bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inhibition of proteoglycan synthesis eliminates left-right asymmetry in Xenopus laevis cardiac looping
Authors: Yost H. Joseph 
Published: April 2021

Abstract
The heart of any vertebrate is formed from an apparently symmetric cardiac tube that loops consistently in the same direction along the left-right axis of the embryo. In the amphibian Xenopus laevis, inhibition of proteoglycan synthesis by p-nitrophenyl-β-D-xylopyranoside during a narrow period of development from late gastrula to early neurula specifically eliminated the looping of the cardiac tube. Most of the proteoglycans synthesized during this period were heparan sulfate proteoglycans. Treatment with p-nitrophenyl-α-D-xylopyranoside, an analogue that does not inhibit proteoglycan synthesis, did not interfere with cardiac looping. The critical period for proteoglycan synthesis was coincident with the migration of cardiac primordia to the ventral midline. The inhibition of cardiac looping was further explored in expiants of cardiac primordia and anterioventral ectoderm. In recombinate embryos in which half the embryo, and thus one of the two heart primordia, was treated with p-nitrophenyl-β-D-xylopyranoside, and the other half was untreated, cardiac looping occurred normally. It is proposed that the left-right axis in Xenopus, as reflected in cardiac looping, is established early in development, and that proteoglycan synthesis is involved in the transduction of left-right axial information to the cardiac primordia during migration.
The dorsoventral axis is specified prior to first cleavage in the direct developing sea urchin Heliocidaris erythrogramma
Authors: Henry Jonathan J. , Wray Gregory A. , Raff Rudolf A. 
Published: April 2021

Abstract
Previous fate mapping studies as well as the culture of isolated blastomeres have revealed that the dorsoventral axis is specified as early as the 2-cell stage in the embryos of the direct developing echinoid, Heliocidaris erythrogramma. Normally, the first cleavage plane includes the animal-vegetal axis and bisects the embryo between future dorsal and ventral halves. Experiments were performed to establish whether the dorsoventral axis is set up prior to the first cleavage division in H. erythrogramma. Eggs were elongated and fertilized in silicone tubes of a small diameter in order to orient the cleavage spindle and thus the first plane of cell division. Following first cleavage, one of the two resulting blastomeres was then microinjected with a fluorescent cell lineage tracer dye. Fate maps were made after culturing these embryos to larval stages. The results indicate that the first cleavage division can be made to occur at virtually any angle relative to the animal-vegetal and dorsoventral axes. Therefore, the dorsoventral axis is specified prior to first cleavage. We argue that this axis resides in the unfertilized oocyte rather than being set up as a consequence of fertilization.
Isolation of an abdominal-A gene from the locust Schistocerca gregaria and its expression during early embryogenesis
Authors: Tear Guy , Akam Michael , Martinez-Arias Alfonso 
Published: April 2021

Abstract
Using sequence homology to Drosophila homeobox-containing genes, we have cloned a homologue of abdominal-A from the locust Schistocerca gregaria. The Schistocerca clone encodes a stretch of 78 amino acids including the homeodomain and its flanking regions identical to the corresponding region of abdominal-A.
We have shown by in situ hybridization that this gene is transcribed and have used an antibody raised against its protein product to examine the expression of abdominal-A during early Schistocerca embryogenesis. Schistocerca is a short germ insect. Although the segmented body plan is very similar to that of Drosophila, the segments are generated sequentially by a process of growth, not simultaneously by subdivision of a syncytial blastoderm. In both organisms, abdominal-A is expressed throughout the abdomen from a sharp anterior boundary located within the first abdominal segment (Al). The initial activation of the genes in the two species differs. Schistocerca initiates expression in a small group of cells in the anterior of A2, shortly after this segment is defined by the appearance of engrailed protein. This contrasts with the appearance of abdominal-A expression in Drosophila, which appears simultaneously throughout the entire abdomen.
Two distinct mechanisms localise cyclin B transcripts in syncytial Drosophila embryos
Authors: Raff Jordan W. , Whitfield William G. F. , Glover David M. 
Published: April 2021

