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At least 775 records · Page 43Linked to original sources
PubMed1978

Teratogenic and cytogenetic effects of some plant-derived antitumor agents (vincristine, colchicine, maytansine, VP-16-213 and VM-26) in mice.

The teratogenic effects of three new plant-derived antitumor agents, maytansine, VP-16-213 and VM-26, were compared to the effects of vincristine and colchicine in pregnant Swiss albino mice that received a single ip injection of drug on day 6, 7 or 8 of gestation. Cytogenetic studies were also performed using maternal bone marrow and embryos obtained 48 hours after injection of maytansine, vincristine, VP-16-213, VM-26 and colchicine on day 6, 7 or 8 of gestation. A close correlation between teratogenic and cytogenetic effects was not noted among the compounds tested. Vincristine had greater embryotoxic and teratogenic activity than maytansine at equimolar doses (0.36 mu moles/kg), with the peak effects appearing after injection on day 7 of gestation. Colchicine, VP-16-213 and VM-26 were comparatively less potent than maytansine and vincristine, since doses of 2.5 mu moles/kg (colchicine and VP-16-213) and 1.5 mu moles/kg (VM-26) were required to elicit embryotoxic effects. At their teratogenic doses, all compounds induced various cranial abnormalities including exencephaly, hydrocephalus, anophthalmia and microtia, as well as major skeletal malformations. The teratogenic dose of vincristine is comparable to its effective antitumor dose in transplantable rodent tumor systems; in contrast, the teratogenic dose of maytansine in approximately 10-fold higher than its antitumor dose. Of the compounds studied, VP-16-213 and VM-26 exerted the most consistent cytogenetic effects in embryonic tissue. Alarge proportion of the structural chromosome aberrations induced in embryonic cells by VM-26 were stable and are most likely capable of surviving at least one cell division.

Abnormalities, Drug-Induced↗
PubMed1989

[Vaginal sonography in the diagnosis of early pregnancy].

In this study is reported on 401 transvaginal sonographic examinations in first trimenon of pregnancy. There were interpreted biometrical and functional findings. With 5 weeks p.m., chorion cavity can be identified by a transvaginal scan probe reaching a diameter of 3-8 mm. The vital embryo is recognized by its cardiac action with a embryonic length of 3 mm at the end of 6 weeks post menstruation. Thus with transvaginal sonography, details of embryonic development in the first trimester are visible 1-2 weeks earlier than with abdominal ultrasound examination. It is possible to estimate embryonic and trophoblastic structures of early gestation and to recognize non-viable early pregnancies.

Embryonic and Fetal Development↗
PubMed2002

Notch1 and Jagged1 expression by the developing pulmonary vasculature.

The molecular mechanisms of pulmonary vascular development are poorly understood. Cell-specific developmental pathways are influenced by cell-cell signaling. Notch signaling molecules are highly conserved receptors active in many cell-fate determination systems. Recent observations of Notch molecules and a Notch ligand, Jagged1, suggest their importance in vascular morphogenesis, and particularly pulmonary vascular development. We performed a systematic evaluation of Notch1/Jagged1 gene and protein expression in the developing mouse lung from embryonic day 11 until adulthood by using quantitative PCR, immunofluorescence, and electron microscopic analysis. mRNA transcripts for Notch1-4 and Jagged1 increased progressively from early to later lung development, accompanied by a simultaneous rise in endothelial cell-specific gene expression, a pattern not seen in other organs. Notch1 mRNA was identified on both epithelial and mesenchymal structures of the embryonic lung. Immunofluorescence staining revealed the progressive acquisition of Notch1 and Jagged1 proteins by the emerging endothelium. Notch1 and Jagged1 were seen initially on well-formed, larger vessels within the embryonic lung bud and progressively on finer vascular networks. Each was also expressed on surrounding nonvascular structures. The localization of Notch1 and Jagged1 on endothelial cell surface membranes within the alveolar microvasculature was confirmed by immuno-electron microscopy. These temporal and spatial patterns in Notch1/Jagged1 gene and protein expression suggest multiple potential paths of cell-cell signaling during lung development and vascular morphogenesis.

