bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coding sequence and expression of the homeobox gene Hox 1.3
Authors: Fibi Mathias , Zink Barbara , Kessel Michael , Colberg-Poley Anamaris M. , Labeit Siegfried , Lehrach Hans , Gruss Peter 
Published: April 2021

Abstract
We have characterized Hox 1.3 (previously described as m2), a murine homeobox-containing gene, which is a member of the Hox 1 cluster located on chromosome 6. A cloned cDNA was isolated from an Okayama-Berg library generated from the chemically transformed cell line MB66 MCA ACL6. The protein sequence of 270 amino acids was deduced from the nucleotide sequence of an open reading frame containing the homeobox. The open reading frame is interrupted at the genomic level by a 960 bp intron and is organized in two exons. The Hox 1.3 protein was found to contain extensive sequence homology with the murine homeodomain protein Hox 2.1, which is encoded on chromosome 11. There are two homologous regions in the first exon, i.e. a hexapeptide conserved in many homeobox-containing genes and the N-terminal domain, which was found to be homologous only to Hox 2.1. Furthermore, in exon 2 the homologies of the homeodomain regions are extended up to the carboxy terminus of Hox 1.3 and Hox 2.1.
During prenatal murine development, maximal expression of Hox 1.3 is observed in 12-day embryonic tissue. The two transcripts carrying the Hox 1.3 homeobox are 1·9 kb and about 4 kb in length. An abundant Hox 1.3-specific 1·9 kb RNA is also found in F9 cells which were induced for parietal endoderm differentiation, whereas F9 teratocarcinoma stem cells do not stably express this specific RNA. Induction of the transcript occurs immediately after retinoic acid/ cAMP treatment and the RNA level remains high for 5 days. Thus, the kinetics are different from the previously described homeobox transcripts Hox 1.1 and Hox 3.1. Interestingly, by analogy to the F9 cell system a negative correlation between transformation and Hox 1.3 expression is observed in 3T3 fibroblasts also. Untransformed 3T3 cells carry abundant 1·9 kb Hox 1.3 RNA, whereas the methylcholanthrene-transformed MB66 and LTK—cells or 3T3 cells transformed by the oncogenes src, fos or SV40 T antigen express only low levels.
Axons regulate Schwann cell expression of the major myelin and NGF receptor genes
Authors: Lemke Greg , Chao Moses 
Published: April 2021

Abstract
The elaboration of myelin by Schwann cells is triggered by contact with appropriate peripheral axons. Among the most prominent features of this interaction is the activation and high-level expression of the genes encoding the major myelin proteins P0 and Myelin Basic Protein (MBP). Although the initial induction of these genes is thought to be dependent upon contact with axons, neither the inductive signal of the axon nor the receptor and associated second messenger system of the Schwann cell that transduces this signal has been identified. In this report, we demonstrate that expression of the P0 and MBP genes in rapidly myelinating Schwann cells is sharply reduced upon withdrawal of axons, but that this expression can be substantially restored by agents that raise the intracellular concentration of cyclic AMP. We further show that Schwann cell expression of a third gene, i.e. that encoding the Nerve Growth Factor receptor, is strongly activated by the withdrawal of axons, and that this activation is largely independent of cAMP.
The positional effect of presumptive primordial germ cells (pPGCs) on their differentiation into PGCs in Xenopus
Authors: Ikenishi Kohji , Tsuzaki Yoshinari 
Published: April 2021

Abstract
To determine whether the location of ‘germ plasm’-bearing cells [presumptive primordial germ cells (pPGCs)] is crucial for their differentiation into PGCs in Xenopus, [3H]thymidine-labelled pPGCs were implanted into the anterior or posterior halves of the endoderm in unlabelted host neurulae. Labelled PGCs in the genital ridges of experimental tadpoles were investigated by autoradiography.
When the labelled pPGCs were implanted into posterior halves of the endoderm where host pPGCs are situated, 65 and 77 % of the experimental tadpoles (designated as p-tadpoles) had the labelled PGCs in series 1 and II, respectively. When implanted into the anterior halves, 20 and 27 % of the experimental tadpoles (a-tadpoles) had the labelled PGCs in series I and II, respectively. In p-tadpoles, the average numbers of labelled PGCs per tadpole were 8·7 in series I and 10 in series II, whereas they were 2· 0 in a-tadpoies of both series. Both the proportion and the average number in p-tadpoles of both series were significantly different from those in a-tadpoles. In both series, labelled PGCs in p-tadpoles were found to be distributed throughout the genital ridges while those in a-tadpoles were localized only in the anterior part of the ridges. These facts indicate that the location of pPGCs in the endoderm affects their successful migration into the genital ridges, and that not only the presence of the germ plasm but also the proper location in endoderm are prerequisites to PGC differentiation of the germ line cells.
Developmental changes of the proliferative response of mouse epidermal melanocytes to skin wounding
Authors: Hirobe Tomohisa 
Published: April 2021

