bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pathogenesis of preaxial polydactyly of the hand in human embryos
Authors: Yasuda Mineo 
Published: April 2021

ABSTRACT
Hand plates with preaxial polydactyly from 13 human embryos of the Carnegie stages 17 – 23 were examined macro- and microscopically. Morphological features in early pathogenesis of preaxial polydactyly are (1) an abnormal extension and a delayed involution of the apical ectodermal ridge on the preaxial border of the hand plate in stages 17 and 18, (2) a precocious development of an interdigital notch between the duplicated thumbs in stages 17 and 18, and (3) bifurcation of the distal part of the first digital ray in stage 19. A disorder of the interaction between limb ectoderm and mesoderm is considered to be the pathogenetic event.
Investigation of the determinative state of the mouse inner cell mass
Authors: Rossant J. 
Published: April 2021

ABSTRACTInner cell masses (ICMs) were dissected from and day blastocysts and cultured in contact with day morulae. Blastocysts and morulae were homozygous for different electrophoretic variants of the enzyme glucose phosphate isomerase (GPI). Aggregation of ICMs and morulae was observed, and such aggregates were able to form blastocysts in vitro and morphologically normal foetuses in utero. GPI analysis of these conceptuses revealed that most were chimaeric. However, donor ICM-type isozyme was only detected in the embryonic and extra-embryonic fractions of the chimaeras and never in the trophoblastic fraction.Thus, ICM cells appear unable to form trophoblast derivatives even when exposed to ‘outside’ conditions as experienced by developing trophoblast cells. This is evidence that ICM cells, although not overtly differentiated, are determined by days.
Aspects of tail muscle ultrastructure and its degeneration in Rana temporaria
Authors: Fox H. 
Published: April 2021

ABSTRACT
Tail muscles of larval Rana temporaria and to a lesser extent Xenopus laevis, at prometamorphosis, were investigated by light and electron microscopy. In the case of Rana their degeneration is described at metamorphic climax. The non-degenerate tail muscles of both genera are generally similar in their ultrastructure and likewise similar to those striated muscles of other adult vertebrates including amphibians. At climax tail muscles of Rana degenerate by autolysis. It seems likely that lysosomal enzymes are directly involved in sarcoplasmic degeneration. The relationship between lysosomes and myofibrillar degradation is difficult to establish. The subject is discussed in the light of relevant information (mainly mammalian) on muscle dystrophies. Anuran tail muscle is highly degraded before its probable phagocytosis by mesenchymal macrophages.
The developmental capacity of nuclei transplanted from keratinized skin cells of adult frogs
Authors: Gurdon J. B. , Laskey R. A. , Reeves O. R. 
Published: April 2021

ABSTRACT
Nuclei from keratinized skin cells of adult Xenopus foot-webs have been transplanted to enucleated eggs of the same species. The cells used to provide donor nuclei were obtained as a monolayer outgrowth from cultured foot-web expiants. When explants were cultured without plasma for 3 days, over 99-9 % of the outgrowth cells contained keratin as revealed by the binding of monospecific fluorescent antibody prepared against purified Xenopus keratin. Nuclei were transplanted from cells which had been cultured for 3days. None of the first transfer embryos developed as far as tadpoles. Eleven clones of embryos were prepared from the nuclei of partial first-transfer blastulae by use of serial nuclear transplantation. Eight of these clones contained swimming tadpoles with functional muscle and nerve cells, and six clones contained tadpoles with beating hearts, well differentiated eyes, and other organs. To prove that the nuclei of nuclear-transplant tadpoles were derived from the transplanted skin cell nuclei and not from a failure of ultraviolet light to inactivate the recipient egg nucleus, 1-nu skin cell nuclei were transplanted to eggs laid by 2-nu frogs. Several advanced tadpoles from six clones were analysed for nucleolar and chromosome number and found to be 1-nu diploids. The six clones of advanced tadpoles which were proved to carry the donor nuclear marker represent six first-transfer nuclei in a total sample of 129 skin cell nuclei originally transplanted. The probability that all six nuclei were derived from the 01 % of the donor cell population not proved to contain keratin is less than one in 1010. We conclude that cell specialization does not involve any loss, irreversible inactivation or permanent change in chromosomal genes required for development.
An experimental investigation into the possible neural crest origin of pancreatic APUD (islet) cells
Authors: Andrew Ann 
Published: April 2021

