bluuebunny/crossref_metadata_2025 huggingface dataset:
The Dependence of the Cellular Transformation of the Competent Ectoderm on Temporal Relationships in the Induction Process
Authors: Toivonen Sulo
Published: April 2021

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

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

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

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

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

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.
The spatio-temporal framework of melanogenic induction in pigmented retinal cells of Xenopus laevis
Authors: Hoperskaya Olga A. , Golubeva Olga N.
Published: April 2021

Using methods involving transplantation of neuroectoderm and eye rudiments between ap/ap mutants and + / + embryos of Xenopus laevis, new aspects of melanogenic induction have been ascertained. The possibility of separate induction of a melanocyte cell type and of the product of terminal differentiation in it - melanosomes, has been demonstrated. Melanogenic induction starts at the late gastrula stage. It has an irreversible character which has been shown using the technique of double transplantation. Melanogenic factor (MgF) is produced only by the region of endomesoderm which is adjacent to eye rudiments in the course of normal development. Competence for melanogenic induction lasts till stage NF 30. Melanogenic induction appears to be species-specific; at least after transplantation of eye vesicles from ap/apXenopus laevis to Rana temporaria the melanoprotein synthesis cannot be switched on. L-Tyrosine, under the conditions of the experiments, is not a factor in the induction of melanogenesis.
Immunosurgical studies on inner cell mass development in rat and mouse blastocysts before and during implantation in vitro
Authors: Spielmann Horst , Jacob-Müller Ursula , Beckord Werner
Published: April 2021

Eighty per cent of rat blastocysts (Wistar, SW72) cultured for 96 h in NCTC-109 supplemented with fetal calf serum (FCS) hatched from the zona pellucida and developed a trophoblast giant cell layer. Thirty seven per cent of the rat blastocysts developed an inner cell mass (ICM) which, in about 7 %, consisted of two germ layers (ectoderm and endoderm), compared to 84% in NMRI mice. A significantly better ICM development was obtained with cultured rat blastocysts that had hatched in vivo. Similar to the in vivo situation LDH-5 was present in rat blastocysts after implantation in NCTC-109-FCS. Differentiation of C57BL mouse blastocysts in NCTC-109-FCS proceeded as poorly as in the rat.

ICM development of rat and mouse blastocysts in NCTC-109-FCS was studied in detail. ICMs of the two species were isolated immunosurgically using complement from different species, e.g. human, rat and rabbit complement, since guinea-pig complement did not lyse trophectoderm cells of rat blastocysts. All immunosurgically isolated rat ICMs degenerated within 48 h, but mouse ICMs isolated with rat or rabbit complement developed significantly better than mouse ICMs isolated with guinea-pig complement. Determinations of the blastocyst total cell number (BTCN) and of the cell number of immunosurgically isolated ICMs were performed in rat and mouse blastocysts to investigate growth kinetics of the ICM before implantation in vitro. In the mouse an exponential increase in both BTCN and cell number of the ICM was observed during the 48 h before implantation in NCTC-109-FCS and also during the 16-24 h before implantation in vivo. In the rat, doubling of the BTCN was found only during the first 24 h in NCTC-109-FCS and there was hardly any increase in the cell number of the ICM during the first 48 h in culture. ICM growth of blastocysts in NCTC-109-FCS is, therefore, stimulated in the mouse before and after implantation and. in the rat it is inhibited already before implantation.
Membrane sterols and the development of the preimplantation mouse embryo
Authors: Pratt Hester P.M. , Keith Jo , Chakraborty Jyotsna
Published: April 2021

The role of membrane sterols in the compaction and subsequent development of the preimplantation mouse embryo was studied by incubating embryos in 7-ketocholesterol and other oxygenated sterols. These sterols have been shown to inhibit sterol synthesis and deplete membranes of cholesterol in a variety of other cell types.

Compaction and subsequent blastocyst formation were normal when embryos were incubated in physiological sterols but were inhibited by oxygenated sterols to a degree which depended upon the concentration of sterol, duration of incubation and developmental age of the embryos. Precompaction 8-cell embryos were most susceptible to the action of these sterols and failed to compact (as assessed by cell flattening and increased intercellular adhesion) but continued to divide, whilst later stage embryos developed normally. 7-keto-cholesterol had a specific effect on the ultrastructure of the smooth endoplasmic reticulum of treated embryos. The developmental and ultrastructural effects induced by the oxygenated sterols could be reversed or prevented by the use of products of the blocked reaction (i.e. mevalonate, desmosterol or cholesterol).