Animals↗
PubMed2000

Chemical analysis of the developmental pattern of polysialylation in chicken brain. Expression of only an extended form of polysialyl chains during embryogenesis and the presence of disialyl residues in both embryonic and adult chicken brains.

Recent studies have demonstrated the involvement of two polysialyltransferases in neural cell adhesion molecule (N-CAM) polysialylation. The availability of cDNAs encoding these enzymes facilitated studies on polysialylation of N-CAM. However, there is a dearth of detailed structural information on the degree of polymerization (DP), DP ranges, and the influence of embryogenesis on the DP. It is also unclear how many polysialic acid (polySia) chains are attached to a single core N-glycan. In this paper we applied new, efficient, and sensitive high pressure liquid chromatography methods to qualitatively and quantitatively analyze the polySia structures expressed on embryonic and adult chicken brain N-CAM. Our studies resulted in the following new findings. 1) The DP of the polySia chains was invariably 40-50 throughout developmental stages from embryonic day 5 to 21 after fertilization. In contrast, glycopeptides containing polySia with shorter DPs, ranging from 15 to 35, were isolated from adult brain. 2) Chemical evidence showed glycan chains abundant in Neu5Acalpha2,8Neu5Ac were expressed during all developmental stages including adult. 3) Levels of both di- and polySia were found to show distinctive changes during embryonic development.

Animals↗
PubMed2003

Platelets with wings: the maturation of Drosophila integrin biology.

The integrin family of cell surface receptors is strongly conserved in metazoans, making simple invertebrate genetic systems valuable contributors to understanding integrin function. The Drosophila integrins have long served as a paradigm for genetic studies of adhesion proteins during development. Currently, Drosophila experiments are exploring more general aspects of integrin biology. Genetic screens are identifying proteins involved in integrin adhesion complexes and signaling, and structures such as embryonic muscle attachments can be manipulated experimentally to dissect the functions of cytoplasmic components of integrin adhesion sites in whole animals. Drosophila also is beginning to yield some insights into integrin heterodimer structure and function.

Adherens Junctions↗
PubMed1998

Three-dimensional intrauterine sonography in the early first-trimester of human pregnancy: preliminary study.

Our purpose was to visualize normal embryonal surface anatomic structures using three-dimensional (3D) intrauterine sonography with a 20 MHz flexible catheter-based high-resolution real-time miniature transducer in the early first trimester of pregnancy. A total of 15 women about to undergo therapeutic abortion at 7-9.9 weeks gestational age were studied by means of 3D intrauterine sonography with a specially developed catheter-based high-resolution real-time miniature (2.4 mm in outer diameter) ultrasound transducer (20 MHz). This imaging system can provide conventional 2D intrauterine sonographic images and can also generate within seconds high-quality 3D images in the surface and transparent mode. At week 8, prominent forehead was evident, and upper and lower limbs and midgut herniation were clearly depicted. At week 9, fingers and toes were depicted as small digital rays, and the sacral tail protruded caudally. The midline cranial ectodermal cleft was also identified. At week 10, embryonic face and fingers were clearly shown. 3D intrauterine sonography provides a novel means for visualizing of surface anatomic structures of the human embryo in utero. These results suggest that 3D intrauterine sonography can become an important modality in future embryological research and in detection of embryonic developmental disorders in the early first-trimester pregnancy.

Embryo, Mammalian↗
PubMed2006

Engineered early embryonic cardiac tissue retains proliferative and contractile properties of developing embryonic myocardium.

