bluuebunny/crossref_metadata_2025 huggingface dataset:
Serine metabolism in rat embryos undergoing organogenesis
Authors: Rowe Peter B. , Kalaizis Annette
Published: April 2021

Rat embryos (9·5 days gestation) were cultured for 48 h in heat-inactivated homologous serum containing [3-14C] serine. Analysis of the distribution of the radioactive label in the conceptus demonstrated that almost one half of the incorporated serine was cleaved to provide one-carbon units for the synthesis of purine and pyrimidine nucleotides. Analysis of the free amino acids in the serum, the exocoelomic fluid and the cells of the yolk sac and the embryo showed that there was a variably selective increase in the concentration of amino acids in the exocoelomic fluid compared with the serum and a significant decrease in the specific radioactivity of the free serine within the conceptus which was the highest in the yolk sac and lowest in the embryo. These findings would support the concept of yolk sac lysosomal degradation of medium serum protein as a major source of amino acids supplying almost 86 % of that required during this phase of embryonic development.

The specific radioactivity of purine bases in cellular nucleotides, RNA and DNA was similar to that of the free serine in both yolk sac and embryo. This indicated that an alternative, as yet unidentified source of one-carbon units was available for purine nucleotide biosynthesis.

Analysis of the cellular purine nucleotides revealed low ATP/GTP ratios in both the embryo and its yolk sac and this may be related to the undifferentiated state of many of the cells of the conceptus.
Sequence and regulation of morphological and molecular events during the first cell cycle of mouse embryogenesis
Authors: Howlett Sarah K. , Bolton Virginia N.
Published: April 2021

Mouse oocytes were fertilized in vitro and the precise timing and sequence of morphological and molecular events occurring during the first cell cycle were investigated. The timing of development through the first cell cycle was found to be initiated by an event associated with sperm penetration rather than with germinal vesicle breakdown. DNA replication is initiated randomly in either pronucleus of a given egg, beginning approximately 11 h post insemination (hpi), and S phase lasting 6−7 h in both. Careful study of polypeptide synthetic profiles revealed three classes of changes in polypeptide synthesis during the first few hours of development: fertilization-independent, fertilization-accelerated, and fertilization-dependent. Pulse-chase experiments and in vitro translation of extracted mRNA showed that the changes in polypeptide synthetic profile result from differential mRNA activation, differential polypeptide turnover and post-translational modifications. These results support the notion that following ovulation, development is controlled at two levels. An endogenous (oocyte) programme, set in train by the terminal events of oocyte maturation, may regulate the ‘housekeeping’ functions of the egg, while sperm penetration activates a further endogenous (fertilization) programme, which may serve to initiate subsequent embryogenesis.
The ontogenesis of cranial neuromeres in the rat embryo I. A scanning electron microscope and kinetic study
Authors: Tuckett Fiona , Lim Lynette , Morriss-Kay Gillian M.
Published: April 2021

The development of the cranial neuromeres, rostral to the level of the first somite, in rat embryos during neurulation is described. Examination of scanning electron micrographs of 4-, 8-, 12- and 16-somite-stage embryos has shown that the neuromeres develop in a strictly ordered pattern but the sequence is not ordered in either a rostrocaudal or caudorostral direction. The two mesomeres are shown to develop by subdivision of a previously formed mesomere, whilst the rhombomeres develop independently of each other. At the completion of cranial neurulation two mesomeres and nine rhombomeres (including the preotic sulcus) but no prosomeres are identifiable.

A direct correlation of the position of peaks in mitotic index along the embryonic axis with the position of sulci on the surface of the neural epithelium, was not possible. However, it is suggested that the mitotic index peak is the initial means of identifying a neuromere, and once the neuromere is expressed morphologically as a surface sulcus the mitotic index returns to its basal level.
Does the oral apparatus of the ciliate Stentor inhibit oral development by release of a diffusible substance?
Authors: De Terra Noël
Published: April 2021

In the ciliate Stentor, many thousands of basal bodies assemble on the ventral cell surface to form a new oral apparatus during cell division, regeneration and reorganization (oral replacement during interphase). During interphase, oral development is normally inhibited by the presence of the anteriorly placed oral apparatus. A glass needle was used to cut the oral apparatus of interphase stentors in two so that the parts remained intact but separate at the anterior end of the cell. These cells initiated basal body assembly and oral development, usually within 8 h. Basal body assembly can therefore result from disconnection of fibrous structures within the oral apparatus but is unlikely to be regulated by an inhibitor diffusing from it.
Adhesiveness of mouse primordial germ cells to follicular and Sertoli cell monolayers
Authors: Felici Massimo De , Siracusa Gregorio
Published: April 2021

The adhesiveness of female and male mouse primordial germ cells (PGCs) to somatic cell monolayers of various origin has been studied in the definite conditions of an in vitro system. PGCs were isolated from the gonads of embryos of various post coital ages according to the method of De Felici & McLaren (1982), and seeded on the cell monolayers. PGCs from 12·5 to 15·5 days post coitum (dpc) embryos specifically adhered to Sertoli and follicular cells obtained from adult gonads. The percentage of female PGCs which adhered to follicular cell monolayers was significantly higher than that of male PGCs. No significant adhesion was seen between PGCs and somatic cell monolayers obtained from various embryonic and adult tissues.

