bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Description of the Technique for Nuclear Transplantation inXenopus laevis
Authors: Elsdale T. R. , Gurdon J. B. , Fischberg M. 
Published: April 2021

ABSTRACTTechnical details are given of a method of transplanting embryonic nuclei in X. laevis. This technique is based on Briggs & King’s method for R. pipiens. Owing to certain differences between the eggs of Rana and Xenopus, their technique has been modified for Xenopus. The main modification for Xenopus concerns the use of ultra-violet irradiation instead of enucleation by a needle. Differences between transplantation techniques for Rana and Xenopus are unlikely to account for the differences in experimental results obtained with these species.
Rat embryonic ectoderm as renal isograft
Authors: Švajger Anton , Levak-Švajger Božica , Škreb Nikola 
Published: April 2021

ABSTRACT
Experimental results obtained many years ago revealed that during gastrulation (with the primitive streak and the mesoderm formation as distinct features) the early rodent embryo undergoes essential changes in its response to extrinsic teratogens (Russell & Russell, 1954; Wilson, 1954; Škreb, 1961; Škreb & Bijelic, 1962; Škreb & Frank, 1963). It has also been shown that the ultrastructural, histochemical and biosynthetic features of the embryo are subject to substantial changes during this period (Solter, Damjanov & Škreb, 1970, 1973; Dziadek & Adamson, 1978; Bode & Dziadek, 1979; Wartiovaara, Leivo & Vaheri, 1979; Jackson et al. 1981; Franke et al. 1982a, b). This suggests a restriction of developmental capacities (i.e. the loss of the capacity of regulation) in groups of embryonic cells at this developmental stage.
The discontinuous visual projections on the Xenopus optic tectum following regeneration after unilateral nerve section
Authors: Willshaw D. J. , Gaze R. M. 
Published: April 2021

ABSTRACT
The establishment of retinotectal projections following transection of one optic nerve in developing Xenopus has been investigated. Between 3 weeks and 11 months after the operation, the nerve fibre tracer horseradish peroxidase (HRP) was applied to either the operated or the unoperated nerve, and the brains were prepared for examination as whole mounts.
In most cases fibres from the operated nerve innervated both tecta, with the result that one tectum was doubly innervated and one tectum singly innervated. Two months after transection of the optic nerve in tadpole life, between stages 50 and 54, this nerve usually made a uniform projection on the contralateral tectum and a striped projection on the ipsilateral, doubly innervated, tectum. The projection made by the unoperated nerve on this tectum was a similar pattern of stripes, which ran generally rostrocaudally. Two months after transection of the optic nerve of newly metamorphosed animals, the projection formed by the operated nerve on the doubly innervated tectum was usually a pattern of spots or spots mixed together with stripes in no particular orientation superimposed on a roughly uniform background. In a small number of cases the projections made by the same nerve on the two tecta were approximately complementary; that is, the presence of label on one tectum corresponded with its absence on the other tectum.
The results are examined in the context of the development of the retina and of the tectum. It is suggested that the consistently oriented stripes which result from nerve transection at a stage at which only a small proportion of the retinal fibres had reached the tectum are formed by the interaction of two equally matched sets of developing fibres, stripe orientation being determined by the mode of growth of the optic tectum. The formation of patterns of spots or spots mixed together with stripes following nerve transection after the end of the main phase of tectal histogenesis, and when 50 % of the optic fibres had already reached the tectum, is attributed to an unequal competition between the two sets of fibres.
A physiological measure of shifting connections in the Rana pipiens retinotectal system
Authors: Fraser Scott E. , Hunt R. Kevin 
Published: April 2021