Abstract
A cut was made on the middorsal skin of mice of various ages of strain C57BL/10J using fine iridectomy scissors. Specimens from the wounded skins were fixed at various days after wounding and were subjected to the dopa reaction and to the combined dopa-premelanin reaction. When the dorsal skins of 1·5-day-old mice were wounded, the melanocyte population positive to the dopa reaction as well as the melanoblast-melanocyte population positive to the combined dopa-premelanin reaction increased dramatically in the epidermis adjacent to a skin wound. Pigment-producing melanocytes in mitosis were frequently found in the vicinity of a wound immediately after wounding. When the dorsal skins of 4·5-day-old mice were wounded, the increase in the melanocyte and melanoblast-melanocyte populations was smaller than that of 1·5-day-old mice. The increase in number of pigment-producing melanocytes in mitosis was reduced and delayed as compared to 1·5-day-old mice. When the dorsal skins of 8·5-, 20·5-, and 60·5-day-old mice were wounded, the increase in the melanocyte and melanoblast-melanocyte populations was much smaller than the newborn mice. Moreover, pigmentproducing melanocytes in mitosis were never found. These results indicate that the proliferative response of mouse epidermal melanocytes to skin wounding becomes delayed and diminished with development.
The influence of cell contact on the division of mouse 8-cell blastomeres
Authors: Pickering Susan J. , Maro Bernard , Johnson Martin H. , Skepper Jeremy N. 
Published: April 2021

Abstract
The pattern of division of polarized 8-cell blastomeres with respect to the axis of cell polarity has been compared (i) for cells dividing alone with cells dividing in pairs, and (ii) for early and late dividing cells within a pair. Cell interactions do not seem to influence significantly the overall pattern of division within the population. The only significant difference found was that the second dividing cell in a pair tended to divide in the same way as its earlier dividing companion slightly more frequently than expected. These results suggest that cell interactions immediately prior to and during division do not influence strongly the orientation and position of the division plane. In contrast, interactions between the cells within an intact early 8-cell embryo, which is subsequently disaggregated to singletons or pairs, do influence the type of progeny generated at division to the 16-cell stage, and seem to do so via an effect on the size of the microvillous region generated at the cell apex.
Patterning of connective tissues in the head: discussion report
Authors: Hall Brian K. 
Published: April 2021

ABSTRACT
The three papers presented by Noden, Thorogood and Lumsden in this session encompassed the connective tissues as broadly defined, i.e. soft (fibrous) connective tissue, cartilage, bone, muscle and the dental tissues, enamel and dentine, and utilized a variety of experimental techniques on both avian and mammalian embryos to explore specificity and patterning of the vertebrate head. Whether similar developmental processes pattern homologous structures in different Vertebrate classes (Amphibia, Aves, Mammalia) was discussed with reference to patterning of the cranial musculature, chondrocranium and dental tissues. A number of challenging ideas emerged during this session. Does the premigratory neural crest consist of a homogenous population of totipotent cells or of subpopulations of bi- or tripotential cells? Is fundamental patterning of the head an early embryonic event, perhaps specified during primary embryonic induction or the consequence of neuroepithelial folding, brain growth, inductive interactions and/or spatially and temporally distributed extracellular matrix products? Can the fact that mesoderm and angioblasts do not display distinctive patterning that relates to their particular embryologic origins be extrapolated to patterning in general? How does the documentation of an ondontogenic trunk neural crest in mammals affect our theories of how patterning mechanisms arose or were modified during vertebrate evolution?
The trigeminal system: an advantageous experimental model for studying neuronal development
Authors: Davies Alun M. 
Published: April 2021