The results obtained indicate that the simple in vitro assay described in the present paper might help to characterize the cellular interactions between somatic and germ cells during gonadal development.
Teratogenic Activity of Several Closely Related Disazo Dyes on the Developing Chick Embryo
Authors: Beaudoin Allan R.
Published: April 2021

Thet eratogenic activity of several disazo dyes during rat embryogenesis has been investigated by Wilson (1955). In addition to the marked teratogenicity of trypan blue Wilson also demonstrated that Evans blue was moderately active and that Niagara blue 4B and Niagara sky blue 6B were possibly active. On the other hand, several other closely related disazo dyes such as Congo red and azo blue were found to cause no malformations in the surviving offspring.
The Block to Polyspermy in Sturgeon and Trout with Special Reference to the Role of Cortical Granules (Alveoli)
Authors: Ginsburg A. S.
Published: April 2021

Treatment of sturgeon eggs with the polyspermy-inducers urethane, ethyl ether, and acetone prolongs the latent period of the cortical reaction and apparently retards the actual secretion of the cortical granules. On activation of sturgeon eggs by pricking and of trout eggs by immersion in water, they lose their fertilizability at the moment of the discharge of cortical granules (the content of the alveoli) in the micropylar region. Before this no decrease in ability of the egg cytoplasm to accept a spermatozoon is observed. After removal of the perivitelline fluid (containing substances discharged from the cortical alveoli) penetration of numerous spermatozoa into activated trout eggs becomes possible. Perivitelline fluid of trout causes an agglutination of spermatozoa. The data obtained provide evidence that the block to polyspermy in fishes is a one-step process realized by means of the discharge of cortical granules (the content of the alveoli).
The Serum Proteins of the Rat During Development
Authors: Heim Werner G.
Published: April 2021

The sera of rats at various stages of development from the 17th day of gestation to adulthood were examined by paper electrophoresis. A component distinct from, and of higher mobility than, the bulk of the albumin was found at the 17th and 18th days of development. However, the mobility of this component is well within the limits of mobility of adult albumin. Evidence supporting the existence of a component in the beta-globulin region specific to the perinatal animal is presented. Gamma globulin and an asymmetry associated with it were demonstrable in all stages examined. The possible relation of this asymmetry to eta globulin is discussed. Problems concerning the physiology of the foetus arising from the changes in the relative concentrations of the serum proteins are pointed out.
La Régénération caudale des Urodèles (Induction et réactivité du territoire)
Authors: Kiortsis par V. , Droin A.
Published: April 2021

The role played by the spinal cord and other tissues in the regeneration of the tail was studied in larval salamanders.

Transverse tail-slices, with or without spinal cord, grafted to the back may undergo a reduction in size, or remain stationary, or even regenerate new structures. A more marked reduction was observed in the despinalized grafts. After partial amputation of the tail, a despinalization of the stump was performed without injuring the other tissues. In all cases where the absence of the spinal cord was proved histologically, no regeneration of the mesodermal axis occurred. Only a fin-like regenerate without muscles or skeleton appeared at the amputation surface. Spinal ganglia or brain (telencephalon), substituted for the spinal cord of the tail, were unable to replace it in its inductive action. An increase of the nerve supply, by introducing the two sciatic nerves into the despinalized tail-stump, also had no effect. It seems that the inductive action exerted by the spinal cord on tail regeneration is specific. The lateral deflexion of the spinal cord was enough to induce a supernumerary tail. If the deflexion was done dorsolaterally, instead of laterally, the induced supernumerary tail formed a half-fin too. Segments of the spinal cord, grafted dorsally or ventrally into the tail-fin, at some distance from the main axis, did not induce any muscular or skeletal structures. It is believed that the organ district of the tail contains at least two zones of different morphogenetic potencies : one mesodermal, which regenerates the main axis of the organ, under the inductive influence of the spinal cord, and one, derived from the neural crest, which produces, even in the absence of the spinal cord, a fin-like structure.
The Effect of Delayed Brain Extirpation and Replacement on Caudal Regeneration in Nereis diversicolor
Authors: Clark R. B. , Evans S. M.
Published: April 2021

Extirpation of the supra-oesophageal ganglion of Nereis diversicolor before or up to 48 hours after amputation of a number of posterior segments inhibits caudal regeneration. Extirpation of the ganglion 3 or more days after amputation of segments retards but does not inhibit regeneration. Injection or implantation of supra-oesophageal ganglia of regenerating worms into decerebrate hosts 48 hours or more after amputating the posterior segments results in segment proliferation in some of the recipients. Replacement of ganglionic material before 48 hours has no effect. The types of regeneration observed following replacement therapy on the 3rd or 4th days is characteristic of that when there has been a limited migration of coelomic cells to the wound. ‘Regeneration’ hormones appear to be present in the ganglion 48 hours after the loss of posterior segments, but they do not circulate in the body in effective quantity until 24 hours later.
Réaction de l’embryon de Poulet au bleu trypan
Authors: Stéphan par F. , Sutter B.
Published: April 2021

