摘要:

AbstractWe report the cloning, partial sequence analysis, and spatiotemporal expression of the chickenPax‐1(chPax‐1) andPax‐9(chPax‐9) gene, two closely related members of the paired box‐containing (PAX) gene family. ThechPax‐1gene encodes RNAs of 2.0 and 4.3 kb and a 42 kD protein while the gene products ofchPax‐9are represented by 1.9 and 3.1 kb transcripts and a 39 kD protein. In situ hybridization and immunohistochemical analyses revealchPax‐1expression in the developing pectoral girdle, in cells of the ventral part of sclerotomes, in sclerotome cells of the perichordal tube, and, later in development, in sclerotome‐derived cells of the intervertebral disks. OtherchPax‐1expression domains detected in the mesenchyme surrounding the atlas and axis and in chondrocytes of immature vertebral bodies, so far unreported for mousePax‐1, correlate with as yet unexplained malformations in the mousePax‐1mutantundulatedandUndulated‐short tail. Overlapping expression ofchPax‐1andchPax‐9is detected in epithelial cells of the embryonic and adult thymus and in cells of the developing intervertebral disks. UnlikechPax‐1, however,chPax‐9is not expressed in those perichordal sclerotome cells which are thought to give rise to vertebral bodies. Furthermore,chPax‐9gene products are detected in circumscribed areas of mesenchyme in the metatarsus and in entodermal derivatives, i.e., in the lining epithelium of the developing pharynx and of the embryonic and adu

ISSN:1058-8388    

DOI:10.1002/aja.1002030102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe olfactory epithelium of adult mammals has the unique property of generating olfactory sensory neurons throughout life. Cells of the basal compartment, which include horizontal and globose basal cells, are responsible for the ongoing process of neurogenesis in this system. We report here that the globose basal cells in olfactory epithelium of rats, as in mice, are the predominant type of proliferating cell, and account for 97.6% of the actively dividing cells in the basal compartment of the normal epithelium. Globose basal cells have not been fully characterized in terms of their proliferative properties, and the dynamic aspects of neurogenesis are not well understood. As a consequence, it is uncertain whether cell kinetic properties are under any regulation that could affect the rate of neurogenesis. To address this gap in our knowledge, we have determined the duration ofboththe synthesis phase (S‐phase) and the full cell cycle of globose basal cells in adult rats. The duration of the S‐phase was found to be 9 hr in experiments utilizing sequential injections of either IdU followed by BrdUor3H‐thy followed by BrdU. The duration of the cell cycle was determined by varying the time interval between the injections of3H‐thy and BrdU and tracking the set of cells that exit S shortly after the first injection. With this paradigm, the interval required for these cells to traverse G2, M, G1,anda second S‐phase, is equivalent to the duration of one mitotic cycle and equals 17 hr. These observations serve as the foundation to assess whether the cell cycle duration is subject to regulation in response to experimental injury, and whether such regulation is partly responsible for changes in the rate of neurogenesis in such settings. ©1995 Wiley

ISSN:1058-8388    

DOI:10.1002/aja.1002030103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe aim of this study was to analyze the temporal sequence of expression of the myosin isoforms in the populations of muscle fibers in the pig and to bring more information on the origin of the strikingly different pattern of fiber composition and distribution between the deep medial red (oxido‐glycolytic) and superficial white (glycolytic) portions of semitendinosus (ST) muscle. Muscle samples were taken from 49‐, 55‐, 75‐, 90‐, 103‐, and 113‐ (birth) day‐old fetuses, from 6‐, 11‐, 21‐, 35‐, 50‐, and 80‐day‐old piglets, and from a 3‐year‐old pig. Our results confirm the sequential formation of primary and secondary generation fibers. The use of immunohistochemistry and heterologous monoclonal antibodies (mAb) directed against specific myosin heavy chain (MHC) isoforms revealed a different pattern of gene expression between the two portions of the ST muscle for both generations of fibers. By 75 days of gestation (dg), primary myotubes from the deep medial portion stained positively for the anti‐slow MHC mAb and negatively for the adult anti‐fast MHC, whereas the opposite was observed in the superficial portion. Secondary fibers never expressed slow MHC until late gestation. Instead, they expressed an adult fast MHC isoform as soon as they formed in the deep medial portion and later on in the superficial portion. From late gestation to the first 3 postnatal weeks, slow MHC began to be expressed in a subpopulation of secondary fibers. These fibers were in the direct vicinity of primary myotubes in the deep medial portion, whereas their location could not be established in the superficial portion. The remaining secondary fibers matured to type IIA in the direct vicinity of these type I fibers and to type IIB at the periphery of the islets. In both portions of the muscle, a subpopulation of secondary fibers, the first ones to express slow MHC, also transitorily expressed a MHC that was identical or closely related to the αcardiac MHC during the early postnatal period. A third generation of small diameter fibers was observed shortly after birth and reacted with the anti‐fetal MHC mAb; their destiny remains to be established. The present work reveals a remarkable pattern of MHC gene expression in the pig and raises many questions on the real nature of these isoforms. In order to answer these questions, we have undertaken to make a cDNA library of pig skeletal muscle and to screen this library with the same mAbs used in

