bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pintallavis, a gene expressed in the organizer and midline cells of frog embryos: involvement in the development of the neural axis
Authors: Altaba A. Ruiz i , Jessell T. M. 
Published: April 2021

ABSTRACT
We have identified a novel frog gene, Pintallavis (the Catalan for lipstick), that is related to the fly fork head and rat HNF-3 genes. Pintallavis is expressed in the organizer region of gastrula embryos as a direct zygotic response to dorsal mesodermal induction. Subsequently, Pintallavis is expressed in axial midline cells of all three germ layers. In axial mesoderm expression is graded with highest levels posteriorly. Midline neural plate cells that give rise to the floor plate transiently express Pin tallavis, apparently in response to induction by the notochord. Overexpression of Pintallavis perturbs the development of the neural axis, suppressing the differentiation of anterior and dorsal neural cell types but causing an expansion of the posterior neural tube. Our results suggest that Pintallavis functions in the induction and patterning of the neural axis.
Mechanisms of early Drosophila mesoderm formation
Authors: Leptin Maria , Casal José , Grunewald Barbara , Reuter Rolf 
Published: April 2021

ABSTRACT
Several morphogenetic processes occur simultaneously during Drosophila gastrulation, including ventral furrow invagination to form the mesoderm, anterior and posterior midgut invagination to create the endoderm, and germ band extension. Mutations changing the behaviour of different parts of the embryo can be used to test the roles of different cell populations in gastrulation. Posterior midgut morphogenesis and germ band extension are partly independent, and neither depends on mesoderm formation, nor mesoderm formation on them. The invagination of the ventral furrow is caused by forces from within the prospective mesoderm (i. e. the invaginating cells) without any necessary contribution from other parts of the embryo. The events that lead to the cell shape changes mediating ventral furrow formation require the transcription of zygotic genes under the control of twist and snail. Such genes can be isolated by molecular and genetic screens.
Xenopus Distal-less related homeobox genes are expressed in the developing forebrain and are induced by planar signals
Authors: Papalopulu Nancy , Kintner Chris 
Published: April 2021

ABSTRACT
The polymerase chain reaction (PCR) was used to isolated five Xenopus homeobox clones (X-dll1 to 5) that are related to the Drosophila Distal-less (Dll) gene and we propose a subdivision of the vertebrate distal-less gene family according to sequence similarities. cDNA clones were isolated for X-dll2, 3 and 4, and their expression was studied by RNase protection and in situ hybridization. X-dll2, which belongs to a separate subfamily than X-dll3 and 4, is not expressed in the neural ectoderm. X-dll3 and X-dll4, which belong to the same subfamily, have a similar but not identical pattern of expression that is restricted to anterior ectodermal derivatives, namely the ventral forebrain, the cranial neural crest and the cement gland. X-dll3 is also expressed in the olfactory and otic placodes while X-dll4 is expressed in the developing eye. X-dll3 differs from the other Xenopus genes and the previously isolated Dll-related mouse genes, in that localized expression can be detected by in situ hybridization very early in development, in the anterior-transverse ridge of the open neural plate. Based on that early expression pattern, we suggest that X-dll3 marks the rostral-most part of the neural plate, which gives rise to the ventral forebrain. Finally, we have used these Xenopus distal-less genes to show that the anterior neural plate can be induced by signals that spread within the plane of neural ectoderm, indicating that at least the initial steps of forebrain development do not require signals from underlying mesoderm.
The role of the ovarian tumor locus in Drosophila melanogaster germ line sex determination
Authors: Pauli Daniel , Oliver Brian , Mahowald Anthony P. 
Published: April 2021

ABSTRACT
The locus ovarian tumor (otu) is involved in several aspects of oogenesis in Drosophila melanogaster. The possible role of otu in the determination of the sexual identity of germ cells has not been extensively explored. Some otu alleles produce a phenotype known as ovarian tumors: ovarioles are filled with numerous poorly differentiated germ cells. We show that these mutant germ cells have a morphology similar to primary spermatocytes and that they express male germ line-specific reporter genes. This indicates that they are engaged along the male pathway of germ line differentiation. Consistent with this conclusion, we found that the splicing of Sex-lethal (Sxl) pre-mRNAs occurs in the male-specific mode in otu transformed germ cells. The position of the otu locus in the regulatory cascade of germ line sex determination has been studied by using mutations that constitutively express the feminizing activity of the Sxl gene. The sexual transformation of the germ cells observed with several combinations of otu alleles can be reversed by constitutive expression of Sxl. This shows that otu acts upstream of Sxl in the process of germ line sex determination. Other phenotypes of otu mutations were not rescued by constitutive expression of Sxl, suggesting that several functions of otu are likely to be independent of sex determination. Finally, we show that the gene dosage of otu modifies the phenotype of ovaries heterozygous for the dominant alleles of ovo, another gene involved in germ line sex determination. One dose of otu+ enhances the ovoD ovarian phenotypes, while three doses partially suppress these phenotypes. Synergistic interaction between ovoD1 and otu alleles leads to the occasional transformation of chromosomally female germ cells into early spermatocytes. These interactions are similar to those observed between ovoD and one allele of the sans fille (snf) locus. Altogether, our results imply that the otu locus acts, along with ovo, snf, and Sxl, in a pathway (or parallel pathways) required for proper sex determination of the female germ line.
Genetic analysis of hedgehog signalling in the Drosophila embryo
Authors: Forbes A. J. , Nakano Y. , Taylor A. M. , Ingham P. W. 
Published: April 2021

