bluuebunny/crossref_metadata_2025_split huggingface dataset:
Correlated onset and patterning of proopiomelanocortin gene expression in embryonic Xenopus brain and pituitary
Authors: Hayes William Pär , Loh Y. Peng 
Published: April 2021

Abstract
To identify cellular interactions that underlie the spatially appropriate transcription of neural genes, we characterized the embryonic development of proopiomelanocortin (POMC) gene expression in Xenopus laevis using in situ hybridization histochemistry. This has led to the establishment of a unique model system for studying how a neuropeptide gene program in four distinct cell groups is set up in pituitary and forebrain.
The embryonic onset and patterning of POMC expression was found to be spatially and temporally correlated inside and outside the brain. The first POMC cells in the pituitary primordium and diencephalon were juxtaposed near the infundibulum at stage 29/30, indicating they undergo molecular differentiation much earlier than previously reported for this system. By stage 31/32, many more POMC cells appeared in the morphologically undifferentiated pituitary primordium and brain. In fact, these cells were seen throughout the presumptive anterior and intermediate lobes of the pituitary and posterior diencephalon at the same time that the pituitary primordium is translocating ventral to diencephalon. By stage 39/40, coordinated morphogenesis produced the adult pattern of POMC cells localized in distinct anterior and intermediate pituitary lobes and two diencephalic nuclei. We propose in light of these findings that embryonic cells in the pituitary primordium and brain are simultaneously induced to transcribe the POMC gene, possibly as a result of reciprocal brain-pituitary interactions.
Nonspecific effects of oligodeoxynucleotide injection in Xenopus oocytes: a reevaluation of previous D7 mRNA ablation experiments
Authors: Smith Rosamund C. , Bement William M. , Dersch Mark A. , Dworkin-Rastl Eva , Dworkin Mark B. , Capco David G. 
Published: April 2021

Abstract
Microinjection of oligodeoxynucleotides (ODNs) complementary to cellular mRNAs has been advanced as an experimental approach to degrade target mRNAs in vivo and thereby obtain information as to the function of their cognate proteins. It is shown here that ODNs can induce a variety of aberrations in cell metabolism and structure when injected into Xenopus oocytes. Examination of histological sections of ODN-injected oocytes revealed the frequent abnormal accumulation of heavily staining basophilic material in the area of the germinal vesicle (gv). Ultrastructural analysis detected further abnormalities including blebbing of the plasma membrane, anomalous cytoskeletal structures, hyperorganised annulate lamellae, hyperinvagination of the gv, and formation of irregular nucleoli within the gv. Analysis of newly synthesised proteins by [35S]methio-nine radiolabelling of oocytes demonstrated that ODN injection can trigger a general decrease in both label uptake and protein synthesis. Qualitative effects on protein synthesis could also be observed, particularly a decrease in synthesis of high molecular weight proteins. The severity of ODN-induced effects is dose-dependent and highly variable from ODN to ODN. The previously reported delay in progesterone-induced maturation observed in oocytes depleted of the maternal mRNA D7 by ODN-directed degradation (Smith R.C., Dworkin M.B. and Dworkin-Rastl E.(1988) Genes and Devpt. 2, 1296-1306) is most likely a result of nonspecific ODN effects in the oocyte. Oocytes injected with effective antisense D7 ODNs that do not display detectable side effects matured with normal kinetics.
The pattern of early cleavage of the marsupial frog Gastrotheca riobambae
Authors: del Pino Eugenia M. , Loor-Vela Sandra 
Published: April 2021