ABSTRACT
The retinotectal connections of developing Rana tadpoles and froglets have been studied using light-pipe techniques to directly assay the pattern of the projection from the retina to the tectum. The projection site of the retina surrounding the optic nerve head was determined at two different stages of development (late larval and metamorphic frog) on the same animal. Small electrolytic marker lesions were used to mark the tectal sites to which the optic nerve head projected at these two times. Comparison of the positions of the two lesions gives a direct measure of the shift in the projection during the interlesion time interval of one week. The results indicate a shift in the projection of 275 μm week−1 in late larval life. Previous work in Xenopus using the light-pipe techniques indicated a qualitatively similar shift during equivalent stages of development, but significantly smaller in magnitude. In the present study, topographic postsynaptic units could be recorded at all stages investigated, indicating functional synapses between the optic nerve fibres and the tectum. Thus, these studies offer evidence of a significant shift in the functional connection pattern of the amphibian retinotectal map during development, in agreement with the recent anatomical data from other laboratories on the Rana and goldfish visual system.
Protein requirements for germinal vesicle breakdown in ovine oocytes
Authors: Moor R. M. , Crosby I. M. 
Published: April 2021

ABSTRACT
The regulation of the cell cycle during the transition from prophase to metaphase I was studied by analysing protein changes and introducing protein blocks during the transition phase. The results show that the progression to metaphase in ovine oocytes is totally dependent on new protein synthesis. By delaying the addition of the inhibitor, cycloheximide, for progressively longer periods after the resumption of meiosis it was established that the required synthesis occurs in the 1–2 h immediately preceding germinal vesicle breakdown (GVBD). The action of cycloheximide was fully reversible: removal of the drug resulted in GVBD between 3 and 4h later.
The synthesis and modification of proteins during these first few hours of maturation were studied by short-term radiolabelling of oocytes with [35S]methionine and [32P]phosphate followed by rapid assessment of their precise nuclear configuration. Changes in phosphorylation of two polypeptides were detected 4–5 h after the beginning of culture, but these changes were not dependent upon protein synthesis. The earliest change in synthesis was the appearance of a new polypeptide 6–8 h after explantation, immediately before GVBD. This polypeptide (Mr 47×103, pI 5·8) was not significantly phosphorylated and was relatively stable. Oocytes released from cycloheximide treatment began to synthesize this molecule 3–4 h later, again coinciding with GVBD. Synthesis of the polypeptide was suppressed by inhibition of transcription with α-amanitin.
Reconstruction of bipinnaria larvae from dissociated embryonic cells of the starfish, Asterina pectinifera
Authors: Dan-Sohkawa M. , Yamanaka H. , Watanabe K. 
Published: April 2021

ABSTRACT
Cells dissociated from swimming embryos of the starfish are able to reconstruct bipinnaria larvae. This process consists of reaggregation (stage 1), formation of the external epithelium (stage 2), development of the internal cavities which will eventually grow either into the blastocoel or the intestinal lumen (stage 3), gastrulation or fusion of the internal and the external epithelia (stage 4), formation of the mouth (stage 5) and the established bipinnaria (stage 6).
The optimal population of cells to support the process of reconstruction is estimated to fall between 500 and 1000, values corresponding to one eighth and one fourth the total number of cells of a normal embryo, respectively.
Morphogenetic events of reconstruction are discussed in relation to the normal course of starfish development and to the reconstruction process of the sea urchin.
A potential role for spectrin during neurulation
Authors: Sadler T. W. , Burridge Keith , Yonker J. 
Published: April 2021

ABSTRACT
An actin-myosin complex located in apical regions of the neurectoderm has been postulated to play a role in neurulation. Numerous studies have documented the presence of microfilaments in this area and confirmed their composition as actin. By necessity, if such a contractile system is to exert a force, these filaments must be anchored in some way to the cell membrane. In this study, the presence of the actin-binding protein, spectrin (fodrin), is demonstrated in the neurectoderm of neurulating mouse embryos using antispectrin antibodies and indirect immunofluorescent techniques. The patterns of spectrin localization correlate with the previously reported regions of increased numbers of microfilaments and also with the morphology of the neural folds. Thus, during the initial stages of cranial fold elevation, a process reportedly dependent on increased glycosaminoglycan synthesis, little spectrin is present in the neuroepithelial cells. Later as the folds begin to converge toward the midline, deposition of the protein, as demonstrated by the intensity of fluorescence, is increased in the apices of these cells, and is most prominent in regions of greatest bending in the neural folds. Caudal neural fold regions show a similar pattern of staining. Thus, the hypothesis that a cytoskeletal system assists in neurulation is supported by these results, which for the first time demonstrate the presence of a putative actin-membrane attachment protein in a morphogenetically active system.
The distribution of fibronectin, laminin and entactin in the neurulating rat embryo studied by indirect immunofluorescence
Authors: Tuckett Fiona , Morriss-Kay Gillian M. 
Published: April 2021

ABSTRACT
This paper forms part of our study of the extracellular matrix and its role in the morphogenesis of the brain during the period of neurulation in the rat embryo. Using indirect immunofluorescence with polyclonal antibodies, we present here a descriptive study of the distribution of the matrix glycoproteins fibronectin, laminin and entactin.
The observed distribution of the fibronectin matrix implicates it in providing a structural element in several morphologically active sites; in addition our observations support the previously suggested involvement of fibronectin in the migration of neural crest cells. Entactin was present only in the basement membranes in conjunction with laminin which was not itself confined to these regions. Laminin was also identified within the mesenchymal extracellular matrix, and its general distribution confirms the previously documented role of laminin in maintaining epithelial structure and organization. No patterning in the distribution of these three glycoproteins could be correlated with the change in shape of the neural epithelium associated with either tube formation or neuromere morphogenesis.
Effect of alterations in follicular steroidogenesis on the nuclear and cytoplasmic maturation of ovine oocytes
Authors: Osborn J. C. , Moor R. M. , Crosby I. M. 
Published: April 2021

ABSTRACT
The effects of inhibitors of follicular steroidogenesis on biochemical changes occurring in oocytes maturing in vitro were studied using radiolabelling and polyacrylamide gel electrophoresis. These effects were correlated with previously investigated developmental abnormalities induced by the same inhibitors.
The most severe effects were generated by inhibition of 17α-hydroxylase with the drug SU10603 which resulted in a greatly increased ratio of progesterone to testosterone and oestrogen. Such treatment halved the rate of meiotic maturation. Treated oocytes were analysed individually on SDS-PAGE gels and quantitative analysis showed that the drug had induced synthetic abnormalities even in those oocytes that resumed meiosis. This conclusion was confirmed by separation of oocyte proteins on two-dimensional gels. The effects of SU were reduced by delaying addition of the drug until 6 h after the beginning of maturation but were not alleviated by the addition of exogenous oestrogen to the culture medium. When oocytes from SU-treated follicles were transferred to inseminated, recipient ewes and recovered 24h later, two-dimensional electrophoresis again revealed abnormalities in their protein synthetic patterns.
Almost total abolition of steroid secretion by aminoglutethimide (AG) had much less effect on oocyte protein synthesis, although the proportion of oocytes maturing was reduced from 65 % to 46 %. The aromatase inhibitor, androstatriendione (AST) although eliminating follicular oestrogen secretion, had no effect on the rate of maturation and very little effect on protein synthesis. These results correlate well with the effects of steroid inhibitors on fertilization and early cleavage.
Size regulation in the mouse embryo: II. The development of half embryos
Authors: Rands G. F. 
Published: April 2021

ABSTRACTThe study describes an analysis of the development of mouse embryos halved at the 2-cell stage by the destruction of one blastomere, in comparison with control embryos of parallel derivation, at 2·5–13·5 dayspostcoitum. The results showed that: (1) half embryos achieve size regulation some time between 7·5 and 10·5 days; (2) there is an indication that by 13·5 days half embryos may have again dropped back significantly in size relative to controls; (3) preregulation half embryos are slightly retarded developmentally, but this does not wholly account for their smaller size: morphogenesis is not size-dependent; (4) early postimplantation half embryos contain a significantly decreased proportion of inner cell mass derivatives and increased proportion of trophectoderm derivatives when compared with controls.A comparison is also made between the up-regulation of half embryos and the downregulation of aggregate embryos, and it is suggested that size regulation may occur by delaying a change in the normal growth rate.
Temporal and regional changes in DNA methylation in the embryonic, extraembryonic and germ cell lineages during mouse embryo development
Authors: Monk Marilyn , Boubelik Michael , Lehnert Sigrid 
Published: April 2021