These results substantiate the evidence that preimplantation mammalian embryos are capable of synthesizing membrane sterols from the 8-cell stage onwards and emphasize the importance of the sterol composition of membranes for normal cytokinesis and compaction of the mouse embryo.
Pattern regulation and the origin of extra parts following axial misalignments in the urodele limb bud
Authors: Thoms Stephen D. , Fallon John F.
Published: April 2021

Pattern regulation following axial misalignments in the stage-38 + to stage-40 urodele limb bud was studied on one newt and two salamander species. Grafts of the distal tip of the limb bud were made to the stump of a host limb bud from which a similar piece had been removed. The grafts were positioned with either their anteroposterior, dorsoventral, or both of these axes reversed with respect to the host axes. Mirror-imaged duplications, positioned posteriorly or both anteriorly and posteriorly, occurred nearly all (96%) of the time when the anteroposterior axis was reversed. Dorsoventral axial misalignment rarely promoted the generation of mirror-imaged duplications (8%) but did affect the organization along the anteroposterior axis by causing a serial repetition of either digit 2 or digit 3. Regulation, therefore, does not always occur along each axis independently of the others. Consistent with the data derived from reversing individual axes, most of the duplications which occurred when both axes were reversed were in the anteroposterior plane. Some were in the dorsoventral plane, and a few had intermediate positions. Of these duplications a few were neither right nor left hands, rather they were of mixed handedness with a change in the dorsoventral polarity from the anterior border to the posterior border.

Whether extra parts which result from axial misalignments arise from the graft, the host, or both the graft and the host was investigated using heteroplastic grafts and grafts exchanged between triploid and diploid axolotls. Duplications were found to have cellular contributions from both the graft and the host. In some cases one source would dominate but usually both made a substantial contribution. The diploid-triploid material suggests that a considerable mixing of host and graft cells may occur in duplications. Additionally, some digits of the graft sequence of digits can be derived from host tissue. The extra digit in those hands displaying a serial repetition was derived from host tissue in some cases and graft tissue in other cases.
Commitment of stem cells to nerve cells and migration of nerve cell precursors in preparatory bud development in Hydra
Authors: Berking Stefan
Published: April 2021

Budding in Hydra starts as an evagination of the double-layered tissue in the parent animal’s gastric region. Five hours later the density of nerve cells in the bud’s tissue doubles, representing the first detectable difference from the cellular composition of the surrounding tissue. These new nerve cells derive from multipotent stem cells which are in S-phase one day before evagination starts. Some of the bud’s new nerve cells derive from stem cells which have migrated into the future bud’s tissue after their commitment, apparently attracted by the bud anlage. The bud anlage recruits precursors of nerve cells even during starvation, during which nerve cell production ceases in other parts of the body. Furthermore, the bud anlage controls the duration of the development from commitment to final differentiation of the resulting nerve cells.

Experiments with an inhibitor purified from hydra tissue indicate a tight correlation between stages of preparatory bud development and stages of recruitment of nerve cells for the bud. Whether or not precursors of nerve cells are involved in the control of bud formation in normal hydra, as compared to epithelial hydra which still bud though consisting of epithelial cells only, will be discussed.
The control of trophoblastic growth in the guinea pig
Authors: Ilgren E. B.
Published: April 2021

The growth of mouse trophectoderm depends upon the presence of the inner cell mass. Whether this applies to other species of mammals is not known. To investigate this problem, the guinea pig was selected for two reasons. Firstly, the growth of guinea-pig trophoblast resembles that of man. Secondly, earlier studies suggest that the proliferation of guinea-pig trophectoderm may not be under ICM control. Therefore, in the present study, the guinea-pig blastocyst was cut microsurgically to yield two tissue fragments. These contained roughly equal numbers of trophectodermal cells, one fragment being composed only of trophectoderm and the other containing ICM tissue as well. Subsequently, the growth of these mural and polar fragments was followed in vitro since numerous technical difficulties make an in vivo analysis of this problem impracticable. In a manner similar to the mouse, the isolated mural trophectoderm of the guinea pig stopped dividing and became giant. In contrast, guinea-pig polar fragments formed egg-cylinder-like structures. The latter contained regions structurally similar to two presumptive polar trophectodermal derivatives namely the ectoplacental and extraembryonic ectodermal tissues. These findings suggest that guinea-pig trophectodermal growth may occur in a manner similar to the mouse and thus be under ICM control.
The effect of microtubule- and microfilament-disrupting drugs on preimplantation mouse embryos
Authors: Siracusa G. , Whittingham D. G. , De Felici M.
Published: April 2021

The sensitivity of early preimplantation mouse embryos to drugs which disrupt microfilament function (cytochalasin B-CB and cytochalasin D-CD) and microtubule assembly (colchicine, colcemid, vinblastine and griseofulvin) was examined. CD inhibited cleavage at a concentration 35-fold lower than CB (3 × 10–7 M v. 1 × 10−5 M). Treatment of 2-cell embryos for 6 h with 1 × 10−5 M CB or 1 × 10−6 M CD or continuous exposure to lower concentrations of CB or CD did not affect development to the blastocyst stage in vitro. Vinblastine inhibited cleavage at a concentration tenfold lower than colcemid or colchicine (1 × 10−8 M v. l × 10−7 M). The continuous presence of colcemid at 10−8 M did not affect the development of 2-cell embryos to the blastocyst stage, but development was reduced with vinblastine at 1 × 10−9 M and completely inhibited with colchicine at 1 × 10−8 M. The drugs produced similar responses when 2-cell embryos were treated for 6 h with concentrations that inhibited cleavage. Complete inhibition of cleavage was obtained after only a 2 h exposure to 2 × 10−7 M colchicine. A similar concentration of lumicolchicine did not affect cleavage or blastocyst formation. Embryos were less sensitive to griseofulvin; the first cleavage division was unaffected by concentrations as high as 3 × 10− 4M and only 50% of 2-cell embryos failed to cleave in 1 × 10 1 and 3 × 10 −4M griseofulvin. At these concentrations a small proportion of 1-cell embryos and the majority of the 2-cell embryos showed unequal cytoplasmic division probably caused by the formation of multipolar spindles. The continuous exposure of 2-cell embryos to 3 × 10−5 M griseofulvin did not affect blastocyst formation.
A method for visualizing the chromosomes of the second polar body of the mouse egg
Authors: Modliński J. , McLaren Anne
Published: April 2021

A second-polar-body nucleus inserted by microinjection into a different mouse egg entered into mitosis synchronously with the pronuclei of the host egg. The extent to which the karyotype of the polar body can yield information on the karyotype of the donor egg is discussed.
Disproportionate micromelia (Dmm): an incomplete dominant mouse dwarfism with abnormal cartilage matrix
Authors: Brown Kenneth S. , Cranley Robert E. , Greene Robert , Kleinman Hynda K. , Pennypacker John P.
Published: April 2021

This paper describes a new autosomal incomplete dominant dwarfism, disproportionate micromelia, which has been characterized genetically and phenotypically, and the cartilage of homozygotes, and heterozygotes has been examined by histochemical, immunofluorescence and biochemical methods. Homozygotes, which die at birth, are disproportionately short and have cleft palates. The heterozygotes appear normal at birth but beginning at 1 week of age dwarfism is apparent and increases during growth. Histochemical and biochemical analyses of the cartilage rudiments of homozygotes at day 18 of gestation demonstrate that the cartilage growth plate is disorganized and that the matrix components, collagen and proteoglycan, are altered. Total collagen synthesis is reduced by approximately 30% and the amount of type II collagen is greatly reduced. By immunofluorescence staining with collagen antibodies, it appears that type II collagen is located primarily near the cell surface of chondrocytes but is poorly distributed throughout the remainder of the matrix. The amount of proteoglycan in the cartilage matrix is reduced by approximately 70% as determined by chemical analysis of hexosamines and by [35S]sulfate incorporation. Although the proteoglycans synthesized by the mutant are normal in size and in glycosaminoglycan composition, they were more easily extractable from the matrix than were normal cartilage proteoglycans. Heterozygotes had reduced cartilage matrix proteoglycan by histochemical methods, but the organization of the epiphyseal cartilage was not abnormal. These data suggest that a reduced or abnormal cartilage matrix is the cause of the dwarfism.
Biochemical studies of intrauterine components of the tammar wallaby Macropus eugenii during pregnancy
Authors: Thornber Elizabeth J. , Renfree Marilyn B. , Wallace Gregory I.
Published: April 2021

The in vitro uptake and incorporation of [3H] uridine by blastocysts of the tammar wallaby showed a 16- and 30-fold increase from day 0 to day 10 after removal of pouch young, respectively. Two of the six non-expanded blastocysts recovered on day 5 showed a tenfold increase in incorporation. During the first ten days after removal of pouch young the diameter of the blastocyst increased threefold. Endometrial exudate from gravid uteri had a higher protein concentration than exudate from nongravid uteri (39·5 ±0·9 and 320 ± 2·0 mg/ml (mean + s.E.M.), respectively). Endometrial exudates from uteri where the blastocyst was actively growing were found to contain six uterine-specific proteins. These were separated by gradient polyacrylamide gel electrophoresis. Two of the proteins were prealbumins and the others were larger molecules (M.W. 153000-670000). Two proteins were only present at particular stages of pregnancy: the other four were present at all stages from diapause to birth, in exudate from gravid and nongravid uteri. The specific binding of progesterone and androstenedione to proteins in endometrial exudates or uterine flushings from pregnant wallabies was less than one per cent of the value obtained from day-5 pregnant rabbits. The ability of mouse blastocysts to take up and incorporate [3H] uridine into acidinsoluble material increased threefold in the presence of day-10 endometrial exudates from wallabies. However, this was less than ten percent of the values obtained in the presence of bovine serum albumin.

The concentration of calcium in endometrial exudates increased from 23·6 to 45·2μg/ml during pregnancy; in endometrium it remained at 88·7μg/g (wet weight) throughout pregnancy, and in plasma it was 53·3 μg/ml. The concentration of zinc in endometrial exudates was 4·5 μg/ml; in endometrium it decreased from 21·8 to 13-3μg/g (wet weight) during pregnancy and in plasma it was 0·6 μg/ml.
Dictyostelium amoebae can differentiate into spores without cell-to-cell contact
Authors: Kay Robert R. , Trevan David J.
Published: April 2021

Amoebae of sporogenous mutants of Dictyostelium discoideum can differentiate into stalk cells and spores in the absence of normal morphogenesis when spread on agar containing cyclic-AMP. The efficiency of differentiation is improved when the amoebae are incubated as submerged monolayers in plastic petri dishes. Under these conditions spore formation is density dependent and hence requires some form of cellular interaction. To determine whether this interaction involves direct cell-cell contact we have made time-lapse films of cells differentiating at intermediate density. These films show that amoebae can develop into spores without making contact with any other cells. In addition, although some cells do divide during incubation, division is not necessary for spore formation. At higher densities small aggregates form which give rise to mixtures of stalk cells and spores. There is no detectable patterning of the two cell types within such aggregates.
Differentiation within the gonads of Drosophila revealed by immunofluorescence
Authors: Brower Danny L. , Smith R. J. , Wilcox Michael
Published: April 2021

The antibody produced by the hybrid cell line DA.1B6 binds to the diploid epithelial cells of Drosophila. In this paper, we describe the immunofluorescence-binding pattern of the antibody to the gonads. A bright sheath of fluorescence extends from the seminal vesicle onto the most proximal part of the adult testis. The only other significant binding to the organ is to the apical cells of the germinal proliferation centre, which fluoresce brightly in testes from adults and from third instar larvae. In the adult ovary, there is strong binding to the cells of the follicular epithelium, although this binding is reduced in the latter stages of follicle development. Soon after the formation of a follicle, a pair of epithelial cells at each pole of the follicle can be seen to fluoresce much more brightly than the other cells. This early differentiation is reflected in the morphogenetic behaviour of these polar cells as the follicle develops. The anterior pair are among the ‘border cells’ which migrate between the nurse cells to the anterior pole of the developing oocyte; and, when the follicular epithelium around the oocyte becomes columnar, the posterior pair of cells do not elongate as much as the surrounding cells.
Neural crest formation in the head of the mouse embryo as observed using a new histological technique
Authors: Nichols David H.
Published: April 2021

