bluuebunny/crossref_metadata_2025_split huggingface dataset:
Segmentally repeated pattern of expression of a cell surface glycoprotein inDrosophilaembryos
Authors: Gauger Ann , Glicksman Marcie A. , Salatino Richard , Condie John M. , Schubiger Gerold , Brower Danny L. 
Published: April 2021

ABSTRACTWe report here that a previously described cell surface antigen (Brower, Smith & Wilcox, 1980) is expressed in a segmentally repeating pattern of stripes in the epidermis and nervous system of segmented Drosophila embryos. We also report that the antigenic activity is found on two closely related cell surface glycoproteins. The pattern of expression of this antigen is reminiscent of the expression of some segmentation genes and is affected by mutation of at least two of these genes, fushi tarazu and paired. Thus these glycoproteins are candidates for cell surface molecules involved in carrying out the patterning processes controlled by segmentation genes.
The growth rate of sensory nerve fibres in the mammalian embryo
Authors: Davies Alun M. 
Published: April 2021

ABSTRACT
I have used a novel quantitative electron microscopic method to determine the rate at which nerve fibres grow towards their targets during development. The rate of recruitment of nerve fibres to the maxillary nerve of the mouse embryo was determined by counting the number of axon profiles in the nerve sectioned close to its emergence from the trigeminal ganglion at closely staged intervals throughout its early development. The rate of change of fibre number with distance along this nerve was determined by counting the number of axon profiles at intervals along the nerve at stages during the period that fibres are growing to their targets. From these two parameters, both of which were linear functions during the mid-period of fibre recruitment to the nerve, it has been possible to calculate that embryonic sensory nerve fibres grow to their peripheral targets at the surprisingly slow rate of just over 20μmh−1.
Cytogenetic analysis of first cleavage fertilized mouse eggs following in vivo exposure to ethanol shortly before and at the time of conception
Authors: O’Neill G. T. , Kaufman M. H. 
Published: April 2021

ABSTRACT
In this study, the chromosome constitution of mouse eggs exposed in vivo to a dilute solution of ethanol during specific stages of the first and second meiotic divisions was determined at the first cleavage mitosis. Exposure to ethanol prior to the completion of the second meiotic division induced an incidence (7-10 %) of aneuploidy involving only one chromosome in 98 % of malsegregation events. This investigation provides indirect evidence that ethanol may induce aneuploidy by disrupting the functioning of the meiotic spindle. Karyological analyses of chromosome spreads prepared at the first cleavage metaphase suggest that only a small proportion of the total chromosome complement may be induced to undergo malsegregation.
Monoclonal antibodies against components of the myoplasm of eggs of the ascidian Ciona intestinalis partially block the development of muscle-specific acetylcholinesterase
Authors: Nishikata Takahito , Mita-Miyazawa Izumi , Deno Takuya , Satoh Noriyuki 
Published: April 2021

ABSTRACT
The myoplasm of Ciona intestinalis eggs, believed to contain cytoplasmic determinants responsible for muscle cell differentiation in ascidian embryos, emits weak pale-blue autonomous fluorescence. Utilizing this feature as a marker, the cytoplasm was isolated according to the method described by Jeffery (1985ft). Electron microscopy showed that the isolated cytoplasm contained mitochondria, pigment granules, yolk particles and fine granular materials; these are ultrastructural components of the myoplasm of the intact egg. Monoclonal antibodies were prepared against the isolated cytoplasm. Twelve monoclonal antibodies, identified by indirect immunofluorescence, stained the myoplasmic region. When unfertilized eggs were centrifuged, stratifying their mitochondria and some other cytoplasmic components, components identified by several antibodies, for example IIG6B2, remained at the peripheral cytoplasm of the egg. Other antibodies recognized components stratified as the mitochondrial layer. Four representative antibodies were microinjected into fertilized eggs in order to examine their inhibitory effects on the muscle differentiation; the IIG6B2 antibody blocked the development of muscle-specific acetylcholinesterase in more than 80 % of the embryos tested.
An analysis of proliferative activity in innervated and denervated forelimb regenerates of the newt, Notophthalmus viridescens
Authors: Goldhamer David J. , Tassava Roy A. 
Published: April 2021

