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PubMed1979

Detecting mutations expressed during early development of cultured mammalian embryos.

Mammalian embryo culture systems can be used to study dominant lethal, recessive lethal, and visible mutations that are expressed between fertilization and early stages of organogenesis. The incidence of dominant lethal mutations has been determined for cultured mouse embryos by morphological observations during pre-implantation and early post-implantation growth in vitro, and the mechanisms of dominant lethal mutations have been studied cytogenetically. Recessive lethal mutations have been studied with cultured embryos, although they can be initially detected only with appropriate breeding protocols. Visible mutations that are due to deletions or single-site base alterations in the DNA can be detected in embryos by isoelectric focusing and gel-electrophoresis techniques.--The principal advantage of cultured embryos for detecting mutations and studying the mechanism of action of particular mutagens is that embryos are accessible for analysis before death with a minimum of indirect maternal effects. The primary disadvantages, which may be alleviated with improved culture conditions, are that only a limited amount of tissue is available, attrition and retardation occur, and offspring are not recovered for further breeding studies.

Animals↗

PubMed1999

High-level expression of the Mnb/Dyrk1A gene in brain and heart during rat early development.

We previously isolated human MNB/DYRK1A cDNA from "the Down syndrome critical region" of human chromosome 21 (Shindoh et al., 1996, Biochem. Biophys. Res. Commun. 225: 92-99). As described herein, we prepared a polyclonal anti-MNB/DYRK1A antibody and used it in a Western blot assay to assess the expression of the MNB/DYRK1A protein during rat development. The MNB/DYRK1A protein was expressed strongly not only in the brain but also in other tissues from embryonic rats. At the early postnatal stage, expression of the protein was high in the central nervous system and heart, but low in liver, lung, spleen, and kidney. The level of MNB/DYRK1A protein in all tissues studied gradually decreased with postnatal growth. Similarly, Northern blot analysis revealed that a major 6.0-kb transcript of the Mnb/Dyrk1A gene was expressed at a high level in the brain during the early postnatal period but that its level was low in the adult. The finding that the MNB/DYRK1A protein is expressed strongly in the central nervous system and heart may indicate a significant role for this protein in the development of these organs.

Amino Acid Sequence↗

PubMed1990

Changes in the orientation of proteoglycans during the early development of natural murine osteoarthritis.

At least 80% of male STR/ORT mice naturally develop osteoarthritis that predominantly affects the medial tibial cartilage. Overt osteoarthritic changes, as judged by radiological and histological abnormalities, become apparent after 30 weeks of age. Consequently, mice less than 30 weeks of age were used to investigate early changes in the cartilage matrix related to the natural development of osteoarthritis, without the need for experimental intervention to induce this condition. Quantitative Alcian blue staining showed little change in the total amount of proteoglycans in mice of this age. Polarized light microscopy of the birefringence induced by such staining demonstrated a progressive decline in the orientation of the proteoglycans in the medial cartilage of these mice. This decline was not found in CBA mice, which only very rarely develop osteoarthritis of this joint. Such progressive disorganization of the proteoglycans would be likely to permit the increase free water-content characteristic of osteoarthritic cartilage.

Aging↗

PubMed2005

Involvement of EDTP, an egg-derived tyrosine phosphatase, in the early development of Drosophila melanogaster.

Previously, we purified a novel protein tyrosine phosphatase from eggs of the flesh fly, Sarcophaga peregrina. This protein tyrosine phosphatase, named egg-derived tyrosine phosphatase (EDTP), is expressed during oogenesis and early embryogenesis but is rapidly degraded in middle embryogenesis by lysosomal cathepsin L. Here, we demonstrate the requirement of EDTP in the development of the fruit fly, Drosophila melanogaster. Deletion of the Drosophila EDTP gene using transposase-catalyzed imprecise excision resulted in homozygous lethals during embryogenesis. Additionally, germline clones generated using the FLP-FRT-ovo(D) system showed severe defects in ovarian development during oogenesis. These results indicate that the Drosophila EDTP gene is crucial in oogenesis and embryogenesis.

Animals↗

PubMed1987

Cell junctions during the early development of the sea urchin embryo (Paracentrotus lividus).