Abstract
Comparison of early development of the marsupial frog Gastrotheca riobambae with Xenopus laevis suggests that the cleavage pattern of Xenopus and the tight coupling of events at the midblastula transition are features of the accelerated development of small amphibian eggs with aquatic reproduction, rather than generalized features of amphibian development. The large eggs of the marsupial frog Gastrotheca riobambae not only display an atypical holoblastic pattern of cleavage and a very slow rate of development, but the events of the midblastula transition are uncoupled, suggesting that amphibians may have a diversity of developmental patterns. Early cleavage of the egg, which measures about 3 mm in diameter, occurs mostly by meridional and vertical furrows. The first cleavage cycle takes about 16 to 20 h and about four days may be required to reach the midblastula stage. Cleavage becomes asynchronous at about the third cleavage cycle evidenced by the formation of cleavage furrows. However, during cleavage (up to 342-cells), the majority of the nuclei divide synchronously and only 15 to 40 % of the nuclei of a given embryo have a different cleavage schedule. At the 8-cell stage, nucleoli become visible (approximately 24 h after amplexus), signaling that transcription of rRNA has started at this early stage. Cell motility was detected in three- to four-day old embryos and seems to be associated with changes in cell shape and with expansion of the blastocoel at this stage.
Postimplantation development of tetraploid mouse embryos produced by electrofusion
Authors: Kaufman M. H. , Webb S. 
Published: April 2021

Abstract
Despite the fact that a variety of experimental techniques have been devised over the years to induce tetraploid mammalian embryonic development, success rates to date have been limited. Apart from the early study by Snow, who obtained development to term of a limited number of cytochalasin B-induced tetraploid mouse embryos, no other researchers have achieved development of tetraploid embryos beyond the early postimplantation period. We now report advanced postimplantation development of tetraploid mouse embryos following electrofusion of blastomeres at the 2-cell stage, and subsequent transfer of these 1-cell ‘fused’ embryos to appropriate recipients. Cytogenetic analysis of the extraembryonic membranes of all of the postimplantation embryos encountered in the present study has provided an unequivocal means of confirming their tetraploid chromosome constitution. A preliminary morphological and histological analysis of the tetraploid embryos obtained by this technique has revealed that characteristic craniofacial abnormalities particularly involving the forebrain and eyes were consistently observed, and these features were often associated with abnormalities of the vertebral axis and heart. The most advanced viable embryo in this series was recovered on the 15th day of gestation, and its morphological features suggest that it was developmentally equivalent to a normal embryo of about 13.5–14 days p.c.
Collagen types IX and X in the developing chick tibiotarsus: analyses of mRNAs and proteins
Authors: Linsenmayer Thomas F. , Chen Qian , Gibney Eileen , Gordon Marion K. , Marchant Jeffrey K. , Mayne Richard , Schmid Thomas M. 
Published: April 2021

ABSTRACT
To examine the regulation of collagen types EX and X during the hypertrophic phase of endochondral cartilage development, we have employed in situ hybridization and immunofluorescence histochemistry on selected stages of embryonic chick tibiotarsi. The data show that mRNA for type X collagen appears at or about the time that we detect the first appearance of the protein. This result is incompatible with translational regulation, which would require accumulation of the mRNA to occur at an appreciably earlier time. Data on later-stage embryos demonstrate that once hypertrophic chondrocytes initiate synthesis of type X collagen, they sustain high levels of its mRNA during the remainder of the hypertrophic program. This suggests that these cells maintain their integrity until close to the time that they are removed at the advancing marrow cavity. Type X collagen protein in the hypertrophic matrix also extends to the marrow cavity. Type EX collagen is found throughout the hypertrophic matrix, as well as throughout the younger cartilaginous matrices. But the mRNA for this molecule is largely or completely absent from the oldest hypertrophic cells. These data are consistent with a model that we have previously proposed in which newly synthesized type X collagen within the hypertrophic zone can become associated with type II/IX collagen fibrils synthesized and deposited earlier in development (Schmid and Linsenmayer, 1990; Chen et al. 1990).
Apical cell shape changes during Drosophila imaginal leg disc elongation: a novel morphogenetic mechanism
Authors: Condic M. L. , Fristrom D. , Fristrom J. W. 
Published: April 2021

