bluuebunny/crossref_metadata_2025_split huggingface dataset:
Somite formation in the early chick embryo following grafts of Hensen’s node
Authors: Hornbruch Amata , Summerbell Dennis , Wolpert L. 
Published: April 2021

ABSTRACT
Quail grafts of Hensen’s node were examined for their potential to induce somites in chick blastoderms. The origin of the structures induced depended on the distance of the graft from the host’s midline. Nodes placed at the margin of the area pellucida resulted in structures differentiated from the cells of the graft, whereas medially the graft organized host cells to form rows of somites. The results are discussed in terms of competence of graft and host mesenchyme and a positional signal from the node.
Ultrastructural studies of lethal c25H/c25H mouse embryos
Authors: Nadijcka Mary D. , Hillman Nina , Gluecksohn-Waelsch Salome 
Published: April 2021

ABSTRACT
Mouse embryos which are homozygous for the c25H deletion at the albino locus are developmentally arrested at the 2-to 6-cell cleavage stages. This study reveals that the mutant embryos cease development before they can be distinguished ultrastructurally from their normal litter-mates. After prolonged developmental delay (24−48 h), the nuclei of the mutant embryos become extremely aberrant in shape, whereas other subcellular organelles remain normal and there are no signs of pyknosis. Eventually, the mutant embryos do become pyknotic and begin to degenerate. The striking effects of this deletion on nuclear ultrastructure of cleavage-stage embryos are discussed in relation to biochemical and ultrastructural defects caused by other lethal deletions at the albino locus.
In vivo and in vitro studies on the early embryonic lethal oligosyndactylism (Os) in the mouse
Authors: Paterson Hugh F. 
Published: April 2021

ABSTRACT
The development of mouse embryos homozygous for oligosyndactylism (Os) is arrested during implantation. Histological investigations confirm a previous report that cells become blocked in mitosis, and air-dried spreads of the mutant embryos reveal that large numbers of cells accumulate in metaphase. Trophoblastic giant cells appear unaffected by the action of the mutant gene both in utero and during culture over the lethal phase. It is proposed that the form of endoreduplication undergone by giant cells renders them refractory to the metaphase block.
An analysis of pigment cell development in the periodic albino mutant of Xenopus
Authors: MacMillan Gillian J. 
Published: April 2021

ABSTRACT
The periodic albino mutant (apap) of Xenopus in which the development of melanophores is impaired, is further reported here to possess an aberrant pattern of iridophore differentiation. The development of mutant and wild-type neural crest explants isolated in vesicles derived from tissues from identical and different genotypes was examined to determine if the mutant effect resides in the pigment cells or is mediated by the environmental tissues. Mutant melanophores and iridophores cultured in either mutant or wild-type tissues exhibited mutant patterns of differentiation. Wild-type pigment cells cultured in both wild-type and mutant tissues exhibited wild-type patterns of differentiation. Hence the mutation affects the capacities of melanoblasts and iridoblasts to differentiate but not the ability of the environmental tissues to support pigment cell differentiation.
Gene expression inDictyostelium discoidium:mutually antagonistic roles of cyclic-AMP and ammonia
Authors: Kay R. R. 
Published: April 2021

ABSTRACTCyclic-AMP and ammonia have been previously identified as extracellular signals during Dictyostelium development. Both are important in controlling morphological movements and cyclic-AMP also in inducing gene expression. The work in this paper is concerned with their effects on developmental gene expression. Cyclic-AMP was found to act as an inducer during the aggregative (as exemplified by phosphodiesterase) and the post-aggregative (glycogen phosphorylase, UDP-galactose polysaccharide transferase, prespore vacuoles and stalk cells) phases of gene expression. Ammonia inhibited the appearance of each of the above markers and antagonized the inductive effects of cyclic-AMP on them. This inhibition by ammonia of cyclic-AMP inducible gene expression may involve a step linking elevated intracellular cyclic-AMP levels to gene activation.It has been suggested that the specification of cells within the aggregate into the stalk and spore pathways of differentiation might be controlled by cyclic-AMP and ammonia. In this model for pattern formation cyclic-AMP would induce stalk cell differentiation and ammonia spore formation. The present results argue against this idea since cyclic-AMP induces and ammonia inhibits differentiation along both pathways. The function of these agents may rather be to coordinate the rates of biochemical differentiation of individual cells and link them to the overall morphological changes occurring during development.
Lethality of radioisotopes in early mouse embryos
Authors: Macqueen Hilary A. 
Published: April 2021

