[The significance of the embryonic blood vessels for the structure as well as for degenerative and inflammatory changes of the vitreous body].
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Humans↗
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Characterization of MEC 14.7, a new monoclonal antibody recognizing mouse CD34: a useful reage for identifying and characterizing blood vessels and hematopoietic precursors.
Endothelial cell-specific molecules are potential targets for new therapeutic strategies in the control of inflammatory reactions, immune responses and neoangiogenesis. We describe the production and characterization of MEC 14.7, a monoclonal antibody directed to murine endothelial cells recognizing a glycosylated protein with an apparent molecular mass of about 100 kDa in cultured endothelioma cell lysate and about 80 kDa in lung lysate. MEC 14.7 antigen was selectively expressed by the endothelium in vivo, particularly in small vessels and neoformed capillaries and by developing vascular structures in embryonal bodies. Deglycosylation of the molecule with neuraminidase, O- and N-glycanase showed that the MEC 14.7 epitope is neuraminidase-sensitive. MEC 14.7 antigen was purified from lung lysates by chromatographic techniques, and sequenced internal peptides indicated it was identical with murine CD34. Thus the apparent molecular mass of CD34 is heterogeneous, depending on the glycosylation state in the different cell types. Immunomagnetic isolation and culture of MEC 14.7-positive bone marrow cells showed that this antibody recognizes hematopoietic progenitors (particularly myelomonocytic) and can be used in murine models of bone marrow reconstitution.
Amino Acid Sequence↗
The Drosophila l(2)35Ba/nocA gene encodes a putative Zn finger protein involved in the development of the embryonic brain and the adult ocellar structures.
The Drosophila l(2)35Ba/nocA gene is involved in the development of the adult ocelli and the embryonic head. Mutations in this gene lead to at least two distinct phenotypes. Several larva lethal l(2)35Ba alleles cause both hypertrophy and mislocation of the embryonic supraesophageal ganglion (brain) to the dorsal surface of the embryo. A second class of mutant alleles (nocA) is homozygous viable, but the surviving adults either lack or have greatly reduced ocelli and associated bristles. The l(2)35Ba/nocA gene encodes an approximately 3.0-kb transcript doublet; all l(2)35Ba alleles which have been physically mapped delete or disrupt the transcribed region, whereas all of the viable nocA alleles are caused by gross chromosomal aberrations with breakpoints near the 3'-flanking region of the gene. Several nocA breakpoint alleles downregulate the level of l(2)35Ba/nocA transcripts in adults, and their defective ocellar phenotype also fails to be complemented by the lethal alleles, implying that l(2)35Ba and nocA are different phenotypic manifestations of mutations in the same gene. In the l(2)35Ba mutant embryos, cells from the procephalic lobe which normally migrate over and overlie the supraesophageal ganglion during head involution can become incorporated into the supraesophageal ganglion; many of these misplaced cells, which normally form the frontal sac, also adopt a neuronal fate. Sequence analysis of two full-length l(2)35Ba/nocA cDNAs with distinct polyadenylation sites shows that they encode the same deduced protein of 537 amino acids with a serine- and threonine-rich N-terminal region, two putative zinc finger motifs near the carboxyl terminus, and several alanine-rich domains. Consistent with the observed embryonic phenotype, l(2)35Ba/nocA shows a complex embryonic expression pattern which includes the procephalic lobe.
Aging↗
The human embryonic myosin heavy chain. Complete primary structure reveals evolutionary relationships with other developmental isoforms.
We have isolated a single 6021-nucleotide cDNA fragment encoding the full length of the myosin heavy chain (MHC) isoform initially expressed in developing human limb muscle. The corresponding transcript is expressed in fetal, but not adult, human muscle, and the corresponding gene maps to human chromosome 17. Comparison of the full length nucleotide sequence with that of the orthologous rat gene transcript reveals 74, 90, and 80% similarities in the 5'-untranslated, coding, and 3'-untranslated regions, respectively. To precisely quantitate the degree of nucleotide sequence divergence between the human embryonic and other developmentally regulated MHC gene transcripts, we utilize the algorithm of Perler et al. (Perler, F., Efstratiadis, A., Lomedico, P., Gilbert, W., Kolodner, R. & Dodgson, J. (1980) Cell 20, 555-566) and make use of the codon-for-codon register attainable in alignments of the MHC rod encoding cDNA fragments. The results allow reconstruction of the order and relative timing of certain gene duplication events involved in the evolution of the multimembered mammalian MHC loci. By this analysis, the principal sarcomeric MHC gene expressed in the 14-day chick embryo is shown to be more distantly related to the mammalian embryonic MHC genes than to those expressed peri- and postnatally. Attention is focused on regional patterns of MHC sequence conservation, ordered with reference to the topology of our phylogenetic tree. We present a composite map depicting the deduced evolutionary age of various primary structural subdomains of the human embryonic MHC.