ABSTRACT
The segment polarity genes play a fundamental role in the patterning of cells within individual body segments of the Drosophila embryo. Two of these genes wingless (wg) and hedgehog (hh) encode proteins that enter the secretory pathway and both are thought to act by instructing the fates of cells neighbouring those in which they are expressed. Genetic analysis has identified the transcriptional activation of wg as one of the targets of hh activity: here we present evidence that transduction of the hh-encoded signal is mediated by the activity of four other segment polarity genes, patched, fused, costal-2 and cubitus interruptus. The results of our genetic epistatsis analysis together with the molecular structures of the products of these genes where known, suggest a pathway of interactions leading from reception of the Aft-encoded signal at the cell membrane to transcriptional activation in the cell nucleus. We have also found that transcription of patched is regulated by the same pathway and describe the identification of cis-acting upstream elements of the ptc transcription unit that mediate this regulation.
Migration of Drosophila germ cells: analysis using enhancer trap lines
Authors: Howard Ken , Jaglarz Mariusz , Zhang Nian , Shah Jaymini , Warrior Rahul 
Published: April 2021

ABSTRACT
Cell migration is a common feature of development. In order to understand more about the factors that controf these movements we have embarked on further analysis of the migration of Drosophila germ cells. This process involves passage of the germ cells across the gut pri mordium and migration toward the mesoderm where the somatic gonad forms. We are particularly interested in the early phase of this migration when the germ cells interact with the amnioproctodeal invagination, the developing gut, before entering into association with the mesoderm. We will summarize the results of our and other studies of these events before describing a number of enhancer trap lines which show expression in the amnioproctodeal invagination during the early phase of germ cell migration. These reveal more about the com plexity of this tissue and suggest this tissue is capable of guiding the early phase of germ cell migration.
Genes controlling cellular polarity in Drosophila
Authors: Gubb David 
Published: April 2021

ABSTRACT
The control of cellular polarity is one of the least under- stood aspects of development. Genes have been identified in Drosophila that affect the polarity of embryonic cells in all three axes, apical-basal, proximodistal and dorsoventral. Mutations that affect adult polarity are also known and mutant Hies show several types of pattern alteration, including rotations and mirror-image duplications, imaginai discs are much greater in size, however, than the embryo, and adult structures contain very large numbers of cells, many of which are not visibly differentiated with respect to their immediate neighbours. In regions where neighbouring cells are similar to each other, the imaginai polarity mutants alter the orientation of bristles and hairs, but do not change cellular fate. Other regions, such as the tarsal segments of the legs, the ommatidia of the eye and the brack’d bristle sockets on the tibia, behave as discrete fields. Within these fields, fine-scale mirror-image reversals and pattern duplications are observed, analogous to those caused by the embryonic segment polarity mutants. Thus, the polarised transmission of informa- tion can affect either orientation or fate depending on whether cells are differentiated from their immediate neighbours. C ellular polarity will be critically dependent on both the internal cytoskeletal arehitecture and the spatial organisation of signal transduction molecules within the cell membrane.
The innervation of supernumerary and replacing grafts of limbs in Eleutherodactylus martinicensis
Authors: Hughes Arthur 
Published: April 2021

ABSTRACT
The innervation of grafted limbs in Eleutherodactylus martinicensis has been studied, mainly in comparison of supernumerary grafts with those which replace a host limb. If batches of each type are fixed at different times after operation, it is found that the extent to which motor nerves penetrate into the grafts decreases with time after operation with supernumerary grafts, but not with replacing grafts. The muscles of supernumerary grafts are innervated from collateral branches of axons, usually from among those which supply the normal limb. It thus seems that these collaterals which develop as far as the formation of functional nerve-muscle junctions become unstable in late stages of embryonic life. In general, grafted fore limbs become functional much more readily than do hind limbs. The degeneration of the nerves to supernumerary fore limbs may be followed in the living animal by the loss of movement in the graft. Their loss of function is more marked when grafted heterotopically than when near the orthotopic position. Histological evidence for the breakdown of the nerves to supernumerary grafts is presented, both in respect to fibres and the Schwann cells. A nerve to a graft degenerates more readily when it belongs outside the brachial or lumbar series. Degeneration of nerves and loss of function of the graft proceeds more drastically with supernumerary homografts than with the corresponding autografts. In supernumerary autografts in which motor nerves have degenerated, cutaneous branches may extend further into the graft. The breakdown of nerves is retarded in embryos kept at sub-normal temperatures.
The embryology of Dacus tryoni (Diptera). 3. Origins of imaginal rudiments other than the principal discs
Authors: Anderson D. T. 
Published: April 2021