Embryonic myocardium has a high rate of cell proliferation and regulates cellular proliferation, contractile function, and myocardial architecture in response to changes in external mechanical loads. However, the small and complex three-dimensional (3D) structure of the embryonic myocardium limits our ability to directly investigate detailed relationships between mechanical load, contractile function, and cardiomyocyte proliferation. We developed a novel 3D engineered early embryonic cardiac tissue (EEECT) from early embryonic ventricular cells to test the hypothesis that EEECT retains the proliferative and contractile properties of embryonic myocardium. We combined freshly isolated White Leghorn chicken embryonic ventricular cells at Hamburger-Hamilton (HH) stage 31 (day 7 of a 46-stage, 21-day incubation period), collagen type I, and matrix factors to construct cylindrical-shaped EEECTs. We studied tissue architecture, cell proliferation patterns, and contractile function. We then generated engineered fetal cardiac tissue (EFCT) from HH stage 40 (day 14) fetal ventricular cells for direct comparison with EEECT. Tissue architecture was similar in EEECT and EFCT. EEECT maintained high cell proliferation patterns by culture day 12, whereas EFCT decreased cell proliferation rate by culture day 9 (P < 0.05). EEECT increased active contractile force from culture day 7 to day 12. The culture day 12 EEECT contractile response to the beta-adrenergic stimulation was less than culture day 9 EFCT (P < 0.05). Cyclic mechanical stretch stimulation induced myocardial hyperplasia in EEECT. Results indicate that EEECT retains the proliferative and contractile properties of developing embryonic myocardium and shows potential as a robust in vitro model of developing embryonic myocardium.

Animals↗
PubMed1985

Cytoplasmic localization and chordamesoderm induction in the frog embryo.

The experiments described here were designed to reveal the distribution in the frog early embryo of components which are sufficient for specification of the dorsal structures of the embryonic body axis. The approach was to allow cleavage planes to divide the embryo into various well-defined regions and to transplant cells from each region into recipient embryos which would otherwise fail to form axial structures. Partial or complete body axis development could then be scored by the use of external criteria or histological methods. Recipients were embryos which had been irradiated before first cleavage with ultraviolet light on the vegetal surface. Irradiated embryos display a well-characterized set of deficiencies in the dorsal structures of the body axis, but their development can be 'rescued' toward normalcy in several ways. In particular, transplantation of certain small groups of blastomeres from the normal 32- to 64-cell embryo into irradiated recipients was sufficient to cause partial or complete axis development. Cell groups which could cause rescue were located in the vegetal and equatorial levels of one quadrant of the normal embryo--the quadrant centered on the future dorsal midline. Clonal marking analysis showed that the vegetal-most cells of this quadrant contribute primarily to endodermal structures in normal development. In rescued recipient embryos, these cells also contributed only to the endoderm; the dorsal mesoderm and central nervous system were formed exclusively by host cells which originated near the transplant. Rescue could also result from transplantation of equatorial cells from the dorsal quadrant of the normal embryo. As in normal development, these cells formed primarily the chordamesoderm of the rescued embryo. Host cells were induced to contribute the somitic mesoderm, central nervous system, and other structures which would have been missing but for the presence of the transplanted cells. The frequency and degree of rescue caused by equatorial and vegetal transplants is variable. This was explained by the discovery that the location of components needed for rescue varies among individual embryos without regard to the positions of cleavage planes. This was true even when donor embryos were selected on the basis of a precisely regular pattern of cleavage. In such selected embryos, particular blastomeres make a predictable contribution of progeny to the body axis. Thus it may be that the positions of components which can cause axis formation vary without exact regard to the fate map of prospective areas. The implications of this for the study of cytoplasmic localization in the early embryo are discussed.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

Neuronal cilia in the embryonic thalamus and striatum of Gallotia galloti (Reptilia, Lacertidae).

Cilia are a common characteristic of the embryonic neurons of the thalamus and striated centers of Gallotia galloti from E.35. The ciliogenesis process occurs around the stages E.33 and E.34. The ciliary morphology shows no substantial variations between the different stages and the ciliary structure in the embryonic period is 8 + 1. On the other hand, the adult cilia has a 9 + 2 arrangement of microtubules. We do not rule out the possibility of other axonemes.

Animals↗
PubMed1980

Immunoperoxidase localization of glial fibrillary acidic protein in radial glial cells and astrocytes of the developing rhesus monkey brain.