Algorithms↗
Imaging the embryonic kidney.
The structural and functional development of the permanent mammalian kidney or metanephros is a complex process involving the actions of thousands of gene products, complex cell movements and tissue patterning in three dimensions (3D). This review focuses on the recent advances made in imaging technology, processing and analysis combined with mouse genetics and the generation of protein-reporter mice which has enabled us to monitor the development and movement of defined cell populations within the developing kidney in 3D and over time (4D).
Animals↗
New method for forming large embryoid bodies using the wall of the culture dish along with an analysis of their structural characteristics.
Early embryonic stem (EES) cells, which were established from 2 cell stage embryos obtained from ddY mice, had similar characteristics as embryonic stem (ES) cells. These cells were maintained in an undifferentiated stage in growth media supplemented with leukemia inhibitory factor (LIF) and were capable of differentiating into triploblastic tissues under various growth factors. It has been known that normal sized embryoid bodies (EBs) are formed by removing LIF. In this study, large EBs gradually formed along the side wall of a culture dish, particularly at the boundary between the air and the growth medium when cells were cultured for a considerable period of time and without subculturing. We call this method the "wall adhesion culture" procedure. The method itself is simple and do not need any instruments except plastic dishes because only the side walls of the dishes were utilized. The mean thickness of the large EBs was about 1.5 mm 3 months after establishing the static culture. Their surface was covered with a monolayer of cells and they contained an eosinophilic cell matrix. By electron microscopy, some characteristic structures was observed, such as intracisternal A particles which were present inside the swelling of the rough endoplasmic reticulum. Since many tissues derived from ES cells are obtained through EBs, it is expected that efficient acquisition of sufficient quantities of these structures using the wall adhesion culture procedure will be a shortcut for using ES cells in regenerative medicine.
Animals↗
[Morphological variability and placental function].
In mammals, the blastocyst defines with the maternal organism, a structure which allows embryonic development during gestation: the placenta. The structure of this organ varies remarkably across species. In this review the different type of placentation have been described in a comparative manner using terms of classification such as: placental materno-fetal interdigitation, matemofetal blood flow interrelationships, layers of the placental interhemal barrier, trophoblast invasiveness and decidual cell reaction, formation of syncytiotrophoblast. The human hemomonochorial placenta is characterized by a strong decidualization of the uterus and a major invasiveness of the extravillous trophoblast. Furthermore, there is a spectrum of placental endocrine activities across species. In some mammals (e.g., mouse and rat) the placenta eclipses the pituitary in the maintenance of ovarian function. In the human and in the sheep, horse, cat and guinea pig, the placenta acquires the ability to substitute for the ovaries in the maintenance of gestation at various time during pregnancy. The human placenta is characterized by a high rate of steroïdogenesis (progesterone and estrogens) and by the production of a primate specific trophoblastic hormone: human chorionic gonadotropin (hCG). Recently, it was demonstrated that mutation of many genes in mice results in embryonic mortality or fetal growth restriction, due to defects in placental development. Furthermore, distinct molecular pathways regulate the differentiation of various trophoblast cell subtype of the mouse placenta. An important question is whether or not placental differentiation in other mammals is regulated by the same molecular mechanisms. Due to the striking diversity in placental structure, endocrine function and gene expression, caution must be exercised in extrapolating findings regarding placental function and development from one species to another.
Animals↗
Embryonic lens of the human eye as an optical structure.