Thin sections, lanthanum tracer and the freeze-fracture technique revealed the presence of different types of cell junctions in early sea urchin (Paracentrotus lividus) embryos. During the first four cleavage cycles, which are characterized by synchrony of cell division, sister blastomeres were connected only by intercellular bridges, formed as a result of incomplete cytokinesis; no trace of other junctions was found at these stages. From the 16-cell stage onwards, septate junctions and gap junctions began to appear between blastomeres. It is postulated that cell-cell interactions may provide a mechanism for the propagation of signals necessary for the coordination of cell proliferation and differentiation.

Animals↗

PubMed2004

Cognitive impairment following status epilepticus and recurrent seizures during early development: support for the "two-hit hypothesis".

Prolonged seizures in immature rats result in minimal behavioral consequences when the animals are studied later in life. Likewise, early-onset seizures are associated with minimal morphological changes. However, it is known that seizures early in life result in changes in the brain that make it more vulnerable to subsequent seizure-induced injury (the so-called two-hit hypothesis). Whether this heightened vulnerability occurs immediately after the first seizure is not known. In this study, immature rats were exposed to status epilepticus (SE) followed by a series of 25 flurothyl-induced seizures, SE alone, 25 flurothyl-induced seizures alone, or no seizures. Rats exposed to SE and flurothyl seizures performed significantly poorer in the water maze 2 weeks following the last seizure compared with the other groups. No histological lesions were seen in any of the four groups. This study suggests that SE renders the immature brain vulnerable to further seizure-induced injury and this enhanced vulnerability occurs very quickly after the SE.

Analysis of Variance↗

PubMed2004

The expression of AmphiMdp during amphioxus early development.

We report here the expression of AmphiMdp in embryos and larvae. Faint AmphiMdp transcripts were first detected in the mesendoderm at the mid-gastrula stage and later in the somites of the early neurula. Expression remained in somites throughout the neurula and early larval stages and then disappeared from the somites starting with the most anterior somite and progressing posteriorly. At the 48-h larval stage, transcripts were detected in the developing tail bud. No transcripts were detectable in the somites of the 72-h larva. The result suggests that AmphiMdp is involved in myogenesis in amphioxus.

Amino Acid Sequence↗

PubMed2001

Cognitive functioning and the early development of PTSD.

Cross-sectional studies of chronic PTSD reveal deficits in verbal memory. We studied cognitive functioning and its relationship to current and subsequent PTSD severity during an early phase of trauma response. Thiry-eight participants with traumatic injuries and only posttrauma incident psychopathology were evaluated shortly after admission to a Level I Trauma Center Neuropsychological measures were obtained at baseline and assessment of PTSD and other psychiatric disorders was conducted at baseline and follow-up, 6 weeks later. Significant negative correlations were found for follow-up PTSD severity with delayed recall and retroactive interference. These relationships were not significant for and were independent of baseline PTSD severity. Relative deficits in select areas of verbal memory after a trauma may confer greater risk for developing PTSD.

Adult↗

PubMed1993

Crossfostering and early development of natural killer cytotoxic activity in various inbred mouse strains.

In the present study using crossfostering among three inbred mouse strains (C57BL/6, DBA/2, and Balb/c) we compared the effects of lactation with milk of different compositions on the development of NK cells cytotoxic activity. The results show that the pups from C57BL/6 and DBA/2 mice exhibit a significant early increase of NK cells cytotoxic activity when fostered by Balb/c dams, in comparison to those fostered by natural mothers. The analysis of proteins, lactose, and lipids showed difference among the strains for all components. Strain effects for days of lactation were also observed. The naso-anal length and the body weight of young mice showed differences with the strain of fostering mothers. The results indicate that the characteristic of maternal milk composition interacts with the inbred genetic susceptibility of the pups to elicit the full expression of the level of NK activity.

Animals↗

PubMed2006

Liver deformation in Ahr-null mice: evidence for aberrant hepatic perfusion in early development.

