bluuebunny/crossref_metadata_2025 huggingface dataset:
A critical period for formation of secondary myotubes defined by prenatal undernourishment in rats
Authors: Wilson S. J. , Ross J. J. , Harris A. J.
Published: April 2021

Rats fed a restricted diet during gestation and lactation gave birth to pups with about 60 % the normal birthweight. Maintaining the undernutrition after birth reduced the rate of growth of the pups so that their body weights were only 40 % of control at PN7. Soleus and lumbrical muscles in these animals had reduced numbers of muscle fibres, and quantitative examination of embryonic muscles revealed that this was due solely to a decreased formation of secondary myotubes; the number of primary myotubes remained normal. Undernutrition did not affect the number of motoneurones surviving normal developmental death. Restoration of normal dietary intake on E21, one day before birth, did not correct the deficit in muscle fibre numbers in soleus muscles examined when the animals reached one month of age. Development of the lumbrical muscle lags behind the soleus and unrestricted feeding from E21 onwards allowed a normal number of fibres to develop from this time on, although the initial deficit was never restored. These experiments define a critical period in muscle development during which the potential maximum number of secondary myotubes is determined.
Development ofDrosophilalarval sensory organs: spatiotemporal pattern of sensory neurones, peripheral axonal pathways and sensilla differentiation
Authors: Hartenstein Volker
Published: April 2021

The sensilla of Drosophila larval thoracic and abdominal segments appear in a constant temporal sequence during stage 13/14 (9 ·5 –11 ·5 h) of embryonic development. Those sensilla innervated by more than one dendrite (basiconical sensilla, chordotonal organs, some of the trichoid sensilla and campaniform sensilla) appear earlier than sensilla innervated by a single dendrite (majority of trichoid sensilla and campaniform sensilla). Furthermore, a dorsoventrally directed gradient underlies the sequence in which sensilla of a given type appear. Sensory axons are emitted in the same sequence. Thus, axons of the polyinnervated sensilla appear first. Together with a distinct set of efferent axons they form ‘pioneer tracts’ of the two fascicles of the segmental nerves. Cytodifferentiation of the sensillum cells resembles the development of larval epidermal cells in many aspects. Thus, the sheath processes formed by sensillum accessory cells and the axons formed by sensory neurones develop from processes transiently formed by all cells. During the phase of cuticle secretion, apical portions of the presumptive accessory cells are modified to form the cuticular apparatus responsible for receiving the sensory stimuli. Finally, two sets of subepidermally located cells which differ with respect to their morphology and, probably, their origin envelop somata and axons of the sensory neurones.
Membrane glycoproteins immunologically related to the human insulin receptor are associated with presumptive neuronal territories and developing neurones inDrosophila melanogaster
Authors: Piovant Michel , Léna Philippe
Published: April 2021

We have generated a monoclonal antibody (Mab E1C) that recognizes the differentiated nervous system in Drosophila embryos. At the cellular blastoderm stage, Mab E1C behaves as a general ectodermal marker but, in subsequent stages, it also labels the mesoderm. As neurogenesis takes place, staining increases within the neuromeres and is almost exclusively restricted to the nervous tissue by the time neuronal differentiation is completed. In third instar larvae, Mab E1C stains the central nervous system (CNS) as well as the imaginai discs which display a staining pattern related to their degree of neuronal differentiation. No labelling can be detected in adult brains or ovaries. Western blots are consistent with this developmental profile and allow the characterization of a major glycoprotein of 135 × 103Mr (135K) which cosediments with a membrane fraction prepared from embryos. Additional glycoproteins (100K and 80K) are extracted from embryo homogenates by immunoaffinity procedures. In larvae, the 100K polypeptide is not detected. The properties of the 135K and 100K components are highly reminiscent of the molecular pattern of the Drosophila insulin receptor homologue (Petruzzelli et al. (1985)J. biol. Chem. 250, 16072 – 16075). It is shown that a Mab directed against the human insulin receptor stains the same cells as Mab E1C in imaginai discs and in the CNS. Moreover, this Mab cross-reacts with the 135K and 100K components of the embryonic antigen E1C.
Bombesin and other growth factors activate cell proliferation in chick embryo otic vesicles in culture
Authors: Represa J. J. , Miner Cristina , Barbosa E. , Giraldez F.
Published: April 2021