The spherical aberration of the excised embryonic (18 to 22 weeks) human lens was determined by photographing the refractive effects of the lens on fine parallel laser beams. All lenses showed little evidence of focal variation with laser position although a slight tendency toward positive (undercorrected) spherical aberration was noted. One lens from the eye of a newborn showed slight negative (overcorrected) aberration. It is assumed that the continued growth of the lens, with central compression of old tissue, produces a refractive index distribution which contributes to lens optical quality, even in the uterine environment. Frozen sections of embryo eyes of the same period (18 to 22 weeks) indicate that a major part of the change from a spherical to an elliptical lens shape takes place between the fourth and fifth month of development.
Fetus↗
Ultrastructure of bovine embryos frozen and thawed by a two-step freezing method.
An ultrastructural evaluation of a rapid tow-step freezing method, by which 6-7-day-old bovine embryos equilibrated in 1.4 M glycerol in Dulbecco's phosphate-buffered saline were frozen and thawed, was undertaken. In all non-frozen control embryos trophoblastic and embryonic cells formed a spherical structure enclosed by an intact zona pellucida. The spacial arrangement of the cells of the frozen embryos was less regular and the surrounding zona pellucida was damaged in approximately half of the cases. Some embryonic cells had increased electron density and lysosomal content showing reaction sites for acid phosphatase. In all frozen embryos, cytoplasmic defects appearing as non-membrane-bound 'empty spaces' were observed more frequently in the trophoblastic cells than in the embryonic cells. Culture of frozen embryos for 24 h revealed that cells appearing nondefective after culture may have the capability of organizing a viable embryonic structure. It was found that the most commonly used freezing method is associated with certain morphological changes. However, no additional cryoinjuries were observed in comparisons with the more complicated freezing procedures using dimethylsulfoxide as cryoprotectant.
Animals↗
Synovial plicae of the knee.
Synovial plicae are remnants of synovial tissue found in the adult knee which in early development partitioned the joint into three compartments. The most common types are the suprapatellar, medial patellar, and infrapatellar plicae. Although they are normally found in up to 60% of adult knees, plicae may become pathologically thickened and symptomatic, resulting in the "plicae syndrome." In addition, persistence of these structures in their embryonic form as complete septa may give rise to a variety of intra-articular compartmental syndromes, medial patellar, and infrapatellar plicae. Although they are normally found in up to 60% of adult knees, plicae may become pathologically thickened and symptomatic, resulting in the "plicae syndrome." In addition, persistence of these structures in their embryonic form as complete septa may give rise to a varietellar, medial patellar, and infrapatellar plicae. Although they are normally found in up to 60% of adult knees, plicae may become pathologically thickened and symptomatic, resulting in the "plicae syndrome." In addition, persistence of these structures in their embryonic form as complete septa may give rise to a variety of intra-articular compartmental syndromes. This report describes the anatomy and embryology of synovial plicae, as well as the clinical and radiographic findings associated with abnormal plicae in a variety of clinical entities.
Arthritis↗
Studies on the mechanism of circus movement in dissociated embryonic cells of a teleost, Oryzias latipes: fine-structural observations.
The fine structure of lobopodia in dissociated embryonic cells of the freshwater fish, Oryzias latipes, was observed with the electron microscope in order to understand the mechanism of the circus movements which they display. Dense material (grandular or fibrillar) is present in the zone between the lobopodium and the endoplasm, as well as in the cortical layer around the cell circumference. The direction of lobopodial movement is related to the distribution of this dense material. The band between the lobopodium and the endoplasm is conspicuous and is connected to the cortical dense layer around the cell periphery at the advancing front of the lobopodium, while the dense material is usually almost absent beneath the cell membrane in the anterior region of the lobopodium. The band between lobopodium and endoplasm is blurred or disrupted near the hind end of the lobopodiu, where the peripheral dense layer is well developed. In situ localization of actin/heavy meromyosin complexes in the cell showed that the dense material has actin-like properties. Cytochalasin B(0-5 mug/ml) induced constriction of the neck of the bleb, shrinkage of the endoplasm, and herniation of the endoplasmic contents to the enlarged hemispherical bleb, and thus arrested the circus movement. On the basis of these results, an hypothesis concerning the mechanism of circus movement is proposed and discussed.
Animals↗
Number, identity, and sequence of the Drosophila head segments as revealed by neural elements and their deletion patterns in mutants.
The development of the insect head tagma involves massive rearrangements and secondary fusions of segment anlagen during embryogenesis. Due to the lack of reliable morphological markers, the number, identity, and sequence of the head segments, particularly in the pregnathal region, are still a matter of ongoing debates. We examined the complex array of internal structures of the embryonic Drosophila melanogaster head such as the sensory structures and nerves of the peripheral and stomatogastric nervous systems, and we used embryonic head mutations causing a lack of overlapping segment anlagen to unravel the segmental identity and the sequence of the neural elements. Our results provide evidence for seven distinct segments in the Drosophila head, each characterized by a specific set of sensory neurons, consistent with the proposal that insects, myriapods, and crustaceans share a monophyletic evolutionary tree from a common annelid-like ancestor.
Animals↗
Vascular injury in transplanted tissues. Fine structural changes in tumor, adult, and embryonic blood vessels.
Adult, embryonic and tumor tissues from the rat were grafted to the chorioallantoic membrane (CAM) of the chick embryo. Fine structural changes in the microvasculature of the transplants were compared, with emphasis on the condition of endothelial cells. Endothelial cells in tumor grafts appeared irreversibly injured 2 h after grafting and most had degenerated by 8 h. In normal adult tissues, endothelial cells disintegrated more slowly, but lipid accumulation and blebbing leading to occlusion of vascular lumina, were prominent by 1 day. Cells were swollen and vacuolated 2 days after grafting and most were disrupted by 3 days. Embryonic endothelial cells were only mildly damaged and vessel lumina were patent for up to 3 days. Vessels were then reperfused with chick blood. It is concluded that the microvasculature in tumor tissue is extremely susceptible to ischemic damage and that this phenomenon may be involved in the central necrosis which develops in many animal tumors after they grow beyond a small size. Furthermore, only blood vessels and endothelium in embryonic tissues were sufficiently resistant to ischemic changes so that the graft microvasculature could be reperfused.
Animals↗
Histogenetic considerations concerning germ cell tumours. Morphological and immunohistochemical comparative investigation of the human embryo and testicular germ cell tumours.
Although it is accepted that the different components of germ cell tumours (GCT) imitate the embryonic and extraembryonic structures in early development, various tumour patterns remain to be interpreted in histogenetic terms. In particular, some patterns of embryonal carcinoma (EC) and yolk sac tumour (YST) have not been given a convincing histogenetic explanation. Combined morphological and immunohistochemical studies of GCT in addition to a three-dimensional analysis permit correlations between certain tumour patterns and normal embryonic and extraembryonic structures to be made. The various tumour patterns which reflect various stages of differentiation or maturation of cells and tissues of the normal conceptus may also be placed in chronological order with regard to embryogenesis. On the basis of such considerations a nomenclature using the embryological terms for the various tumour components may be considered, although not recommended as a new system of classification.
Chorionic Gonadotropin↗
[The structure of the centriolar apparatus of the endothelial cells in the embryonic and definitive human aorta].
The fine structure of the centriolar system was studied on serial sections of 90 endothelial cells of human aorta (50 to 60 years) in regions without atherosclerotic platelets and with fibrous and atheromatous platelets and of 30 endothelial cells of human embryonic aorta (22-24 weeks). The vast majority (95%) of endothelial cells of the atheromatous platelets were shown to have a primary cilium over 1 micron long which gives on the basal surface in all the cells. In the regions without platelets and with fibrous platelets a cilium was observed in about 20% of cells and it gives in the vessel lumen. Endothelial cells with a cilium fully embedded in the cytoplasm and with abnormal cilium structure were found in the embryonic aorta. A suggestion is put forward that cilia of the endothelial cells of embryonic aorta and those of adult aorta differ by the mechanism of their formation and can have different functions.
Adult↗
Vasculogenesis of the embryonic heart: origin of blood island-like structures.