ABSTRACT
Pulse and continuous labelling with [3H]thymidine combined with mitotic index determinations provided data on the kinetics of cell cycling in innervated and denervated early and mid-bud forelimb blastemas of the adult newt, Notophthalmus viridescens. Most or all blastema cells cycle during regeneration and are thus part of the proliferative fraction. At any given moment, however, only 26 % of the blastema cells are actively progressing through the cell cycle, with the remainder being in a state of transient quiescence (TQ). The small size of the actively cycling (AC) population may in part explain the relatively slow rate of regeneration exhibited by the adult newt. The pulse-labelling index and mitotic index of denervated blastemas paralleled control values for 48 h following nerve withdrawal, but both parameters were significantly reduced by 72 h. By 5 days postdenervation, cell cycle activity was essentially zero. The combined pulse and continuous labelling data suggest that nerves may be primarily involved in the entry of TQ cells into the AC population, with subsequent progression through the cell cycle being less dependent on innervation. Relative to controls, no early postdenervation increases in TCA-precipitable [3H]thymidine incorporation, pulse-labelling index or mitotic index were observed.
Trophectoderm surface expression of the cell adhesion molecule cell-CAM 105 on rat blastocysts
Authors: Svalander Peter C. , Odin Per , Nilsson B. Ove , Öbrink Björn 
Published: April 2021

ABSTRACTA variety of cellular interactions is involved in the process of implantation of the mammalian embryo into the uterine tissue. Recent discoveries have demonstrated that intercellular recognition and adhesive events are governed by a class of cell surface molecules known as cell adhesion molecules (CAMs). In the present report, we have investigated the occurrence of the well-characterized cell adhesion molecule cell-CAM 105 on the surface of rat pre- and periimplantation embryos of various stages. This was carried out by indirect immunofluorescence microscopy employing affinity-purified rabbit antibodies against cell-CAM 105. The embryonal stages investigated comprised morulae, normal day-4 blastocysts, and delayed and adhesive blastocysts obtained by using the method of experimentally delayed implantation. Cell-CAM 105 was absent in the early-morula stage, but in normal day-4 blastocysts and delayed blastocysts a specific staining for cell-CAM 105 was seen on the entire surface. However, adhesive-stage blastocysts exhibited a marked polarity with staining of the polar trophoblast cells. Scanning electron microscopy of adhesive-stage blastocysts revealed that the stronger staining of the polar region was not due to a greater number of microvilli on the polar trophoblast cells. Thus, it seems as if cell-CAM 105 is lost or masked from the surface of the mural trophoblast cells of adhesive-stage rat blastocysts. Since the mural trophoblast cells are the first to adhere to the uterine luminal epithelium during the onset of implantation and subsequently invade the uterine stroma, we suggest that the apparent downregulation of cell-CAM 105 in the mural trophoblast cells might be linked to the acquisition of trophoblast invasiveness.
The effect of pancreatic mesenchyme on the differentiation of endocrine cells from gastric endoderm
Authors: Kramer Beverley , Andrew Ann , Rawdon B. B. , Becker P. 
Published: April 2021

ABSTRACT
To determine whether mesenchyme plays a part in the differentiation of gut endocrine cells, proventricular endoderm from 4- to 5-day chick or quail embryos was associated with mesenchyme from the dorsal pancreatic bud of chick embryos of the same age. The combinations were grown on the chorioallantoic membranes of host chick embryos until they reached a total incubation age of 21 days. Proventricular or pancreatic endoderm of the appropriate age and species reassociated with its own mesenchyme provided the controls.
Morphogenesis in the experimental grafts corresponded closely to that in proventricular controls, i.e. the pancreatic mesenchyme supported the development of proventricular glands from proventricular endoderm. Insulin, glucagon and somatostatin cells and cells with pancreatic polypeptide-like immunoreactivity differentiated in the pancreatic controls. The latter three endocrine cell types, together with neurotensin and bombesin/gastrin-releasing polypeptide (GRP) cells, developed in proventricular controls and experimental grafts. The proportions of the major types common to proventriculus and pancreas (somatostatin and glucagon cells) were in general similar when experimental grafts were compared with proventricular controls but different when experimental and pancreatic control grafts were compared. Hence pancreatic mesenchyme did not materially affect the proportions of these three cell types in experimental grafts, induced no specific pancreatic (insulin) cell type and allowed the differentiation of the characteristic proventricular endocrine cell types, neurotensin and bombesin/GRP cells. However, an important finding was a significant reduction in the proportion of bombesin/GRP cells, attributable in part to a decrease in their number and in part to an increase in the numbers of endocrine cells of the other types. This indicates that mesenchyme may well play a part in determining the regional specificity of populations of gut endocrine cells.
Retinoids reprogramme pre-bud mesenchyme to give changes in limb pattern
Authors: Wilde Susan M. , Wedden S. E. , Tickle C. 
Published: April 2021

ABSTRACT
Retinoic acid was locally applied to presumptive limb regions of chick embryos to find out the earliest time at which the limb pattern can be reprogrammed. When beads soaked in retinoic acid were placed in the appropriate positions in embryos at stage 10 or older, duplicated or reduced leg patterns resulted. To pin point the time at which the cells in the limb rudiment respond to the retinoid, beads were removed at various times and the lengths of exposure required to reprogramme limb development found. The early limb rudiments require longer exposures to give duplications than late rudiments. The effective treatment periods last at least until stage 17 when the limb bud and apical ectodermal ridge develop. In contrast, the length of exposure to reduce the limb is constant at early stages. Retinoids first start acting to produce duplicated structures between stages 10 and 13. Therefore, retinoids appear to begin to reprogramme the cells as soon as they are determined to give rise to a limb.
Two distinct classes of prestalk-enriched mRNA sequences inDictyostelium discoideum
Authors: Jermyn K. A. , Berks M. , Kay R. R. , Williams J. G. 
Published: April 2021

ABSTRACTWe have isolated cDNA clones derived from three mRNA sequences which are inducible by DIF, the putative stalk-specific morphogen of Dictyostelium. The three mRNA sequences are selectively expressed in cells on the stalk cell pathway of differentiation and we have compared them with previously characterized prestalk-enriched mRNA sequences. We find these latter sequences are expressed without a dependence on DIF, are much less highly enriched in prestalk over prespore cells and are expressed earlier during development than the DIF-inducible mRNA sequences. We propose two distinct mechanisms whereby a mRNA may become enriched in prestalk cells. An apparently small number of genes, represented by those we have isolated, is inducible by DIF and accumulates only in prestalk cells. We suggest that a second class of prestalk-enriched mRNA sequences are induced by cAMP to accumulate in all cells during aggregation and then become enriched in prestalk cells by selective loss from prespore cells.
The molecular basis for metameric pattern in the Drosophila embryo
Authors: Akam Michael 
Published: April 2021

ABSTRACT
The metameric organization of the Drosophila embryo is generated in the first 5 h after fertilization. An initially rather simple pattern provides the foundation for subsequent development and diversification of the segmented part of the body. Many of the genes that control the formation of this pattern have been identified and at least twenty have been cloned. By combining the techniques of genetics, molecular biology and experimental embryology, it is becoming possible to unravel the role played by each of these genes.
The repeating segment pattern is defined by the persistent expression of engrailed and of other genes of the ‘segment polarity’ class. The establishment of this pattern is directed by a transient molecular prepattern that is generated in the blastoderm by the activity of the ‘pair-rule’ genes.
Maternal determinants at the poles of the egg coordinate this prepattern and define the anteroposterior sequence of pattern elements. The primary effect of these determinants is not known, but genes required for their production have been identified and the product of one of these, bicoid is known to be localized at the anterior of the egg. One early consequence of their activity is to define domains along the A–P axis within which a series of ‘cardinal’ genes are transcribed.
The activity of the cardinal genes is required both to coordinate the process of segmentation and to define the early domains of horneotic gene expression. Further interactions between the homeotic genes and other classes of segmentation genes refine the initial establishment of segment identities.
Histochemical localization of IGF-I and -II mRNA in the developing rat embryo
Authors: Beck Felix , Samani N. J. , Penschow Jennifer D. , Thorley Bruce , Tregear Geoffrey W. , Coghlan John P. 
Published: April 2021