The ability of the mitogenic peptide bombesin and other growth factors to trigger and support early development of the inner ear was studied on chick embryo otocysts in culture. The normal pattern of development was preserved in cultured otic vesicles in the presence of 20 % fetal calf serum in the medium. Differentiation proceeded from stage 18 to 22 during the first 24 h and further to stage 24 in 48 h. Estimates of cell number and mitotic rates revealed a distinct period of proliferative growth which was maximum at the 24 h period of incubation. This was coincident with a high rate of DNA synthesis as measured by the acidprecipitable incorporation of [3H]thymidine. Development could be arrested by deprivation of serum during 24 h. It could then be reactivated by readmission of serum to proceed with the normal pattern of morphological differentiation and cell proliferation. Bombesin (100 nM) was able to reactivate development in growth-arrested vesicles. Its effect was dose-dependent, saturable and potentiated by insulin (5 μg ml-1) which was ineffective if used alone. When associated with insulin, bombesin carried differentiation to stage 21 and stimulated mitotic activity above the level of serum as judged from estimates of cell number and [3H]thymidine uptake. EGF and PDGF were also effective in reinitiating development although their potency was smaller than bombesin. The reactivation by serum or bombesin was blocked by amiloride. The results show that (1) the otic vesicle can provide a useful model for studying the mechanisms that control proliferative growth and differentiation during normal development and (2) bombesin and other growth factors are able to activate growth in embryonic developing tissues.
Patterns of N-CAM expression during myogenesis in Xenopus laevis
Authors: Kay B. K. , Schwartz L. M. , Rutishauser U. , Qiu T. H. , Peng H. B.
Published: April 2021

The neural cell adhesion molecule (N-CAM) is seen in the membrane of nerves and muscles from several vertebrate species. Using indirect immunofluorescence, we have examined the expression of this protein during embryonic and postembryonic myogenesis in the African clawed frog, Xenopus laevis. While good staining for N-CAM was seen in neuronal tissues at all stages examined, no staining of embryonic muscle was observed, including both mononucleated and polynucleated myoblasts. In contrast, limb muscles formed at metamorphosis showed strong expression of N-CAM. The developing limb muscles eventually lose their N-CAM, but will reexpress it dramatically when denervated. These observations suggest that myogenesis programs executed at different stages of development can display distinct patterns of N-CAM expression.
Normal embryogenesis occurs in starfish eggs induced to mature by microinjection of cytoplasm containing maturation-promoting factor (MPF)
Authors: Picard André , Labbé Jean-Claude , Dorée Marcel
Published: April 2021

Oocytes arrested at the first meiotic prophase re-initiate meiosis under the influence of a variety of signals, including hormones. These signals are thought to act indirectly to produce a maturation-promoting factor (MPF) which triggers transition to the metaphase. We show here that non-hormone-stimulated starfish oocytes, induced to mature by microinjection of MPF-containing cytosol taken from hormone-stimulated oocytes, produce normal bipin-naria larvae once fertilized.

The same result was obtained when donor oocytes were induced to mature by microinjecting heterologous MPF partially purified from amphibian oocytes. These results argue against the hypothesis that maturation events essential for normal embryo-genesis occur independently of MPF, at least in starfish.
The expression of rat homeobox-containing genes is developmentally regulated and tissue specific
Authors: Falzon Miriam , Chung Su Yun
Published: April 2021

Seven rat homeobox-containing sequences have been isolated by screening a genomic library with a probe derived from a Drosophila antennapedia cDNA clone. The characterization of two of these homeobox-containing clones has been described (Falzon, M., Sanderson, N. D. and Chung, S. Y. (1987) Gene 54, 23 – 32). Sequence analysis of the remaining five homeobox regions reveals a 180 bp domain sharing 70 – 95 % identity at the amino acid level with the homeodomain from the Drosophila antennapedia gene and with the homeodomains from other metazoan species. Genomic blot analysis shows that each of the homeobox-containing DNA segments is probably present in a single copy per haploid genome. Northern blot analysis of RNA transcripts indicates that the rat homeobox-containing sequences are expressed during embryogenesis and in newborn and adult tissues in a tissue-specific manner; RNA expression is predominantly detected in spinal cord and kidney. Moreover, the pattern of RNA transcripts observed is distinct for each homeobox sequence, indicating differential regulation. Among the seven rat homeobox-containing sequences, the flanking sequences of five of the clones have no obvious sequence similarity with previously published sequences of homeobox-containing genes from other species. Two of the rat clones have been identified as potential homologues to mouse homeobox-containing sequences. For both pairs, a high degree of amino acid conservation (>95 %) is oberved within the homeodomain and its immediate flanking regions between the putative homologous genes in mouse and rat. This strengthens the assertion that some of the mammalian homeobox-containing genes encode highly conserved proteins and may serve important biological functions.
Identification of a component ofDrosophilapolar granules
Authors: Hay Bruce , Ackerman Larry , Barbel Sandra , Jan Lily Y. , Jan Yuh Nung
Published: April 2021

Information necessary for the formation of pole cells, precursors of the germ line, is provided maternally and localized to the posterior pole of the Drosophila egg. The maternal origin and posterior localization of polar granules suggest that they may be associated with pole cell determinants. We have generated an antibody (Mab46Fll) against polar granules. In oocytes and early embryos, the Mab46Fll antigen is sharply localized to the posterior embryonic pole. In pole cells, it becomes associated with nuclear bodies within, and nuage around, the nucleus. Immunoreactivity remains associated with cells of the germ line throughout the life cycle of both males and females. This antibody recognizes a 72–74 ×103Mr protein and is useful both as a pole cell lineage marker and in biochemical studies of polar granules.
Detection of spatially- and stage-specific proteins in extracts from single embryos of the domesticated carrot
Authors: Racusen R. H. , Schiavone F. M.
Published: April 2021

Single embryos, representing each of four distinct morphological stages, were selected from cultures of the domesticated carrot for analysis of total [3SS]methionine-labelled proteins. Following exposure to radiolabel for 12 to 18 h, embryos were individually disrupted in a 3 mm diameter, precisely-matched, plastic mortar and pestle. Radiolabelled proteins extracted by this procedure were separated by two-dimensional electrophoresis procedures, consisting of isoelectric focusing in 1 mm tubes, followed by SDS-PAGE in a small slab gel. Comparisons of autoradiographs of these gels revealed that the levels of a number of proteins were modulated during the conversion of disordered callus cells into maturing embryos. In addition, miniature surgical techniques were used to separate the apex (cotyledon end) from the base (root end) of late-stage embryos, for extraction of proteins and analysis of spatial differences in protein distribution. About five proteins in extracts from each section were observed to be synthesized at different rates in the two halves, indicating that there are molecular correlates for early polarized growth. About half of the proteins, whose appearances were unique to apical and basal sections of embryos, were also observed to fluctuate in comparisons of autoradiographs of two-dimensional protein separations from embryos at different developmental stages.
Patterns of junctional communication during development of the early amphibian embryo
Authors: Guthrie Sarah , Turin Luca , Warner Anne
Published: April 2021

Cell-cell communication through gap junctions was examined in Xenopus laevis embryos between the 16cell and early blastula stages using Lucifer Yellow, Fluorescein, lead EDTA and dicyanoargentate as probes of junctional permeability. Injections were made into cells whose position was identified with respect to the primary cleavage axis and the grey crescent. FITC dextrans revealed cytoplasmic bridges between the injected cell and its sister only. In the animal pole at the 16-cell stage at the future dorsal side of the embryo, Lucifer Yellow was frequently and extensively transferred between cells through gap junctions. At the future ventral side gap junctional transfer of Lucifer Yellow was significantly less frequent and less extensive. The asymmetry of transfer between future dorsal and ventral sides of the animal pole was more marked at the 32-cell stage. In the vegetal pole also at the 32-cell stage, a dorsoventral difference in junctional permeability to Lucifer Yellow was observed. At the 64-cell stage the transfer of Lucifer Yellow was relatively frequent between cells lying in the same radial segment in the animal pole; transfer into cells outside each segment was infrequent, except at the grey crescent. At the 128-cell stage, Lucifer transfer between future dorsal or future ventral cells in the equatorial region was infrequent. A high incidence of transfer was restored at the future dorsal side at the 256-cell stage. At the 32-cell stage, fluorescein was infrequently transferred between animal pole cells although lead EDTA moved from cell to cell with high, comparable frequency in future dorsal and ventral regions. Dicyanoargentate always transferred extensively, both at the 32- and 64-cell stages. Treatment of embryos with methylamine raised intracellular pH by 015 units, increased the electrical conductance of the gap junction and produced a 10fold increase in the frequency of Lucifer Yellow transfer through gap junctions in future ventral regions of the animal pole at the 32-cell stage.
Cell proliferation and early differentiation during embryonic development and metamorphosis ofHydractinia echinata
Authors: Plickert G. , Kroiher M. , Munck A.
Published: April 2021

The early embryonic development of Hydractinia lasts about 2-5 days until the developing planula larva acquires competence for metamorphosis. Most embryonic cells stop cycling on reaching the larval stage. In older larvae of Hydractinia, cells that are still proliferating occur exclusively in the endoderm in a typical distribution along the longitudinal axis. During metamorphosis, proliferation activity begins again. The number of S-phase cells has increased by the 9th hour after induction of metamorphosis. Proliferative activity starts in the middle gastric region and in basal parts of primary polyps. Tentacles and stolon tips are always free of replicating cells.
Theoretical aspects of stripe formation in relation to Drosophila segmentation
Authors: Lacalli T. C. , Wilkinson D. A. , Harrison L. G.
Published: April 2021

Many aspects of Drosophila segmentation can be discussed in one-dimensional terms as a linear pattern of repeated elements or cell states. But the initial metameric pattern seen in the expression of pair-rule genes is fully two-dimensional, i.e. a pattern of stripes. Several lines of evidence suggest a kinetic mechanism acting globally during the syncytial blastoderm stage may be responsible for generating this pattern. The requirement that the mechanism should produce stripes, not spots or some other periodic pattern, imposes preconditions on this act, namely (1) sharp anterior and posterior boundaries that delimit the pattern-forming region, and (2) an axial asymmetrizing influence in the form of an anteroposterior gradient. Models for Drosophila segmentation generally rely on the gradient to provide positional information in the form of concentration thresholds that cue downstream elements of a hierarchical control system. This imposes restrictions on how such models cope with experimental disturbances to the gradient. A shallower gradient, for example, means fewer pattern elements. This need not be the case if the gradient acts through a kinetic mechanism like reaction-diffusion that involves the whole system. It is then the overall direction of the gradient that is important rather than specific concentration values. We illustrate this and some related properties of reaction-diffusion models with computations using a specific model, a variant of the Brusselator, and discuss features that appear to be both relevant to Drosophila and of general significance: (1) sharp boundaries and gradients can together orient and stabilize multistripe patterns and (2) boundaries, including fixed boundaries established within a pattern-forming region, may be important for controlling the subdivision of large pattern domains into smaller elements as is observed in the expression of pair-rule genes.
The effect of epidermal growth factor, insulin and transferrin on the growth-promoting properties of serum depleted by repeated culture of postimplantation rat embryos
Authors: Pratten M. K. , Brooke A. M. , Broome S. C. , Beck F.
Published: April 2021

Homologous serum, when repeatedly used for the culture of postimplantation rat embryos, rapidly loses its capacity to support growth and development. Replenishment of the ‘exhausted’ serum with glucose and vitamins (MEM vitamin concentrate -Flow Laboratories) together with gentle dialysis to remove small molecular weight toxic metabolites (lactate etc) fails to restore the growth-promoting properties of the serum. This suggests that ‘recycled’ serum has been depleted of specific growth-promoting factors. Such serum that has been subjected to dialysis can be completely replenished by addition of 30 % normal rat serum. It is therefore probable that the growth promoters are originally present at very low concentrations and become rate limiting when serum is recycled. Many growth factors and hormones fall into this category and it is likely that a considerable number are involved when serum is ‘exhausted’ by repeated use. When insulin, epidermal growth factor or rat transferrin are added to dialysed ‘exhausted’ serum each effects a partial restoration of growth of rat embryos.
Tissue effects on the expression of serotonin, tyrosine hydroxylase and GABA in cultures of neurogenic cells from the neuraxis and branchial arches
Authors: Mackey Harris M. , Payette Robert F. , Gershon Michael D.
Published: April 2021

The phenotypically diverse neurones of the enteric nervous system are developmentally derived from precursors that migrate to the bowel from the vagal and sacral regions of the neuraxis. In order to gain insight into the generation of enteric neuronal diversity, we examined the expression of serotonin (5-HT), tyrosine hydroxylase and GABA in vitro. In the mature avian intestine, intrinsic neurones contain 5- HT or GABA but not tyrosine hydroxylase. These markers were demonstrated immunocytochemically, singly or simultaneously. All three phenotypic markers developed in cultures of cranial, vagal or truncal neural crest when the cultures were grown in enriched medium, containing horse serum and chick embryo extract; however, 5-HT and GABA, but not tyrosine hydroxylase-immunoreactive cells, also developed in cultures that were grown in partially defined medium. Tyrosine hydroxylase immunoreactivity was seen when partially defined medium was supplemented with nerve growth factor (NGF). Cultures of branchial arches (III and IV) contained cells that displayed tyrosine hydroxylase immunoreactivity, but not that of 5-HT- or GABA-; however, 5-HT immunoreactivity was seen when branchial arches were cocultured with aneuronal hindgut (from 4-day chick embryos). Cultures of cells from chick gut dissociated at 7 days contained tyrosine hydroxylase as well as 5- HT and GABA immunoreactivities; however, no cultures of bowel dissociated at 8 days or later expressed tyrosine hydroxylase immunoreactivity. When neur- axial cells were cocultured with branchial arches or heart instead of gut, no 5-HT-immunoreactive cells were seen; nevertheless, the further addition of explants of gut to the heart/crest cocultures did permit the expression of 5-HT immunoreactivity. These results are consistent with the hypotheses that precursors with the potential to give rise to cells that express 5-HT, GABA and tyrosine hydroxylase are found at several levels of the neuraxis; however, the ability to express these phenotypes may be suppressed either while the crest cells are migrating (for example, 5-HT and GABA expression by crest cells passing through the branchial arches) or in their final destination (for example, tyrosine hydroxylase in the gut). This suppression may be transient and reversed by the microenvironment of the target organs.
Monitoring positional information during oogenesis in adultDrosophila
Authors: Fasano Laurent , Kerridge Stephen
Published: April 2021

About 184 P[lac,ry+]A insertions (O’Kane & Gehring, 1987) have been incorporated into the genome via P element-mediated transformation. The temporal-spatial localization of β-galactosidase, synthesized by these insertions during oogenesis, is described. 32 % present control levels of endogenous β-galactosidase expression and 68 % show novel patterns. 13 % of the insertions are germline-specific; 33%, follicle-cell-specific; 20 % are expressed in both germ line and follicle cells; and 2%, specific to the germarium. Several lines exhibit strict temporal-spatial localiz ations of β-galactosidase; notably those expressed in specific populations of follicle cells. The results are discussed with respect to some of the positional information encoded in the genome to which the insertions respond, the use of the insertions as markers for cell differentiation and the potential of the technique for isolating new genes involved in egg production.
A gene with sequence similarity to Drosophila engrailed is expressed during the development of the neural tube and vertebrae in the mouse
Authors: Davidson Duncan , Graham Elizabeth , Sime Christina , Hill Robert
Published: April 2021

The mouse genes En-1 and En-2 display sequence similarity, in and around the homeobox region, to the engrailed family in Drosophila. This paper describes their pattern of expression in the 12 ·5-day mouse embryo as determined by in situ hybridization.