ABSTRACT
It has recently been contended that pancreatic APUD cells are neural crest derivatives. In an experimental investigation, isotopic grafts of neural tube containing neural crest cells were transplanted from chick and quail embryos labelled with tritiated thymidine, and from unlabelled quail embryos, to host chick embryos at the same stage of development. Transplantations were performed at various levels between somites 5 and 24 in embryos at 6- to 24-somite stages. In operated embryos at days of incubation, the pancreatic APUD cells were not labelled; nor did their nuclei show quail features. Migration of cells from the graft was evidenced by the presence of quail nuclei and/or radioactive label in autoradiographs, in spinal and sympathetic ganglia in the operated region.
It is concluded that the pancreatic APUD cells of the -day-old chick embryo are not derived from the trunk neural crest up to the level of somite 24. It is unlikely that more caudal levels contribute, because APUD cells are already concentrated in the dorsal pancreatic bud region at the 24-somite stage, by which time no migration of crest cells has occurred caudal to somite 24. This conclusion probably concerns A, B and D pancreatic endocrine cells.
High tyrosinase activity in albino Xenopus laevis oocytes
Authors: Wyllie A. H. , Robertis E. M. De 
Published: April 2021

ABSTRACT
Tyrosinase was measured in oocytes of the recently described albino mutant (apap) of Xenopus laevis. Although these oocytes show no pigmentation and the eggs are known to contain no melanosomes, tyrosinase -which is probably the only enzyme necessary for melanin synthesis from tyrosine -was increased more than twofold relative to the wild type. Tyrosinase recovered from albino and wild type oocytes showed the same K31 with respect to tyrosine, and this was not altered by previous gonadotrophin stimulation in vivo. The tyrosinase assay, based on [14]tyrosine incorporation into acid-insoluble products, was of greater sensitivity than previously described methods of the same type, through removal of low molecular weight material from the oocyte homogenate prior to incubation, and the use of tyrosine of high specific activity.
An Autoradiographic Study on the Uptake of Radiosulphate in the Rat Embryo1
Authors: Friberg U. , Ringertz N. R. 
Published: April 2021

ABSTRACT
The uptake of radiosulphate in rat embryos 7–22 days old was investigated with autoradiography and compared with the occurrence of metachromasia after toluidine blue staining and a positive PAS reaction. The youngest embryos retained rather small amounts of radiosulphate, which was evenly distributed. In the older embryos the amount of retained radiosulphate was considerably higher and regionally well differentiated. Marked changes in the autoradiographic pattern of certain organs occurred with growth. The uptake of radiosulphate was as a rule paralleled by metachromasia with toluidine blue. No direct relationship was found between fixation of radiosulphate and PAS reactivity of the tissues. Radiosulphate was found to be incorporated into cells and tissues containing inorganic sulphate (mineral part of bony tissues) and sulpho-mucopoly-saccharides (mesenchyme, mast-cells, &c.).
Development of Embryonic Mouse Gonads Transferred to the Spleen: Effects of Transplantation Combined with Genotypic Autonomy
Authors: Russell Elizabeth S. , Murray Louise M. , Small Eleanor M. , Silvers Willys K. 
Published: April 2021

ABSTRACT
Certain aspects of the pleiotropic relationship between the embryonic anaemia and germ-cell defect produced by deleterious alleles of the W-series in the mouse were tested by transfer of gonads from new-borns and 12–16-day embryos into a neutral site with rich blood-supply, the spleen of adult castrates. Splenic residence cut down the recovery of ovarian tissue from transplants at early stages, and slightly inhibited the amount of spermatogenesis at all stages. In spite of such environmental limitations, it was clear that at all stages transplants of both ovaries and testes contained fewer germ-cells at the 14-day post-natal stage if the donor were of defective sterile genotype than if it were of normal fertile type. This supports the hypothesis that genotypic autonomy of germ-cell level is established by the 12th day of embryonic life, and further development is independent of the W-genotype of surrounding tissue. The implications of these findings for understanding of pleiotropic relations are discussed.
Cell division, cell elongation and distribution of α-, β- and γ-crystallins in the rat lens
Authors: Mcavoy J. W. 
Published: April 2021