En 1941, Ancel & Lallemand signalaient que le bleu trypan était tératogène pour l’embryon de Poulet. Depuis lors de nombreux chercheurs ont utilisé le même produit avec des résultats quelque peu différents suivant les groupes de vertébrés testés : Oiseaux, Mammifères et Batraciens.
Perturbations indirectes de l’organogénèse cardio-vasculaire obtenues par la destruction aux rayons X de territoires situés en arrière de l’ébauche du cœur
Authors: Douarin par Nicole Le
Published: April 2021

De nombreuses techniques permettent de perturber l’organogénèse du cœur et des arcs aortiques chez les embryons de Vertébrés. Les unes agissent sur l’ensemble de l’organisme embryonnaire: action de la thyroxine (Bauman & Pfister, 1936), carence vitaminique de la femelle gestante (Wilson & Warkany, 1949) ou hypoxie temporaire de l’œuf en incubation (Rubsaamen & Schellong, 1953). D’autres techniques, au contraire, ont été appliquées directement sur le système artériel. Elles ont consisté en des destructions par l’électrocautère (Bremer, 1928) ou en des ligatures (Stéphan, 1952). Elles ont eu pour conséquence non seulement des perturbations du système artériel, mais également des malformations cardiaques. Enfin, l’irradiation aux rayons X du cœur de l’embryon de Poulet, réalisée suivant la technique mise au point par Ancel & Ét. Wolff (1934), a permis d’obtenir des embryons présentant d’importantes anomalies du cœur et des vaisseaux (G. Le Douarin & N. Le Douarin, 1959; G. Le Douarin, 1960).
Malformations résultant d’irradiations localisées de différentes parties de l’ébauche cardiaque chez l’embryon de Poulet
Authors: Douarin par Georges Le
Published: April 2021

L’irradiation aux rayons X de la totalité de l’ébauche cardiaque, pratiquée sur l’embryon de Poulet au 3ème jour de l’incubation, provoque des malformations cardiovasculaires qui, en ce qui concerne le cœur, intéressent la morphologie externe de l’organe ainsi que sa constitution interne. Ces résultats ont été décrits dans un travail antérieur (G. Le Douarin, 1960).
A quantitative analysis of regeneration from chimaeric limb stumps in the axolotl
Authors: Muneoka Ken , Holler-Dinsmore Gregory V. , Bryant Susan V.
Published: April 2021

We have analysed the cellular contribution and cellular displacement which occur during regeneration from chimaeric (half triploid, half diploid) lower arms in the axolotl. In general both anterior and posterior halves contribute approximately 50 % of the regenerated limb cells. Deviations from equal contribution were observed only when anterior tissue was grafted, suggesting that anterior tissue is more sensitive to grafting operations. Approximately 25 % of all cells in the regenerated limb were found to be displaced to the opposite side of the limb. Cellular displacement was not random; 63 % of all displaced cells were found in regions adjacent to the tissue of origin.
The differentiation of germ cells and gonads during development of carp (Cyprinus carpio L.). A study with anti-carp sperm monoclonal antibodies
Authors: Parmentier H. K. , Timmermans L. P. M.
Published: April 2021

Gonadal development, germ cell differentiation and the appearance of membrane antigenic determinants, specific for male and female germ cells during gonadogenesis, was studied in larval and juvenile carp (Cyprinus carpio L.) until 25 weeks after fertilization.

Indirect immunofluorescence studies with four monoclonal antibodies raised against carp spermatozoa revealed that monoclonal antibody WCS 29 stained the outer membranes of primordial germ cells in larvae from 3 days after fertilization. The monoclonal antibodies WCS 3 and 17 reacted with the outer membranes of germ cells from 7 weeks after fertilization onwards, simultaneously with the onset of germ cell proliferation. With monoclonal antibody WCS 28 germ cell membranes were clearly stained from 18 weeks after fertilization. Similar reactions were observed in both sexes, however, female germ cells reacted at an earlier developmental stage with the monoclonal antibody WCS 28 than male germ cells.

In the developing testis the monoclonal antibodies stained all types of spermatogenic cells. In the ovary, however, only oogonia and early prophase oocytes showed a positive reaction with the four monoclonal antibodies.

The results indicate that germline-specific antigens are present on the outer membranes of primordial germ cells and their male and female descendants, with the exception of elderly oogenic stages. It is assumed that the appearance and disappearance of these membrane antigens reflect differentiation steps of germ cells during gonadogenesis.
Action of phorbol myristate acetate (PMA) at fertilization of mouse oocytes in vitro
Authors: Niemierko Anna , Komar Aldona
Published: April 2021

Phorbol ester (PMA) in concentration 5 and 10 ng ml-1 blocks cytokinesis of the second maturation division in mouse oocytes. Karyokinesis is not impaired and digynic triploid oocytes are obtained which undergo first cleavage division.

Effectiveness of blocking cytokinesis is dependent on the timing of exposure of oocytes to PMA action. When oocytes are subjected to PMA at the onset of the second maturation division only 14·5 % of eggs are triploid. PMA present during fertilization in vitro (about 1 h exposure to PMA) induces triploidy in 40 % eggs. Extending the time of exposure of oocytes to 2 h produces 76 % tripronucleate eggs.

Applicability of PMA is compared with the use of cytochalasin B to induce triploidy in the mouse.
Contrabithorax and the control of spatial expression of the bithorax complex genes of Drosophila
Authors: Casanova Jordi , Sánchez-Herrero Ernesto , Ginés Morata Ginés
Published: April 2021

Cbx 1 is a dominant mutation of the bithorax complex (BX-C) of Drosophila partially transforming the second thoracic (T2) segment towards the third one (T3). Molecular analysis has shown that Cbx1 arose from a transposition within the BX-C of a DNA fragment of 17 kb containing pbx+ inserted into the Ubx area. In addition to the dominant phenotype, the Cbx1 mutation produces a set of recessive homeotic transformations that we show are characteristic of the Ubx mutations. We present evidence that the dominant and the recessive transformations arise from different mechanisms and suggest the dominant transformation is caused by an alteration of the normal regulatory role of pbx+ resulting in an adventitious expression of some Ubx+ products in T2, while the Ubx phenotype is caused by the breakpoint of the insertion.
A Monoclonal antibody against mouse oocyte cytoskeleton recognizing cytokeratin-type filaments
Authors: Lehtonen E.
Published: April 2021

Monoclonal antibodies were raised to detergent-extracted cytoskeleton preparations of mouse oocytes. In immunofluorescence microscopy, one of the antibodies, OCS-1, localizes exclusively to epithelial cells in frozen tissue sections, including various simple and stratified epithelia. The antibody decorates a keratin-type of fibrillar, vinblastine-resistant network in various cultured, epithelial-type cells, but not in myoid or fibroblastoid cells.

In mouse oocytes and cleavage-stage embryos, the OCS1 antibody gives a diffuse, spotty staining pattern. In blastocyst-stage embryos, the antibody reveals a keratin-type filamentous organization in the trophectoderm cells. In immunoelectron microscopy, the OCS-1 antibody decorates 10 nm-thick filaments, often identifiable as desmosome-attached tonofilaments, in detergent-treated trophectoderm cells.

The antigen(s) recognized by the OCS-1 antibody is apparently present in, or closely associated with, cytokeratin filaments. In addition to mouse oocytes and early embryos, a wide variety of epithelial cells in various species seem to share this antigen(s). The present results suggest that at the early stages, the cytokeratin-related antigen(s) defined by the OCS-1 antibody are stored in a non-fibrillar form which is then converted into a fibrillar network at the blastocyst stage. A pre-existing supply of cytokeratin-related protein may be essential for the development of the blastocyst.
Induction of cell–cell adhesion by monovalent antibodies in a germ cell culture
Authors: Ho Wai Chang , Bechtol Kathleen B.
Published: April 2021

Four monoclonal antibodies, XT-I, MT-23, MT-24 and MT-29, that bind the XT-1-differentiation-antigen of male germ cells have been used to investigate the biological role of the XT-1-molecule of germ cells in short-term primary culture. Cultures from 10 days postpartum mice demonstrate increasing numbers of antigen-positive germ cells and increased antigen expression per cell with succeeding days of culture. Treatment of the antigen-positive cultures with three of the monoclonal antibodies, XT-I, MT-23 and MT-24, increases germ cell-germ cell adhesion in a dose-dependent fashion. Treatment with the fourth monoclonal antibody, MT-29, does not induce cell adhesion. The monovalent, Fab fragment of XT-I-antibody also elicits tight cell adhesion, thus ruling out antibody cross linking of molecules or cells. Saturating or near saturating amounts of the positive antibodies are required to produce adhesion, a result consistent with perturbation of a function that is performed by the sum of action of many of the XT-1-molecules on the cell. The ability of germ cells to undergo antibody-elicited tight adhesion is dependent on germ cell age and/or XT-1-antigen concentration. We hypothesize that the XT-1-molecule is involved in regulation of cell adhesion, an event which must occur in normal development.
Factors guiding regenerating retinotectal fibres in the frog Xenopus laevis
Authors: Fawcett J. W.
Published: April 2021

I have examined the pathways of retinotectal fibres regenerating back to the contralateral tectum, and also to innervated and ‘virgin’ ipsilateral tecta in postmetamorphic Xenopus. The fibres were visualized by HRP labelling of either the whole optic nerve, or a selected quadrant of the retina.

Most fibres grow into either the ipsilateral or contralateral optic tract, although a small proportion go down the outside of the contralateral optic nerve. In the tracts, many fibres grow superficially, close beneath the pia, but a variable proportion runs more deeply. Axonal growth is not, therefore, restricted absolutely to the subpial region in the postmetamorphic Xenopus brain.

Fibres growing onto the contralateral, or a ‘virgin’ tectum mostly grow straight onto the rostral margin of the tectal lobe, without growing around its margin in the form of a medial or lateral brachium. Most of these fibres grow through the deeper part of the tectal layer which normally contains optic neuropil, but a proportion of them grow immediately deep to the pia. Fibres regenerating to an innervated ipsilateral tectum mostly enter either the medial or lateral brachium of the optic tract, and only leave this close to their site of termination. In the brachia the fibres run superficially under the pia, but when they leave the brachia they mostly run through the deeper retinorecipient layers. These observations provide further evidence that ingrowing optic fibres have their pathways influenced by the axons which have preceded them.
Cytological analyses of factors which determine the number of primordial germ cells (PGCs) in Xenopus laevis
Authors: Akita Yasuko , Wakahara Masami
Published: April 2021

Correlation of the number of primordial germ cells (PGCs) at stage 47 with the amount of germ plasm at the 8-cell stage and with the number of the germ-plasm-containing cells (GPCCs) was analysed using two different laboratory-raised colonies of Xenopus laevis, HD and J groups. The average number of PGCs in J group tadpoles was significantly larger than that in HD group tadpoles. The amount of germ plasm in J group embryos was also demonstrated to be larger than in HD group embryos. The amount of germ plasm was related positively to the number of GPCCs at the 8-cell stage and to the resulting number of PGCs; embryos which contained larger amounts of germ plasm developed larger numbers of PGCs at stage 47.