En-2 is expressed in a subset of cells expressing En-1. Both genes are expressed in the developing midbrain and its junction with the hindbrain. In addition, En-1 is expressed in the floor of the hindbrain, a restricted ventrolateral segment of the neural tube throughout the trunk and anterior part of the tail, the dermatome of tail somites, the centrum and costal processes in developing vertebrae, a restricted region of facial mesenchyme and the limb-bud ectoderm. Supplementary studies of 9 ·5-day and 10 ·-5-day embryos showed that the same pattern of expression pertained in the neural tube, but that expression in the somites is at first confined to the dermatome and later found at a low level in restricted sclerotomal regions. Both genes are expressed in restricted domains which do not cross tissue-type boundaries. In several instances, however, boundaries of expression lie within morphologically undifferentiated tissue.

These results suggest that En-1 and En-2 may be involved in the establishment or maintenance of the spatial integrity of specific domains within developing tissues.
Heat shock causes repeated segmental anomalies in the chick embryo
Authors: Primmett D. R. N. , Stern C. D. , Keynes R. J.
Published: April 2021

A single heat shock, given to 2-day-old chick embryos, can generate multiple but discrete somite and skeletal anomalies. Each of these anomalies is restricted to one, or at the most two, consecutive segments. The anomalies are separated from each other by a distance of 6–7 somites or vertebrae, or a multiple of this distance. These results argue against the ‘clock and wavefront’ model; while they support the idea of a cellular clock, they are not consistent with a single propagating wave gating cells destined to form each segment.

Heat shock also alters the size and number of segments, as well as the rostrocaudal proportions of the sclerotome. The results are consistent with the rostrocaudal fate of sclerotome cells being determined during segmentation. From our observations, we speculate on the implications for regionalization of the vertebral column.
Features of embryonic induction
Authors: Jacobson Antone G. , Sater Amy K.
Published: April 2021

The patterned distribution of different organs in the amphibian embryo begins with the establishment of two domains, the animal and vegetal regions, that differ in developmental potency. Differences amplify as inductive interactions occur across boundaries between areas of different potency. Embryonic induction establishes a temporally and spatially dynamic area of developmental potency - a morphogenetic field. The final arrangement and differentiation of cell types within the field emerge from subsequent interactions occurring primarily within the field. These principles are illustrated in a review of the induction of the lens and the heart. Recent studies show that the induction of the lens of the eye and the induction of the heart begin early in development. Most of lens inductions occurs before the formation of the optic vesicle, and the heart appears to be part of a complex of dorsal structures whose formation is dependent upon the establishment of the dorsoventral axis. Suppressive as well as inductive tissue interactions occur during the determination of both of these organs, affecting their position and time of appearance. The complex processes of induction defined by the past nine decades of experimental work present many challenging questions that can now be addressed, especially in terms of the molecular events, cellular behaviour and regulatory physiology of the responding tissue.
Patterns of fibronectin gene expression and splicing during cell migration in chicken embryos
Authors: Ffrench-Constant Charles , Hynes Richard O.
Published: April 2021

A variety of evidence suggests that fibronectin (FN) promotes cell migration during embryogenesis, and it has been suggested that the deposition of FN along migratory pathways may also play a role in cell guidance. In order to investigate such a role for FN, it is important to determine the relative contribution of migrating and pathway-forming cells to the FN in the migratory track, as any synthesis of FN by the migrating cells might be expected to mask guidance cues provided by the exogenous FN from pathwayforming cells. We have therefore used in situ hybridization to determine in developing chicken embryos the distribution and alternative splicing of FN mRNA during three different cell migrations known to occur through FN-rich environments; neural crest cell migration, mesenchymal cell migration in the area vascu-losa and endocardial cushion cell migration in the heart. Our results show that trunk neural crest cells do not contain significant FN mRNA during their initial migration. In contrast, migrating mesenchymal cells of the area vasculosa and endocardial cushion cells both contain abundant FN mRNA. Furthermore, the FN mRNA in these migrating mesenchymal and endocardial cells appears to be spliced in a manner identical with that present in the cells adjacent to their pathways. This in vivo evidence for FN synthesis by migrating and pathway cells argues against a generalized role for exogenously produced FN as a guidance mechanism for cell migration.
Beige granules as a cell marker for clonal analysis in kidney and liver of mouse aggregation chimaeras, and three-dimensional reconstruction from serial paraffin sections
Authors: Nakatsuji Norio
Published: April 2021