ABSTRACT
The trigeminal system is a well-characterized sensory system that has been studied extensively in mammals and birds. The clear definition and easy accessibility of the components of this system throughout development have facilitated investigation of several fundamental aspects of neural development. This has led to important advances in our understanding of the mechanism of axonal guidance, the physiology of neurotrophic factors and the establishment and refinement of neural connections. The first convincing evidence for axonal guidance by chemotropism has been obtained. The site and timing of nerve growth factor (NGF) synthesis and NGF receptor expression have been elucidated, thereby clarifying the role of this neurotrophic factor in development. A novel concept in neurotrophic factor physiology has emerged: the survival of neurones that innervate two separate target fields is regulated by two different neurotrophic factors derived from the respective target fields. The development of somatotopic maps of the periphery in the central nervous system (CNS) is dependent on spatial information provided by the periphery. The transfer of this information from the periphery to the CNS is not simply achieved by the ordered growth and arrangement of the intervening sensory nerve fibres.
Histochemical localization of IGF-I and IGF-II mRNA in the rat between birth and adulthood
Authors: Beck Felix , Samani N. J. , Byrne S. , Morgan K. , Gebhard R. , Brammar W. J. 
Published: April 2021

ABSTRACT
We describe the postnatal ontogeny and localization of insulin-like growth factors I and II (IGF-I and -II) in the rat. We have used oligodeoxyribonucleotide probes for in situ hybridization (hybridization histochemistry) and for Northern blotting. IGF-II mRNA is strongly expressed in liver, skeletal muscle, perichondrium, leptomeninges and choroid plexus of the newborn. Demonstrable levels fall dramatically in the liver at 18-20 days postnatally but persist for longer periods in muscle and remain undiminished throughout life in the pia/choroid plexus, indicating that different control mechanisms operate in these tissues. IGF-I mRNA is predominantly found in the liver. Its level in this organ rises well before levels of IGF-II fall. This suggests that distinct factors govern the expression of IGF-I and -II genes.
Anterior determinants in embryos of Chironomus samoensis: characterization by rescue bioassay
Authors: Elbetieha Ahmed , Kalthoff Klaus 
Published: April 2021

ABSTRACT
Embryos of Chironomus samoensis are programmed, by anterior u.v. irradiation, to form the abnormal body pattern ‘double abdomen’. Most double abdomen embryos show a mirror-image duplication of abdominal segments in the absence of cephalic or thoracic segments. Such embryos can be ‘rescued’, i.e. restored to normal development, by microinjection of cytoplasm or RNA from unirradiated donor embryos. Most of the rescued embryos look completely normal and many of them hatch spontaneously. The rescuing activity decreases from the anterior to the posterior pole in the donor cytoplasm and must be delivered near the anterior pole of the recipient for maximum efficiency. Rescuing activity is present in total RNA extracted from whole, unirradiated embryos. Upon fractionation, the activity is associated with poly(A)+RNA, with LiCl precipitate depleted of RNA smaller than 250 nucleotides (nt) and with a sucrose gradient fraction depleted of RNA larger than 500 nt. Corresponding fractions of RNA from Xenopus oocytes have no rescuing activity. The activity of Chironomus RNA is sensitive to u.v. irradiation with low fluence affecting less than 2 % of the pyrimidine bases. Rescuing activity is present in cytoplasm until the blastoderm stage but disappears earlier from poly(A)+RNA. Rescuing activity is also present, and localized, in cytoplasm of embryos from two related dipterans, Smittia sp. and Drosophila melanogaster, although the extent of rescue observed in Chironomus decreases with the phylogenetic distance between donor and recipient. The results of these and previous experiments indicate that dipteran embryos contain localized RNP particles acting as anterior determinants. In Chironomus, the activity of these particles seems to depend on the integrity of polyadenylated RNA of about 250 to 500 nt length.
Regulation of transcript encoding the 43K subsynaptic protein during development and after denervation
Authors: Baldwin Timothy J. , Theriot Julie A. , Yoshihara Corinne M. , Burden Steven J. 
Published: April 2021