ISSN:1058-8388    

DOI:10.1002/aja.1002030104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractDuring the early stages of embryonic development, the heart is a smooth‐walled, muscle‐wrapped tube that bends and rotates in a vital, but poorly understood, morphogenetic process called looping. Since looping involves biomechanical forces, this paper examines two mechanically based hypotheses for the bending component of cardiac looping. The first hypothesis is that an initial tension in or near the dorsal mesocardium (DM), a longitudinal structure along the outside of the ventricle, drives the deformation. To relieve the bending stresses in the tube, the myocytes change shape passively, and then they deform actively to continue the process to completion of a full loop. In the second hypothesis, contraction of circumferentially arranged actin macrofilaments produces circumferential compression and longitudinal expansion (due to incompressibility) of the myocytes. The DM locally constrains the longitudinal deformation, forcing the tube to bend. The feasibility of these hypotheses was evaluated using theoretical models and published experimental results. The models, which consist of beams composed of two layers representing the DM and the ventricular myocardium, show that the hypotheses are consistent with most of the known data, but further studies are necessary. In this regard, the models provide a conceptual framework for designing experiments to investigate the mechanics of looping. ©1995 Wiley‐Lis

ISSN:1058-8388    

DOI:10.1002/aja.1002030105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe spatiotemporal distribution of EAP‐300 (embryonic avian polypeptide of 300 kDa) was analyzed in embryonic chick heart using immunohistochemistry and confocal microscopy. EAP‐300 is a developmentally regulated protein initially characterized in neural cells from chick retina. Myocardial cells all along the early tubular heart were ubiquitously immunolabeled for EAP‐300 by embryonic day 2 (E2, Stage 13). At E5 (Stage 24), myocardial EAP‐300 expression levels remained significant in both atrial and ventricular myocardium. At E6 (Stage 28), distinct populations of EAP‐300 immunolabeled cells were also observed external to the heart, in septal mesenchymal tissue and neural ganglia adjacent to the outflow tract; these cell populations were confirmed as neural crest‐derived by co‐localization of EAP‐300 and HNK‐1. At E13 (Stage 39), myocardial immunolabeling for EAP‐300 was no longer ubiquitous, but increasingly restricted to conduction tissues, including the atrioventricular bundle and subendocardial Purkinje cells. This restriction of immunolabeling could be demonstrated definitively at E15 (stage 41), by which stage subendocardial and periarterial Purkinje fibers were clearly immunoreactive for EAP‐300 and several known markers of chick conduction tissue, including specific myosin heavy chain isoforms and connexin42, a gap junctional protein preferentially expressed by Purkinje fibers. Just prior to hatching at E21 (Stage 46), immunolabeling of conduction tissues was reduced, although still above that of non‐conductile myocardium. This spatiotemporal map of cardiac EAP‐300 expression indicates that it is independently and transiently expressed in early myocardium, cardiac conduction tissue, and neural crest derivatives during developme

ISSN:1058-8388    

DOI:10.1002/aja.1002030106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractTheDrosophila runtlocus controls early events in embryogenesis. A human homologue (CBFA2) was criginally identified because of its involvement in the t(8;21) associated with a subtype of acute myeloid leukaemia. The phylogenetically conserved region (runt box) was reported to correspond to a DNA binding domain. In order to investigate whetherruntalso plays a role in mammalian development, we have conducted a preliminary survey of its expression in the mouse embryo. Expression in embryonic tissues was detected starting from day 9.2 post coitum. From day 10.5 post coitum, highest levels are found in the neural tube, sensory ganglia, specialised sensory epithelial structures (olfactory and gustatory mucosa, follicles of the vibrissae), all chondrogenic centres (both of neural crest and of mesodermal origin), and the genital system (the gonad, the paramesonephros, and the genital tubercle). Unambiguous expression in the haemo‐poietic system could be established for the thymus. The data suggest a pleiotropic role for mammalianruntin embryogenesis. ©1995 Wiley‐Liss,

ISSN:1058-8388    

DOI:10.1002/aja.1002030107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractVitronectin (Vn) is not only a major adhesive glycoprotein in plasma but also regulates cell‐mediated proteolytic enzyme cascades, including the complement, coagulation, and fibrinolytic systems. This broad functional activity suggests that Vn may also play a critical role in development. To begin to investigate this possibility, we studied Vn gene expression during murine embryogenesis. In situ hybridization analysis of embryonic tissues revealed Vn mRNA primarily in the liver and the central nervous system (CNS). In the liver, Vn mRNA was detected by day 10, the level increasing at later developmental stages. In the CNS, Vn mRNA was also detected as early as day 10 and was confined to the floor plate. However, as development proceeded, high levels of Vn transcripts became prominent in the meninges of the cortex and spinal cord, and in close proximity to brain capillaries. The perikarya of most neurons lacked Vn mRNA. Unexpectedly, high levels of Vn mRNA were associated with capillaries of the CNS, but not with blood vessels of peripheral organs. These results indicate that Vn is expressed in a spatially and temporally distinct pattern during murine embryogenesis, and suggest that the Vn transcript may be a CNS‐specific vascular marker. ©1995 Wiley‐Lis