ABSTRACT
We describe the histological localization of embryonic and fetal tissues whose cells express the genes coding for insulin-like growth factors I and II (IGF-I and IGF-II) in the developing rat. Our studies span the period between early somite stages and full term. We have used oligodeoxyribonucleotide probes and obtained results which are both topographically precise and highly reproducible. The gene coding for IGF-II is predominant throughout development. It is strongly expressed in the liver and yolk sac. A variety of other tissues also expresses the IGF-II gene, especially many mesodermally derived structures in the process of differentiation. Many tissues do not express IGF genes. Thus no IGF mRNA was demonstrable in ectodermally derived structures, including the central and peripheral nervous systems as well as the skin and its derivatives.
Somatomedins/insulin-like growth factors, their receptors and binding proteins are present during mouse embryogenesis
Authors: Smith Eric P. , Sadler Thomas W. , D’Ercole A. J. 
Published: April 2021

ABSTRACT
Somatomedins/insulin-like growth factors (Sm/IGFs) are considered to have important roles in regulating fetal growth; however, because of limited quantities of tissue, few studies have been performed on their effects on embryonic growth. To assess a potential role for these factors, we evaluated mouse embryonic tissues for the presence of Sm/IGF and insulin receptors and Sm/IGF-binding proteins by chemical affinity labelling. In addition, we measured extractable Sm-C/IGF-I radioimmunoactivity in mouse embryonic tissues. Finally, we compared these data with those from the embryonal carcinoma cell line, PC13. All embryos from day 9 (3–4 somites) to day 12 (45 somites) possessed both Sm-C/IGF-I and IGF-II receptors in apparent greater abundance than insulin receptors. The visceral yolk sac appeared to have proportionally more insulin receptors than the corresponding embryonic tissue. Extracts from the embryos contained immunoreactive Sm-C/IGF-I and binding proteins of 30–45×103MT. PC13 cells possessed all three receptors and the apparent abundance of the insulin and IGF-II receptors was reduced after differentiation was induced with retinoic acid. PC13 cells released both immunoreactive Sm-C/IGF-I- and Sm-C/IGF-I-binding proteins into their medium. When differentiated, the binding proteins resembled the native ones extracted from the intact embryos. The presence of Sm/IGF activity, receptors and binding proteins in early embryogenesis suggests a role for these factors in embryonic growth. The PC13 cell line appears to only partially reflect normal development.
Posterior expression of a homeobox gene in early Xenopus embryos
Authors: Condie Brian G. , Harland Richard M. 
Published: April 2021

ABSTRACT
The homeobox containing transcript Xhox-36 is expressed exclusively in the posterior mesoderm and ectoderm of early Xenopus embryos. Therefore, the transcript shows region-specific rather than tissuespecific expression in the gastrula and neurula, a time when cells are becoming committed to defined fates. Exposure of early embryos to LiCl, which shifts posterior cells to more anterior fates, reduces the abundance of this posterior-specific transcript. In contrast, embryos ventralized by u.v. treatment express normal levels of the transcript, implying that expression of the gene is not absolutely linked to dorsal cell identity. The sequence of a full-length cDNA corresponding to this transcript predicts a homeodomain-containing protein of 209 amino acids.
A monoclonal antibody stains myogenic cells in regenerating newt muscle
Authors: Griffin Kevin J. P. , Fekete Donna M. , Carlson Bruce M. 
Published: April 2021

ABSTRACT
Monoclonal antibodies have been used to study minced muscle regeneration in the adult newt, Notophthalmus viridescens. The contralateral limb was amputated and the immunostaining patterns in the regenerating blastema were compared with the minced tissue in sectioned material. Staining with a myofibre-specific antibody, called 12/101 (Kintner & Brockes, 1984), showed that myofibre degeneration was complete by 8– 10 days after mincing, with myogenesis commencing 2 days later. Another monoclonal antibody, called 22/18, previously shown to label a subset of cells in the regeneration blastema of the newt (Kintner & Brockes, 1984, 1985), was found also to recognize a population of cells in regenerating minced muscle. At 6 days after mincing, the number of 22/18-positive (22/18+) cells was low but by days 12– 16, during the period of myogenesis, their number had increased to become a major population within the minced tissue. A small number of the 22/18+ cells could be double labelled with 12/101 at this time.
Prior to this, there was a phase in which 12/101 staining had disappeared from the mince. Cells immunoreactive with both antibodies after this phase confirm that at least some of the 22/18+ cells are myogenic. The number of 22/18+ cells decreased as muscle repair and maturation progressed. These results show that 22/18 is not specifically associated with blastemal cells but is a more general marker for regenerating systems in the newt. They further suggest an alternative interpretation of the doublelabelled cells used by Kintner & Brockes (1984) as evidence for myofibre dedifterentiation in limb regeneration. Instead, we propose that such cells represent new myogenesis occurring by tissue repair of locally damaged muscle fibres.
Initial disorder and secondary retinotopic refinement of regenerating axons in the optic tract of the goldfish: signs of a new role for axon collateral loss
Authors: Becker David L. , Cook Jeremy E. 
Published: April 2021