ABSTRACT
The imaginal segmental abdominal hypodermis, salivary glands, fore-, mid-and hind-gut, lateral cerebral ganglia and segmental tracheal system each arise from a group of blastoderm cells situated within the blastodermal presumptive area of the corresponding larval structure.
The cyclorrhaphan blastoderm can be zoned into presumptive areas for all major parts of the body. Each area includes presumptive larval cells and also presumptive cells of the imaginal part which replaces the larval part at metamorphosis. Except for mesodermal structures, all major imaginal parts and their larval equivalents are probably determined in the blastoderm. The theory is developed that one of the fundamental steps in cyclorrhaphan evolution has been separation of the blastodermal rudiments of the major parts of the hypodermal body wall and gut into determined larval and adult components. In addition, it is suggested, the larval components have acquired a capacity to evócate differentiation of mesodermal structures independently of the adult components.
Further experiments on the innervation and function of grafted supernumerary limbs in the embryo of Eleutherodactylus martinicensis
Authors: Hughes Arthur 
Published: April 2021

ABSTRACT
Previous studies on the transplantation of limbs in the embryo of Eleuthero-dactylus martinicensis have shown that supernumerary limbs tend to be less well innervated than are corresponding replacing grafts, and that the innervation of the former, either autografts or homografts, is progressively less extensive with increase in time after operation. The degree to which grafted supernumerary forelimbs show movement in life parallels the extent of their motor innervation when studied subsequently in serial sections. The loss of innervation and of movement is particularly drastic near the time when the animal normally hatches and the tail undergoes atrophy.
The radiosensitivity of oögonia and oöcytes in the chick embryo
Authors: Hughes Gillian C. 
Published: April 2021

ABSTRACT
The effect of X-irradiation on the germ cells of the developing chick ovary depends on both the dose administered, and on the age of the embryo at the time of exposure. Germ cells are particularly radiosensitive at 11 days’ incubation; they become less so up to 17 days. Peak radiosensitivity at 11 days’ incubation coincides with a high mitotic activity of oögonia, but not with its maximal incidence (9th day of incubation). Oögonia undergoing their last (pre-meiotic) mitosis may be particularly radio-sensitive. Oocytes at the leptotene, zygotene and pachytene stages of meiotic prophase apparently become increasingly radioresistant. X-irradiation induces a slight retardation in the subsequent development of the ovary.
Initial stimulus and subsequent interactions in embryonic induction
Authors: Saxén Lauri , Toivonen Sulo , Vainio Tapani 
Published: April 2021

ABSTRACT
An Artificial environmental stimulus of short duration (10-15 min.) leads to either mesodermal or neural differentiation of competent amphibian ectoderm in certain experimental conditions (Johnen, 1956a; Yamada, 1962). Subsequent to this stimulus development into well organized structures is autonomous, independent of environmental ‘inductive’ factors. Hence, two alternatives for the control mechanism have to be considered; either the whole pathway to the complex end-result is triggered and determined during the short-term initial pulse (primary induction), or only the first step of a long chain reaction has been activated, and this is followed by secondary interactions between the tissue components. Recently Grobstein (1963) discussed these alternatives in the mechanism of embryonic induction and concluded that a single step process is most unlikely in many known examples of induction (kidney tubule induction, induction of cartilage etc.). Seen from the viewpoint of primary induction, there seems to be good reason to agree with him, and we have in previous discussions often stressed the obvious significance of a neural/mesodermal interaction subsequent to the primary inductive stimulus (Saxén & Toivonen, 1961, 1962). The following experiment was planned to gain further evidence with this view in mind.
Methylation of nucleolar RNA during development of the amphibian oöcyte
Authors: Ozban N. , Tandler C. J. , Sirlin J. L. 
Published: April 2021

ABSTRACT
Transmethylation is known to occur from methionine to ribonucleic acid (RNA) derivatives (Fleissner & Borek, 1962). Most of these methylated derivatives are typical of transfer RNA (Dunn, 1959). In dipteran salivary cells it was possible to distinguish with autoradiography between the transmethylation to RNA and the incorporation of methionine into protein (Sirlin, Jacob & Tandler, 1963). The same approach was used in the present experiments to trace the formation of transfer RNA in amphibian oöcytes.
The abnormalities of the inner ear in kreisler mice
Authors: Deol M. S. 
Published: April 2021

