bluuebunny/crossref_metadata_2025_split huggingface dataset:
Induction of brain and sensory pigment cells in the ascidian embryo analyzed by experiments with isolated blastomeres
Authors: Nishida Hiroki 
Published: April 2021

ABSTRACT
Tadpole larvae of ascidians have a brain and two kinds of sensory pigment cells within the brain. These neural tissues are formed through folding of the neural plate and, as in vertebrates, neural induction is involved in the formation of the nervous system. The brain and pigment cells are derived from anterior-animal (a-line) blastomeres, and inductive interaction with anterior-vegetal (A-line) blastomeres is necessary for formation of neural tissues from the a-line cells. In order to investigate the characteristics of this process in detail, blastomeres were isolated from embryos of Halocynthia roretzi at the 110cell (late blastula) stage, and then their developmental capacity was examined. In the first set of experiments, brain- and pigment-lineage cells, isolated prior to neural induction, failed to develop three specific features of epidermis (epithelial morphology, secretion of larval tunic and expression of epidermis-specific antigen). These observations suggested a process different from amphibian neural induction, indicative perhaps of a permissive type of induction in ascidian embryogenesis.
Next, in order to identify which type of tissueprecursor cell is the inducer of the sensory pigment cells, various sets of blastomeres were isolated from 110-cell embryos, in which the fates of most of the blastomeres are restricted to a single type of tissue. The results suggested that spinal-cord precursor blastomeres, which are cells of the A-line, are sufficient to induce the a-line cells to form pigment cells. In addition, embryos from which all spinal cord precursors had been ablated, failed to form sensory pigment cells as well as a brain structure. Therefore, it is probable that the inducers of the ascidian sensory pigment cells are the spinal-cord precursor cells.
Hyaluronan as a propellant for epithelial movement: the development of semicircular canals in the inner ear ofXenopus
Authors: Haddon Catherine M. , Lewis Julian H. 
Published: April 2021

ABSTRACTThe membranous labyrinth of the inner ear, with its three semicircular canals, originates from a simple spheroidal otic vesicle. The process is easily observed in Xenopus. The vesicle develops three dorsal outpocketings; from the two opposite faces of each outpocketing pillars of tissue are protruded into the lumen; and these paired ‘axial protrusions’ eventually meet and fuse, to form a column of tissue spanning the lumen of the outpocketing like the hub of a wheel, with a tube of epithelium forming the semicircular canal around the periphery. Each axial protrusion consists of epithelium encasing a core of largely cell-free extracellular matrix that stains strongly with alcian blue. In sections, at least 60 % of the stainable material is removed by treatment with Streptomyces hyaluronidase. When Streptomyces hyaluronidase is microinjected into the core of a protrusion in vivo, the protrusion collapses and the corresponding semicircular canal fails to form. Hyaluronan (hyaluronic acid) in the core of the protrusion therefore seems to be essential in driving the extension of the protrusion. Autoradiography with tritiated glucosamine indicates that the hyaluronan-rich matrix is synthesised by the epithelium covering the tip of the protrusion; the basal lamina here appears to be discontinuous. These findings indicate that the epithelium of the axial protrusion propels itself into the lumen of the otocyst by localised synthesis of hyaluronan. Hyaluronan may be used in a similar way in the development of other organs, such as the heart and the secondary palate.
Diversity of expression of engrailed-like antigens in zebrafish
Authors: Hatta Kohei , Bremiller Ruth , Westerfield Monte , Kimmel Charles B. 
Published: April 2021

ABSTRACT
We have studied developmental expression of zebrafish engrailed-like (Eng) antigens. Many cell types are reproducibly labeled by two antibodies that recognize the Eng homeodomain, but other cells are labeled by only one or the other, suggesting a hitherto unrecognized complexity of Eng proteins. Expression patterns vary remarkably according to cell type and location. In the undifferentiated primordia of the brain and of each myotome, expression by a stripe of cells spatially subdivides the primordium at a location where a morphological boundary forms later, suggesting expression may be required for development of the boundaries. Supporting this hypothesis, trunk myotomal cells that express Eng are absent in spt-1 mutant embryos, just where the myotomal boundaries fail to form. Another pattern is present in rhombomeres, pharyngeal arches, and the pectoral girdle. In each of these cases, cells (neuron, muscle, cartilage) generating a subset of a series of repeated elements selectively express Eng. These subsets then form specialized derivatives, suggesting Eng homeoproteins are involved in determining the specializations. Epidermal expression is present in the ventral half of the pectoral fin rudiment, precisely ‘compartmentalizing’ the fin. Neuronal cells at a certain dorsoventral level in each hindbrain and spinal cord segment selectively express Eng, suggesting segmental control of neuronal identity. Specific expression patterns are observed in taste buds, otic vesicles and teeth. Thus we propose that eng genes function in diverse cell types in zebrafish, but play selector roles that can be classified into a few basic types.
F-actin localization during trochoblast differentiation in Patella vulgata embryos
Authors: Serras Florenci , Speksnijder Johanna E. 
Published: April 2021

ABSTRACT
We have studied the development of the ciliated, locomotory organ of Patella vulgata trochophore larvae. This organ, the prototroch, arises from different clones of trochoblasts. In each of these trochoblasts, a band of filamentous (F-) actin is formed at the time that ciliogenesis starts. This band, which we visualized with TRITC-phalloidin, is positioned at the base of the row of cilia that crosses each trochoblast. Isolated trochoblasts, as well as isolated quartets of animal micromeres (from which the trochoblasts are derived), similarly form rows of cilia and F-actin bands at the proper time in development. In whole embryos, the trochoblasts shift their position following ciliogenesis, and finally form a ring of differentiated prototroch cells with a continuous band of F-actin encircling the entire larva. At the dorsal side, a double row of prototroch cells and thus a double band of F-actin is present. In contrast, multiple regions with a double F-actin band are found in trochophores in which the establishment of a dorsoventral axis is inhibited experimentally. Confocal laser scanning microscopy shows that the F-actin band extends from the apical surface deep into the cytoplasm of the prototroch cells. At the ultrastructural level, a single striated rootlet connected to the basal body of each cilium can be seen to extend deep into the cytoplasm toward the nucleus, and a band of actin-like filaments is found to interconnect neighboring basal apparatus. Treatment of trochophores with cytochalasin B disrupts the organization of the F-actin band as visualized with TRITC-phalloidin, affects the angle of the effective stroke of ciliary beat and reduces their swimming capacity. This suggests that the F-actin band is essential for the normal locomotory behavior of the Patella trochophore larva.
The development of the sensory neuron pattern in the antennal disc of wild-type and mutant (lz
3, ss
a
) Drosophila melanogaster
Authors: Lienhard M. C. , Stocker R. F. 
Published: April 2021

ABSTRACT
The development of the sensory neuron pattern in the antennal disc of Drosophila melanogaster was studied with a neuron-specific monoclonal antibody (22C10). In the wild type, the earliest neurons become visible 3h after pupariation, much later than in other imaginai discs. They lie in the center of the disc and correspond to the neurons of the adult aristal sensillum. Their axons join the larval antennal nerve and seem to establish the first connection towards the brain. Later on, three clusters of neurons appear in the periphery of the disc. Two of them most likely give rise to the Johnston’s organ in the second antennal segment. Neurons of the olfactory third antennal segment are formed only after eversion of the antennal disc (clusters tl-t3). The adult pattern of antennal neurons is established at about 27 % of metamorphosis.
In the mutant lozenge3(Iz3), which lacks basiconic antennal sensilla, cluster t3 fails to develop. This indicates that, in the wild type, a homogeneous group of basiconic sensilla is formed by cluster t3. The possible role of the lozenge gene in sensillar determination is discussed.
The homoeotic mutant spineless-aristapedia (ssa) transforms the arista into a leg-like tarsus. Unlike leg discs, neurons are missing in the larval antennal disc of ssa. However, the first neurons differentiate earlier than in normal antennal discs. Despite these changes, the pattern of afferents in the ectopic tarsus appears leg specific, whereas in the non-transformed antennal segments a normal antennal pattern is formed. This suggests that neither larval leg neurons nor early aristal neurons are essential for the outgrowth of subsequent afferents.
Phosphorylation, expression and function of the Ultrabithorax protein family in Drosophila melanogaster
Authors: Gavis Elizabeth R. , Hogness David S. 
Published: April 2021