ABSTRACT
The vertebrate lens comprises cells from only one cell lineage and these exist in two distinct forms. Fibre cells make up the bulk of the lens and a monolayer of epithelial cells covers the anterior surface of the fibres. A quantitative analysis of cell division and cell specialization (elongation) in the lenses of 1-day-old and 6-to 7-week-old rats showed that the rat lens can be separated into two compartments; a proliferation compartment in the epithelium of the anterior lens and an elongation compartment in the posterior lens. In 6-to 7-week-old rats the proliferation compartment is divided into three sub-compartments which appear to be related to the anatomy of the anterior eye. Lens epithelial cells lying in the vicinity of the ciliary body have an average cell cycle time of 7·2 days, epithelial cells which lie below the iris have an average cell cycle time of 32·3 days, and cells in the central epi-thelium divide most slowly. The epithelium is bathed for the most part by the aqueous humour and the posterior part of the lens is surrounded by the vitreous humour. From this analysis as well as evidence from other laboratories it is suggested that a proliferation factor(s) may be present in the aqueous and that an elongation factor(s) which comes from the retina may be present in the vitreous.
There are three major groups of lens specific proteins, α-, β-and γ-crystallins. These proteins were separated by gel chromatography and antibodies raised against them in rabbits. Alpha-, β-and γ-crystallins were localized in sections of the 1-day-old rat lens by the indirect immunofluorescence method. Epithelial cells in the proliferation compartment contained only α-crystallin but all three groups of crystallins were detected in cells of the elongation compartment. β-Crystallin was detected first in elongating cells that had stopped dividing and γ-crystallin was detected later in the elongation process. Thus, synthesis of α-and γ-crystallins may normally depend on the elongation factor(s) from the retina. Also, since there is a close relationship between cessation of cell division and detection of β-crystallin, another factor governing the synthesis of β-crystallin may be whether the cells have ceased dividing. In this way the expression of crystallin genes may be co-ordinated as the lens grows and cells make the transition from proliferation to elongation compartments.
Chromosome analysis of early postimplantation presumptive haploid parthenogenetic mouse embryos
Authors: Kaufman Matthew H. 
Published: April 2021

ABSTRACT
The chromosome constitution of early postimplantation presumptive haploid parthenogenetic mouse embryos was examined. All the embryos isolated were at the egg-cylinder stage and seven contained dividing cells. In two of the apparently healthy embryos only haploid mitoses were seen, whereas in five others an approximately equal proportion of haploid and diploid mitoses was observed. Out of 52 cells in which unequivocal counts could be made, only one contained more than the euploid number of chromosomes (mouse, n = 20). Possible reasons for the poorer development of haploid compared to diploid parthenogenetic embryos are discussed.
In vitro development of inner cell masses isolated immunosurgically from mouse blastocysts: I. Inner cell masses from 3·5-day p.c. blastocysts incubated for 24 h before immunosurgery
Authors: Hogan Brigid , Tilly Rita 
Published: April 2021

ABSTRACT
This paper describes the in vitro development of inner cell masses isolated immunosurgically from mouse blastocysts which had been collected on 3 ·5 days p.c. and then incubated for 24 h. The inner cell masses continue to grow in culture and develop through a series of stages with increasing complexity of internal organization. By day 1 all of the cultured ICMs have an outer layer of endoderm, and by day 3 some of them have two distinct kinds of inside cells; a columnar epithelial layer and a thin hemisphere of elongated cells. Later, mesodermal cells appear to delaminate from a limited region of the columnar layer, close to where it forms a junction with the thinner cells. By day 5, about 25 % of the cultured ICMs have a striking resemblance to normal 7 ·5-day p.c. C3H embryos, with embryonic ectoderm, extra-embryonic ectoderm and chorion, embryonic and extra-embryonic mesoderm, and visceral endoderm. When mechanically disrupted and grown as attached clumps of cells in a tissue dish, these embryo-like structures give rise to trophoblast-like giant cells. These results suggest that the inner cell mass of 4 ·5-day p.c. blastocysts contains cells which can give rise to trophoblast dérivâtes in culture.
Cell division and cell allocation in early mouse development
Authors: Kelly S. J. , Mulnard J. G. , Graham C. F. 
Published: April 2021