Mice harboring mutations in the Ahr locus display a patent ductus venosus and smaller livers throughout life. We tested the hypothesis that these hepatic aberrations are secondary to a developmental defect in hepatovascular blood flow by performing a detailed analysis of hepatic development in wild-type and Ahr-/- mice. This study revealed necrotic lesions in the peripheries of Ahr-/- fetal livers as early as embryonic day 15.5, with an increasing incidence up to postnatal day 1 and resolution by 2 weeks post partum. To visualize perfusion of fetal livers, we injected fluorescein isothiocyanate-labeled dextran into the cranial artery and monitored hepatic fluorescence by microscopy. The peripheries of the median and left lobes displayed decreased perfusion in regions corresponding to those regions that displayed necrosis at later developmental times. An examination of adult Ahr-/- animals revealed that smaller livers are predominantly due to decreased sizes of the left and right lobes, corresponding to regions of decreased perfusion and hepatic necrosis observed in fetal livers. Histological aberrations in the portal vein also support a model in which perfusion is compromised in the Ahr-/- liver. Taken in sum, these results indicate that the Ahr locus is required for normal perfusion of the developing liver and that disruption of the AHR signaling pathway gives rise to fetal hepatic necrosis and consequent liver deformation which persists through adult-hood.

Animals↗

PubMed2000

Early development of mouse embryos null mutant for the cyclin A2 gene occurs in the absence of maternally derived cyclin A2 gene products.

Progression through the mammalian cell cycle is regulated by the sequential activation and inactivation of the cyclin-dependent kinases. In adult cells, cyclin A2-dependent kinases are required for entry into S and M phases, completion of S phase, and centrosome duplication. However, mouse embryos lacking the cyclin A2 gene nonetheless complete preimplantation development, but die soon after implantation. In this report, we investigated whether a contribution of maternal cyclin A2 mRNA and protein to early embryonic cell cycles might explain these conflicting observations. Our data show that a maternal stock of cyclin A2 mRNA is present in the oocyte and persists after fertilization until the second mitotic cell cycle, when it is degraded to undetectable levels coincident with transcriptional activation of the zygotic genome. A portion of maternally derived cyclin A2 protein is stable during the first mitosis and persists in the cytoplasm, but is completely degraded at the second mitosis. The ability of cyclin A2-null mutants to develop normally from the four-cell to the postimplantation stage in the absence of detectable cyclin A2 gene product indicates therefore that cyclin A2 is dispensable for cellular progression during the preimplantation nongrowth period of mouse embryo development.

Amanitins↗

PubMed2006

Role of calcium signals in early development.

The mammalian egg appears to transduce the duration, amplitude, and temporal presentation of the increase in the intracellular calcium concentration ([Ca(2+)](i)) upon fertilization. These Ca(2+) parameters have important short-term effects on the initiation and completion of early events of egg activation, as well as much later consequences for the extent of peri-implantation development. Recent studies have begun to shed light on how the egg quantitatively interprets the Ca(2+) signal (e.g., by summation of individual Ca(2+) rises) and the mechanisms by which down-stream Ca(2+) effectors, such as Ca(2+)/Calmodulin (CaM)-dependent protein kinase II (CaMKII), utilize this ionic signal to promote biological events that initiate development.

Animals↗

PubMed1992

Differential expression and subcellular localization of secretogranin II and synaptophysin during early development of mouse hypothalamic neurons in culture.

Mature neurons contain two distinct regulated secretory pathways, characterized electron microscopically by so-called large dense core vesicles and small synaptic vesicles, respectively. Each vesicle type is characterized by vesicle-specific proteins, such as the granins (chromogranins/secretogranins) for the matrix of large dense core vesicles and synaptophysin for the membrane of small synaptic vesicles. So far, no data exist on the biogenesis of these two distinct vesicle types during neuronal development. We have used secretogranin II and synaptophysin as markers for the biogenesis of these two vesicle types during the development of mouse hypothalamic neurons in culture, using immunocytochemistry and biochemical analyses. By immunofluorescence, we found that secretogranin II appears as early as synaptophysin, but in a subset of neurons only, and with different subcellular localizations. It was observed in cytoplasmic areas where little or no synaptophysin immunofluorescence was detected, such as lamellipodia, emerging neurites and growth cones. At later stages, the proportion of secretogranin II-containing varicosities remained steady whereas that of synaptophysin-containing varicosities increased dramatically. By quantitative analysis we found that the level of expression of synaptophysin increased several-fold during synaptogenesis whereas that of secretogranin II decreased. These data suggest that large dense core vesicles and small synaptic vesicles can be formed separately and expressed at different levels. They provide evidence for a differential biogenesis of these two distinct vesicle types.