The average number of PGCs in experimentally induced triploid tadpoles was exactly two-thirds of that in normal diploid tadpoles. Furthermore, in somatic cells (e.g. epidermis, muscle, pancreas), the number of cells in the triploid was also two-thirds of that in diploid tadpoles.

These findings suggest that the number of PGCs is regulated by at least two different mechanisms: first, the number of PGCs is primarily specified by the intrinsic amount of germ plasm in the fertilized egg. Second, it is regulated by an unknown mechanism which controls the total number of cells of whole embryos, such as the nucleocytoplasmic ratio.
Changes in the distribution of membranous organelles during mouse early development
Authors: Maro Bernard , Johnson Martin H. , Pickering Susan J. , Louvard Daniel
Published: April 2021

The unfertilized oocyte, fertilized egg and early embryo (2-cell to 16-cell) of the mouse have been examined immunocytochemically for the distribution of antigens associated with the endoplasmic reticulum, the lysosomal and acidic vesicle fraction (100kD antigen), Golgi apparatus (135kD antigen) and coated vesicles (clathrin). The distribution of these antigens has also been examined in isolated 8-cell and 16-cell-stage blastomeres of various ages and phenotypes. Endoplasmic reticulum is detected only weakly in the oocyte and egg, but is seen abundantly at later stages both in association with the nuclear membrane and evenly distributed throughout the cytoplasm, except in regions of cell: cell apposition from which it is excluded. Intracellular clathrin is associated with the spindle in mitotic and meiotic cells. During interphase, clathrin is distributed throughout the cell until the mid-8-cell stage when it is concentrated into the apical region of the cell under the region of membrane at which a surface pole of microvilli will form subsequently. Thus, the cytoplasmic polarization of clathrin precedes overt polarization at the surface. At mitosis, the clathrin relocates to the spindle and is distributed to both daughter cells. It resumes an apical location beneath the surface pole of microvilli in polar daughter 1/16 cells, but remains dispersed in apolar daughter 1/16 cells. Both the lysosomal and Golgi antigens are distributed throughout the cytoplasm until the early 16-cell stage. In pairs of 16-cell blastomeres both antigens aggregate in a single cluster and do so whether the surface phenotype of the blastomeres is polar or apolar. The position of this cluster is not consistently related to the point of contact with the other cell in the pair but there is a suggestion that in cells with a polar surface phenotype the polar foci of Golgi/lysosomal antigens are located between the nucleus and the surface pole at earlier time points, but shift to a position between the basolateral membrane and the nucleus at the later time point. In intact 16-cell embryos also, the aggregated Golgi/lysosomal antigens of polar cells appear to localize to the basal region. The distributions of these various organelles in embryonic cells reported here show a number of differences from those reported previously for mature, differentiated cells.
Saccharide structures of the mouse embryo during the first eight days of development: Inferences from immunocytochemical studies using monoclonal antibodies in conjunction with glycosidases
Authors: Pennington J. E. , Rastan S. , Roelcke D. , Feizi T.
Published: April 2021

Monoclonal anti-carbohydrate antibodies have been used in conjunction with glycosidases in immunofluorescence studies to derive information about the structures and in situ distribution of saccharides of the mouse embryo during the first 8 days of development. The salient findings are as follows: Branched poly-N-acetyllactosamine sequences of I-antigen type are detectable from the first day onwards and are widely distributed in cells of the endoderm, ectoderm and mesoderm.Linear poly-N-acetyllactosamine sequences of i-antigen type are detectable from the fifth day onwards in cells of all three lineages, but have a more restricted distribution than the sequences of I-type.Poly-N-acetyllactosamine sequences that are susceptible to digestion with endoβ-galactosidase are the main carriers of the SSEA-1, C14 and the blood group B-like antigens, which have the following structures and are found in endoderm and ectoderm but not in mesoderm cells. In the trophoblast however, these antigens are borne on saccharides that are resistant to endo-β-galactosidase.A proportion of the poly-N-acetyllactosamine structures in the endoderm and the ectoderm of the 5- and 6-day embryos may contain the following novel structures: in which antigenicities of SSEA-1 and C14 determinants are masked.There are several types of sialyl-oligosaccharides: (1) those reactive with anti-Gd, which has a specificity for NeuAc α2 –3Gal β1 –4GlcNAc sequence in the extraembryonic mesoderm and the heart; (2) those reactive with anti-Pr2 but not with anti-Gd, which may correspond to other N-acetylneuraminic acid containing sequences such as NeuAc α2 –3Gal β1 –3GalNAc or NeuAc α2 –6Gal in preimplantation embryos and in the yolk sac, neural ectoderm and mesenchyme of the 8-day embryo; (3) those with other sialic acid forms or linkages that do not react with anti-Gd and Pr2; among these are sialosyl-i sequences in the extraembryonic ectoderm, and sialosyl-I sequences in most cell types during the first 8 days. The latter are the main poly-N-acetyllactosamine structures in the neural ectoderm of the 8-day embryo.The sequence Gal β1 –3GlcNAc β1 –3Gal βl –4Glc/GlcNAc, or cross-reactive structures, which bind FC10.2 antibody occur in the extraembryonic endoderm and yolk sac.