Anomalous giant granules of beige (bg) mice have been used as a cell marker in the study of cell lineage of mast cells. Similar granules are known to exist in other tissues including kidney proximal tubules and liver parenchymal cells. In the present study, these granules were found to give yellow or orange autofluorescence when the tissue had been fixed with formaldehyde and embedded in paraffin. Thus, the granules can be used as a cell marker that can be visualized in serial paraffin sections without any specific histochemical staining. Chimaeric mice were produced by aggregation of 8-cell-stage embryos of beige (C57BL/ 6J-bgJ/bgJ) and A/J strains. The chimaeric liver showed beige cell patches with complicated shapes, although the patches frequently conformed to the shape of parenchymal cell cord or plate structures. In chimaeric kidney, beige cells formed coherent patches in the proximal tubules. The tubules were found to contain more than one clone. The patches frequently had long extended shapes suggesting growth of the clone along the tubule axis. Three-dimensional image reconstruction from the serial paraffin sections was carried out with the aid of a computer-assisted image analysis system, resulting in a clearer image of the patch shape.
The localization of laminin mRNA and protein in the postimplantation embryo and placenta of the mouse: anin situhybridization and immunocytochemical study
Authors: Senior Paul V. , Critchley David R. , Beck Felix , Walker Rosemary A. , Varley Jennifer M.
Published: April 2021

In situ hybridization (ISH) and immunocytochemistry were used to localize sites of synthesis and deposition of the basement membrane glycoprotein laminin during development in the postimplantation mouse embryo and extraembryonic membranes. In addition, similar studies were performed on postnatal viscera during the first 20 days after birth. Up to 10 days post coitum, embryonic laminin synthesis was confined to parietal endoderm. In maternal tissue, intense laminin mRNA expression was detected in decidual cells in the mesometrial and antimesometrial endometrium at 5–7 days. At 10 days, uniform expression was still seen within the mesometrial endometrium, with higher levels around migrating trophoblast, but in the antimesometrial aspect expression was restricted to the basal zone. High levels of mRNA expression persisted in parietal endoderm throughout gestation but much lower levels were detected in visceral yolk sac. In the mature placenta, laminin mRNA expression was also found associated with fetal vessels in the labyrinth and giant cells at the fetal/maternal boundary. In the embryo, the external limiting membrane of the cerebral vesicles and spinal cord stained for laminin protein and detectable mRNA was found in the pia mater. Growing peripheral nerves and dorsal and ventral root fibres expressed laminin mRNA and stained for laminin protein. Laminin mRNA expression was found in ureteric buds and nephrogenic vesicles (but not in metanephric blastema) during early prenatal kidney development, and in glomeruli, Bowman’s capsule, loops of Henle and collecting duct cells at later stages of development, and after birth. All these structures possessed laminin-rich basement membrane (BM). Laminin mRNA expression fell to below detectable levels in the kidney around weaning. In the gut, laminin expression and protein staining was confined to the muscularis externa and the lamina propria during embryogenesis. After birth, the muscularis externa, muscularis mucosa and lamina propria cells corresponding to fibroblasts had detectable laminin mRNA, but in adult gut no laminin mRNA could be demonstrated in any cell type. In liver, low levels of laminin mRNA were seen in the capsule and in periportal connective tissue. After birth, laminin mRNA was associated with intrahepatic bile channels; no laminin mRNA was detected in the parenchyma and protein deposition was restricted to blood sinus BM. In the adult liver, no laminin mRNA was detected in any cell type. The developing heart showed uniform expression of laminin mRNA from 12 days to before birth. Postnatally, labelling was restricted to connective tissue cells.
The pattern of cell death infushi tarazu, a segmentation gene ofDrosophila
Authors: Magrassi Lorenzo , Lawrence Peter A.
Published: April 2021

The pair-rule mutant, fushi tarazu, causes deletion of alternate metameres. Here we show that there is cell death in the mutant which begins at the completion of germ band extension. We map the dying cells in the epidermis; they occur scattered all over those regions that, in the wild type, would form the even-numbered parasegments and are also found in posterior parts of the odd-numbered parasegments. In the affected zones, dying and dividing cells are intermingled; we suggest that cells from these zones may still give descendents that contribute to the larval cuticle. Cell death is not limited to those cells that would normally express ftz+, suggesting that it is some indirect consequence of the abnormal situation in the mutant embryo.
Expression of injected HPRT minigene DNA in mouse embryos and its inhibition by antisense DNA
Authors: Ao Asangla , Monk Marilyn , Lovell-Badge Robin , Melton David W.
Published: April 2021

We have used a highly sensitive biochemical micro-assay to monitor the expression of a cloned minigene for hypoxanthine phosphoribosyl transferase (HPRT, EC.2.4.2.8) in preimplantation mouse embryos. The mouse HPRT promoter and the mouse metallothionein promoter (MT-I) function equally well in embryos at the 2-cell stage whereas the viral SV40 promoter does not allow HPRT expression. Induced HPRT activity from the MT-I HPRT minigene construct occurs in cleavage embryos cultured in the presence of cadmium. In contrast, negation of enzyme expression from the injected minigene DNA is mediated by simultaneous injection of HPRT antisense DNA.
Cell lineage in the rat cerebral cortex: a study using retroviral-mediated gene transfer
Authors: Price Jack , Thurlow Linda
Published: April 2021