ABSTRACTCell division was observed in intact and dissociated mouse embryos between the 2-cell stage and the blastocyst in embryos developing in culture. Division to the 4-cell stage was usually asynchronous. The first cell to divide to the 4-cell stage produced descendants which tended to divide ahead of those cells produced by its slow partner at all subsequent stages of development up to the blastocyte stage. The descendants of the first cell to divide to the 4-cell stage did not subsequently have short cell cycles. The first cell or last cell to divide from the 4-cell stage was labelled with tritiated thymidine. The embryo was reassembled, and it was found that the first pair of cells to reach the 8-cell stage contributed disproportionately more descendants to the ICM when compared with the last cell to divide to the 8-cell stage.
Effect of oxygen concentration on morphogenesis of cranial neural folds and neural crest in cultured rat embryos
Authors: Morriss Gilltan M. , New D. A. T. 
Published: April 2021

ABSTRACT
Rat embryos, days old, cultured with a 5 % or 10% O2 gas phase underwent normal or near-normal cranial neurulation; however, culture at 20% or 40% O2 resulted in abnormal morphogenesis of the cranial neural folds from the 9-somite stage onwards, and the brain tube frequently failed to close. Normal morphogenesis was characterized by a narrowing V-shaped profile, development of a slightly concave neuroepithelial surface, and formation of a sharp mediad curvature of the most lateral region prior to midline apposition and fusion. These morphogenetic events were related to cellular changes within the neuroepithelium, namely cell death, onset of neural crest cell migration, and loss of apical microfilament bundles from the most lateral cells. In 20% and 40% O2-cultured embryos, failure of curvature of the neuroepithelium was associated with failure or retardation of the related cellular changes; it may therefore have been due to the maintenance of an excessive rigidity which opposed the forces involved in bringing about the final stage of brain-tube formation.
Mitochondria in normal (low O2 and in vivo) embryos were of the anaerobic type, having few cristae; in high O2-cultured embryos they were of the characteristic aerobic type, indicating an adaptation to the abnormal environment.
Fine structure of the lumbosacral neural folds in the mouse embryo
Authors: Wilson Doris B. , Finta Laurel A. 
Published: April 2021

ABSTRACTThe neural folds in the lumbosacral region of the normal 8-day and 9-day mouse embryo were studied by means of transmission electron microscopy with and without lanthanum treatment. The cells showed an abundance of ribosomes, microtubules arranged parallel to the long axes of the cells, and microfilaments extending across the apices. At the luminal border junctional complexes were common, and an occasional midbody was seen stretching between adjacent cells nearing the end of telophase. In the 8-day embryos, gap junctional vesicles (annular nexuses) bounded by layered membranes and containing cytoplasm with ribosome-like material were commonly observed; at 9 days the vesicles were relatively rare. The lanthanum-treated material demonstrated that the tracer was able to pass through the subluminal junctional complexes and throughout the intercellular spaces. However, the space between the membranes of the gap junctional vesicles lacked lanthanum and thus apparently did not communicate with the intercellular space.
The Dependence of the Cellular Transformation of the Competent Ectoderm on Temporal Relationships in the Induction Process
Authors: Toivonen Sulo 
Published: April 2021

ABSTRACT
In 1952, Nieuwkoop et al. suggested a new hypothesis concerning the induction phenomenon determining the early development of the amphibian embryo. This hypothesis was based on cleverly planned experiments in which folds of competent epidermis were transplanted on to different regions of the neural plate of the neurula. According to this hypothesis, the invaginating archenteron roof is supposed first to activate the overlying ectoderm, enabling it to develop autonomously to archencephalon and its derivatives. This same archenteron roof is later thought to exert a second effect, which they called transformation. This second action is considered responsible for modifying the differentiation tendencies of the activated archencephalon so as to result in structures typical of more caudal regions of the nervous system. This process is regarded as a quantitative one, so that with increasing strength of transformation, the differentiation tendencies would be progressively more caudal.
Contribution to the Study of Germ-cells in the Anura
Authors: Blackler A. W. 
Published: April 2021