The roles of specific carbohydrate structures as receptors during embryonic development and cell growth are important topics of current research. The cytochemical approach with monoclonal antibodies in conjunction with glycosidases, as in the present study, provides a unique opportunity to visualize the in situ disposition of specific carbohydrate sequences in individual cells of the whole organism, and should facilitate systematic investigations of their functions.
Measurement of biological shape: a general method applied to mouse vertebrae
Authors: Johnson D. R. , O’Higgins P. , Mcandrew T. J. , Adams L. M. , Flinn R. M.
Published: April 2021

A method is described for recording and analysing the projected shape of mouse vertebrae. The image of the shape is captured by a television camera, cleaned, digitized and subjected to mathematical analysis. A visual representation is obtained by reconstructing the shape in polar coordinates about its centre of area. Further statistical analysis of the whole shape is performed after a Fourier transform. This allows the shape to be represented by and reconstructed from 15 numbers. The method does not rely on homologous points or expert opinion and allows mean shapes to be constructed. It successfully distinguished between 92 % of the test data, T1 and T2 vertebrae from two strains of mice.
Myogenic differentiation in early chick wing mesenchyme in the absence of the brachial somites
Authors: Kenny-Mobbs Terry
Published: April 2021

A controversy exists in the literature over the ability of wing mesenchyme of somatopleural origin to form skeletal muscle. Experimental approaches used in such studies leave open the possibility of postoperative accessibility of the experimental wings to somitic cell invasion. In the present study wing somatopleural tissue was isolated from HH stage-12 to -21 chick embryos and grown either in organ culture (OC) or on the chorioallantoic membrane (CAM) of host chicks, conditions under which postoperative entry of somitic cells is impossible. In the presence of axial and somitic tissues of the brachial region, the wing territories from all four stages underwent comparable growth and tissue differentiation. However, isolated wing regions showed a stagedependency in the differentiation of skeletal muscle but not of other limb tissues. The incidence and amount of skeletal muscle was markedly reduced in HH stage-12 and -15 isolated wing regions while myogenesis in HH stage-18 and -21 wing buds was not affected by the absence of the somitic tissues. These results are consistent with reported stages of somitic cell migration into wings with the exception of HH stage-12 explants which should have been muscleless if somitic cells are the sole source of wing myofibres. The possibility that somitic cells had been included in these explants was investigated by 1) testing the myogenic potential of lateral plate tissue adjacent to the wing, 2) altering the dissection procedure for isolating wing territories and 3) using antibodies to skeletal muscle myosin and actin to detect myotubes. The results from this series of experiments illustrate the need for extraordinary care in the isolation of wing regions when investigating limb– somite relationships and suggest that the myogenic capacity attributed to wing somatopleural cells in the past can be accounted for by either postoperative entry of somitic cells into experimental wings or inadvertent inclusion of somitic cells in the primordia when dissected. Overall, the results show that somitic cells are the sole source of wing myofibres for, in their absence, somatopleural cells form all mesodermally-derived wing cell types except skeletal myofibres.
The migration of neural crest cells and the growth of motor axons through the rostral half of the chick somite
Authors: Rickmann M. , Fawcett J. W. , Keynes R. J.
Published: April 2021

We have studied the pathway of migration of neural crest cells through the somites of the developing chick embryo, using the monoclonal antibodies NC-1 and HNK-1 to stain them. Crest cells, as they migrate ventrally from the dorsal aspect of the neural tube, pass through the lateral part of the sclerotome, but only through that part of the sclerotome which lies in the rostral half of each somite. This migration pathway is almost identical to the path which presumptive motor axons take when they grow out from the neural tube shortly after the onset of neural crest migration. In order to see whether the ventral root axons are guided along this pathway by neural crest cells, we surgically excised the neural crest from a series of embryos, and examined the pattern of axon outgrowth approximately 24 h later. In somites which contained no neural crest cells, ventral root axons were still found only in the rostral half of the somite, although axonal growth was slightly delayed. These axons were surrounded by sheath cells, which had presumably migrated out of the neural tube, to a point about 50 μm proximal to the growth cones. With appropriate antibodies we found that the extracellular matrix components fibronectin and laminin are evenly distributed between the rostral and caudal halves of the somite. Neither of these molecules therefore plays a critical role in determining the specific pathway of neural crest cells or motor axons through the rostral half of the somite.
The effect of egg rotation on the differentiation of primordial germ cells in Xenopus laevis
Authors: Cleine J. H. , Dixon K. E.
Published: April 2021