We have used a retroviral vector that codes for the bacterial enzyme β-galactosidase to study cell lineage in the rat cerebral cortex. This vector has been used to label progenitor cells in the cerebral cortices of rat embryos during the period of neurogenesis. When these embryos are allowed to develop to adulthood, the clones of cells derived from the marked progenitor cells can be identified histochemically. In this way, we can ask what are the lineage relationships between different neural cell types. From these studies, we conclude that there are two distinct types of progenitor cells in the developing cortex. One generates only grey matter astrocytes, whereas the second gives rise to neurones -both pyramidal and nonpyramidal - and to another class of cells that we have tentatively identified as glial cells of the white matter. We have also been able to address the question of how neurones are dispersed in the cortex during histogenesis. It had been previously hypothesized that clonally related neurones migrated radially to form columns in the mature cortex. However, we find that clones of neurones do not form radial columns; rather, they tend to occupy the same or neighbouring cortical laminae and to be spread over several hundreds of micrometers of cortex in the horizontal dimension. This spread occurs in both mediolateral and rostro-caudal directions.
Requirements for autosomal gene activity during precellular stages of Drosophila melanogaster
Authors: Merrill Pauline T. , Sweeton Dari , Wieschaus Eric
Published: April 2021

To identify early requirements for zygotic gene activity in Drosophila, we used compound autosomes and autosome-Y translocations to generate embryos deficient for cytologically defined portions of the genome. No obvious gross morphological defects were observed in any deficiency class until the beginning of cycle 14. Only seven autosomal regions were identified with discrete effects visible prior to the onset of gastrulation. These regions include genes with locus-specific effects on the clearing of the cortical cytoplasm during early cycle 14, (22AB), the initiation of the slow and fast phases of cellularization (26BF and 40AC, respectively), the apical-basal distribution of nuclei during cycle 14 (71C–75C) and the closing off of furrow canals during cellularization (100AC). The distal tip of the third chromosome also contains two loci (99DF and 100AC) whose deletion causes multiple nuclei to be cellularized into single cells, a phenotype similar to that produced in embryos totally lacking the X-chromosome.
Shaping and bending of the avian neural plate as analysed with a fluorescent-histochemical marker
Authors: Schoenwolf Gary C. , Sheard Philip
Published: April 2021

Shaping and bending of the neural plate are cardinal events of neurulation. These processes are initiated in avian embryos shortly after the onset of gastrulation and concluded concomitantly with the completion of gastrulation. The epiblast undergoes extensive morphogenetic movements during gastrulation and neurulation, but the directions, distances, rates, mechanisms and roles of such rearrangements are largely unknown. To begin to understand these morphogenetic movements, we have mapped regional displacements of the epiblast by injecting a fluorescent-histochemical marker into selected prenodal, nodal and postnodal levels of the blastoderm. Lateral epiblast regions (600 μm lateral to the midline and consisting primarily of surface epithelium) are displaced craniomedially, medial regions (300 μm lateral to the midline and consisting of neural plate and preingressed mesoderm) predominantly medially, and midline regions (consisting of neural plate and primitive streak) predominantly caudally. Displacements within the avian neural plate parallel those previously described for the amphibian neural plate. Furthermore, similar tissue displacements occur within the prenodal and postnodal levels of the avian epiblast despite the fact that neurulation is occurring in the former and gastrulation in the latter. Finally, our results show that ectodermal rudiments contained within a single crosssectional level of the embryo are a composite of cells derived from multiple craniocaudal and mediolateral levels. Thus, regional tissue displacements are important events to consider in the analysis of the early morphogenesis of axial and paraxial organ rudiments derived from the epiblast.
A whole-mount immunocytochemical analysis of the expression of the intermediate filament protein vimentin in Xenopus
Authors: Dent Joseph A. , Polson Andrew G. , Klymkowsky Michael W.
Published: April 2021

We have developed a whole-mount immunocytochemical method for Xenopus and used it to map the expression of the intermediate filament protein vimentin during early embryogenesis. We used two monoclonal antibodies, 14h7 and RV202. Both label vimentin filaments in Xenopus A6 cells. RV202 reacts specifically with vimentin (Mr, 55×103) on Western blots of A6 cells and embryos. 14h7 reacts with vimentin and a second, insoluble polypeptide of 57×103Afr found in A6 cells. The 57 ×103Afr polypeptide appears to be an intermediate filament protein immunochemically related to vimentin. In the whole-mount embryo, we first found vimentin at the time of neural tube closure (stage 19) in cells located at the lateral margins of the neural tube. By stage 26, these cells, which are presumably radial glia, are present along the entire length of the neural tube and in the tail bud. Cells in the optic vesicles express vimentin by stage 24. Vimentin-expressing mesenchymal cells appear on the surface of the somites at stage 22/23; these cells appear first on anterior somites and on progressively more posterior somites as development continues. Beginning at stage 24, vimentin appears in mesenchymal cells located ventral to the somites and associated with the pronephric ducts; these ventral cells first appear below the anterior somites and later appear below more posterior somites. The dorsal fin mesenchyme expresses vimentin at stage 26. In the head, both mesodermally-derived and neural-crest-derived mesenchymal tissues express vimentin by stage 26. These include the mesenchyme of the branchial arches, the mandibular arch, the corneal epithelium, the eye, the meninges and mesenchyme surrounding the otic vesicle. By stage 33, vimentin-expressing mesenchymal cells are present in the pericardial cavity and line the vitelline veins. Vimentin expression appears to be a marker for the differentiation of a subset of central nervous system cells and of head and body mesenchyme in the early Xenopus embryo.
Tissue-specific expression of c-jun and junB during organogenesis in the mouse
Authors: Wilkinson David G. , Bhatt Sangita , Ryseck Rolf-Peter , BRAVO RODRIGO
Published: April 2021