Animals↗

PubMed1991

Isolation and characterization of the gene encoding EF-1 alpha O, an elongation factor 1-alpha expressed during early development of Xenopus laevis.

In Xenopus laevis, the gene encoding the elongation factor 1-alpha variant EF-1 alpha O, where O stands for oocyte, is expressed in oocytes and early embryos. A genomic library from X. laevis was screened with a cDNA probe coding for EF-1 alpha O. Two recombinant phages were isolated, one of which carries an entire EF-1 alpha O gene. This clone was characterized by restriction enzyme mapping and sequencing. Comparison of cDNA and genomic sequences revealed that EF-1 alpha O consists of seven exons spanning about 6.5 kb. The structure of the gene is very homologous to the human EF-1 alpha gene, as all locations of the splice junctions are conserved between the two genes. The sequence immediately upstream from the transcription start point (tsp) contains a CCAAT box, but does not contain either a TATA box or a Sp1-binding site. Interestingly, this sequence has a sequence homologous to the negative regulatory element from the TFIIIA promoter. A region located about 400 bp upstream from the tsp contains an additional number of possible regulatory sequence elements. The first intron contains G + C-rich elements which exist both isolated and as part of longer inverted repeats. Furthermore, one octamer and four Sp1-binding sites are found in this intron.

Amino Acid Sequence↗

PubMed1987

Intercellular gaps in the early development of chick mural endocardium. A TEM study.

Embryonic chick hearts stages 15 to 21 according to the Hamburger-Hamilton series (1951) were subjected to TEM and light-microscopical examination to investigate ventricular mural endocardium during early trabeculation. Serial sectioning of consecutively-aged embryos indicated an invagination of the endocardial layer which lines the intertrabecular and intermuscular spaces. During the proceeding development, frequently occurring approaches and contacts between mural endocardium and myocardium could be observed. At all stages examined, the cardiac jelly appeared as an acellular, at particular sites very attenuated matrix. The intercellular gaps of the endocardium could not be correlated to the invagination and the endothelialization of the intertrabecular spaces.

Animals↗

PubMed1990

Patterns of epithelial cell death during early development of the human inner ear.

A light microscopic study of cell death in a developmental series of otic primordia from 23 human embryos (Carnegie stages 9 to 14) was completed. Degenerated cells were noted predominantly in the placode (stages 9 and 10), cup (stages 11 and 12), and otocyst (stages 13 and 14). A systematic camera lucida study of the appearance and topography of degenerating epithelial cells showed four different areas of cell death in the otic primordia that related to 1) invagination and detachment of the otic anlage, 2) early histogenesis of the statoacoustic ganglion, and 3) development of the endolymphatic duct. The possible role of cell death in the morphogenesis of the inner ear related to morphogenetic movements is discussed.

Cell Survival↗

PubMed2000

Expression of CD44 during early development of the chick embryo.

CD44, the major cell-surface receptor for hyaluronate, is expressed on many cell types to mediate different functions including cell activation, homing and adhesion. The early pattern of CD44 expression was determined in the avian embryo by using a specific monoclonal antibody in whole-mount and tissue sections. CD44 was first expressed on cephalic neural fold cells and later on by subpopulations of pre-and migratory cranial neural crest cells. Trunk neural crest cells did not express CD44. At the 18-20 somite stage, CD44 expressing cells were also localized in the caudal region of the embryo, in the mesoderm of the remaining primitive streak and in the caudal ectoderm and above the secondary neural tube during the process of cavitation. In addition, some hemopoietic cells present in the blood stream were also CD44 positive.

Animals↗

PubMed2000

Early development of ocular dominance columns.

The segregation of lateral geniculate nucleus (LGN) axons into ocular dominance columns is believed to involve a prolonged, activity-dependent sorting process. However, visualization of early postnatal ferret LGN axons by direct LGN tracer injections revealed segregated ocular dominance columns <7 days after innervation of layer 4. These early columns were unaffected by experimentally induced imbalances in retinal activity, implying that different mechanisms govern initial column formation and their modification during the subsequent critical period. Instead of activity-dependent plasticity, we propose that ocular dominance column formation relies on the targeting of distinct axonal populations to defined locales in cortical layer 4.

Animals↗