Abstract
The postsynaptic membrane of vertebrate neuromuscular synapses is enriched in the four subunits of the acetylcholine receptor (AChR) and in a peripheral membrane protein of Mr = 43×103 (43K). Although AChRs are virtually restricted to the postsynaptic membrane of innervated adult muscle, developing and denervated adult muscle contain AChRs at nonsynaptic regions. These nonsynaptic AChRs accumulate because the level of mRNA encoding AChR subunits increases in response to a loss of muscle cell electrical activity. We have determined the level of mRNA encoding the 43K subsynaptic protein in developing muscle and in innervated and denervated adult muscle. We isolated a cDNA that encodes the entire protein-coding region of the 43K subsynaptic protein from Torpedo electric organ and used this cDNA to isolate a cDNA that encodes the 43K subsynaptic protein from Xenopus laevis. We used the Xenopus cDNA to measure the level of transcript encoding the 43K protein in embryonic muscle and in innervated and denervated adult muscle by RNase protection. The level of transcript encoding the 43K protein is low in innervated adult muscle and increases 25- to 30-fold after denervation. The level of transcript encoding the alpha subunit of the AChR increases to a similar extent after denervation. Moreover, during development, transcripts encoding the 43K protein and the alpha subunit are expressed initially at late gastrula and are present in similar quantities in embryonic muscle. These results demonstrate that transcripts encoding the 43K protein and AChR subunits appear coordinately during embryonic development and that the level of mRNA encoding the 43K protein is regulated by denervation.
Implants of quail thymic epithelium generate permanent tolerance in embryonically constructed quail/chick chimeras
Authors: Ohki Hiroko , Martin Claude , Coltey Monique , Douarin Nicole M. LE 
Published: April 2021

Abstract
In situ implantation of a quail wing bud into a chick embryo at 4 days of incubation (E4) regularly results in the normal development of the implant followed by its acute rejection starting within two weeks post-hatching. If the epithelial thymic rudiments of the quail donor are implanted into the branchial arch area of the chick recipient after partial removal of its own thymic primordia, a chimeric thymus develops in the chick host and this induces tolerance to the quail wing by the chick recipient. The species identity of cells in chimeric thymuses was mapped using Feulgen-Ros-senbeck’ staining and immunolabelling with monoclonal antibodies directed against quail or chick B-L antigens. Certain lobes contained only chick cells both at the stromal and hemopoietic cell levels. Others had a quail epithelial stroma containing host hemopoietically derived cells. Only chimeras in which at least one third of the thymic lobes were chimeric showed permanent tolerance to the grafted wing.
Since the two species exhibit distinct developmental rates, we decided to study the kinetics of thymic involution after birth. Although the changes in thymus weight and histological structure are fundamentally similar in quail and chick, those in the quail start about 7-8 weeks earlier. In the chimeric thymuses, the lobes whose epithelial cells were quail involuted at the rate of control quail showing no influence of the hemopoietic thymic compartment in this process. Tolerance induced by the thymic epithelium during embryogenesis and in early postnatal life was maintained after a profound involution of the quail thymic graft had occurred.
The interaction of proteins encoded by Drosophila homeotic and segmentation genes with specific DNA sequences
Authors: Laughon Allen , Howell William , Scott Matthew P. 
Published: April 2021

ABSTRACT
The ANT-C gene cluster is part of a network of genes that govern pattern formation in the development of Drosophila. The ANT-C genes encode proteins that contain a conserved 60 amino acid sequence, the homeodomain. Here we show that the homeodomains encoded by two of the ANT-C loci confer sequencespecific DNA-binding activity. The DNA sequence specificities of the Dfd and ftz homeodomains appear to overlap completely in vitro, indicating that differences in regulatory specificity among ANT-C and BX-C proteins (assuming that differences exist) must be a consequence of the nonconserved protein sequences found outside of the homeodomains. Deletions that remove sequences from either end of the ftz homeodomain abolish DNA-binding activity, consistent with the commonly held assumption that the homeodomain is a structural domain. The relevance of in vitro DNA-binding experiments to the regulatory function of ftz is supported by our finding that a temperature-sensitive ftz mutation that causes a pairwise fusion of embryonic segments also reduces the affinity of the ftz homeodomain for DNA. Restriction fragments containing ftz homeodomain binding sites were identified within a 90 kb stretch of DNA extending the Antp Pl and P2 promoters. Binding sites appear to be clustered near the Pl promoter but also occur near P2 and in the region between the two. The task remains of determining which of these sequences mediate regulation of Antp by ftz or by other genes that encode closely related homeodomains.
Expression of intermediate filament proteins during development of Xenopus laevis: II. Identification and molecular characterization of desmin
Authors: Herrmann Harald , Fouquet Bernadette , Franke Werner W. 
Published: April 2021