Abstract
We demonstrate that two independent mechanisms act on maternally derived cyclin B transcripts to concentrate the transcripts at the posterior pole of the Drosophila oocyte and at the cortex of the syncytial embryo. The cortical accumulation occurs because the cyclin B transcript is concentrated around nuclei and comigrates with them to the cortex. The perinuclear localisation of the transcript is blocked by inhibitors of microtubule polymerisation and the transcript colocalises with microtubular structures during the cell cycle, suggesting that the transcript is associated either directly or indirectly with microtubules. Neither microtubules nor actin filaments are required to maintain the posterior concentration of cyclin B transcripts. Instead, this seems to depend on the association of the transcripts with a component of the posterior cytoplasm. The distribution pattern of the transcript at the posterior pole throughout embryogenesis and in a variety of mutant embryos suggests that this component is associated with polar granules.
Expression in non-lens tissues of an enzyme activity related to the ‘lensspecific’ protein, δ crystallin
Authors: Pomerai D. I. De , Ip W. K. , Laughlin M. Mc , Perry K. C. 
Published: April 2021

ABSTRACT
When chick embryo neural retina (NR) cells are cultured for long periods in vitro, they undergo extensive trans differentiation into lens and express the lens protein, δcrystallin. We now demonstrate that this process is accompanied by a change in the chromatin conformation of the δ-gene locus from DNAasel-resistant to DNAasel-sensitive in the nuclei of most cells. Transcripts hybridising to a δprobe are also much more prevalent among the in vitro transcription products from lens or transdifferentiated NR culture nuclei, as compared to nuclei from fresh NR tissue. Published evidence indicates that the chick δ1 crystallin gene encodes the major structural protein of embryonic lens fibres, whereas the closely related δ2 gene may encode the urea-cycle enzyme argininosuccinate lyase (ASL). Our present data lends further support to this view. Both immunodetectable δ-related protein(s) and ASL activity are present in fresh embryonic NR tissue, as well as in mouse and Rana liver, and in Rana lens. Our polyclonal anti-δ antibody also cross-reacts with a major constituent of commercial bovine ASL, of the same molecular size as chick δcrystallin. Immunoselection studies suggest that the ASL activity in chick embryonic NR is conferred mainly by the δ-related protein band. So-called ‘ectopic’ expression of δ crystallin in embryonic NR (and other tissues) may thus involve the δ2/ASL gene, and could reflect some metabolic requirement for ASL activity.
In situ localization of storage protein mRNAs in developing meristems of Brassica napus embryos
Authors: Fernandez Donna E. , Turner F. Rudolf , Crouch Martha L. 
Published: April 2021

Abstract
Probes derived from cDNA clones of napin and cruciferin, the major storage proteins of Brassica napus, and in situ hybridization techniques were used to examine changes in the spatial and temporal distribution of storage protein messages during the course of embryogeny, with a special emphasis on the developing apical meristems. Napin mRNAs begin to accumulate in the cortex of the axis during late heart stage, in the outer faces of the cotyledons during torpedo stage and in the inner faces of the cotyledons during cotyledon stage. Cruciferin mRNAs accumulate in a similar pattern but approximately 5 days later. Cells in the apical regions where root and shoot meristems develop do not accumulate storage protein messages during early stages of embryogeny. In the upper axis, the boundary between these apical cells and immediately adjacent cells that accumulate napin and cruciferin mRNAs is particularly distinct. Our analysis indicates that this boundary is not related to differences in tissue or cell type, but appears instead to be coincident with the site of a particular set of early cell divisions. A major change in the mRNA accumulation patterns occurs halfway through embryogeny, as the embryos enter maturation stage and start drying down. Final maturation of the shoot apical meristem is associated with the development of leaf primordia and the accumulation of napin mRNAs in the meristem, associated leaf primordia and vascular tissue. Cruciferin mRNAs accumulate only in certain zones of the shoot apical meristem and on the flanks of leaf primordia. Neither type of mRNA accumulates in the root apical meristem at any stage.
Development of the Xenopus laevis hatching gland and its relationship to surface ectoderm patterning
Authors: Drysdale Thomas A. , Elinson Richard P. 
Published: April 2021

Abstract
An antibody that recognizes tyrosine hydroxylase can be used as a marker for hatching gland cells in Xenopus embryos. Using this marker, we have shown that hatching gland cells are induced at the end of gastrulation and that presumptive hatching gland cells are localized to the anterior neural folds in Xenopus. The movements of neurulation bring the hatching gland cells together to form a characteristic Y pattern on the dorsoanterior surface of the head. The Y pattern delineates several zones of surface ectoderm which can be visualized by the presence or absence of ciliated cells. As development proceeds the hatching gland pattern is altered, demonstrating the active changes involved in forming the face. Lithium, UV irradiation and retinoic acid can be used to alter the hatching gland pattern in specific ways which help to understand the underlying mechanisms of ectodermal patterning.
Identification and expression of a regeneration-specific homeobox gene in the newt limb blastema
Authors: Brown Robin , Brockes Jeremy P. 
Published: April 2021

Abstract
Adult urodele amphibians are able to regenerate their limbs through the formation of a blastema, a growth zone of undifferentiated mesenchymal cells that arises locally at the plane of amputation. In an effort to define genes involved in pattern formation by the blastema, we isolated from a newt forelimb blastema library cDNA clones that identify a homeobox gene termed NvHbox 2. The amino acid sequence of the homeodomain is identical to that of the recently identified human H0X-4f gene (Acampora et al. 1989) and of the mouse Hox-5.5 (Dolle et al. 1989). NvHbox 2 is expressed in the limb blastema as a transcript of 3.4 kb that is not detectable in the normal limb. Analysis by RNAase protection demonstrates expression in limb and tail blastemas, but not in any of the adult tissues or organs tested. In the limb blastema NvHbox 2 was expressed in mesenchymal but not epithelial tissue. When matched and normalised samples of RNA from proximal (mid-humerus) and distal forelimb (mid-radius) blastemas were compared, the level of expression of NvHbox 2 was found to be 3- to 5-fold higher proximally. At two time points after injection of a proximalising dose of retinoic acid, the level of expression in a distal blastema was not increased in comparison to controls.
Isolation and characterisation of a testis-expressed developmentally regulated gene from the distal inversion of the mouse t-complex
Authors: Mazarakis Nicholas D. , Nelki Daniel , Lyon Mary F. , Ruddy S. , Evans E. P. , Freemont Paul , Dudley Keith 
Published: April 2021

Abstract
We differentially screened a pool of mouse testis clones in order to identify genes important in germ cell development. One of the isolated clones was found to be expressed only in the male germ line where it is first detected at around the pachytene spermatocyte stage. This gene maps to a subregion of the t-complex in the distal inversion near, but not within, the twI8 and the th20 deletions. A comparison of the t and wild forms of the gene reveals a high degree of sequence conservation. This gene is associated with a CpG-rich island at its 5’ end. It encodes a novel protein with extensive α-helical structure indicative of coiled-coil interactions.
Inherited type of allelic methylation variations in a mouse chromosome region where an integrated transgene shows methylation imprinting
Authors: Sasaki Hiroyuki , Hamada Tsuyoshi , Ueda Takayuki , Seki Ritsuko , Higashinakagawa Toru , Sakaki Yoshiyuki 
Published: April 2021

Abstract
It is still unclear whether or not parent-of-origin-dependent differential methylation observed in some transgenes reflects genomic imprinting of endogenous genes. We have characterized a transgene locus showing such methylation imprinting together with the corresponding-native chromosome region. We show that only part of the transgene is affected by methylation imprinting and the methylation pattern is established before early prophase I during spermatogenesis. Interestingly, the native genomic region, which is mapped to the proximal chromosome 11, shows no evidence of methylation imprinting but displays heri-table, strain-specific type of allelic methylation differences. The results demonstrate that transgenes do not necessarily reflect the methylation status of either the surrounding or corresponding chromosome region. In addition, inherited type of allelic methylation variations previously described in human may be widespread in mammals.
Mitogenic activity of chicken chorioallantoic fluid is temporally correlated to vascular growth in the chorioallantoic membrane and related to fibroblast growth factors
Authors: Flamme Ingo , Schulze-Osthoff Klaus , Jügen Jacob Heinz 
Published: April 2021

ABSTRACT
The chorioallantoic membrane (CAM) is one of the most vascularized tissues in the chicken embryo. Capillary growth proceeds until day 10 of development and thereafter abruptly regresses. As it is generally accepted that the formation of new blood vessel is regulated by growth factors, we have investigated the presence of angiogenic and mitogenic factors in the chicken chorioallantois.
In the present study, we show that chorioallantoic fluid (CAF) contains angiogenic substances that are probably synthesized in the CAM or the embryonic kidney. When applied in the chorioallantoic membrane assay, CAF from 9 day chicken embryos elicits a strong angiogenic response. This angiogenic activity of CAF is associated with pronounced mitogenic effects in vitro. Comparison of different embryonic fluids reveals that mitogenic activity is particularly evident in the CAF but not detectable in embryonic serum and amnion fluid. Expression of mitogenic activity is found to be temporally correlated with vascular growth in the CAM. High activity is detected in CAF prior to day 10 and then sharply decreases, thus preceding termination of capillary growth by one day.
Heparin–sepharose affinity chromatography suggests that the biological activities of CAF probably correspond to the presence of acidic and basic fibroblast growth factor (aFGF and bFGF). In Western blot analyses of CAF, an immunoreactive bFGF-like protein of about 17×103Mr is recognized by a monospecific anti-bFGF antiserum. This protein elutes at 2.4 M NaCl from the heparin-sepharose. The mitogenic activity of the CAF can be specifically blocked by the anti-bFGF antibody indicating bFGF to be the active mitogenic principle of the CAF.
These results strongly suggest that basic and probably acidic FGF play an important role in the regulation of chorioallantoic vascular growth.
Differential expression of type I and type III collagen genes during tooth development
Authors: Andujar Mauricio B. , Couble Pierre , Couble Marie-Lise , Magloire Henri 
Published: April 2021

ABSTRACT
Collagen gene expression during mouse molar tooth development was studied by quantitative in situ hybridization techniques. Different expression patterns of type I and type HI collagen mRNAs were observed in the various mesenchymal tissues that constitute the tooth germ. High concentration for pro-alpha 1(1) and proalpha 2(1) collagen mRNAs were found within the osteoblasts. We found that the cellular content of type I collagen mRNAs in the odontoblasts varies throughout the tooth formation: whereas mRNA concentration for pro-alpha 1(1) collagen decreases and that of pro-alpha 2(1) increases, during postnatal development. Moreover, different amounts of pro-alpha 1(1) and pro-alpha 2(1) collagen mRNAs were observed in crown and root odontoblasts, respectively. Type HI collagen mRNAs were detected in most of the mesenchymal cells, codistributed with type I collagen mRNAs, except in odontoblasts and osteoblasts.
Finally, this study reports differential accumulation of collagen mRNAs during mouse tooth development and points out that type I collagen gene expression is regulated by distinct mechanisms during odontoblast differentiation process. These results support the independent expression of the collagen genes under developmental tissue-specific control.
The Drosophila gene Serrate encodes an EGF-like transmembrane protein with a complex expression pattern in embryos and wing discs
Authors: Thomas Ulrich , Speicher Stephan A. , Knust Elisabeth 
Published: April 2021

ABSTRACT
We describe the molecular characterization of the Drosophila gene Serrate (Ser), which encodes an integral membrane protein. The extracellular domain contains two cysteine-rich regions, one of which is organized in a tandem array of 14 EGF-like repeats. Antibodies directed against part of the extracellular region confirm the localization of the protein in the membrane. In the wing imaginai discs, the protein is detected in those regions that are affected in the wings of two dominant mutations, SerD and SerBd. Both mutations as well as three out of eight newly induced revertants of SerD could be mapped molecularly to the transcribed region, confirming the identity between the gene Ser and the transcription unit characterized. During embryonic development, RNA and protein exhibit a complex expression pattern, which is, however, not correlated with an appropriate embryonic phenotype. Phenotypic interactions of Ser alleles with the neurogenic genes Notch and Delta coupled with the structural similarity of the proteins encoded by these three genes suggest close interactions at the protein level.
Patterns of microtubule polymerization relating to cortical rotation in Xenopus laevis eggs
Authors: Houliston Evelyn , Elinson Richard P. 
Published: April 2021