Eggs of X. laevis were rotated (sperm entrance point downwards) either through 90° (1×90 embryos) or 180° in two 90° steps (2×90 embryos) at approximately 25–30 min postfertilization after cooling to 13 °C. The embryos were kept in their off-axis orientation and cooled until the early gastrula stage. Rotation resulted in relocation of egg constituents with slight changes in the distribution of outer cortical and subcortical components and major changes in inner constituents where the heavy yolk and cytoplasm appeared to reorient as a single coherent unit to maintain their relative positions with respect to gravity. Development of rotated embryos was such that regions of the egg which normally give rise to posterior structures instead developed into anterior structures and vice versa. Germ plasm was displaced in the vegetal-dorsal-animal direction (the direction of rotation) and was segregated into dorsal micromeres and intermediate zone cells in 2×90 embryos and dorsal macromeres and intermediate zone cells in 1×90 embryos. In consequence, at the gastrula stage, cells containing germ plasm were situated closer to the dorsal lip of the blastopore after rotation - in 2×90 gastrulas around and generally above the dorsal lip. Hence, in rotated embryos, the cells containing germ plasm were invaginated earlier during gastrulation and therefore were carried further anteriorly in the endoderm to a mean position anterior to the midpoint of the endoderm. The number of cells containing germ plasm in rotated embryos was not significantly different from that in controls at all stages up to and including tail bud (stage 25). However at stages 46,48 and 49 the number of primordial germ cells was reduced in 1×90 embryos in one experiment of three and in 2×90 embryos in all experiments. We tested the hypothesis that the decreased number of primordial germ cells in the genital ridges was due to the inability of cells to migrate to the genital ridges from their ectopic location in the endoderm. When anterior endoderm was grafted into posterior endodermal regions the number of primordial germ cells increased slightly or not at all suggesting that the anterior displacement of the cells containing germ plasm was not the only factor responsible for the decreased number of primordial germ cells in rotated embryos. Other possible explanations are discussed.
Calcium and neurulation in mammalian embryos: II. Effects of cytoskeletal inhibitors and calcium antagonists on the neural folds of rat embryos
Authors: Smedley Martin J. , Stanisstreet Martin
Published: April 2021

The role of calcium in neurulation in mammalian embryos has been studied by culturing rat embryos at 10·4 days of gestation, when the cephalic neural folds have elevated but not fused, in serum containing cytoskeletal inhibitors or calcium antagonists. The effects of these antagonists on the morphology of the cephalic neural folds have been examined by scanning electron microscopy. The different agents caused the cephalic neural folds to part to varying degrees. The neural folds were classified as intact (normal), open (folds parted up to 90° with each other), flattened (folds parted from 90° to 180°) or collapsed (folds parted more than 180°).

The microtubule inhibitors colchicine and nocodazole at 10−4M and 6·6×10−4M respectively cause the cephalic neural folds of 10·4-day embryos to collapse after 60 min. At 5·2×10−6M the microfilament inhibitor cytochalasin B causes the folds to open after 60 min. Longer term culture of 9·5-day embryos for 24 h in diazepam, which is reported to inhibit myosin synthesis, causes general developmental retardation including a delay in the closure of the neural tube.

Culture of 10·4-day rat embryos for 60 min in papaverine at 2·4 × 10−4 M or gallapomil (D-600) at 5·0×10−4M, agents which reduce the entry of calcium into cells, causes opening of the elevated cephalic neural folds. In contrast TMB-8, which is purported to perturb some intracellular calcium-dependent functions, does not cause opening of the elevated cephalic neural folds, even at high concentrations.

The results suggest that both microtubules and microfilaments are essential to the maintenance of the elevated cephalic neural folds in rat embryos. The results are also compatible with the idea that calcium ion flux across the membranes of the neuroepithelial cells might be important for the elevation of the neural folds, and thus for successful neurulation.
Axolotl retina and lens development: mutual tissue stimulation and autonomous failure in the eyeless mutant retina
Authors: Cuny Robert , Malacinski George M.
Published: April 2021

During eye development in the axolotl (Ambystoma mexicanum Shaw), morphogenetic movements bring together tissues from head epidermis, neuroectoderm and neural crest. The stages 0 to 14 of axolotl eye development were expanded from Rabi’s (1898) stages 1 to 10 and correlated with Harrison’s (1969) stages. At the onset of neurulation (stage 13 of Harrison), the head epidermis is already determined to form skin, and the neuroectoderm is committed to form brain, because these tissues develop autonomously in 60% Leibovitz L-15 culture medium. However, a sequence of mutual tissue interactions is necessary to stimulate eye development. When head epidermis and neuroectoderm were cocultured, eyes developed, containing retinas with photoreceptors (stage 8) and lenses with secondary lens fibres (stage 8). The first event needed in this case appears to be the secretion of a growth factor from the head epidermis which stimulates retina development from the neuroectoderm. When neuroectoderm cultures were exposed to nondialysable extracts (30μgml−1) of an adult epidermis derivative, the bovine cornea, pigmented retinas (stage 6) and at higher concentrations (3000 µg ml−1) neural retinas developed (stage 6). In turn, lens formation is stimulated in the head epidermis by a retina-derived growth factor. A mutation that causes adult eyelessness (e eyeless, nonlethal, recessive) affects the earliest event in eye development (stage la), while a mutation that causes arrest of eye development (mi microphthalmic, lethal, recessive) acts in a later event (stage 8). Two possibilities have been considered in the case of mutation e: either the head epidermis does not secrete sufficient amounts of active growth factor, or the presumptive retina itself is defective. The latter statement turned out to be correct, because mutant e neural plates rarely developed early retina stages (stage 5) in organ culture when combined with wild-type head epidermis. On the other hand, wild-type neural plates formed advanced retinas (stage 8) in all cases when combined with mutant e head epidermis. As expected, no retina or lens developed when both neural plate and head epidermis were from mutant e donors. The heterozygous presence of genes e and r (renal insufficiency, lethal, recessive) produces duplications of the presumptive retina at the optic stalk. This observation is consistent with the notion that the mutation e, assisted by the r locus, causes a primary failure in the presumptive retinal region.
Lack of inactivation of a mouse X-linked gene physically separated from the inactivation centre
Authors: Lyon Mary F. , Zenthon J. , Evans E. P. , Burtenshaw M. D. , Wareham Kathryn A. , Williams E. D.
Published: April 2021