ABSTRACT
During embryogenesis of avian and mammalian species the formation of intermediate filaments (IFs) containing desmin is characteristic for myogenesis. In view of important differences of patterns of IF protein expression in embryogenic pathways of amphibia on the one hand and birds and mammals on the other, we have decided to study the expression of desmin during early embryogenesis of Xenopus laevis by cDNA hybridization and antibody reactions. Here we describe the isolation of a cDNA clone encoding Xenopus desmin and the deduced amino acid sequence (458 residues; Mr52800) which displays a very high degree of conservation during vertebrate evolution from Xenopus to chicken and hamster, with a similar degree of sequence divergence between all three species compared. In addition, we have noted, by both cDNA-hybrid-selection-translation and immunoblotting of cytoskeletal proteins a second desmin-related polypeptide of Mr∼49000. RNA (Northern) blot analyses show the occurrence of three different desmin mRNAs (1 · 9, 2 · 6 and 3 · 0kb) which seem to represent different polyadenylation sites, displaying quantitative differences in different kinds of muscle tissues. During embryogenesis, desmin mRNA has first been detected in stage-14 embryos and then increases drastically to high levels at stage 18 and thereafter. Immunofluorescence microscopy using desmin-specific antibodies shows that this synthesis of desmin is restricted to somite tissue. The embryonic time course of synthesis of desmin and desmin mRNA is discussed in relation to those of other muscle proteins.
Polyspermic eggs in the anuran Discoglossus pictus develop normally
Authors: Talevi Riccardo 
Published: April 2021

ABSTRACT
Fertilization and development in 400 eggs of the anuran Discoglossus pictus has been followed. In these eggs successful sperm interaction is restricted to a small area of the animal dimple called DI and causes a rapid depolarization. A high incidence of polyspermy (36 %) was detected by in vivo observations of fertilization cone formation. Polyspermie eggs gave rise to fertilization potentials comparable to monospermic eggs and developed normally. By using current-injection technique it is shown that sperm penetration is independent of mem-brane potential. The role of the egg envelopes in regulating sperm–egg interaction is discussed.
Three Strongylocentrotus purpuratus actin genes show correct cell-specific expression in hybrid embryos of S. purpuratus and Lytechinus pictus
Authors: Nisson Paul E. , Dike Laura E. , Crain William R. 
Published: April 2021

ABSTRACT
The cell-specific expression of three actin genes from the sea urchin species Strongylocentrotus purpuratus was examined in hybrid embryos of S. purpuratus and another species, Lytechinus pictus, by in situ hybridization. The mRNAs from each of these genes displayed distinct spatial patterns of expression in late-stage hybrid embryos (constructed in either direction), being detected only in the cell lineages where they are normally found in S. purpuratus embryos (i.e. Cyllla, only in the aboral ectoderm lineage; Cyl, in the gut, oral ectoderm and some mesenchyme cells of plutei, and preferentially in the archenteron of gastrulae; M, only in two small clusters of cells near the esophagus in plutei). These results, together with our previous observation that expression of each of these genes is activated at the same stage in these hybrid embryos as in normal S. purpuratus embryos, demonstrate that the trans-acting factors which are necessary to regulate both the temporal and spatial expression of these genes are present in the hybrid embryos. Previous experiments have shown that the expression of a chimeric gene containing the Cyllla promotor fused to a bacterial chloramphenicol actetyl-transferase (CAT) gene is not confined to the correct cell lineage (aboral ectoderm) when injected into Lytechinus embryos. The conclusion from these sets of data is that the factor(s) that regulate the spatial expression of at least one of the actin genes must derive from transcription of the zygotic genome.