ABSTRACT
The recessive gene kreisler (symbol kr) was discovered by Hertwig (1942a), who later described its effects on behaviour (1942b) and the inner ear (1944, 1956). She found that it was possible to trace the anomalies of the ear back to 9-day embryos, when the otic vesicle can be seen to be situated in an abnormal position. The present study was aimed at discovering the cause of this abnormality, and at giving a fuller account of the later development of the ear.
The use of inherited abnormalities in studies on the embryogenesis ofDermestes maculatus(Coleoptera)
Authors: Ede D. A. , Rogers Anne M. 
Published: April 2021

ABSTRACTThe possibility of using inherited abnormalities in place of conventional experimental embryological methods has been explored by several workers in Drosophila, where there is a large range of lethal and female sterile genes readily available (reviewed Waddington, 1956). These genes are usually pleiotropic, i.e. with manifold effects, and tracing these diverse effects back as far as possible to a single primary defect gives information about the corresponding developmental mechanisms in the normal embryo. Two disadvantages have attended these studies: (1) dipteran embryology is extremely specialized and difficult to relate to that of other insects, (2) it is almost entirely mosaic in character, and therefore throws no light on the important subject of tissue interactions.
The formation of the second maturation spind le in the eggs of various Limnaeidae
Authors: Raven Chr. P. 
Published: April 2021

ABSTRACT
In a number of papers (Raven, 1949; Raven et al., 1958; Raven, 1959) I have reported on egg maturation, especially the formation of the second maturation spindle, in various pulmonate snails. It appeared that this early and quite fundamental process of development exhibits a surprising variation.
β4 integrin expression in myelinating Schwann cells is polarized, developmentally regulated and axonally dependent
Authors: Feltri M. Laura , Scherer Steven S. , Nemni Raffaello , Kamholz John , Vogelbacker Helen , Scott Marion Oronzi , Canal Nicola , Quaranta Vito , Wrabetz Lawrence 
Published: April 2021

ABSTRACT
In developing and regenerating peripheral nerve, Schwann cells interact with axons and extracellular matrix in order to ensheath and myelinate axons. Both of these interactions are likely to be mediated by adhesion molecules, including integrins, which mediate cell-cell and cell-extracellular matrix interactions. Recently, the β4 integrin subunit was reported to be expressed by Schwann cells in peripheral nerve. We have examined the expression of β4, β1 and their common heterodimeric partner, the α6 integrin subunit, in developing and regenerating rat peripheral nerve. β4 and α6 are enriched in peripheral nerve and they co-localize at the abaxonal surface of myelinating Schwann cells, opposite the Schwann cell basal lamina, which contains possible ligands of α6β4. In contrast, β4 and α6 are expressed in a different pattern in non-myelinating Schwann cells. The level of 4, but not α6 or β1 mRNAs, increases progressively in developing nerves, reaching a peak in adult nerves well after the peak of the myelinspecific mRNAs. After axotomy, the expression of β4 mRNA and protein, but not α6 or β1 mRNAs, fall rapidly but subsequently are reinduced by regenerating axons. Similarly, in cultured Schwann cells, the expression of β4 mRNA, but not α6 mRNA, is significantly modulated by forskolin, a drug that elevates cAMP and mimics some of the effects of axonal contact. β4 integrin expression in Schwann cells, therefore, is regulated by Schwann cellaxon interactions, which are known to be critical in determining the Schwann cell phenotype. Furthermore, the polarized expression of α6β4 to the abaxonal surface of myelinating Schwann cells suggests that α6β4 may mediate in part the morphological changes required of Schwann cells in the process of myelination in the peripheral nervous system.
Expression of the HSP 70.1 gene, a landmark of early zygotic activity in the mouse embryo, is restricted to the first burst of transcription
Authors: Christians Elisabeth , Campion Evelyne , Thompson Eric M. , Renard Jean-Paul 
Published: April 2021

ABSTRACT
Activation of the mouse embryonic genome at the 2-cell stage is characterized by the synthesis of several α-amanitin-sensitive polypeptides, some of which belong to the multigenic hsp 70 family. In the present work we show that a member of this family, the HSP 70.1 gene, is highly transcribed at the onset of zygotic genome activation. Transcription of this gene began as early as the 1-cell stage. Expression of the gene continued through the early 2-cell stage but was repressed before the completion of the second round of DNA replication. During this period we observed that the level of transcription was modulated by in vitro culture conditions. The coincidence of repression of HSP70.1 transcription with the second round of DNA replication was not found for other transcription-dependent polypeptides synthesized at the 2-cell stage.