A histological technique is described which results in the differential staining of neural crest cells. This is used to describe the formation and early migration of crest cells in the head of the mouse embryo. The first indications of crest formation are seen in the midbrain/anterior hindbrain at 3–4 somites where crest cells accumulate in the basal surface of the ectodermal epithelium near the future margin of the neural plate. Shortly thereafter (4–6 somites) these cells disrupt the basal surface of the epithelium and escape as mesenchyme. The apical epithelial cells in this region become the surface ectoderm adjacent to the neural plate. Subsequently, crest is formed from neural plate rather than surface ectoderm. In addition, mesenchyme is formed from presumptive surface ectoderm in a groove in the lateral portion of the fold between the forebrain and the midbrain. By 5–7 somites, crest mesenchyme is formed at all levels of the midbrain, hindbrain, and from the margins of the forebrain adjacent to the optic pits. Because of the bending of the embryonic axis, forebrain crest cells appear to migrate dorsally over the presumptive eye where they are met by ventrally migrating midbrain crest cells. Crest formation continues in the region of the midbrain and hindbrain during, and for an undetermined period after closure of the head folds at between 8 and 16 somites.

These results demonstrate differences in the origin and timing of crest formation between chick and mouse. From this may be inferred different patterns of crest migration as well.

In addition, the ability to directly observe early crest formation should aid in the analysis of the mechanisms by which epithelial cells are converted into mesenchyme.
The induction of neural crest-derived cartilage and bone by embryonic epithelia: an analysis of the mode of action of an epithelial-mesenchymal interaction
Authors: Hall Brian K.
Published: April 2021

The formation of membrane bone from neural crest-derived mesenchyme of the maxillary and mandibular processes of the embryonic chick depends upon prior interactions between the mesenchyme and maxillary or mandibular epithelia. The present study explores the specificity of these interactions using tissue recombinations between heterotypic epithelia and mesenchyme. Mandibular and maxillary mesenchyme responded to maxillary and mandibular epithelia by forming bone. A third osteogenically inductive epithelium, the scleral epithelium with its specialized scleral papillae, also allowed mandibular mesenchyme to form bone, indicating that mesenchyme can form bone in response to osteogenic epithelia other than its own. Epithelia which normally do not induce membrane bone formation in situ (wing and leg bud, back and abdominal epithelia) also allowed mandibular epithelia to ossify as did mandibular epithelia from the 10-day-old foetal mouse. Thus this tissue interaction is neither site nor species specific.

Mandibular epithelium allowed bone to form in osteogenic mesenchyme from the maxilla and the sclera of the chick and from the mouse mandible but would not induce bone formation from normally non-osteogenic mesenchyme of the limb buds, chorioallantoic membrane or trunk neural crest.

The results obtained with all of the tissue recombinations were consistent with the epithelial-mesenchyme interactions that initiate osteogenesis in both the mandibular and the maxillary processes being permissive interactions. The distinction between permissive and instructive interactions is discussed.
Sequence of regeneration in the Drosophila wing disc
Authors: Karlsson Jane
Published: April 2021

The sequence of appearance of different structures during regulation was ascertained for three wing disc fragments. It was found that structures were added sequentially from the cut edge. Regeneration in one fragment was very fast and successful, and it is suggested that this is difficult to explain in terms of wound healing being responsible for the decision to regenerate rather than duplicate. In another fragment, regeneration appeared to proceed from one part of the cut edge only, this being the region through which the anteroposterior compartment boundary runs. Compartment boundaries have been implicated in both proximodistal and circumferential regeneration, and it is suggested that regeneration is controlled at these sites. The decision to regenerate rather than duplicate may be made on the basis of which compartment boundaries are exposed at the cut edge, and their preferred direction of regeneration. The implications of this interpretation for the control of growth are discussed.
The role of the visceral yolk sac in mediating protein utilization by rat embryos cultured in vitro
Authors: Freeman Stuart J. , Beck Felix , Lloyd John B.
Published: April 2021

Conceptuses from 9·5-day pregnant rats have been cultured for 48 h in heat-inactivated homologous serum. Embryonic development was normal. The protein contents of embryos and visceral yolk sacs after different periods of culture were recorded.

When 125I-labelled polyvinylpyrrolidone or [3H]dextran were added to the culture serum, radioactivity was accumulated by the yolk sac, but only background levels were detected in the embryo itself. The amount of radioactivity found in the yolk sac varied with the length of the interval before harvesting during which 125I-labelled PVP or [3H]dextran was present.

When formaldehyde-denatured 125I-labelled bovine serum albumin was added to the culture serum, little radioactivity accumulated in the yolk sac and only background levels were found in the embryo. Trichloroacetic acid-soluble radioactivity steadily appeared in the culture serum, however.

When conceptuses were cultured in glucose- and vitamin-supplemented dialysed serum from rats injected 2 h previously with [3H]leucine, radioactivity was found in both embryos and yolk sacs. The amount of radioactivity in these tissues increased with duration of exposure to 3H-labelled serum proteins. After short exposures little of the yolk sac and embryonic radioactivity was acid-insoluble, but this proportion increased with duration of exposure.

These results are interpreted as follows. Intact macromolecules cannot enter the cells of the embryo itself, but are captured by pinocytosis into the cells of the visceral yolk-sac endoderm. Indigestible macromolecules such as 125I-labelled polyvinylpyrrolidone and [3H]- dextran accumulate within the yolk-sac lysosomes, but proteins are digested there by the lysosomal enzymes. The radiolabelled digestion product of 125I-labelled bovine albumin is [125I]iodotyrosine, which cells cannot utilize and so is excreted into the culture serum. The labelled digestion product of the 3H-labelled rat serum proteins is [3H]leucine, which is used for protein synthesis in both embryo and yolk sac.

The experiments provide direct evidence for the long-suspected role of the yolk sac in mediating embryonic nutrition in the period of development prior to the establishment of a functional chorioallantoic placenta.
Size regulation inDictyostelium
Authors: Kopachik Will
Published: April 2021

The division of large aggregate centres into separate slugs was examined in two strains of Dictyostelium discoideum which differ in size. The evidence is consistent with the hypothesis that the size of the slugs is determined by two factors; one is the ability of a tip to inhibit surrounding cells from forming an independent, rival tip; the other is the ability of the surrounding cells to resist being subjected to the inhibition of the newly arisen tip. If the surrounding cells are easily inhibited, then the slugs produced will be large; if they are resistant to inhibition the resulting slugs will be correspondingly small. An assay for tip inhibition was developed which was used to estimate the volume and distance over which inhibition occurs, the time over which it acts and the effect of tip size and cell mass shape on size regulation. The measurements and the results of experiments which showed inhibition across a thin agar layer are consistent with the hypothesis that an inhibitor spreads out from the tip by simple diffusion. In further studies it was found that although inhibition strength varies with the size of the tip, the ability to inhibit was the same in both strains whereas the resistance to inhibition was greater in the smaller strain.
A correlation between the capacity of cavity formation and the subsequent differentiation of teratocarcinoma embryoid body lines
Authors: Uno Kazuko
Published: April 2021

Seven different embryoid body (EB) lines of mouse teratocarcinoma were isolated from a single EB. With regard to each of the lines, a comparison was made of the following developmental properties, including potentiality: (1) cavity formation in a short term intraperitoneal passage, (2) growth in vivo, (3) cardiac muscle differentiation in vitro following intraperitoneal passage and (4) differentiation of solid tumours in vivo. These lines could be divided into three distinct groups with respect to their capacity for cardiac muscle differentiation. It has been shown that a high capacity for cell differentiation in vitro correlates well with the capacity for cavity formation of an EB during the in vivo period. This cavity formation was followed by the appearance of primitive-streak-like structures, from which mesodermal cells were subsequently formed.
Cell migration from the chick olfactory placode: a light and electron microscopic study
Authors: Mendoza A. S. , Breipohl W. , Miragall F.
Published: April 2021

The differentiation of the olfactory placode in the chick has been studied using light and electron microscopy. Special attention was paid to the appearance of neuronal cells within the placodal ectodermal thickening, the migration of cells out of this tissue and the appearance of the first fila olfactoria in the differentiating olfactory mucosa.