ABSTRACTThis paper shows stage- and tissue-specific global demethylation and remethylation occurring during embryonic development. The egg genome is strikingly undermethylated and the sperm genome relatively methylated. Following a loss of genomic methylation during preimplantation development, embryonic and extraembryonic lineages are progressively and independently methylated to different final extents. Methylation continues postgastrulation and hence could be a mechanism initiating, or confirming, differential programming in the definitive germ layers. It is proposed that much of the methylation observed in somatic tissues acts to stabilize and reinforce prior events that regulate the activity of specific genes, chromosome domains or the X chromosome (in females). Fetal germ cell DNA is markedly undermethylated and we favour the idea that the germ lineage is set aside before the occurrence of extensive methylation of DNA in fetal precursor cells.
Fate map for the 32-cell stage ofXenopus laevis
Authors: Dale L. , Slack J. M. W. 
Published: April 2021

AbstractA complete fate map has been produced for the 32-cell stage of Xenopus laevis. Embryos with a regular cleavage pattern were selected and individual blasto-meres were injected with the lineage label fluorescein–dextran–amine (FDA). The spatial location of the clones was deduced from three-dimensional (3D) re-constructions of later stages and the volume of each tissue colonized by labelled cells in each tissue was measured.The results from 107 cases were pooled to give a fate map which shows the fate of each blastomere in terms of tissue types, the composition of each tissue by blastomere, the location of each prospective region on the embryo and the fate of each blastomere in terms of spatial localization.Morphogenetic movements up to stage 10 (early gastrula) were assessed by carrying out a number of orthotopic grafts at blastula and gastrula stages using donor embryos uniformly labelled with FDA.Although there is a regular topographic projection from the 32-cell stage this varies a little between individuals because of variability of positions of cleavage planes and because of short-range cell mixing during gastrulation. The cell mixing means that the topographic projection fails for anteroposterior segments of the dorsal axial structures and it is not possible to include short segments of notochord or neural tube or individual somites on the pregastrulation fate map.
The ultrastructure of normal fetal and neonatal pig testis germ cells and the influence of fetal decapitation on the germ cell development
Authors: Van Vorstenbosch C. J. A. H. V. , Spek E. , Colenbrander B. , Wensing C. J. G. 
Published: April 2021

AbstractThe development of germ cells in the male pig was investigated ultrastructurally in normal and decapitated fetuses. The age ranged respectively from 30 days p.c. till one month after birth and from 52 days p.c. until birth. The ultrastructural organization of the germ cells changes dramatically between 30 days p.c. and 52 days p.c. which coincides with the formation of ‘true’ sex cords. From 52 days p.c. onwards the morphology is rather stable: cells show a ‘hydrated’ appearance and typical cell bridges. There is no obvious difference in the ultrastructure of germ cells in decapitated animals, their normal littermates and control animals. Therefore germ cell development in the pig is likely to be insensitive to gonadotropins during the fetal period. The development of pig germ cells follows closely the pattern described for several species. Quantitatively there is an increase in the ratio of germ cell/Sertoli cell per cross sectional diameter in the decapitated animals.
BDNF-GFP containing secretory granules are localized in the vicinity of synaptic junctions of cultured cortical neurons
Authors: Haubensak Wulf , Narz Frank , Heumann Rolf , Leβmann Volkmar 
Published: April 2021

ABSTRACT
The protein family of mammalian neurotrophins, comprising nerve-growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 and -4/5 (NT-3, NT-4/5), supports the survival and the phenotype of neurons from the central as well as the peripheral nervous system (CNS, PNS). In addition, exogenous application of neurotrophins has recently been found to modulate synaptic transmission in the rodent CNS. However, to provide evidence for a role of neurotophins as endogenous fast acting modulators of synaptic transmission, the synaptic localization and secretion of neurotrophins needs to be shown.
We have now constructed a fusion protein consisting of N-terminal BDNF (the most abundant neurotrophin in the rodent hippocampus and neocortex) and C-terminal green fluorescent protein (GFP) to elucidate the cellular localization of BDNF in cortical neurons. Transient expression of BDNF-GFP in COS-7 cells revealed that the cellular localization in the trans-Golgi network (TGN), the processing of precursor proteins and the secretion of mature BDNF-GFP is indistinguishable from the properties of untagged BDNF.
Upon transient transfection of primary rat cortical neurons, BDNF-GFP was found in secretory granules of the regulated pathway of secretion, as indicated by colocalization with the secretory granule marker secretogranin II. BDNF-GFP vesicles were found in the neurites of transfected neurons with a pattern reminiscent of the localization of endogenous BDNF in untransfected cortical neurons. BDNF-GFP vesicles were found predominantly in the somatodendritic compartment of the neurons, whereas additional axonal localization was found less frequently. Immunocytochemical staining of synaptic terminals with synapsin I antibodies revealed that the density of BDNF-GFP vesicles is elevated in the vicinity of synaptic junctions, indicating that BDNF is localized appropriately to function as an acute modulator of synaptic transmission.
These data suggest that BDNF-GFP will be a useful tool to investigate synaptic release of BDNF during physiological synaptic stimulation, and will thereby allow us to elucidate the participation of neurotrophin release in activity dependent synaptic plasticity.
The RNP protein, RNPS1, associates with specific isoforms of the P34CDC2 related PITSLRE protein kinase in vivo
Authors: Loyer Pascal , Trembley Janeen H. , Lahti Jill M. , Kidd Vincent J. 
Published: April 2021