Previous evidence had shown that, when a mammalian X-chromosome is broken by a translocation, only one of the two X-chromosome segments shows cytological signs of X-inactivation in the form of late replication or Kanda staining. In the two mouse X-autosome translocations T(X;4)37H and T(X;11)38H the X-chromosome break is in the A1 –A2 bands; in both, the shorter translocation product fails to exhibit Kanda staining. By in situ hybridization, the locus of ornithine carbamoyltransferase (OCT) was shown to be proximal to the breakpoint (i.e. on the short product) in T37H and distal to the breakpoint in T38H. Histochemical staining for OCT showed that in T38H the locus of OCT undergoes random inactivation, as in a chromosomally normal animal, whereas in T37H the OCT locus remains active in all cells. The interpretation is that, when a segment of X-chromosome is physically separated from the X-inactivation centre, it fails to undergo inactivation. This point is important for the understanding of the mechanism of X-inactivation, since it implies that inactivation is a positive process, brought about by some event that travels along the chromosome. It is also relevant to the interpretation of the harmful effects of X-autosome translocations and the abnormalities seen in individuals carrying such translocations.
The formation of mesodermal tissues in the mouse embryo during gastrulation and early organogenesis
Authors: Tam P. P. L. , Beddington R. S. P.
Published: April 2021

Orthotopic grafts of [3H]thymidine-labelled cells have been used to demonstrate differences in the normal fate of tissue located adjacent to and in different regions of the primitive streak of 8th day mouse embryos developing in vitro. The posterior streak produces predominantly extraembryonic mesoderm, while the middle portion gives rise to lateral mesoderm and the anterior region generates mostly paraxial mesoderm, gut and notochord. Embryonic ectoderm adjacent to the anterior part of the streak contributes mainly to paraxial mesoderm and neurectoderm. This pattern of colonization is similar to the fate map constructed in primitive-streak-stage chick embryos. Similar grafts between early-somite-stage (9th day) embryos have established that the older primitive streak continues to generate embryonic mesoderm and endoderm, but ceases to make a substantial contribution to extraembryonic mesoderm.

Orthotopic grafts and specific labelling of ectodermal cells with wheat germ agglutinin conjugated to colloidal gold (WGA-Au) have been used to analyse the recruitment of cells into the paraxial mesoderm of 8th and 9th day embryos. The continuous addition of primitive-streak-derived cells to the paraxial mesoderm is confirmed and the distribution of labelled cells along the craniocaudal sequence of somites is consistent with some cell mixing occurring within the presomitic mesoderm.
Ventral duplication of the autopod: chemical induction by methoxyacetic acid in rat embryos
Authors: Scott William J. , Nau H. , Wittfoht W. , Merker H.-J.
Published: April 2021

Administration of 2-methoxyethanol to pregnant rats on day 12 of gestation induced ventral duplication of the autopod, presumably via its oxidative metabolite, methoxyacetic acid. Morphological observations indicate that the limb bud periderm is severely damaged by methoxyacetic acid so that large patches of this structure are actually missing during an extended period of limb bud development. A high concentration of methoxyacetic acid (10 mM) was found in the extra-embryonic fluid and we postulate that the damage to the periderm was initiated from this extraembryonic exposure. The ventral duplication of the autopod is thought to arise through an attempt by the embryo to repair the periderm lesion.
Changes in ploidy level of epidermal cells during last larval instar of the tobacco hornworm, Manduca sexta
Authors: Kato Y. , Nair K.K. , Dyer K.A. , Riddiford L.M.
Published: April 2021

The relative DNA content of Manduca sexta abdominal epidermal nuclei during the final larval instar was measured by cytophotometry of whole-mount preparations of the epidermis. In the middle intrasegmental region, epidermal cells showed a ploidy level of 4C to 32C on the day of ecdysis. During the subsequent period of feeding, the proportion of higher ploidy cells, such as 16C and 32C, increased. This situation remained until the day of apolysis preceding pupal cuticle formation when mitoses reduced the cells to 2C, 4C, 8C and 16C, except for the pupal pock-mark cells, which increased to 32C or 64C. Metaphase cells showed various ploidy levels, correlated with the size of their mitotic figures. By contrast, in the anterior and posterior margin of a segment where no mitoses occurred, the cells continued to increase in ploidy throughout the instar.