Between the third and fifth day of incubation a large number of cells is observed leaving the base of the invaginating olfactory placode, often in contact with thin axon bundles. These cells are characterized by a well-developed Golgi apparatus, a considerable number of mitochondria and dense-core vesicles. The morphology of these migrating cells resembles that of cells observed near the basement membrane within the developing olfactory epithelium and is clearly different from the mesenchymal cells which are filled with poly-ribosomes. At the sixth day of incubation thick axon bundles can be observed within the epithelium and the underlying lamina propria. The possible fate of the migrated epitheloid cells is discussed.
La Région caudale d’une Planaire est-elle capable d’induire la régénération d’un pharynx?
Authors: Sengel Catherine
Published: April 2021

Experiments involving amputation and irradiation have been made on the fresh-water planarians Dugesia lugubris and Polycelis nigra to ascertain the precise roles of head and tail (Fig. 1) in the induction of a pharyngeal zone and of a pharynx. During the normal regeneration of a prepharyngeal cephalic fragment (region I, Fig. 2a), a pharynx regenerates in the original tissues of the fragment at the same time as the caudal blastema appears. During the normal regeneration of a postpharyngeal caudal fragment (region III, Fig. 2b), the pharynx appears in the new tissues of the blastema. The eyes of the regenerated head have by then already appeared. The caudal blastemata of cephalic fragments were cut away every day or every second day. A pharynx appears after a few days in the fragment (Fig. 3a). The cephalic blastemata of caudal fragments were cut away every second day. No pharynx regenerated under these conditions (Fig. 3 b). A zone close to the cut was irradiated with X-rays, which prevents the fragments regenerating for a long time. A pharynx appears in the cephalic fragment long before the regeneration blastema. In the caudal fragments, the pharynx cannot regnerate before the blastema has formed. It appears only after the blastema has differentiated into a head (Fig. 5). The same results have been obtained in another species of planarian, Polycelis nigra. The regeneration of the pharynx is therefore possible in a cephalic fragment, devoid of any blastema. The regeneration of a pharynx is impossible in a tail without cephalic, prepharyngeal or pharyngeal regions.
The Responses of Some Developing Feathers to X-rays
Authors: ’espinasse Paul G.
Published: April 2021

Doses of up to 1,000 r. of X-rays administered to a patch on the back of the neck of Brown Leghorn capons had no permanent effects on either the structure or the colours of the feathers subsequently produced in the patch. A dose of 2,000 r. was followed by a marked and permanent loss of colour, but no recognizable structural abnormalities, beyond a slight reduction in size, in the feathers subsequently produced in the patch. The immediate response of an actively growing feather-germ to a dose of 2,000 r. was closely comparable with its known response to traumatic treatment such as cauterization. It can be understood as an abnormal and local moult. Feathers growing in the patch after a dose of 2,000 r., if they had colour at all, had it mostly at their distal ends. Series of feathers which were white with coloured tips were produced from identified follicles. The irradiation appears to have affected the physiological situation of the feather-germs in such a way as to forbid the melanocytes, though present and potentially functional, to enter the ectoderm in the normal way and to donate pigment. The melanocytes in these abnormal circumstances fail to develop normal processes. The melanin in them is in an abnormal physical state of aggregation. This condition is also to be seen in the non-donating ‘mulberry cells’ and in the coloured elements of some melanomata. This effect is probably due to a change in the ectoderm, but this change must be of a most restricted character since it does not interfere with the capacity of the ectoderm to produce structurally normal feather. Its nature is not yet understood.
Host-transplant Interactions in Biosynthesis of Drosophila Pteridines
Authors: Goldschmidt Elisabeth , Hadorn Ernst
Published: April 2021