ABSTRACT
Imaginal discs of Drosophila are simple epithelial tissues that undergo dramatic changes in shape during metamorphosis, including elongation to form adult appendages such as legs and wings. We have examined the cellular basis of leg disc morphogenesis by staining filamentous actin to outline cell boundaries in discs and observing cell shapes with scanning confocal laser microscopy (SCLM). Surprisingly, we found that prior to the onset of morphogenesis, cells in the dorsal-lateral regions of leg discs are compressed in the proximal-distal axis and greatly elongated circumferentially. These cells are also asymmetric in the apical-basal axis, being more elongated in the apical-most region of the cell than they are subapically, and frequently contacting different sets of neighbors apically and basally. Elongated cells were first observed in early third instar discs, and persisted through several rounds of cell division as the discs matured. During appendage elongation in vivo and trypsin-accelerated elongation in vitro, these highly asymmetric cells became isometric. As the apical cell profiles changed shape, apical and basal cell contacts came into register. Measurements of apical cell dimensions suggest that changes in cell shape account for most of the elongation in the basitarsal and tibial leg segments between 0 and 6h after puparium formation (AP). The conversion of a stable population of anisometric cells to isometric dimensions constitutes a novel mechanism for altering the proportions of an epithelial sheet during development.
Hairless is required for the development of adult sensory organ precursor cells in Drosophila
Authors: Bang Anne G. , Hartenstein Volker , Posakony James W. 
Published: April 2021

ABSTRACT
Reduction of the wild-type activity of the gene Hairless (H) results in two major phenotypic effects on the mechanosensory bristles of adult Drosophila. Bristles are either ‘lost’ (i.e. the shaft and socket fail to appear) or they exhibit a ‘double socket’ phenotype, in which the shaft is apparently transformed into a second socket. Analysis of the phenotypes conferred by a series of H mutant genotypes demonstrates (1) that different sensilla exhibit different patterns of response to decreasing levels of H+ function, and (2) that the ‘bristle loss’ phenotype results from greater loss of H+ function than the ‘double socket’ phenotype. The systematic study of H allelic combinations enabled us to identify genotypes that reliably produce specific mutant defects in particular positions on the bodies of adult flies. This permitted us to investigate the cellular development of sensilla in these same positions in larvae and pupae and thereby establish the developmental basis for the mutant phenotypes. We have found that H is required for at least two steps of adult sensillum development. In positions where ‘double socket’ microchaetes appear on the notum of H mutant flies, sensillum precursor cells are present in the developing pupa and divide normally, but their progeny adopt an aberrant spatial arrangement and fail to differentiate correctly. In regions of the notum exhibiting ‘bristle loss’ in adult H mutants, we were unable at the appropriate stages of development to detect sensillum-specific cell types, the precursor cell divisions that generate them, or the primary precursor cells themselves. Thus, the H ‘bristle loss’ phenotype appears to reflect a very early defect in sensillum development, namely the failure to specify and/or execute the sensory organ precursor cell fate. This finding indicates that H is one of a small number of identified genes for which the loss-of-function phenotype is the failure of sensillum precursor cell development.
Patterns of epithelial expression of Fos protein suggest important role in the transition from viable to cornified cell during keratinization
Authors: Fisher Chris , Byers Margaret R. , Iadarola Michael J. , Powers Elaine A. 
Published: April 2021

