bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temporal and spatial gradients of Fgf8 and Fgf17 regulate proliferation and differentiation of midline cerebellar structures
Authors: Liu Jingsong Xu, Zhonghao , Ornitz David M. 
Published: April 2021

ABSTRACT
The midbrain-hindbrain (MHB) junction has the properties of an organizer that patterns the MHB region early in vertebrate development. Fgf8 is thought to mediate this organizer function. In addition to Fgf8, Fgf17 and Fgf18 are also expressed in the MHB junction. Fgf17 is expressed later and broader than either Fgf8 or Fgf18. Disrupting the Fgf17 gene in the mouse decreased precursor cell proliferation in the medial cerebellar (vermis) anlage after E11.5. Loss of an additional copy of Fgf8 enhanced the phenotype and accelerated its onset, demonstrating that both molecules cooperate to regulate the size of the precursor pool of cells that develop into the cerebellar vermis. However, expression patterns of Wnt1, En2, Pax5 and Otx2 were not altered suggesting that specification and patterning of MHB tissue was not perturbed and that these FGFs are not required to pattern the vermis at this stage of development. The consequence of this developmental defect is a progressive, dose-dependent loss of the most anterior lobe of the vermis in mice lacking Fgf17 and in mice lacking Fgf17 and one copy of Fgf8. Significantly, the differentiation of anterior vermis neuroepithelium was shifted rostrally and medially demonstrating that FGF also regulates the polarized progression of differentiation in the vermis anlage. Finally, this developmental defect results in an ataxic gait in some mice.
Calmodulin and Son of sevenless dependent signaling pathways regulate midline crossing of axons in the Drosophila CNS
Authors: Fritz Janice L. , VanBerkum Mark F. A. 
Published: April 2021

ABSTRACT
The establishment of axon trajectories is ultimately determined by the integration of intracellular signaling pathways. Here, a genetic approach in Drosophila has demonstrated that both Calmodulin and Son of sevenless signaling pathways are used to regulate which axons cross the midline. A loss in either signaling pathway leads to abnormal projection of axons across the midline and these increase with roundabout or slit mutations. When both Calmodulin and Son of sevenless are disrupted, the midline crossing of axons mimics that seen in roundabout mutants, although Roundabout remains expressed on crossing axons. Calmodulin and Son of sevenless also regulate axon crossing in a commissureless mutant. These data suggest that Calmodulin and Son of sevenless signaling pathways function to interpret midline repulsive cues which prevent axons crossing the midline.
The autoregulation of retinal ganglion cell number
Authors: González-Hoyuela Maritza , Barbas Julio A. , Rodríguez-Tébar Alfredo 
Published: April 2021

ABSTRACT
The development of the nervous system is dependent on a complex set of signals whose precise co-ordination ensures that the correct number of neurones are generated. This regulation is achieved through a variety of cues that influence both the generation and the maintenance of neurones during development. We show that in the chick embryo, stratified retinal ganglion cells (RGCs) are themselves responsible for providing the signals that control the number of RGCs that are generated, both by inhibiting the generation of new ganglion cells and by killing incoming migratory ganglion cells. Selective toxicological ablation of RGCs in the chick embryo resulted in the achronic generation of ganglion cells, which eventually led to the repopulation of the ganglion cell layer and a large decrease in the physiological cell death affecting postmitotic migratory neurones. Interestingly, the application of exogenous NGF reversed the effects of ganglion cell ablation on ganglion cell death. Because the only source of NGF in the retina is that produced by the stratified ganglion cells, we infer that these differentiated neurones regulate their own cell number by secreting NGF, a neurotrophin that has previously been shown to be responsible for the death of migrating ganglion cells.
DNA damage-induced neural precursor cell apoptosis requires p53 and caspase 9 but neither Bax nor caspase 3
Authors: D’Sa-Eipper Cleta , Leonard Jeffrey R. , Putcha Girish , Zheng Timothy S. , Flavell Richard A. , Rakic Pasko , Kuida Keisuke , Roth Kevin A. 
Published: April 2021

ABSTRACT
Programmed cell death (apoptosis) is critical for normal brain morphogenesis and may be triggered by neurotrophic factor deprivation or irreparable DNA damage. Members of the Bcl2 and caspase families regulate neuronal responsiveness to trophic factor withdrawal; however, their involvement in DNA damage-induced neuronal apoptosis is less clear. To define the molecular pathway regulating DNA damage-induced neural precursor cell apoptosis, we have examined the effects of drug and γ-irradiation-induced DNA damage on telencephalic neural precursor cells derived from wild-type embryos and mice with targeted disruptions of apoptosis- associated genes. We found that DNA damage-induced neural precursor cell apoptosis, both in vitro and in vivo, was critically dependent on p53 and caspase 9, but neither Bax nor caspase 3 expression. Neural precursor cell apoptosis was also unaffected by targeted disruptions of Bclx and Bcl2, and unlike neurotrophic factor-deprivation- induced neuronal apoptosis, was not associated with a detectable loss of cytochrome c from mitochondria. The apoptotic pathway regulating DNA damage-induced neural precursor cell death is different from that required for normal brain morphogenesis, which involves both caspase 9 and caspase 3 but not p53, indicating that additional apoptotic stimuli regulate neural precursor cell numbers during telencephalic development.
Axial skeletal patterning in mice lacking all paralogous group 8 Hox genes
Authors: Akker Eric van den , Fromental-Ramain Catherine , Graaff Wim de , Le Mouellic Hervé , Brûlet Philippe , Chambon Pierre , Deschamps Jacqueline 
Published: April 2021

ABSTRACTWe present a detailed study of the genetic basis of mesodermal axial patterning by paralogous group 8 Hox genes in the mouse. The phenotype of Hoxd8 loss-of- function mutants is presented, and compared with that of Hoxb8- and Hoxc8-null mice. Our analysis of single mutants reveals common features for the Hoxc8 and Hoxd8 genes in patterning lower thoracic and lumbar vertebrae. In the Hoxb8 mutant, more anterior axial regions are affected. The three paralogous Hox genes are expressed up to similar rostral boundaries in the mesoderm, but at levels that strongly vary with the axial position. We find that the axial region affected in each of the single mutants mostly corresponds to the area with the highest level of gene expression. However, analysis of double and triple mutants reveals that lower expression of the other two paralogous genes also plays a patterning role when the mainly expressed gene is defective. We therefore conclude that paralogous group 8 Hox genes are involved in patterning quite an extensive anteroposterior (AP) axial region. Phenotypes of double and triple mutants reveal that Hoxb8, Hoxc8 and Hoxd8 have redundant functions at upper thoracic and sacral levels, including positioning of the hindlimbs. Interestingly, loss of functional Hoxb8 alleles partially rescues the phenotype of Hoxc8- and Hoxc8/Hoxd8-null mutants at lower thoracic and lumbar levels. This suggests that Hoxb8 affects patterning at these axial positions differently from the other paralogous gene products. We conclude that paralogous Hox genes can have a unique role in patterning specific axial regions in addition to their redundant function at other AP levels.
Patterning of angiogenesis in the zebrafish embryo
Authors: Childs Sarah , Chen Jau-Nian , Garrity Deborah M. , Fishman Mark C. 
Published: April 2021

Little is known about how vascular patterns are generated in the embryo. The vasculature of the zebrafish trunk has an extremely regular pattern. One intersegmental vessel (ISV) sprouts from the aorta, runs between each pair of somites, and connects to the dorsal longitudinal anastomotic vessel (DLAV). We now define the cellular origins, migratory paths and cell fates that generate these metameric vessels of the trunk. Additionally, by a genetic screen we define one gene, out of bounds (obd), that constrains this angiogenic growth to a specific path.We have performed lineage analysis, using laser activation of a caged dye and mosaic construction to determine the origin of cells that constitute the ISV. Individual angioblasts destined for the ISVs arise from the lateral posterior mesoderm (LPM), and migrate to the dorsal aorta, from where they migrate between somites to their final position in the ISVs and dorsal longitudinal anastomotic vessel (DLAV). Cells of each ISV leave the aorta only between the ventral regions of two adjacent somites, and migrate dorsally to assume one of three ISV cell fates. Most dorsal is a T-shaped cell, based in the DLAV and branching ventrally; the second constitutes a connecting cell; and the third an inverted T-shaped cell, based in the aorta and branching dorsally. The ISV remains between somites during its ventral course, but changes to run mid-somite dorsally. This suggests that the pattern of ISV growth ventrally and dorsally is guided by different cues.We have also performed an ENU mutagenesis screen of 750 mutagenized genomes and identified one mutation, obd that disrupts this pattern. In obd mutant embryos, ISVs sprout precociously at abnormal sites and migrate anomalously in the vicinity of ventral somite. The dorsal extent of the ISV is less perturbed. Precocious sprouting can be inhibited in a VEGF morphant, but the anomalous site of origin of obd ISVs remains. In mosaic embryos, obd somite causes adjacent wild-type endothelial cells to assume the anomalous ISV pattern of obd embryos.Thus, the launching position of the new sprout and its initial trajectory are directed by inhibitory signals from ventral somites. Zebrafish ISVs are a tractable system for defining the origins and fates of vessels, and for dissecting elements that govern patterns of vessel growth.
Studies on the functional activity of organotypically cultured mouse ovary
Authors: Chapekar T. N. , Nayak G. V. , Ranadive Kamal J. 
Published: April 2021

ABSTRACT
Short-term maintenance of mouse and rat ovary in organotypic culture system is no longer a problem (Martinovitch, 1938; Gaillard, 1953; Trowell, 1959). Gaillard (1953) cultivated ovaries from 7-to 8-day-old and 21-day-old mice for a week on the plasma clot. Trowell (1959) maintained ovaries of 8-day-old mice on a synthetic medium in an O2-CO2 atmosphere for 9 days. He observed no histological differentiation in the tissues of the ovary. What needs confirmation and further investigation is the possibility of maintenance of functional activity of the ovary under culture conditions. A study was therefore undertaken to investigate if an ovary, cultivated in vitro for some time, shows hormonal activity when transplanted in vivo. In the present work cultured ovaries were grafted in the anterior eye-chamber of spayed female mice and the development of secondary sex organs such as mammary glands and uterus was studied.
Congenital malformations induced by dimethyl sulphoxide in the golden hamster
Authors: Ferm Vergil H. 
Published: April 2021

ABSTRACT
Dimethyl sulphoxide (DMSO) is a relatively simple organic compound with a molecular weight of 78. It has been reported to be exceptionally non-toxic and has been used extensively in biological systems as a cell preservative, including freeze storage (Porterfield & Ashwood-Smith, 1962; Dougherty, 1962), and as a radioprotective agent against X-irradiation in mice (Ashwood-Smith, 1961). Recent clinical investigations in man have suggested that DMSO has a remarkable array of effects, including anti-inflammatory activity, bacteriostatic effects, and analgesic activity (Jacob, Bischel & Herschler, 1964). It has been used extensively as a vehicle for the topical application of various drugs because of its dramatic effect on enhancement of penetration of various drugs through the skin (Kligman, 1965).
Autoradiographic patterns of [3H]uridine incorporation during the development of the mollusc, Acmaea scutum
Authors: Karp Gerald C. 
Published: April 2021

ABSTRACT
Autoradiographic experiments on eggs and embryos of the gastropod mollusc, Acmaea scutum, have provided information on the time of initiation of [3H]uridine incorporation into RNA, the relative degree to which different embryonic regions are participating, and the relative rates of incorporation at different times of development. The unfertilized egg does not incorporate exogenous [3H]uridine. After fertilization the first indication of incorporation in the stages examined was at the beginning of the sixth cleavage. There is a marked increase in the level of incorporation during the sixth cleavage which marks the beginning of gastrulation in these embryos. After this stage there is a gradual increase in incorporation per embryo, throughout development to the mid-veliger. Very little indication of significant differences in the level of incorporation among the cells of any embryo was found. The most pronounced exception was the lower activity of the anterior ectodermal cells of the trochophore larva. At later stages the derivatives of these cells were as active as the cells of other regions.
Analyse de la morphogenèse du pied des Oiseaux à l’aide de mélanges cellulaires interspécifiques: I. Etude morphologique
Authors: Pautou Marie-Paule 
Published: April 2021

ABSTRACT

Morphogenesis of the feet of birds, studied in limbs developed from reaggregated heterospecific mesoderm
Experiments were undertaken to determine whether species-specific characters of chick and duck mesodermal leg-bud cells are retained after dissociation and reaggregation in homo-and heterospecific mixtures.
Prospective zeugopod and autopod mesoderm from chick and/or duck leg buds were isolated, dissociated into a cell suspension and pelleted by centrifugation. The reaggregated mesoderm was packed into a leg-bud ectodermal jacket; the recombined leg bud was then grafted on the wing stump of a host embryo. Recombinants whose mesoderm was a homo-specific reaggregate developed into typical chick or duck leg parts according to the specific origin of the mesodermal component; the feet of nearly all these legs lacked an tero-posterior polarity. Recombinants containing heterospecific reaggregates were also capable of forming reasonably organized leg structures.
The foot was not, as a rule, of the specific type expected of the majority component. In a mixture of 75% chick mesoderm cells and 25% duck mesoderm cells, the feet which developed were either of chick type or of composite chick/duck type, where typical chick areas were next to typical or aberrant (steganoid) duck areas. When the ratio was reversed (25% chick, 75% duck), the majority of the feet were again of chick type or of composite chick/duck type, the typical duck phenotype being exceptional. Even in a mixture of 10% chick cells and 90% duck cells, duck-type feet were not obtained. They were all of composite type: half of their interdigital zones were of chick type, the other half were occupied, in most cases, by under-developed, indented webbing or by one or several discrete flaps, and, in a few cases, by normal webbing.
The vast majority of the feet developed from heterospecific mesoderm were characterized by the profusion of the toes, which were not polarized along the a-p axis.
Distribution of the head-activating substance in hydra and its localization in membranous particles in nerve cells
Authors: Schaller H. , Gierer A. 
Published: April 2021

ABSTRACT
The low-molecular-weight substance activating head and bud formation in hydra is shown to occur in the animal as a gradient decreasing from the hypostomal to the basal region. The concentration of head-activating substance increases during head regeneration and during bud initiation.
Most of the low-molecular-weight head-activating substance is present in the animal in a structure-bound form. More than 90% was sedimentable; 70% was recovered in a highly purified fraction consisting of membranous particles of ∽1200 Å diameter. This implies that in the animal only a minor portion of the total activating activity is freely diffusible, i.e. present in the low-molecular-weight form.
The head-activating substance is mainly produced by and/or stored in nerve cells or a subgroup of the nerve cells. Nerve cells were enriched tenfold in a fraction containing most of the head-activating substance in a more than 10 times higher specific activity than in the animal. In addition, it is shown that only the nerve cells are positively correlated with the distribution of head-activating activity both with regard to localization within the animal as to time sequence of appearance during head regeneration and bud formation.
The effect of hydrocortisone on limb regeneration in the bullfrog tadpole, Rana catesbeiana
Authors: Weis Judith S. , Bleier Larry P. 
Published: April 2021

ABSTRACT
Tadpoles of the bullfrog Rana catesbeiana lose the ability to regenerate limbs amputated through the femur at a very early stage in development. Well-differentiated limbs which in other species can regenerate if amputated through the ankle, cannot in this species. Non-regenerating tadpole limbs either show rapid healing of the cut surface by connective tissue with no breakdown of skeletal structures, or the beginning of dedifferentiation in the cartilage. However, the cells of the rudimentary blastema that forms do not undergo proliferation; instead they become separated from the epidermis by the regrowth of the connective tissue layer which acts as a block to regeneration. This condition, termed the critical stage, is reached more often by animals that received injections of hydrocortisone than by control animals. Experimental animals furthermore, produced larger blastemata. No advanced regeneration could be obtained however.
Competence tests of early amphibian gastrula tissue containing nuclei of one species (Rana palustris) and cytoplasm of another (Rana pipiens)
Authors: Hennen Sally 
Published: April 2021

ABSTRACTCompetence tests of tissue from lethal nucleocytoplasmic hybrids consisting of diploid R. palustris nuclei in R. pipiens cytoplasm were carried out by grafting pieces of early gas-trulae to normal R. palustris early gastrula hosts. In the majority of cases, early gastrula ectoderm of the nucleoplasmic hybrids failed to differentiate further than if left in the intact embryo, although the grafts healed nicely and survived for several days. Grafts of the dorsal lip of the blastopore from nucleocytoplasmic hybrids to normal R. palustris hosts induced small secondary embryos with prominent suckers or sucker Anlage, a characteristic of nucleocytoplasmic hybrid development. These results indicate that the abnormal behaviour of the nucleocytoplasmic hybrids is an inherent property of the tissue, in the sense that contact with normal host does not alter its expression. Furthermore, the results with dorsal lip grafts suggest that nucleocytoplasmic hybrid tissue influences the direction in which normal tissue differentiates.
Etude autoradiographique des premiers stades du développement de l’ébauche du membre antérieur chez deux espèces de Chéloniens (Testudo graeca L. et Emys orbicularis L.)
Authors: Vasse J. 
Published: April 2021

ABSTRACT

Autoradiographic study of early stages of the anterior limb-bud in two species of chelonian embryos
Embryos of two chelonian species (Testudo graeca L., Emys orbicularis L.) from 20-somites stage to 34-somites stage, fixed 2–4 h after an injection of tritiated thymidine or uridine or leucine, then emulsion-exposed 12–14 days, showed the following results:
These results are compared with results obtained in other reptiles and chick embryos, in the light of the theories on the role of the somites and of the apical crest in the development of the anterior limb-bud.
Gap junctions and electrotonic coupling in foetal rabbit adrenal cortical cells
Authors: Joseph T. , Slack C. , Gould R. P. 
Published: April 2021

ABSTRACT
In an electron-microscope study of the developing rabbit adrenal gland numerous gap junctions and desmosomes were identified between the cortical cells, particularly in the juxtamedullary cortical tissue. An electrophysiological examination of the cortical cells showed them to be electrotonically coupled. Such couplings were more frequently found in the juxtamedullary cortical tissue than in the outer cortex.
Immunochemical analysis of chick phosvitin
Authors: Carinci P. , Grossi C. E. , Locci P. 
Published: April 2021

ABSTRACT
Phosvitin is a yolk phosphoglycoprotein bound to lipoproteins within the yolk granules. Its absorption and utilization during chick embryogenesis is still unclear.
The presence of phosvitin was investigated by immunodiffusion techniques in the watersoluble fraction (WSF) of the yolk during oocyte maturation and chick development and in the embryonic fluids.
The immunochemical analysis showed that phosvitin consists of two components, one of which is detectable during oocyte maturation, while both are shown in the yolk WSF of the incubated egg. The appearance of the second phosvitin component during incubation is probably dependent on granule dissolution, as suggested by the immunochemical and biochemical determinations on the embryonic fluids.
The Anatomy and Development of Brachypodism in the Mouse
Authors: Grüneberg H. , Lee A. J. 
Published: April 2021

ABSTRACT
The autosomal recessive gene for brachypodism (bp) in the mouse affects the appendicular, but not the axial skeleton. Manus and pes are more severely affected than the rest of the limbs; the girdles are normal. In digits 2–5, the basal and middle phalanges of the normal are replaced by a short and thin element which never ossifies properly; by contrast, the terminal phalanges are normal or nearly so. Up to the 13-day stage, the limbs of brachypods are externally quite normal, but anomalies of the digital blastemata are detectable in the 12-day embryo already, i.e. before the onset of chondrification. In the 14-day embryo, the overall length of metapod + phalanges is still nearly normal; but the basal and middle phalanges of the normal are represented by a single thin element which is absolutely longer whereas the metacarpale (metatarsale) is correspondingly reduced in length and calibre. This situation is subsequently reversed by heterogonie growth as the phalangeal element of brachypods grows very little. The normality of the terminal phalanges is largely due to the fact that, in the mouse, much of the terminal phalanx is formed directly from membrane and not by replacement of its cartilaginous ‘model’ on which it sits like a thimble. Brachypodism is thus due to an abnormality of the limb blastemata which precedes chondrification, but whose nature is unknown. Generally, muscular and tendinous anomalies parallel those of the skeleton.
Early cyclical changes in polyamine synthesis during sea-urchin development
Authors: Manen Carol-Ann , Russell Diane H. 
Published: April 2021

ABSTRACT
The polyamines, putrescine, spermidine, and spermine, undergo dramatic cyclical variation in both synthesis and accumulation during the early cleavage stages of sea-urchin development. Ornithine decarboxylase activity (putrescine synthesis) in developing Strongylocentrotus purpuratus exhibits maxima at and 2 h after fertilization; increases in ornithine decarboxylase activity appear to correspond to the first and second S phases. Putrescine-stimulated S-adenosyl-L-methionine decarboxylase (spermidine synthesis) and spermidine-stimulated S-adenosyl-L-methionine decarboxylase (spermine synthesis) activities reflect rises during prophase-metaphase of the first and second divisions in two species of sea urchins. Cyclical changes in the concentrations of these three amines were evident also. In general, there were drops in the levels of the amines prior to cleavage. These rapid declines in polyamine concentrations may reflect (1) selective degradation or (2) selective secretion.