ABSTRACT
Shortly after fertilization of the egg of R. temporaria there arise, near the vegetal pole, small islets of specifically stainable cytoplasm that eventually become included in cells lying in the blastocoel floor. From this time forward the special cytoplasm becomes increasingly difficult to identify with the cytological techniques used, but not until it is possible to confirm that the cells in question are primordial germ-cells. Thus the findings of Bounoure (1934) for this species are confirmed and extended. This germinal cytoplasm has also been found in the eggs and embryos of X. laevis and B. bufo, but, rather surprisingly, not in R. esculenta. The germ-plasm is, at first, rich in pentosenucleic acid (PNA) but loses this property shortly after an intracellular change in its position which occurs in the earliest stages of gastrulation. Examination of parthenogenetically activated eggs reveals that germinal cytoplasm can be formed in the absence of sperm.
Acléiencéphalie expérimentale in vitro
Authors: Lutz par Hubert , Lutz-Ostertag Yvonne 
Published: April 2021

ABSTRACT
Le terme d’acléiencéphalie (du grec κ λ ϵ ι ω = je ferme) a été créé par Ancel (1955) pour désigner les monstres chez qui la gouttière nerveuse reste ouverte. C’est là une malformation qui peut être obtenue expérimentalement par des procédés divers: par action des rayons X (Kaven, 1938; Snell, 1941; Warkany & Schraffen-berger, 1947; Russell, 1950; Hicks, 1953); par action ultra-sons (Lutz & Lutz-Ostertag, 1957); par action de substances variées (Ancel, 1955; Lefèvre-Boisselot, 1951; Giroud & Martinet, 1957); par anoxie (Gallera, 1951; Büchner, Rüb-saamen, & Rothweil, 1951; Naujoks, 1953; Müshett, 1953; Büchner, 1955; Lutz &Lepy, 1958).
Morphogenesis of the epidermis of adult abdomen of Drosophila
Authors: Mandaravally Madhavan Mekkara , Madhavan Kornath 
Published: April 2021

ABSTRACT
Mitotic pattern in the different histoblast nests, and the temporal sequence of fusion and differentiation of these nests and spiracular anlagen resulting in the formation of the different regions of the adult abdomen of Drosophila melanogaster were studied by examining whole mount preparations and histological sections of the epidermis from closely timed develop-mental stages. The relationship between the boundaries of the primary (larval) and secondary (adult) segments was determined by following the points of insertion of the dorsal internal oblique muscles which persist through metamorphosis. These studies indicate that the descendants of the anterior dorsal histoblast nest form the hairy and bristled region of the tergum, while those of the anterior and posterior groups of the posterior dorsal nest give rise to the intersegmental membrane and acrotergite respectively; the ventral histoblast cells give rise to the sternum and pleural region while the spiracular anlage forms the spiracle. These findings confirm and extend the conclusions derived from genetic analyses or after experi-mental induction of defects, on the lineage of the various histoblast nests.
Blastoderm formation in the silkworm egg (Bombyx mori L.)
Authors: Takesue Sachiko , Keino Hiroomi , Onitake Kazuo 
Published: April 2021

ABSTRACT
Embryogenesis in the egg of the silkworm, Bombyx mori, up to 24 h after oviposition was studied by light microscopy with special reference to nuclear migration and blastoderm formation. In Bombyx eggs blastoderm cells seem to form in a mechanism different from that usually seen in many other insect species; that is, in Bombyx eggs no typical cleavage furrows were seen. Cleavage nuclei which had migrated, accompanied by the associated cytoplasm, to the egg surface pushed up the plasma membrane and protruded beyond the initial level of the periplasm. The periplasm fused with their associated cytoplasm was partitioned among and pulled around the nuclei. Then each nucleus was separated by a laterally-invading limiting membrane from the yolk-granules-occupied region to yield a blastoderm cell.
Regeneration of optic nerve fibres from a compound eye to both tecta in Xenopus: evidence relating to the state of specification of the eye and the tectum
Authors: Gaze R. M. , Straznicky C. 
Published: April 2021

ABSTRACT
Xenopus with one double-nasal (NN), double-temporal (TT) or double-ventral (VV) eye were induced to regenerate optic fibres from the compound eye to both tecta after metamorphosis. The extent of the projection from the compound eye was then estimated autoradiographically at various intervals after nerve section. The regenerated projection covered the whole of the contralateral tectum but covered only a restricted part of the ipsilateral tectum; thus NN eyes innervated caudomedial tectum only, TT eyes innervated rostrolateral tectum only and VV eyes innervated medial tectum only. Since the tectum ipsilateral to the compound eye also received the projection from the normal eye these results are taken to indicate that NN, TT and VV eyes are unregulated systems in terms of the retinal positional markers that they carry; each such eye bears only the appropriate half-set of such markers.