Abstract
An antibody directed against the DNA-binding region of c-fos was used to localize the distribution of cells positive for Fos protein in epithelial tissues. The antibody consistently bound to the nuclei of epithelial cells in the late stages of differentiation, just prior to cornification. The epidermis, palate, buccal mucosa, gingiva, tongue, forestomach and vagina in estrus all produced this type of labelling, suggesting a burst of expression immediately before cell death and cornification. The differentiating cells of the hair follicle, including the hair and inner root sheath, were also labelled. Non-keratinized tissues including junctional epithelium, embryonic epidermis and diestrus vaginal epithelium showed little or no Fos labelling. With the onset of keratinization at 18 days gestation or with induction of estrus in ovariecto-mized mice with estradiol benzoate, the epidermis and vagina expressed Fos protein in the manner typical for keratinized tissues. The Erf Er mutant epidermis, a tissue that is blocked in its ability to keratinize, overexpresses Fos with Fos-positive cells appearing in virtually every cell layer. Gel shift analysis demonstrates the presence of a functional AP-1 complex in epidermal extracts that is recognized by our antibody. Our data suggest that the expression of Fos is intricately related to epithelial cell differentiation, specifically in relation to the process of cornification and cell death.
Multiple hematopoietic lineages develop from embryonic stem (ES) cells in culture
Authors: Wiles Michael V. , Keller Gordon 
Published: April 2021

Abstract
When embryonic stem cells are cultured directly in semisolid media (methyl cellulose), they proliferate and differentiate to generate colonies known as embryoid bodies (EBs). These EBs consist of differentiated cells from a number of lineages including those of the hematopoietic system. Following 10 days of culture in the presence of 10 % fetal calf serum, more than 40 % of all EBs from three different ES cell lines, CCEG2, D3 and SQ1.2S8 contained visible erythropoietic cells (i.e. red with hemoglobin). βH1 (z globin) mRNA is detectable in EBs within 5 days of differentiation, whilst βmaj-globin RNA appears by day 6. In the presence of erythropoietin (Epo), the frequency of EBs with erythropoietic activity increases to greater than 60%; Epo also prolongs this erythropoietic activity. Interleukin-3 (IL-3) does not significantly increase the frequency of EBs that contain erythroid cells, but increases slightly the number of erythropoietic cells associated with them. In the presence of IL-3, in addition to cells of the erythroid lineage, macrophages, mast cells and in some instances neutrophils are found within differentiating EBs. The development of macrophages is significantly enhanced by the addition of IL-3 alone or in combination with IL-1 and M-CSF or GM-CSF. When well-differentiated EBs are allowed to attach onto tissueculture plates and grown in the presence of IL-3, a longterm output of cells from the mast cell lineage is observed. These findings indicate that early hematopoietic precursor cells can be readily generated from ES cells under well-defined culture conditions, and thus provides a unique in vitro model with which to analyze the earliest events involved in the development of the hematopoietic system.
Examining pattern formation in mouse, chicken and frog embryos with an En-specific antiserum
Authors: Davis Claytus A. , Holmyard Douglas P. , Millen Kathleen J. , Joyner Alexandra L. 
Published: April 2021

Abstract
We have raised an antiserum, designated αEnhb-1, to a portion of the mouse En-2 protein containing the homeodomain. The antiserum detects both the En-1 and En-2 proteins in mouse, chick and Xenopus embryos by Western blot analysis. Using whole-mount immunohistochemistry, combined in some cases with scanning electron microscopy, we have examined the distribution of the proteins in the early embryos of these species. The major features of expression were similar. The initial production of En protein occurred, just before or during the formation of the first somites, in a band of the anterior neural plate in the prospective mid/hindbrain region. Later in development En-1 protein accumulated in the ventral ectoderm of the developing mouse and chick limb buds, indicating that a dorsal-ventral polarity is present as soon as any limb bud swelling is apparent and that, at least in the mouse, this polarity is established independently of the apical ectodermal ridge. In all three species, aEnhb-1 bound to a subset of ventro-lateral differentiating neurons in the spinal cord and bindbrain and their pattern of birth in the mouse reflected the division of the hindbrain into rhombo-meres. En-1 protein also accumulated in a lateral stripe of dermatome in the mouse and chick, indicating a dorsal-ventral subdivision of this tissue. The results show that En expression is a good marker for pattern formation in a variety of tissues and will be useful in experimental studies designed to characterize further these processes.
Branching morphogenesis of mouse salivary epithelium in basement membrane-like substratum separated from mesenchyme by the membrane filter
Authors: Takahashi Yu , Nogawa Hiroyuki 
Published: April 2021