ABSTRACT
The PITSLRE protein kinases are members of the p34cdc2 superfamily, with &gt;20 different isoforms expressed from two linked genes in humans. PITSLRE homologues have been identified in mouse, chicken, Drosophila, Xenopus, and possibly Plasmodium falciparum, suggesting that their function may be well conserved. A possible role for a caspase processed PITSLRE isoform has been suggested by studies of Fas- and TNF-induced cell death. However, the function of these kinases in proliferating cells is still unknown. Here we demonstrate that the 110 kDa PITSLRE isoforms (p110) are localized to both the nucleoplasm and nuclear speckles, and that these isoforms specifically interact in vitro and in vivo with the RNA-binding protein RNPS1. RNPS1 is also localized to nuclear speckles, and its over expression disrupts normal nuclear speckle organization by causing the aggregation of many nuclear speckles into ∼6 ‘mega’ speckles. This type of nuclear speckle aggregation closely resembles what occurs when cells are treated with several transcriptional inhibitors. These data indicate that the PITSLRE p110 isoforms interact with RNPS1 in vivo, and that these proteins may in turn influence some aspect of transcriptional and/or splicing regulation.
Role of fungal dynein in hyphal growth, microtubule organization, spindle pole body motility and nuclear migration
Authors: Inoue S. , Turgeon B. G. , Yoder O. C. , Aist J. R. 
Published: April 2021

ABSTRACT
Cytoplasmic dynein is a microtubule-associated motor protein with several putative subcellular functions. Sequencing of the gene (DHC1) for cytoplasmic dynein heavy chain of the filamentous ascomycete, Nectria haematococca, revealed a 4,349-codon open reading frame (interrupted by two introns) with four highly conserved P-loop motifs, typical of cytoplasmic dynein heavy chains. The predicted amino acid sequence is 78.0% identical to the cytoplasmic dynein heavy chain of Neurospora crassa, 70.2% identical to that of Aspergillus nidulans and 24.8% identical to that of Saccharomyces cerevisiae. The genomic copy of DHC1 in N. haematococca wild-type strain T213 was disrupted by inserting a selectable marker into the central motor domain. Mutants grew at 33% of the wildtype rate, forming dense compact colonies composed of spiral and highly branched hyphae. Major cytological phenotypes included (1) absence of aster-like arrays of cytoplasmic microtubules focused at the spindle pole bodies of post-mitotic and interphase nuclei, (2) limited postmitotic nuclear migration, (3) lack of spindle pole body motility at interphase, (4) failure of spindle pole bodies to anchor interphase nuclei, (5) nonuniform distribution of interphase nuclei and (6) small or ephemeral Spitzenkörper at the apices of hyphal tip cells. Microtubule distribution in the apical region of tip cells of the mutant was essentially normal. The nonuniform distribution of nuclei in hyphae resulted primarily from a lack of both post-mitotic nuclear migration and anchoring of interphase nuclei by the spindle pole bodies. The results support the hypothesis that DHC1 is required for the motility and functions of spindle pole bodies, normal secretory vesicle transport to the hyphal apex and normal hyphal tip cell morphogenesis.