Peroxidase-antiperoxidase (PAP) immunohistochemical staining, utilizing a specific antibody to the glial fibrillary acidic protein (GFA), was employed to analyze gliogenesis in the central nervous system of rhesus monkeys ranging in age from embryonic day 38 (E38) to birth (E165) and through the second postnatal month. All major subdivisions of the brain contain glial cells, recognized by the presence of dark brown horseradish peroxidase (HRP) reaction product. Neuronal elements are not stained with this immunocytochemical technique. The first class of glial cells to appear during development are the radial glial cells; the radial fibers fan out from the ventricular and subventricular zones, where their cell bodies reside, to the pial surface where they terminate with conical endfeet. These glial cells appear within the first third of gestation, being present in the spinal cord and brainstem by E41; in the diencephalon by E45; and in the telencephalon and cerebellum by E47. The next class of glia to appear is the Bergmann glial cell of the cerebellar cortex, which can be stained by E54. Bergmann glial cells located below the Purkinje cell layer issue parallel processes which extend up to the pial surface. Within each major subdivision of the brain, massive numbers of elongated glial fibers continually alter their distinctive patterns to maintain constant ventricular-pial surface relationships during the major tectogenetic changes which occur throughout embryonic development. In Nissl-counterstained sections columns of migrating neurons are observed juxtaposed to GFA-positive radial and Bergmann glial fibers. Radial glial cells assume a variety of transitional forms during the process of their transformation into maturea astrocytes. This transformation occurs in each structure at specific embryonic ages and is initiated after neuronal migration has begun to subside. The number of astroglial cells increases at an accelerated pace after neurogenesis is complete. The immunohistochemical localization of radial fibers at relatively early stages of embryonic development indicates that glial cells are present concomitantly with neurons, raising the possibility that at least two distinct populations of cell precursors compose the proliferative zones. Furthermore, the demonstration of large numbers of radial glial cells in all brain regions during the peak of neuronal migration and a close structural relationship between elongated glial fibers and migrating neurons support the concept that glia play a significant role in the guidance and compartmentalization of neuronal elements during development.

Animals↗
PubMed2005

Sexual differentiation of the copulatory neuromuscular system in green anoles (Anolis carolinensis): normal ontogeny and manipulation of steroid hormones.

The copulatory neuromuscular system of green anoles is sexually dimorphic and differentiates during embryonic development, although details of the process were unknown. In Experiment 1, we determined the time course of normal ontogeny. Both male and female embryos possessed bilateral copulatory organs (hemipenes) and associated muscles until incubation day 13; the structures completely regressed in female embryos by incubation day 19 (total incubation 34 days). In Experiment 2, we treated eggs with testosterone, dihydrotestosterone, estradiol, or vehicle on both incubation days 10 and 13 to determine whether these steroid hormones mediate sexual differentiation. These time points fall between gonadal differentiation, which was determined in Experiment 1 to complete before day 10, and regression of the peripheral copulatory system in females. Tissue was collected on the day of hatching. Gonads were classified as testes or ovaries; presence versus absence of hemipenes and muscles, and the number and size of copulatory motoneurons were determined. Copulatory system morphology of vehicle-treated animals matched their gonadal sex. Hemipenes and muscles were absent in estradiol-treated animals, and androgens rescued the hemipenes and muscles in most females. Both testosterone and dihydrotestosterone treatment also caused hypertrophy of the hemipenes, which were everted in animals treated with these steroids. Copulatory motoneurons, assessed on the day of hatching in both experiments, were not dimorphic in size or number. Steroid treatment significantly increased motoneuron size and number overall, but no significant differences were detected in pairwise comparisons. These data demonstrate that differentiation of peripheral copulatory neuromuscular structures occurs during embryonic development and is influenced by gonadal steroids (regression by estradiol and enhancement by androgens), but associated motoneurons do not differentiate until later in life.

Animals↗
PubMed2003

Xenopus hoxc8 during early development.