ABSTRACT
Alternative splicing of the Ultrabithorax homeotic gene transcript generates a family of five proteins (UBX isoforms) that function as transcription factors. All isoforms contain a homeodomain within a common 99 aa C-terminal region (C-constant region) which is joined to a common 247 aa N-terminal (N-constant) region by different combinations of three small optional elements. Unlike the UBX proteins expressed in E. coli, UBX isoforms expressed in D. melanogaster cells are phosphorylated on serine and threonine residues, located primarily within a 53 aa region near the middle of the N-constant region, to form at least five phosphorylated states per isoform. Similar, if not identical states can be generated in vitro from purified E. coli UBX protein by a kinase activity in nuclear extracts from D. melanogaster cells. Temporal developmental profiles of UBX isoforms parallel those for the respective mRNAs, and all isoforms are similarly phosphorylated throughout embryogenesis. Analysis by cotransfection assays of the promoter activation and repression functions of mutant UBX proteins with various deletions in the N-constant region shows that repression is generally insensitive to deletion and, hence, presumably to phosphorylation. By contrast, the activation function is differentially sensitive to the different deletions in a manner indicating the absence of a discrete activating domain and instead, the presence of multiple activating sequences spread throughout the region.
Roles of wingless in patterning the larval epidermis of Drosophila
Authors: Bejsovec Amy , Arias Alfonso Martinez 
Published: April 2021

ABSTRACT
The larval epidermis of Drosophila shows a stereotyped segmentally repeating pattern of cuticular structures. Mutants deficient for the wingless gene product show highly disrupted patterning of the larval cuticle. We have manipulated expression of the wg gene product to assess its role in this patterning process. We present evidence for four distinct phases of wg function in epidermal cells: (1) an early requirement in engrailed- expressing cells to establish and maintain stable expression of en, (2) a discrete period when wg and en gene products act in concert to generate positional values in the anterior portion of the ventral segment and all values of the dorsal and lateral epidermis, (3) a progressive function (dependent on prior interaction with the en- expressing cells) in conferring positional values to cells within the posterior portion of the segment, and (4) a late continuous requirement for maintaining some ventral positional values.
The nuclear-cytoplasmic distribution of the Xenopus nuclear factor, xnf7, coincides with its state of phosphorylation during early development
Authors: Miller Mill , Reddy Bramham A. , Kloc Malgorzata , Li Xiao Xia , Dreyer Christine , Etkin Laurence D. 
Published: April 2021

ABSTRACT
We describe the characterization in Xenopus laevis of a nuclear protein, xnf7, which is first detected in the oocyte GV and is eventually enriched in nuclei of cells of the adult brain. Previous studies have shown that this protein contains zinc-finger-like structures and acidic domains typical of transcriptional activators, and is phosphorylated in vitro by p34cdc2 protein kinase. The protein also binds to double-stranded DNA. These data suggest that xnf7 may function as a transcription factor. During oocyte maturation, xnf7 is released into the cytoplasm and is not detectable in nuclei until the mid-blastula-gastrula stage of development. Western blot analysis of xnf7 isolated from oocytes and eggs showed the existence of multiple bands or isoforms of the protein. Unique isoforms that are generated during oocyte maturation are the result of phosphorylation. The phosphorylated isoforms remain in the cytoplasm until the mid-blastula stage. The re-accumulation of protein in the embryonic nuclei at this time correlates with the increase in abundance of the less phosphorylated isoforms. The xnf7 protein possesses a nuclear localization signal (NLS) similar to the bipartite signal found in nucleoplasmin. Newly synthesized xnf7 accumulated in the oocyte GV to detectable levels within a few hours following synthesis suggesting that retention of the protein in the cytoplasm during early cleavage may be due to a process that interferes with the function of the NLS. These data suggest that compartmentalization and/or post-translational modification of the nuclear protein xnf7 may be involved in regulating its function during early development.
Basic fibroblast growth factor induces retinal pigment epithelium to generate neural retina in vitro
Authors: Pittack C. , Jones M. , Reh T. A. 
Published: April 2021

ABSTRACT
During embryogenesis, the cells of the eye primordium are initially capable of giving rise to either neural retina or pigmented epithelium (PE), but become restricted to one of these potential cell fates. However, following surgical removal of the retina in embryonic chicks and larval amphibians, new neural retina is generated by the transdifferentiation, or phenotypic switching, of PE cells into neuronal progenitors. A recent study has shown that basic fibroblast growth factor (bFGF) stimulates this process in chicks in vivo. To characterize further the mechanisms by which this factor regulates the phenotype of retinal tissues, we added bFGF to enzymatically dissociated chick embryo PE. We found that bFGF stimulated proliferation and caused several morphological changes in the PE, including the loss of pigmentation; however, no transdifferentiation to neuronal phenotypes was observed. By contrast, when small sheets of PE were cultured as aggregates on a shaker device, preventing flattening and spreading on the substratum, we found that a large number of retinal progenitor cells were generated from the PE treated with bFGF. These results indicate that bFGF promotes retinal regeneration in vitro, as well as in ovo, and suggest that the ability of chick PE to undergo transdifferentiation to neuronal progenitors appears to be dependent on the physical configuration of the cells.
FGFR-4, a new member of the fibroblast growth factor receptor family, expressed in the definitive endoderm and skeletal muscle lineages of the mouse
Authors: Stark Kevin L. , McMahon Jill A. , McMahon Rew P. 
Published: April 2021

ABSTRACT
We have used the polymerase chain reaction to clone from fetal cerebellar RNA a novel member of the fibroblast growth factor receptor family, FGFR-4. cDNAs encoding a full-length receptor were isolated and RNA expression examined in adult and fetal tissues by RNA blot analysis. Transcripts were detected in adult lung, liver and kidney and in fetal RNAs from 11.5 to 16.5 days post coitum (p.c.). In situ hybridization was performed to examine developmental expression. FGFR-4 RNA was expressed in definitive endoderm of the developing gut and extraembryonic endoderm of the yolk-sac from 8.5 to 14.5 days p.c. At early somite stages, FGFR-4 was also expressed in the myotomal component of the somite, and by 14.5 days p.c. in the myotomally derived skeletal muscle. No expression was seen at any stage in cardiac muscle. Several endodermal derivatives, the liver, lung and pancreas, expressed FGFR-4 at 14.5 days p.c. In addition, FGFR-4 RNA was detected in the adrenal cortex, collecting tubules of the kidney and condensing cartilage at this time. These results suggest that FGFR-4 is likely to have diverse roles in development, which may include regulation of definitive endoderm and skeletal muscle lineages.
Expression of the cut locus in the Drosophila wing margin is required for cell type specification and is regulated by a distant enhancer
Authors: Jack Joseph , Dorsett Dale , Delotto Yvonne , Liu Su 
Published: April 2021

ABSTRACT
The cut locus is a complex gene whose function is necessary for specification of a number of cell types, including the external sensory organs. The cut wing class of mutations of the cut locus are homozygous viable and lack tissue from the wing margin, which is normally composed of external sensory organs and noninnervated bristles. Expression of cut was examined in the developing wings of wild-type and mutant pupae using an antiserum against Cut protein. Cut is expressed in all of the external sensory organs of the wing and the noninnervated bristles of the posterior margin. The cut wing class of mutations prevents Cut expression specifically in the wing margin mechanoreceptors and noninnervated bristles, apparently preventing neural differentiation. The transformed cells die soon after differentiation would have occurred. We identify an enhancer, located about 80 kb upstream of the cut gene promoter, that confers expression in the cells of the mechanoreceptors and noninnervated bristles from a heterologous promoter. The 27 gypsy retrotransposon insertions that prevent expression in these margin cells, all occur between this enhancer and the promoter. These, gypsy insertions probably interfere with the interaction between the enhancer and the cut gene promoter.
Human acrosome biogenesis: immunodetection of proacrosin in primary spermatocytes and of its partitioning pattern during meiosis
Authors: Escalier Denise , Gallo Jean-Marc , Albert Martine , Meduri Geri , Bermudez Diego , David Georges , Schrevel Joseph 
Published: April 2021