ISSN:1058-8388    

DOI:10.1002/aja.1002030108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractWe report the detailed developmental expression profiles of three endothelial specific receptor tyrosine kinases (RTKs)flk‐1, tek, tie, as well as vascular endothelial growth factor (VEGF), theflk‐1ligand. We also examined the expression of the other VEGF receptor,flt‐1, during placental development.flk‐1, tek, andtietranscripts were detected sequentially at one‐half day intervals starting at E7.0, suggesting that each of these RTKs play a unique role during vascularization of the mouse embryo. All three RTKs were expressed in the extraembryonic and embryonic mesoderm in regions that eventually give rise to the vasculature. Except for the expression oftekandflk‐1in the mesoderm of the amnion, the expression of these RTKs from E8.5 onwards was virtually indistinguishable. An abundant amount offlt‐1transcripts was found in the spongiotrophoblast cells of the developing placenta from E8.0 onwards. This cellular compartment is located between the maternal and labyrinthine layers of the placenta, which both express VEGF. VEGF transcripts were detected as early as E7.0 in the endoderm juxtaposed to theflk‐1positive mesoderm, and later in development VEGF expression displayed an expression profile both contiguous with that offlk‐;1, and also in tissues found some distance from theflk‐1‐expressing endothelium. These results suggest a possible dual role for VEGF which includes a chemotactic and/or a cellular maintenance role for VEGF during vascularization of the mouse embryo.

ISSN:1058-8388    

DOI:10.1002/aja.1002030109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractPericardial cavity formation and epithelialization of the cardiac precursor cell population constitute a critical developmental period that precedes stable cardiac cell commitment and differentiation. These events delineate the myocardial and endocardial precursor population in the embryo. Restriction of Na/K‐ATPase (the sodium pump) expression to the pre‐cardiomyocyte lateral membranes coincides with these events. Na/K‐ATPase has been implicated developmentally in cavitation and in maintaining membrane potential. Experiments were undertaken to determine if the effects of perturbing sodium pump activity will affect pericardial cavity formation and, in turn, whether heart formation and/or cardiac cell commitment will be affected. We incubated whole chick embryos in vitro between stages 5 to 8 in the presence of the highly specific Na/K‐ATPase inhibitor ouabain. Exposure of whole embryos to 10 μM ouabain (10−5M) demonstrated that heart development and precardiomyocyte differentiation are inhibited principally between stage 5 through stage 7. In each stage the degree of inhibition follows a rostrocaudal gradient as development proceeds along the anterior to posterior axis. After stage 8 ouabain no longer affects heart development or cardiomyogenesis. The inhibition is concentration‐ and developmental stage‐dependent. The inhibition is reversible by elevating the outside potassium ion concentration [Ko] in the culture medium or by transferring the embryos into normal medium minus ouabain even after 20 hr of ouabain exposure. The results also suggest that the regulation of the formation of the three‐dimensional organ is independent from regulation of myogenesis. ©199

ISSN:1058-8388    

DOI:10.1002/aja.1002030110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractWe describe here the expression ofc‐kitandSteel(Sl) genes during the development of melanocytes in normally pigmented strains of chick and quail compared to unpigmented (White Leghorn) and hyperpigmented (Silky Fowl) strains of chickens. By using the quail/chick chimera system, we found that the neural crest cells, which migrate dorso‐laterally in the subectodermal mesenchyme to give rise to the melanocytes, expressc‐kitas early as E4, that is about 2 days after they have left the neural primordium. TheSlgene is expressed from E4 onward in the epidermis but not at all in the dermis at any developmental stage. As feather buds develop,SlmRNA becomes restricted to the apical region of the feather filaments. During formation of the barbs and barbules of the down feather, production of the Steel factor is restricted to the external epidermal cells of the barbules. The cell bodies of thec‐kit‐positive melanocytes are then located in the internal border of the epidermal ridges and extend their processes toward the source of the Steel factor. We propose that the spatial restriction ofSlgene activity at that stage accounts for the morphology of the melanocytes and their vectorial secretion of melanin to the external barbule cells. As a whole, these results show that during skin developmentc‐kitpositive cells are present in the Steel factor‐producing areas at the time when melanoblasts proliferate and differentiate. Interestingly, in the mouse, previous studies showed that theSlgene is activated in the dermis where melanoblasts undergo most of their expansion (Nishikawa et al. [1991] EMBO J. 10:2111‐2118). In the unpigmented and hyperpigmented mutants that we studied, expression of theSlmessage, as judged quantitatively in Northern blots (for the SF embryos) or spatially by in situ hybridization, is similar to that observed in normal birds. In SF embryos thec‐kitexpressing melanoblasts migrate initially in the dorso‐lateral migration pathway as in normal birds. However their number increases considerably in the dermis from E5 onward. From E7, they invade mesodermally derived organs that do not express theSlgene. This suggests that another, still unknown, factor(s) is responsible for the survival, the proliferation, and the extensive spreading of melanocytic cells within the mesoderm of this mutant. ©

ISSN:1058-8388    

DOI:10.1002/aja.1002030111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY