated in the context of an abrupt and a gradual change in the properties of the segmental clock. Experimental observations provide evidence that the latter is involved in the early development of many vertebrates.

Algorithms↗
PubMed2003

Assessment of mammalian embryo quality: what can we learn from embryo morphology?

Embryo morphology assessment, however imperfect it may be, is at present the most popular method for embryo selection prior to transfer, both in human and bovine assisted reproduction. A major difference between human and bovine embryos is the fact that in the latter, assessment of morphology is jeopardized by the opacity of the blastomeres, which is caused by lipid droplet accumulation. This opacity makes it difficult to assess nuclear and nucleolar morphology, aspects which can easily be evaluated in human zygotes or early cleaving embryos. However, recent research which focused on correlation between bovine embryo morphology and embryonic ultrastructure, gene expression and cryoresistance, has provided evidence that much more can be deduced from mere embryo morphology than previously thought. Morphological features such as colour of the blastomeres, the extent of compaction, timing of blastocyst formation and expansion and diameter of the embryo at hatching can be linked with embryo quality. On the other hand, cattle embryos of deviant chromosomal constitution or with aberrant genetic make-up cannot be selected against by means of the current morphological techniques. Possible solutions include the visualization of bovine pronuclei at the zygote stage by means of ultracentrifugation or multiphoton laser scanning microscopy, and adjustment of genetic analysis in order to reconstruct embryo genetic make-up starting from the biopsy material.

Animals↗
PubMed1994

Mathematical models of the early embryonic cell cycle: the role of MPF activation and cyclin degradation.

Recent advances in cell biology indicate that the interactions between two proteins, cdc2 and cyclin, together with the activity of the cdc2/cyclin complex called MPF in the cytoplasm form the basis of a universal biochemical control mechanism for the cell division cycle in eukaryotes. Based on experimental facts that total cdc2 level is constant throughout the cell cycle and that onset of mitosis is subsequent to activation of MPF, we propose and analyze two different but related models--an ordinary differential equations model and a delay differential equations model--for the control of the early embryonic cell division cycle. Assuming very general reaction terms in the model equations, it is shown that MPF activation and rapid cyclin degradation triggered by active MPF drive cells to alternate between interphase and mitosis, the two phases of the cell cycle.

Animals↗
PubMed2006

Gene expression changes during step-wise differentiation of embryonic stem cells along the inner ear hair cell pathway.

CONCLUSION: Our study outlines an alternative approach for the selection and investigation of genes involved in inner ear function. OBJECTIVE: To gain understanding of the gene pathways involved in the development of the normal cochlea. MATERIALS AND METHODS: Microarray technology currently offers the most efficient approach to investigate gene expression and identify pathways involved in cell differentiation. Epidermal growth factor (EGF) induces cultures derived from the organ of Corti to proliferate and produce new hair cells. Since pluripotent embryonic stem (ES) cells have the capacity to generate all tissues, we induced murine ES cells to differentiate towards ectodermal and neuroectodermal cell types and from there investigated their commitment towards the hair cell lineage in the presence of EGF. Cells were collected at three points along the differentiation pathway and their expression profiles were determined using the Soares NMIE mouse inner ear cDNA library printed in microarray format. RESULTS: Three genes up-regulated after addition of EGF (serine (or cysteine) proteinase inhibitor, clade H, member 1 (Serpinh1), solute carrier family 2 (facilitated glucose transporter), member 10 (Slc2a10) and secreted acidic cysteine-rich glycoprotein (Sparc)) were selected for further analysis and characterization. Of the three genes, Serpinh1 and Slc2a10 have never been implicated in the hearing process.

Animals↗
PubMed2006

Challenges and prospects for the establishment of embryonic stem cell lines of domesticated ungulates.

Embryonic stem (ES) cell lines provide an invaluable research tool for genetic engineering, developmental biology and disease models. These cells can be maintained indefinitely in culture and yet maintain competence to produce all the cells within a fetus. While mouse ES cell lines were first established over two decades ago and primate ES cells in the 1990 s, validated ES cell lines have yet to be established in ungulates. Why competent, pluripotent ES cells can be established from certain strains of mice and from primates, and not from cows, sheep, goats or pigs is an on-going topic of interest to animal reproduction scientists. The identification of appropriate stem cell markers, functional cytokine pathways, and key pluripotency-maintaining factors along with the release of more comprehensive bovine and porcine genomes, provide encouragement for establishment of ungulate ES cell lines in the near future.

Animals↗
PubMed2003

The Drosophila myosin VI Jaguar is required for basal protein targeting and correct spindle orientation in mitotic neuroblasts.

Asymmetric cell divisions generate cellular diversity. In Drosophila, embryonic neuroblasts target cell fate determinants basally, rotate their spindles by 90 degrees to align with the apical-basal axis, and divide asymmetrically in a stem cell-like fashion. In this process, apically localized Bazooka recruits Inscuteable and other proteins to form an apical complex, which then specifies spindle orientation and basal localization of the cell fate determinants and their adapter proteins such as Miranda. Here we report that Miranda localization requires the unconventional myosin VI Jaguar (Jar). In jar null mutant embryos, Miranda is delocalized and the spindle is misoriented, but the Inscuteable crescent remains apical. Miranda directly binds to Jar, raising the possibility that Miranda and its associated proteins are translocated basally by this actin-based motor. Our studies demonstrate that a class VI myosin is necessary for basal protein targeting and spindle orientation in neuroblasts.

Animals↗
PubMed1991

Importance of cell-aggregation during induction of neural differentiation in PCC-7 embryonal carcinoma cells.

The importance of cell-aggregation during retinoic acid-induced neural differentiation of embryonal carcinoma cells was studied on the PCC-7 cell line. These cells were chosen as they display low tendency for spontaneous aggregation, and they develop preferentially to neurons upon induced in vitro differentiation. Forced aggregation of these cells, in the absence of retinoic acid, did not result in development of neuron- or glial-like cells. Application of retinoic acid prior to or after the cell-aggregation did not result in neural tissue-like differentiation, either. Irreversible induction of neural development was achieved if cell-aggregation and retinonic acid acted simultaneously, and for a period longer than 48 h. Retinoic acid, on the other hand, was found to be toxic on non-aggregated PCC-7 cells. Our data suggest that cell to cell contacts alter the response of these cells to retinoic acid, and their close apposition is a prerequisite for the retinoic acid-induced neural differentiation.

Animals↗
PubMed2006

Neural stem cells, neurons, and glia.

Embryonic stem (ES) cells are a unique resource, providing in principle access to unlimited quantities of every cell type in vitro. They constitute an accessible system for modeling fundamental developmental processes, such as cell fate choice, commitment, and differentiation. Furthermore, the pluripotency of ES cells opens up opportunities for use of human ES cells as a source of material for pharmaceutical screening and cell-based transplantation therapies. Widespread application of ES cell-based technologies in both basic biology and medicine necessitates development of robust and reliable protocols for controlling self-renewal and differentiation in the laboratory. This chapter describes protocols that enable the conversion of mouse ES cells in simple adherent conditions to either terminally differentiated neurons and glia or self-renewing but lineage-restricted neural stem cell lines. It also reports on the current status in transfer of these approaches to human ES cells.

Animals↗
PubMed1989

Effects of asynchrony on rabbit blastocyst development.

The development of synchronously and asynchronously transferred rabbit morulae (recovered at Day 3 p.c.) and blastocysts (recovered at Day 4 p.c.) was investigated before the anticipated time of implantation. The results obtained with various techniques (evaluation of gross morphology, measurement of diameter, thymidine incorporation, light and electron microscopy) led basically to the same conclusions. Embryos being asynchronously transferred to the uterus of recipient rabbits survived, at least in terms of certain cellular functions like cell proliferation, for more than 2 days. Development, however, was clearly retarded and ultrastructural examination revealed substantial cell damage. Some blastocysts showed, even after 3 days, normal growth and cell proliferation indicating considerable differences between individuals in the ability to compensate for suboptimal developmental conditions before implantation. In general, this ability was greater in the transferred Day-3 morulae than in the Day-4 blastocysts. Embryonic growth and the ability to dissolve the zona pellucida, to synthesize crystalloid bodies and to differentiate extraembryonic endoderm indicated the maintenance of some developmental functions under asynchronous conditions. Blastocyst development was influenced by the progestational stage of the recipient. At 1 day after transfer into asynchronous older uteri, blastocyst diameters were larger and cell proliferation was increased compared with all other groups, suggesting an attempt of the blastocyst to adjust to the more advanced maternal milieu. Development in asynchronous younger uteri was delayed. No comparable differences in development were found in cultured embryos for which the media had been supplemented with flushings from the same progestational uterine stages as used for transfer. Thymidine incorporation in cultured embryos did not differ between the various supplements (P greater than 0.05) and was generally lower than in chronologically aged asynchronously transferred embryos (P less than 0.05 for Day-3 and P less than 0.001 or P greater than 0.05 for Day-4 embryos).

Animals↗
PubMedDate not supplied

Inductive interactions and embryonic equivalence groups in a basal metazoan, the ctenophore Mnemiopsis leidyi.

Ctenophores undergo locomotion via the metachronal beating of eight longitudinally arrayed rows of comb plate cilia. These cilia are normally derived from two embryonic lineages, which include both daughters of the four e1 micromeres (e11 and e12) and a single daughter of the four m1 micromeres (the m12 micromeres). Although the e1 lineage is established autonomously, the m1 lineage requires an inductive interaction from the e1 lineage to contribute to comb plate formation. Successive removal of the e1 progeny at later stages of development indicates that this interaction takes place after the 32-cell stage and likely proceeds over a prolonged period of development. Normally, the e1, cell lies in closest proximity to the m12 cell that generates comb plate cilia; however, either of the e1 daughters (e11 or e12) is capable of emitting the signal required for m1 descendants to form comb plates. Previous cell lineage analyses indicate that the two e1 daughters generate the same suite of cell fates. On the other hand, the m1 daughters (m11 and m12) normally give rise to different cell fates. Reciprocal m1 daughter deletions show that in the absence of one daughter, the other cell can generate all the cell types normally formed by the missing cell. Together, these findings demonstrate that the two m1 daughters (m11 and m12) represent an embryonic equivalence group or field and that differences in the fates of the two m1 daughters are normally controlled by cell-cell interactions. These combined properties of ctenophore development, including the utilization of deterministic cleavage divisions, inductive interactions, and the establishment of embryonic fields or equivalence groups, are remarkably similar to those present in the development of various bilaterian metazoans.

Animals↗
PubMed2001

Coordinate expression of Fgf8, Otx2, Bmp4, and Shh in the rostral prosencephalon during development of the telencephalic and optic vesicles.

Previous studies suggest that Fgf8 has a key role in regulating vertebrate development. In the rostral head of the embryonic chicken, there are increasing numbers of separate Fgf8 domains; these are present in tissues that appear to have previously expressed Otx2. As Fgf8 expression becomes established, Otx2 expression weakens, but remains in cells abutting the Fgf8 expression domain. These Fgf8 expression domains are closely associated with tissues expressing Bmp4 and Shh. Based on analogy with the embryonic limb, we suggest that Fgf8, Bmp4 and Shh function together in patterning regions of the embryonic head. Gene expression changes are particularly prominent in 14-21 somite stage embryos in the rostral forebrain, during early morphogenesis of the telencephalic and optic vesicles, when several new interfaces of Fgf8, Bmp4 and Shh are generated. To gain insights into the functions of fibroblast growth factor 8 (FGF8) in the embryonic forebrain, we studied the effects of implanting beads containing this protein in the dorsal prosencephalon of embryonic day 2 chicken embryos. Ectopic FGF8 had profound effects on morphogenesis of the telencephalic and optic vesicles. It disrupted formation of the optic stalk and caused a transformation of the pigment epithelium into neural retina. Within the telencephalon, FGF8 beads frequently induced a sulcus that had features of an ectopic rostral midline. The sulcus separated the telencephalon into rostral and caudal vesicles. Furthermore, we present evidence that FGF8 can regulate regionalization of the prosencephalon through inhibition of Otx2 and Emx2 expression. Thus, these experiments provide evidence that FGF8 can regulate both morphogenesis and patterning of the rostral prosencephalon (telencephalic and optic vesicles). FGF8 beads can induce midline properties (e.g. a sulcus) and can modulate the specification and differentiation of adjacent tissues. We suggest that some of these effects are through regulating the expression of homeobox genes (Otx2 and Emx2) that are known to participate in forebrain patterning.

Age Factors↗
PubMed1995

Fibroblast growth factor-mediated stimulation of differentiating teratocarcinoma cells: evidence for paracrine growth regulation.

Tera 2 human embryonal carcinoma cells proliferate rapidly in culture but are capable of differentiating into quiescent cells with neuronal features. We have characterized the effects of exogenous and endogenous fibroblast growth factors on the proliferation of differentiating Tera 2 cells. Exogenous basic fibroblast growth factor (bFGF) stimulated DNA synthesis and induced the proliferation-associated antigen Ki 67 in differentiated Tera 2 cells. Heparin-binding growth factors isolated from the undifferentiated cells excerted a similar stimulatory effect on their differentiated derivatives. The functional potential of these endogenous growth factors was further demonstrated by their ability to stimulate plasminogen activator production by capillary endothelial cells. A major part of the growth promoting activity was removed by absorption with immobilized bFGF antibodies. bFGF was also detected in Tera 2 cells by immunoblotting. The production of heparin-binding growth-promoting activity decreased during differentiation. The results demonstrate a potential role for heparin-binding growth factors in the autocrine or paracrine growth regulation of teratocarcinoma cells.

Cell Differentiation↗
PubMed2003

Influence of the neural tube/notochord complex on MyoD expression and cellular proliferation in chicken embryos.

Important advances have been made in understanding the genetic processes that control skeletal muscle formation. Studies conducted on quails detected a delay in the myogenic program of animals selected for high growth rates. These studies have led to the hypothesis that a delay in myogenesis would allow somitic cells to proliferate longer and consequently increase the number of embryonic myoblasts. To test this hypothesis, recently segmented somites and part of the unsegmented paraxial mesoderm were separated from the neural tube/notochord complex in HH12 chicken embryos. In situ hybridization and competitive RT-PCR revealed that MyoD transcripts, which are responsible for myoblast determination, were absent in somites separated from neural tube/notochord (1.06 and 0.06 10(-3) attomol MyoD/1 attomol beta-actin for control and separated somites, respectively; P<0.01). However, reapproximation of these structures allowed MyoD to be expressed in somites. Cellular proliferation was analyzed by immunohistochemical detection of incorporated BrdU, a thymidine analogue. A smaller but not significant (P = 0.27) number of proliferating cells was observed in somites that had been separated from neural tube/notochord (27 and 18 for control and separated somites, respectively). These results confirm the influence of the axial structures on MyoD activation but do not support the hypothesis that in the absence of MyoD transcripts the cellular proliferation would be maintained for a longer period of time.

Animals↗
PubMed1984

Genesis of neurons in the dorsal lateral geniculate nucleus of the cat.

Neurons that will ultimately form the dorsal and ventral lateral geniculate nuclei, the medial interlaminar nucleus, the perigeniculate nucleus, and the nucleus reticularis of the cat undergo their final cell division beginning on, or slightly before, embryonic day 22 (E22) and ending on, or before, E32. Early in this period, neurogenesis proceeds for all of these geniculate nuclei, whereas only in the dorsal lateral geniculate nucleus does cell birth continue until E32. Distinct spatiotemporal gradients of cell birth are not obvious within any of the individual geniculate nuclei. For the dorsal lateral geniculate nucleus in particular, and for the other geniculate nuclei in general, neurons born early in this period exhibit a full range of adult soma sizes, including large and small neurons. Neurons born late in this period exhibit only small adult somas. The location and size of a neuron within the dorsal lateral geniculate nucleus provide clues to that cell's functional properties. On the basis of presently available information regarding the relationship between structure and function of neurons in the cat's dorsal lateral geniculate nucleus, the findings described here suggest that all functional classes of neurons in the dorsal lateral geniculate nucleus are born at the same time throughout most of this period.

Animals↗
PubMed1984

A comparative study of the cell cycles of nullipotent and multipotent embryonal carcinoma cell lines during exponential growth.

Three embryonal carcinoma (EC) cell lines F9, PCC4 Azal, and PCC3 N/1 with a common origin from the transplantable ascites teratoma OTT6050 were analyzed with regard to cell cycle characteristics during exponential growth in the undifferentiated state. The three lines, in the sequence mentioned, have been shown to represent successive stages in early normal mouse embryogenesis from morula to blastocyst, as reflected in their cell surface antigens. In the multipotent lines an increased intraclonal variability in intermitotic times was found when analyzing family trees. In the PCC3 N/1 line the distribution was almost bimodal. The increased intermitotic time variability was found to be represented in the G1 period that varied from less than 1 hr up to about 6 hr in the PCC3 N/1 line, with a mean value of 3.4 hr. The G1 period of the F9 line had a range of only 3.5 hr, with a mean value of 1.5 hr. The S-G2 period was found to be very similar in length in all three lines.

Alkaline Phosphatase↗
PubMed1985

Commitment in a murine embryonal carcinoma cell line during differentiation induced by retinoic acid.

Murine embryonal carcinoma (EC) cells are induced to differentiate when cultured in the presence of retinoic acid (RA). Whereas the EC cells have a high plating efficiency, the differentiated cells have little or no colony-forming ability under the same conditions. We have assumed that the loss of colony-forming ability following exposure of EC cells to RA corresponds to the irreversible commitment of EC cells to differentiate. We found that uncommitted EC cells persist in RA-treated aggregates of EC cells and that the proportion of EC cells stabilizes at a level inversely related to the RA concentration. Both experimental evidence and mathematical modelling results are consistent with the interpretation that there is a dynamic equilibrium achieved by a balance between the processes of EC cell proliferation and differentiation. Since different cell types are induced by different RA concentrations, our results suggest that the commitment to differentiate is not related in any simple way to the developmental program which ensues.

Animals↗