ABSTRACT
The optic tract of the goldfish splits into two brachia just before it reaches the tectum, normal optic axons being distributed systematically between the two according to their retinal origins. The orderliness of this division, like that of the retinotectal projection itself, is conventionally attributed to a system of specific axonal guidance cues. However, the brachial distribution of regenerated axons is much less orderly; and, since there is evidence that these axons have many collateral branches in the nerve and tract, the gross order that remains after regeneration could potentially arise secondarily, in parallel with refinement of the retinotectal map, by a preferential loss of collaterals from the inappropriate brachium.
The brachial paths of normal axons, and axons regenerated after optic nerve cut for periods ranging from 19 days to 5 years, were therefore studied by anterograde labelling with horseradish peroxidase from discrete retinal lesions or retrograde labelling of ganglion cells from a cut brachium.
From 19 to 28 days, regenerating axons showed little or no preference for their normal brachium. During this period (which includes the first week of tectal synaptogenesis) an average of 46·3 % of cells retrogradely labelled from a cut medial brachium were in dorsal retina, compared with only 1· 45% in normal fish. Some preference for the normal brachium was evident at 35 days and significant order had returned by 42–70 days, when the average proportion of labelled cells in dorsal retina had fallen to 25·4 % though the average number in the whole retina was unchanged. Thus a brachial refinement had occurred in parallel with refinement of the retinotectal map.
These results support the idea of a selective loss of axon collaterals from the inappropriate brachium, though they do not exclude the possibility of some concurrent gain in the appropriate one. We suggest that refinement may depend on a process we term ‘sibling rivalry’: competition between different collaterals of the same axon to form a critical number of stable tectal synapses, in which the most-normally-routed branches have the best chance of succeeding and surviving. Developing normal axons might also make use of collateral formation and ‘sibling rivalry’ to generate and refine the complex interwoven patterns of the normal optic tract.
Comparative development of the extensor and flexor tibiae muscles in the legs of the locust, Locusta migratoria
Authors: Myers Camilla M. , Ball Eldon E. 
Published: April 2021

ABSTRACT
The embryonic development of the extensor and flexor tibiae muscles in the pro- and mesothoracic legs of the locust, Locusta migratoria, is described, and compared to the previously described development of these muscles in the metathoracic legs. The basic pattern of development of each muscle is the same in all three pairs of legs. The extensor tibiae (ETi) forms a giant syncytium, or supramuscle pioneer, which then breaks up into a series of muscle pioneers. The flexor tibiae muscle (FITi) is formed directly by sequential addition of individual muscle pioneers. Thus, there are at least two fundamentally different patterns of muscle development in the embryonic locust, as exemplified by these two muscles, and supramuscle pioneer formation is not a unique feature of the metathoracic ETi associated with its evolutionary hypertrophy.
In spite of a basically similar pattern of development of homologous muscles in all three pairs of legs, there are significant developmental differences between the metathoracic ETi and FITi and their homologues in the anterior legs. First, during development of the ETi muscles, the ETi MP forms a double row of attachment sites along both walls of the metathoracic leg, while in the anterior legs there is only a single row. Second, during development of the FITi muscles, the proximal MP, which lies at the tip of the apodeme, dies and breaks down in the metathoracic limbs. In the pro- and mesothoracic limbs it remains intact and eventually forms a large proximal muscle bundle. Third, the accessory ETi and FITi muscles, which develop in the metathoracic legs, are not formed in the anterior legs.