ABSTRACT
The development of pre-implantation mouse embryos was found to be prevented by exposure of the embryos to [35S]methionine, but not to [3H]methionine. Such embryos have also been shown to be highly sensitive to [3H]thymidine. These observations are discussed with reference to the path lengths and energies of electrons emitted from the different radioisotopes.
DNA synthesis after polyspermic fertilization in the axolotl
Authors: Wakimoto B. T. 
Published: April 2021

ABSTRACT
Cytological and autoradiographic studies were done to investigate the cytoplasmic control of DNA synthesis under conditions of physiological polyspermy. The DNA synthetic phases of the egg, principal sperm and accessory sperm nuclei were determined and correlated with nuclear morphology and developmental fate. Results show that accessory sperm nuclei undergo morphological transition to pronuclei. Their DNA synthetic phase is the same as that of the principal sperm nucleus. Hence accessory sperm nuclei are capable of initiating and completing DNA replication before any cytological evidence of their degeneration is observed.
Physiologie du cœur de l’embryon de Poulet in vitro après congélation à très basse température
Authors: Rey Louis R. 
Published: April 2021

ABSTRACT
La découverte (Rostand, 1946; Polge, Smith, & Parkes, 1949) des remarquables propriétés protectrices de la glycérine a permis de soumettre à des froids très intenses, divers tissus et organes, tout en leur conservant un degré de survie important. Nous avons voulu analyser sur un exemple précis quelles étaient les conditions de protection qu’offrait le traitement par la glycérine.
Observations on Rabbit Blastocysts Prepared as Flat Mounts
Authors: Moog Florence , Lutwak-Mann Cecilia 
Published: April 2021

ABSTRACT
The structure of the mammalian blastocyst has generally been studied on whole mounts in fluid, or on sections of embedded preparations. If the blastocyst of the rabbit is split open and mounted flat, however, the intact cells in their correct topographical relationships may be examined under the high powers of the microscope. This technique, which is quick and simple, may be employed in cytological and cytochemical studies of the large blastocyst cells, in study of mitotic patterns in the blastocyst wall, and in evaluation of the effects of culture media and of various experimental techniques applied to the blastocysts themselves or to the mother.
The Effects of Homologous Testicular and Brain and Heterologous Testicular Homogenates combined with Adjuvant upon the Testes of Guinea-Pigs
Authors: Katsh Seymour , Bishop David W. 
Published: April 2021

ABSTRACT
Numerous efforts have demonstrated antibody production after injection of spermatozoa into animals of the same species. For example, Metalnikoff (1900) and Kennedy (1924) reported anti-guinea-pig sperm ‘toxins’ in guinea-pigs; McCartney (1923) noted anti-rat sperm ‘toxins’ in rats; Pfeiffer (1905), Dittler (1920), and Pommerenke (1928) demonstrated anti-rabbit ‘spermatotoxins’ in rabbits. Antibody production against heterologous sperm has also been disclosed: Mudd & Mudd (1929) injected human, guinea-pig, bull, and ram sperm into rabbits and reported that the resultant antibodies were species specific. The absoluteness of specificity, both organ and species, however, has been qualified by the study of Lewis (1934), who found that brain and testicles possess common antigens, and Henle (1938) has extended Mudd & Mudd’s (1929) observations on cross-reaction between sperm of closely related species. In the above-mentioned studies the methods for determining antisperm activity of antisera included complement-fixation, sperm-immobilization, agglutination, and precipitin tests.
Le développement du péroneé dans les expériences sur la régulation des déficiences et des excédents dans la patte du Poulet
Authors: Hampé Armand 
Published: April 2021

ABSTRACTSi le but des expériences sur la régulation est d’obtenir un développement correct et harmonieux d’un organe ou d’un organisme à partir d’une ébauche anormale, il n’est pas moins vrai que l’attention est souvent attirée par les individus s’écartant de façon plus ou moins importante du type parfait. Ceux-ci permettent souvent des conclusions intéressantes sur les mécanismes de la régulation.
Rates of Growth and of Remodelling as Factors in the Genesis of Vascular and Osseous Lesions of Odoratism in Rats
Authors: Gillman Theodore , Hathorn Michael 
Published: April 2021

ABSTRACT
Evidence is presented in support of the view that lesions in vessels, bones, and perhaps in connective tissues generally, induced by feeding L. odoratus seeds to rats, may be attributable primarily to some disturbance in the neogenesis of fibres during the growth, regeneration, and/or repair of connective tissues. This failure seems to be at a stage after sulphation of those mucopolysaccharides which accumulate in connective tissue ground substance during fibre formation. It is suggested that the aortic ruptures may be the result of some derangement in the balance between lysis and regeneration of elastic membranes, which probably occur simultaneously during the normal growth and remodelling of the aorta. This interpretation differs from that provided by other workers who attribute aortic ruptures solely to elastolysis. Evidence from the study of lesions in bones and alterations in repair processes around the aorta in L. odoratus-fed adult and weanling rats supports the interpretations here presented. The frequency of ‘double-shafts’ as well as other deformities of long bones are taken as clear indications of disorganized remodelling of bones during growth. These studies of the aortic reactions in rats fed L. odoratus seeds also substantiate our previous contention that the integrity of the collagen-like ‘cores’ of the VEM’s is probably intimately dependent upon their ‘sleeves’ of reticulin and polysaccharides. The association of damage to the elastic membranes with distinct alterations in the reticulin and mucopolysaccharide contents immediately around and also between aortic VEM’s confirm our previous findings in this regard. There are indications, too, from histochemically detectable increases in circulating mucopolysaccharides, from the marked increases in osseous mast-cells and from reported delay in blood-clotting, that widespread disturbances in polysaccharide metabolism prevail in odoratus-intoxicated rats. Some possible implications of these findings for understanding the genesis of human arterial lesions are briefly discussed with special reference to a developmental approach to the aetiology and pathogenesis of these vascular reactions in terms of general features of connective tissue regeneration and repair.
Epithelial Regeneration and Wound Healing in the Oesophagus of the Cat
Authors: Mcminn R. M. H. , Johnson F. R. 
Published: April 2021

ABSTRACT
Histological and histochemical techniques have demonstrated that the epithelium in the lower end of the oesophagus of the cat consists of three well-defined zones, namely superficial, intermediate, and basal. Wound healing in the lower end of the oesophagus has been studied following the removal of small areas of mucosa. Epithelial repair occurred by migration of cells, accompanied by increased mitotic activity in the surrounding undisturbed epithelium. The alkaline phosphatase and PAS-positive material (other than glycogen) that were present in normal epithelium were not seen in migrating cells, which contained considerable quantities of glycogen. The newly forming connective tissue elements in the floor of the wound did not contain alkaline phosphatase at any stage of the healing process.
Stages in the Development of the Stickleback Gasterosteus aculeatus (L.)
Authors: Swarup H. 
Published: April 2021

ABSTRACT
Much good work has been done on the developmental morphology of the teleostean fishes from the works of Ryder (1884), Cunningham (1886), and McIntosh & Prince (1890) onwards. With the advent of experimental embryology the need for tables of development of different species was felt. Meek (1924), Ballantyne (1930), and Oppenheimer (1937) provide some normal tables for the teleosts Gadus, Callichthys, and Fundulus respectively, but much work is still needed on other species which are suitable for experimental work. Gasterosteus aculeatus, the three-spined stickleback, has become a laboratory fish because of its small size, easy availability, wide distribution, and very interesting breeding habits. This fish breeds mainly during April and May, but it is possible in the laboratory to bring it into breeding condition during most of the year. The factors controlling the time of reproduction are intensity of light and amount of food. When the author began experimental work on G. aculeatus it was soon realized that no complete table of normal development of this fish exists. Kuntz & Radcliffe (1917) described only a few stages, and though Vrat (1949) has given the main stages, he has omitted many important developmental features. A more detailed account of the development of this fish has therefore been prepared.
The Effect of Sodium Thiocyanate on Isolates of the Presumptive Ectoderm and Medio-ventral Marginal Zone of Triturus Gastrulae
Authors: ôgi Ken-Ichi 
Published: April 2021

ABSTRACT
As shown by Holtfreter (1944, 1945, 1947), the isolated presumptive ectoderm of Triturus torosus develops into a mass of epidermal cells when cultured in a physiological medium. However, if it is treated with injurious media such as acid, alkaline, or Ca-free solutions, or alcohol, and then cultured in a physiological medium, it differentiates neural structures and mesenchyme. These observations were confirmed in experiments made with the ectoderm of T. pyrrhogaster (Yamada, 1950; Karasaki, 1957a) except for the following points: treatment with Ca-free media or with alcohol does not cause neural or mesenchymal differentiation in the ectoderm of this species, although these treatments lead to a disaggregation of the ectoderm just as with acid and alkali (Karasaki, 1957a). For the ectoderm of T. pyrrhogaster ammonia was found most effective in producing neural structures. Even differentiation of the mesoderm is altered by treating with ammonia: an isolate of the ventral marginal zone of T. pyrrhogaster, with an inherent tendency to form blood-island and mesothelium, differentiate notochord and muscle after a treatment with ammonia (Yamada, 1950). It was emphasized by Yamada that ammonia shifts the mode of differentiation of the isolated ectoderm and mesoderm from ventral towards dorsal. Such effects were designated as dorsalization. Similarly it was demonstrated by Kawakami & Okano (1955) that lactic acid is capable of dorsalizing the presumptive ectoderm and ventral marginal zone.
Experimental Demonstration of Tongue Muscle Origin in Chick Embryos
Authors: Deuchar E. M. 
Published: April 2021

ABSTRACT
Since in all classes of vertebrates the tongue muscles are innervated by nerve XII, a segmental nerve of the occipital region, it is usually argued on this criterion alone that they originate from occipital myotome tissue. Descriptive evidence in support of this generalization is, however, far from adequate. The most complete accounts that exist refer to one amphibian and two reptile species. In the amphibian Necturus, Platt (1897) observed that ventral outgrowths of the 3rd and 4th occipital myotomes became tongue muscles, and Edgeworth (1935) has described the development of tongue muscles in the reptiles Sphenodon and Lacerta, from ventral parts of two occipital and two cervical myotomes, all innervated by nerve XII. In avian and mammalian embryos, however, early muscle rudiments are extremely difficult to recognize with any certainty histologically. Although Butcher (1929) and Bates (1948) have observed ventral outgrowths of occipital myotomes in rat and cat embryos, and Bates claimed that these are recognizable as tongue muscle primordia in later stages, both these authors drew their conclusions from relatively few fixed specimens, and in Bates’s photographs the rudiments are not nearly as distinct as his diagrams suggest they are. The same criticism applies to Hunter’s description (1935) of occipital myotome rudiments that apparently develop into tongue muscles in the chick. The only other detailed description of tongue muscle development in birds is that of Kallius (1905) who dealt with advanced stages when the muscle primordia are already in situ.
The structure of supernumerary limbs formed after 180° blastemal rotation in the newt Triturus cristatus
Authors: Papageorgiou Spyros , Holder Nigel 
Published: April 2021

ABSTRACT
The structure of supernumerary limbs formed following 180° ipsilateral blastema rotations in the arm of the newt Triturus cristatus is analysed. Both the skeletal pattern and the muscle patterns are examined. As is the case after comparable experiments in the axolotl (see, for example, Maden & Mustafa, 1982) the extra limbs which form show a range of anatomies. Limbs symmetrical about the dorsal-ventral and anterior-posterior axis are reported as well as some limbs which were part symmetrical and part asymmetrical. It is clear that newts and axolotls appear to react in similar ways to this particular experimental procedure.
Evidence for translation of HPRT enzyme on maternal mRNA in early mouse embryos
Authors: Harper Mary I. , Monk Marilyn 
Published: April 2021