The earliest vascular structures (blood island-like) in the embryonic heart are clusters of angioblasts and nucleated red blood cells (NRBCs), which differentiate into endothelial cells and erythrocytes, respectively. Our purpose was to define the area and chronology of NRBC appearance in the mouse embryonic heart at the stages before a patency between coronary vessels and peripheral circulation is established (10.5-13.5 dpc). Before and at the onset of vascularization, NBCs were not present within the proepicardium; however, Ter/119+ differentiating erythroblasts and single scattered CD45+ were found in the heart beginning from 10.5 dpc. The Ter/119+ cells were in close apposition to angioblasts (PECAM1+) and were recognized as components of blood island-like structures or vascular vesicles in transmission electron microscope and were located mostly in the subepicardium. Some of the NRBCs were not accompanied by angioblasts and located close to the endocardial endothelium or at the border of the endocardial endothelium or in the subepicardium. These erythroblasts were beginning to assemble with angioblasts. CD34+ NBCs as well as progenitor cells of erythroid lineage were not detected in the heart at these stages of development. The state of differentiation of NRBCs of blood islands was similar/the same as the morphology of circulating blood cells at the respective stages of embryo development. The presence of mature NRBCs in the subendocardial area and lack of progenitor cells of erythroid lineage within the heart indicate that erythroid commitment occurs outside the heart. We suggest that NRBCs enter the heart from the blood stream at 10.5-12 dpc independently from angioblasts.
Animals↗
The essential role of RI alpha in the maintenance of regulated PKA activity.
Cloning of the individual regulatory (R) and catalytic (C) subunits of the cAMP-dependent protein kinase (PKA) and expression of these subunits in cell culture have provided mechanistic answers about the rules for PKA holoenzyme assembly. One of the central findings of these studies is the essential role of the RI alpha regulatory subunit in maintaining the catalytic subunit under cAMP control. The role of RI alpha as the key compensatory regulatory subunit in this enzyme family was confirmed by gene knockouts of the three other regulatory subunits in mice. In each case, RI alpha has demonstrated the capacity for significant compensatory regulation of PKA activity in tissues where the other regulatory subunits are expressed, including brain, brown and white adipose tissue, skeletal muscle, and sperm. The essential requirement of the RI alpha regulatory subunit in maintaining cAMP control of PKA activity was further corroborated by the knockout of RI alpha in mice, which results in early embryonic lethality due to failed cardiac morphogenesis. Closer examination of RI alpha knockout embryos at even earlier stages of development revealed profound deficits in the morphogenesis of the mesodermal embryonic germ layer, which gives rise to essential structures including the embryonic heart tube. Failure of the mesodermal germ layer in RI alpha knockout embryos can be rescued by crossing RI alpha knockout mice to C alpha knockout mice, supporting the conclusion that inappropriately regulated PKA catalytic subunit activity is responsible for the phenotype. Isolation of primary embryonic fibroblasts from RI alpha knockout embryos reveals profound alterations in the actin-based cytoskeleton, which may account for the failure in mesoderm morphogenesis at gastrulation.
Animals↗
[Formation of striatum structural and ultrastructural organization in the early postnatal ontogenesis of rats subjected to altered conditions of their embryonic development].
Formation of the structure of striatum during two postnatal weeks in rats subjected to acute hypoxia during various periods of their embryonic development was studied using light microscopic (Nissl's stain and Golgi's silver nitrate impregnation) methods and electron microscopy. This study was supplemented by a simultaneous investigation of physiological development of the same population of rats. The data obtained demonstrated that prenatal hypoxia on day 13.5 of embryonic development (E13.5) led to a delayed neurogenesis (retardation in the development of neuropil elements and cell differentiation) as well as to the malformation of the structure of striatum (degeneration, in particular, chromatolysis of neurons and glial nodule formation). Morphometric analysis demonstrated that prenatal hypoxia on E13.5 resulted in a statistically significant decrease in cell number in the striatum, these changes being especially pronounced in large neurons. Prenatal hypoxia on E18.5, however, caused no significant changes in striatum. Structural changes in the striatum were shown to be accompanied by significant changes in the physiological development of animals. The data obtained demonstrated that the alteration of the conditions of embryogenesis (hypoxia) during the period of most intensive proliferation of forebrain neuroblasts resulted in the disturbances of the formation of both striatum nervous tissue of the organism as a whole during early postnatal ontogenesis.
Animals↗