Abstract
Branching morphogenesis of mouse salivary gland has been studied with organ-culture system. We developed a novel transfilter culture system for analyzing branching morphogenesis of the salivary epithelium. The submandibular salivary epithelium from early 13-day mouse fetus, clotted with Matrigel and separated from the mesenchyme by membrane filter, showed extensive growth and branching morphogenesis, morphological differentiation of lobules and stalks, and a typical cleft shape. The epithelium showed little growth and no branching without Matrigel clot or without the mesenchyme. This branching morphogenesis was induced even when the pore size of the filter was reduced to 0.05 fan. Use of type I collagen gel instead of Matrigel mostly induced incomplete morphogenesis with various histological abnormalities. These results suggest that the salivary epithelium can undergo branching morphogenesis in the absence of the mechanical action of mesenchymal cells although it needs an appropriate extracellular matrix and some mesenchymal factors transmitted through the filter.
Patterns of Evi-1 expression in embryonic and adult tissues suggest that Evi-1 plays an important regulatory role in mouse development*
Authors: Perkins Archibald S. , Mercer John A. , Jenkins Nancy A. , Copeland Neal G. 
Published: April 2021

Abstract
Evi-1 is a putative protooncogene first identified as a common site of retroviral integration in murine myeloid leukemias. It encodes a 145×103Afr nuclear DNA-binding protein that contains ten zinc-finger motifs separated into two domains, as well as an acidic domain. These features suggest that Evi-1 encodes a transcriptional regulatory protein. In Drosophila, zinc-finger proteins such as Kruppel are involved in body plan patterning, and exhibit a spatially restricted pattern of expression in the embryo. To determine if Evi-1 may be involved in morphogenetic processes in the mouse embryo, we have performed in situ hybridization and Northern blot analysis on embryonic and adult mouse tissues to delineate the spatial and temporal pattern of Evi-1 expression. Our results show that Evi-1 is expressed at high levels in a few tissues in the embryo and is widely expressed, albeit at generally low levels, in the adult. Regions that exhibit high-level expression in the embryo include: the urinary system and the Mullerian ducts; the bronchial epithelium of the lung; focal areas within the nasal cavities; the endocardial cushions and truncus swellings in the heart; and the developing limbs. Expression in the limb occurs at the highest levels from 9.5 to 12.5 days, is present in both hind and forelimbs, is absent at the apical ectodermal ridge, and does not appear to establish a gradient. This pattern of expression in the limb is reminiscent of other putative transcriptional factors such as Hox-5.2 and retinoic acid receptor-gamma, consistent with the hypothesis that particular combinations or networks of transcriptional regulatory proteins are required for morphogenesis. Overall, these results suggest that Evi-1 plays an important role in mouse development.
Spatial regulation of the gap gene giant during Drosophila development
Authors: Kraut Rachel , Levine Michael 
Published: April 2021

Abstract
We describe the regulated expression of the segmen-tation gene giant (gt) during early embryogenesis. The gt protein is expressed in two broad gradients in precellu-lar embryos, one in anterior regions and the other in posterior regions. Double immunolocalization studies show that the gt patterns overlap with protein gradients specified by the gap genes hunchback (hb) and knirps (kni). Analysis of all known gap mutants, as well as mutations that disrupt each of the maternal organizing centers, indicate that maternal factors are responsible for initiating gt expression, while gap genes participate in the subsequent refinement of the pattern. The maternal morphogen bicoid (bcd) initiates the anterior gt pattern, while nanos (nos) plays a role in the posterior pattern. Gene dosage studies indicate that different thresholds of the bcd gradient might trigger hb and gt expression, resulting in overlapping but noncoincident patterns of expression. We also present evidence that different concentrations of hb protein are instructive in defining the limits of kni and gt expression within the presumptive abdomen. These results suggest that gt is a bona fide gap gene, which acts with hb, Krüppel and kni to initiate striped patterns of gene expression in the early embryo.