Vertebrate hoxc8 homologous genes have been shown to be involved in the formation of lower thoracic/lumbar vertebrae during early embryonic development. We report the isolation of a Xenopus hoxc8 (Xhoxc8), which shows 94% amino acid sequence identity to the mouse counterpart. Xhoxc8 is initially expressed in a broad region of blastopore lip at gastrular stage; however, at later stages, the region of expression is progressively restricted to the dorsal region caudal to the third somite and to the central trunk region of abdomen. Retinoic acid treatment that caused a severe malformation in antero-posterior axis did not induce any significant change in the spatio-temporal expression pattern of Xhoxc8 mRNA. Antisense RNA injection into 2- or 4-cell stage embryos resulted in a severe malformation in the abdominal structure leading to embryonic death. The results strongly indicate that Xhoxc8 expression is critical for the formation of abdominal structure.

Abdomen↗
PubMed1984

Early cellular interactions promote embryonic axis formation in Xenopus laevis.

We have attempted to define the location and mode of action of axial determinants in the egg of Xenopus laevis. To this end, we transplanted small numbers of blastomeres from normal 64-cell stage embryos into synchronous recipient embryos which had been irradiated with ultraviolet light prior to first cleavage. Without transplantation, such embryos fail to develop dorsal structures of the embryonic body axis. We found that one to three blastomeres transplanted from the vegetal-most octet of cells can effect complete or partial rescue of of axis development in a recipient, provided that the donor cells derive from the quadrant just under the prospective dorsal marginal region. These same cells, when transplanted into the ventral vegetal quadrant of a normal 64-cell embryo, cause the formation of a complete second body axis. In contrast, other cells from the vegetal octet of normal donors fail to cause axis formation. When the rescuing donor cells are labeled with a lineage-restricted fluorescent marker, we find that their progeny do not contribute to the axial structures of the recipient. Progeny of the transplanted cells are found below the level of the blastopore in the early gastrula and eventually give rise to portions of the gut, as is their fate in normal development. These results, in agreement with those of Nieuwkoop (P.D. Nieuwkoop, 1977, Curr. Top. Dev. Biol. 11, 115-132), imply that the dorsal-most vegetal cells of the 64-cell embryo receive from the egg cytoplasm a set of determinants enabling them to induce neighboring cells to undertake axis formation. We discuss the relationship between axis induction in rescued irradiated embryos and axis determining processes in normal embryogenesis.

Animals↗
PubMed1993

The microvilli and hyaline layer of embryonic asteroid epithelial collar cells: a sensory structure to determine the position of locomotory cilia?

Early stage embryos of the starfish Pisaster ochraceus exhibit one cilium per cell which is primarily involved in locomotion. SEM observations have demonstrated two types of microvilli "stage horn"-like and "finger-like" microvilli (CMs), both of which probably serve to anchor and support the hyaline layer (HL). The CMs arise from the cellular membrane a short distance from the base of the ciliary shaft and form a circle around the base of each cilium. This arrangement is found in embryos and larvae as well as in adult tissues of many other marine organisms. TEM observations of material prepared by freeze substitution has demonstrated that the HL unites the circle of CMs and forms two collars. The outer ECM collar is single and attached directly to the CMs, while the inner collar consists of multiple rings of ECM located between the cilium and the CMs. The inner collar elements are not attached to the cilium but are attached to the inner aspects of the CMs by a complex arrangement consisting of a loop of ECM and two short ECM fibers. The arrangement of the ECM of the collars could provide an excellent way to transmit the movements of the cilium to the surrounding microvilli. Although the bases of the CMs always encircle the ciliary shaft, the shafts of the CMs are seen in different positions. This suggests that the CM/ECM collar may be able to change position relative to the cilium. Confocal laser scanning microscopy demonstrates that the CMs contain phalloidin positive material which extends into a phalloidin positive region located in the apex of the cells. The CMs and apical web contain microfilaments which are probably actin and could be involved in movement of the CMs. A movable circle of CMs with their associated ECM could represent a mechanism to sense the position of the cilium and/or to define the direction and extent of the stroke.

Animals↗