ABSTRACT
This paper presents evidence that maternal mRNA is responsible for the early increase in HPRT activity in preimplantation mouse embryos. Increase of HPRT activity is demonstrable from as early as 6 h postfertilization when there is barely detectable synthesis of embryonic RNA. The increase is sensitive to cycloheximide and thus requires protein synthesis, whereas it is insensitive to α-amanitin and therefore independent of mRNA synthesis. These results suggest that translation of HPRT occurs on pre-existing maternal mRNA.
Embryo-coded HPRT activity is detectable by the 4- to 8-cell stage when the increase in HPRT activity becomes sensitive to a-amanitin. The transition from maternal- to embryo-coded enzyme activity is completed by the time of compaction. At this stage there is an unexplained yet reproducible loss of HPRT activity. Other maternally-inherited enzymes show a marked degradation occurring at a similar time. It is possible that the enzyme degradation observed reflects some common mechanism directing the changeover from maternally-derived to embryonically-derived enzymes.
Quantitative aspects of RNA synthesis and polyadenylation in 1-cell and 2-cell mouse embryos
Authors: Clegg Kerry B. , Pikó Lajos 
Published: April 2021

ABSTRACT
Mouse embryos at the late 1-cell and late 2-cell stages were labelled with [3H]adenosine for periods of up to 320 min during which the specific activity of the ATP pool was constant. The time course of the molar accumulation of adenosine was calculated for tRNA, high-molecular-weight poly(A)— RNA and poly(A) tails versus internal regions of poly(A)+ RNA. Most of the adenosine incorporation into tRNA is due to turnover of the 3’-terminal AMP but some new synthesis of tRNA also appears to take place in both 1-cell and 2-cell embryos at a rate of about 0·2 pg/embryo/h. In the poly(A)-RNA fraction, an unstable component which is assumed to be heterogeneous nuclear RNA is synthesized at a high rate and accumulates at a steady-state level of about 1·5 pg/embryo in the 1-cell embryo and about 3·0pg/embryo in the 2-cell embryo. Both 1-cell and 2-cell embryos synthesize relatively stable heterogeneous poly(A)-RNA, assumed to be mRNA, at a rate of about 0·3 pg/embryo/h; 2-cell embryos also synthesize mature ribosomal RNA at a rate of about 0·4 pg/embryo/h. Internally labelled poly(A)+ RNA is synthesized at a low rate in the 1-cell embryo, about 0·045 pg/embryo/h, but the rate increases to about 0·2 pg/embryo/h by the 2-cell stage. A striking feature of the 1-cell embryo is the high rate of synthesis of poly(A) tails, about 2·5× 106 tails/embryo /h of an average length of (A)43, due almost entirely to cytoplasmic polyadenylation. This and other evidence suggests a turnover of the poly(A)+ RNA population in 1-cell embryos as a result of polyadenylation of new RNA sequences and degradation of some of the pre-existing poly(A)+ RNA. In the 2-cell embryo, the rate of synthesis of poly(A) tails (average length (A)93) is estimated at about 0·8 × 106tails/embryo/h and a significant fraction of poly(A) synthesis appears to be nuclear.
X-chromosome inactivation mosaicism in the three germ layers and the germ line of the mouse embryo
Authors: McMAHON A. , Fosten M. , Monk M. 
Published: April 2021

ABSTRACT
Electrophoretic variant forms of the X-linked enzyme phosphoglycerate kinase (PGK-1, E.C.2,7,2,3) have been used to examine X-chromosome mosaicism in tissues from -day post coitum heterozygous female mouse embryos. Samples of yolk-sac endoderm, neural ectoderm, heart (mesoderm), liver (endoderm) and germ cells were analysed from each embryo. In all tissues except yolk-sac endoderm, both PGK-1 isozymes were expressed. The extent of covariance among tissues with respect to the PGK-1 isozyme contribution is consistent with all tissues being derived from the same pool of cells after X-inactivation. The covariance among tissues gives an estimate of the size of this pool (47 cells) and places the earliest time of X-inactivation in epiblast cells between and days post coitum. From the independent variance among tissues within an individual, the average primordial precursor pool size for the three germ layers and the germ line itself was estimated as 193 cells.