ABSTRACT
Following fertilization, the Xenopus egg cortex rotates relative to the cytoplasm by 30° about a horizontal axis. The direction of rotation, and as a result the orientation of the embryonic body axes, is normally specified by the position of sperm entry. The mechanism of rotation appears to involve an array of aligned microtubules in the vegetal cortex (Elinson and Rowning, 1988, Devi Biol. 128, 185–197). We performed anti-tubulin immunofluorescence on sections to follow the formation of this array. Microtubules disappear rapidly from the egg following fertilization, and reappear first in the sperm aster. Surprisingly, astral microtubules then extend radially through both the animal and vegetal cytoplasm. The cortical array arises as they reach the vegetal cell surface. The eccentric position of the sperm aster gives asymmetry to the formation of the array and may explain its alignment since microtubules reaching the cortex tend to bend away from the sperm entry side. The radial polymerization of cytoplasmic microtubules is not dependent on the sperm aster or on the female pronucleus: similar but more symmetric patterns arise in artificially activated and enucleate eggs, slightly later than in fertilized eggs.
These observations suggest that the cortical microtubule array forms as a result of asymmetric microtubule growth outward from cytoplasm to cortex and, since cortical and cytoplasmic microtubules remain connected throughout the period of the rotation, that the microtubules of the array rotate with the cytoplasm.
The effect of age on motor neurone death following axotomy in the mouse
Authors: Pollin M. M. , Mchanwell S. , Slater C. R. 
Published: April 2021

ABSTRACT
The ability of mouse motor neurones to survive axotomy during the first month of life was studied. The motor neurones that lie in the dorsolateral columns of spinal segments C7 and C8 and supply the flexor muscles of the forepaw were axotomized by cutting and removing part of the median and ulnar nerves above the elbow. The number and position of cell bodies with axons in these nerves were confirmed by retrograde labelling of the cut axons with horseradish peroxidase. The ability of these neurones to survive axotomy varies with the age of the animal at the time of axotomy. When the axons are sectioned within the first four postnatal days, 80—90 % of the cell bodies will die, more than half of this death occurring in less than one week after axotomy. If the animals are one week old at the time the nerves are cut, a significantly smaller number (50 %) die (P=0.013), and the time-course of death is different, with eight to ten days elapsing before half the death has occurred. 40 % of the neurones will die if sectioned at two weeks of age, and it is not until four weeks of age that more than 90 % of the cells can survive axotomy.
We conclude, therefore, that the kinetics of motor neurone death, as well as the final extent of neuronal loss, are affected by the age at which the animal is axotomized.
Changes in the expression of laminin during intestinal development
Authors: Simo P. , Simon-Assmann P. , Bouziges F. , Leberquier C. , Kedinger M. , Ekblom P. , Sorokin L. 
Published: April 2021

ABSTRACT
The expression of laminin, a major glycoprotein constituent of basement membranes, was investigated in the rat developing intestine. The biosynthesis of laminin was studied after metabolic labeling of intestinal segments taken at various stages of development; the neosynthesized laminin was purified by affinity chromatography on heparin–Sepharose. Immunoblotting and immunoprecipitation experiments allowed us to analyze its constitutive chains. The data show that laminin is synthesized in very large amounts at 16–18 days of gestation concomitant with the onset of intestinal morphogenetic movements, i.e. villus emergence. Evaluation of the relative proportion of individual laminin polypeptides shows that laminin B1/B2 chains are produced in excess of A chains whatever the developmental stage considered. Interestingly at 17 days of gestation, levels of laminin A subunits are maximal. A second rise in the A/B chain ratio starts around birth and continues until adulthood. These quantitative data are corroborated by the immunocytochemical detection of laminin A and B chains, which revealed a specific spatiotemporal pattern. The finding that laminin A chains are located in the basement membrane of growing villi and of adult crypts raises the possibility that they may be involved in the process of cell growth and/or in the establishment of cell polarity by creating a specialized extracellular microenvironment.