c-jun and junB are cellular genes related to the viral oncogene v-jun and encode members of the AP-1 transcription factor gene family. These genes have been implicated in the control of the G0/G1 transition in fibroblasts. Here, we have investigated the potential roles of c-jun and junB during fetal growth and organogenesis in the mouse by in situ hybridization analysis of their expression patterns, c-jun expression is detected throughout organogenesis, and transcripts are detected in many tissues, although in restricted cell populations within developing cartilage, gut and the central nervous system (CNS). In cartilage, c-jun expression is associated with rapidly proliferating perichondrial cells, but occurs in postmitotic motor neurones in the CNS. junB expression is initiated between 14 · 5 and 17 · 5 days of development, and is restricted to differentiating epidermal cells and endodermal gut epithelium. These data suggest that c-jun and junB have distinct, tissue-specific roles in cell proliferation and differentiation during fetal development.
The segment polarity gene armadillo interacts with the wingless signaling pathway in both embryonic and adult pattern formation
Authors: Peifer Mark , Rauskolb Cordelia , Williams Michelle , Riggleman Bob , Wieschaus Eric
Published: April 2021

The segment polarity genes of Drosophila were initially defined as genes required for pattern formation within each embryonic segment. Some of these genes also function to establish the pattern of the adult cuticle. We have examined the role of the armadillo (arm) gene in this latter process. We confirmed and extended earlier findings that arm and the segment polarity gene wingless are very similar in their effects on embryonic development. We next discuss the role of arm in pattern formation in the imaginal discs, as determined by using a pupal lethal allele, by analyzing clones of arm mutant tissue in imaginal discs, and by using a transposon carrying arm to produce adults with a reduced level of arm. Together, these experiments established that arm is required for the development of all imaginal discs. The requirement for arm varies along the dorsal-ventral and proximal—distal axes. Cells that require the highest levels of arm are those that express the wingless gene. Further, animals with reduced arm levels have phenotypes that resemble those of weak alleles of wingless. We present a description of the patterns of arm protein accumulation in imaginal discs. Finally, we discuss the implications of these results for the role of arm and wingless in pattern formation.
The emergence of sense organs in the wing disc of Drosophila
Authors: Huang Françoise , Dambly-Chaudière Christine , Ghysen Alain
Published: April 2021

We have examined the origin of a set of precisely located sense organs in the notum and wing of Drosophila, in transformant flies where lacZ is expressed in the progenitor cells of the sense organs (the sensory mother cells) and in their progeny. Here we describe the temporal pattern of appearance and divisions of the sensory mother cells that will form the eleven macro-chaetes and the two trichoid sensilla of the notum, and five campaniform sensilla on the wing blade. The complete pattern of sensory mother cells develops in a strict sequence that extends over most of the third larval instar and the first 10 h after puparium formation. The delay between the onset of lacZ expression and the first differentiative division ranges from 30 h, in the case of the earliest mother cells, to 2 h for the latest mother cells.

The first division shows a preferential orientation which is also specific for each sensory mother cell. Up to this stage, there is no marked difference between the three types of mechanosensory organs.
Progressively restricted expression of a new homeobox-containing gene during Xenopus laevis embryogenesis
Authors: Su Ming-Wan , Suzuki Hiroaki R. , Solursh Michael , Ramirez Francesco
Published: April 2021

We have isolated cDNAs encoding a novel Xenopus homeodomain-containing protein homologous to the mouse Hox-7.1 and the Drosophila muscle segment homeobox (msh). Northern blot and RNAase protection experiments established that transcripts of the frog gene, termed Xhox-7.1, first appear at about the beginning of gastrulation. After a rapid increase, mRNA levels plateau between the neurula and mlddle-tailbud stages, and decrease steadily thereafter. In situ hybridization localized the Xhox-7.1 message to the dorsal mesodermal mantle of gastrula stage embryos. Comparison of the hybridization patterns of progressively more anterior cross-sections of tailbud stage embryos localized the signal to the dorsal neural tube and neural crest, to specific regions of the lateral plate mesoderm, and to the cardiogenic region. By the tadpole stage, the Xhox-7.1 message appears only at specific sites in the central nervous system, such as in the dorsal hindbrain. Thus, during embryonic development levels of Xhox-7.1 expression decrease as the transcript becomes more progressively localized. Finally, evidence is presented of a distinct msh-like transcript (provisionally termed Xhox-7.1’) which begins to accumulate at early-gastrula stage, as well.