ABSTRACT
Proacrosin biosynthesis timing during human spermatogenesis has been studied using the monoclonal antibody 41)4 (mAb 4D4). Frozen and paraffin-embedded sections of testicular biopsies were labelled by standard indirect immunofluorescence and avidin-biotin immunoperoxidase procedures. The labelling specificity was checked by immunochemistry assays on unrelated tissues and by western blotting of testis extracts showing that only the 50–55×103 Mr proacrosin was recognized by mAb 4D4. Proacrosin was first observed in the Golgi region of midpachytene primary spermatocytes. In late pachytene primary spermatocytes, proacrosin was observed in two regions located at opposite nuclear poles. During the subsequent steps of the first meiotic division, the two bodies containing proacrosin were located: (i) on opposite sides of the equatorial plate during metaphase; along the microtubular spindle during anaphase; and close to each chromosomal aggregate during telophase. Two bodies containing proacrosin were still observed in interphasic secondary spermatocytes. The single labelled area observed in early spermatids was found to increase considerably in size during spermiogenesis. Anomalies of proacrosin scattering were observed in patients with Golgi complex partitioning failure. These data’ reveal proacrosin biosynthesis during diploid and haploid phases of human spermatogenesis and the proacrosin partitioning pattern during meiosis.
Embryogenesis of the murine endocrine pancreas; early expression of pancreatic polypeptide gene
Authors: Herrera Pedro-Luis , Huarte Joaquin , Sanvito Francesca , Meda Paolo , Orci Lelio , Vassalli Jean-Dominique 
Published: April 2021

ABSTRACT
By immunofluorescence on cytospin preparations and on semithin sections of mouse pancreatic buds, we have found glucagon and pancreatic polypeptide (PP)-containing cells at embryonal day 10.5 (E 10.5) in dorsal buds and at E 11.5 in ventral buds. Insulin-containing cells appear in dorsal buds at E 11.5, and one to two days later in ventral buds. Somatostatin-containing cells are detectable from E 13.5 in both dorsal and ventral buds. A quantitative analysis shows that up to E 15.5, PP-containing cells are relatively abundant in both buds. By PCR amplification of oligo(dT)-primed cDNAs prepared from total pancreatic RNA, we also detect PP mRNA from E 10.5 onwards, thus confirming the early expression of the PP gene in the developing mouse pancreas.
Analysis of endocrine cells in situ suggests three major patterns of cell distribution in embryonic pancreas. First, individual hormone-containing cells are located within the epithelium of pancreatic ducts. In both dorsal and ventral buds, the majority of these endocrine cells contain PP, but many also contain glucagon, insulin or somatostatin. Secondly, clusters of endocrine cells are found in the pancreatic interstitium. Many of these cells contain both glucagon and PP which, by inununogold labelling of consecutive thin sections, can be shown to co-exist within individual secretory granules. Finally, starting on E 18.5, typical islets are formed with centrally located B cells and with the adult ‘one cell – one hormone’ phenotype. These results suggest an intriguing ontogénie relationship between A- and PP-cells, and also indicate that PP-containing cells may occupy a hitherto unexpected place in the lineage of endocrine islet cells.
Dosage dependence of maternal contribution to somatic cell division in Drosophila melanogaster
Authors: Carmena Mar , Gonzalez Cayetano , Casalf Jose , Ripoll Pedro 
Published: April 2021

ABSTRACT
Most mitotic mutants in Drosophila do not lead to lethality in early development despite the highly abnormal chromosome behaviour that they elicit. This has been explained as being the effect of maternally provided wild-type products. We have tested this hypothesis by studying cuticular clones derived from cells in which there has been loss of a marked Y chromosome due to chromosome nondisjunction in individuals homozygous for the mutation abnormal spindle who are progeny of heterozygous mothers. We have found that the size and frequency of these clones are higher than in control flies. Furthermore, by analysing flies whose female parents have different doses of the asp+ gene, we have found that there is a correlation between the amount of maternally contributed asp+ product and the frequency and size of cuticular clones. We have also estimated the time in development when the first mitotic mistakes take place, i.e. the time when maternal products are no longer sufficient to carry out normal cell division.