The isoxanthopterin deficiency of the mutant sepiaoid is a non-autonomous character. Non-autonomous changes in the level of isoxanthopterin are correlated with changes in three other pteridine fractions. A sepiaoid host is able to normalize the red pigments in implanted eyes of the mutant rosy, but does not repair its isoxanthopterin defect. The reaction of other pteridines to drosopterin formation can thus be separately observed. While isoxanthopterin synthesis may generally be host dependent, its retention in the imago is autonomous. Wild-type eyes maintain their pteridine levels in a white host that excretes its own fluorescent materials. Compression of the testis by numerous eye transplants diminishes its isoxanthopterin storage. The surplus of diffusible precursors leads to increased deposition in host eyes and eye-transplants.
The Effects of the Chelating Agent Ethylenediamine Tetra-acetic Acid on Cell Adhesion in the Slime Mould Dictyostelium discoideum
Authors: Dehaan Robert L.
Published: April 2021

Vegetative myxamoebae and pseudoplasmodia of the slime mould Dictyostelium discoideum were treated with the chelating agent ethylenediamine tetra-acetic acid. The myxamoebae first respond by rounding up, and then by throwing out active, continuously moving, hyaline lobopodia. At high concentrations of EDTA the cells are unable to migrate, although cellular ‘writhing’ continues for hours. At lower concentrations writhing also occurs, but the cells are able to move together into loose heaps. A migratory pseudoplasmodium immersed in 5 mM EDTA begins disaggregating rapidly. Its smooth surface breaks down and individual cells exhibit membrane activity similar to that described above. The cells lose their attachments to one another, and are maintained in a loose pile only by a tenuous matrix in which they appear to be embedded. Mild agitation now easily separates them into single cells and small clumps of cells. The effects noted on both myxamoebae and pseudoplasmodia are reversible by replacing the EDTA with Bonner’s solution. Moreover, preparations treated with EDTA in the presence of equimolar concentrations of calcium chloride are unaffected. How the removal of cations from cells might result in their dissociation from one another is discussed. It is suggested that EDTA may have its effects by (a) dissolving extra-cellular ground substance or sheath material, and (b) producing a state of instability in the cell membrane allowing continuous pseudopodia! activity and distortion of relations between apposed cell surfaces.
Identification of the Type of Blood-cell Responsible for the Graft-versus-Host Reaction in Chicks
Authors: Terasaki P. I.
Published: April 2021

An attempt has been made to identify the cell responsible for the splenic enlargement caused by the injection of adult homologous blood and spleen cell suspensions into embryonic or newborn chicks. Adult chicken blood lymphocytes 99–100 per cent, pure produced marked splenic enlargement when injected intravenously into chick embryos of a different breed or strain. As little as 30,000 lymphocytes could produce a detectable effect. Adult chicken spleen-cells also produced enlargement of the embryonic spleen. Adult monocytes and thymocytes did not cause significant enlargement. Evidence is presented that the development of inflammatory nodules after the local intracutaneous injection of cells from adult homologous donors is, like splenic enlargement, principally the result of a reaction of the grafted cells against the host. Adult blood lymphocytes when injected intracutaneously were shown to cause the production of a nodule in 3–5 days. Monocytes and thymocytes did not cause the formation of these nodules. From these experiments it is concluded that, in chickens, cells of the peripheral blood lymphocyte family are immunologically competent, and are capable of producing an iso-immune reaction against antigens present in their embryonic or juvenile host.
Hair Growth and its Relation to Vascular Supply in Rotated Skin Grafts and Transposed Flaps in the Albino Rat
Authors: Ebling F. J. , Johnson Elizabeth
Published: April 2021

Hair follicles of albino rats were translocated and allowed to develop vascular connexions in new sites. The translocation was achieved either by rotation of skin grafts in the mid-flank before the expected start of the first wave of growth (4 weeks after birth), or by transposition of flaps—in two stages—so that they were never completely cut off from a blood-supply. The first and second waves of hair-growth on the body adjacent to the grafts or flaps continued as in intact rats; the waves of growth moved from ventral to dorsal, and the dorsal hairs were longer than ventral ones. The appearance of hair of the first wave on unrotated control grafts was in retard of that on the body, but passed from ventral to dorsal in the normal way. During the second wave of growth, follicular activity on the graft continued out of phase with that on the body. The first and second waves of hair-growth on rotated grafts were similarly retarded, but began in the dorsal region and passed ventrally. There was no retardation of growth on the transposed flaps. Hairs first appeared on the dorsally transposed ventral skin of the flaps at the same time as on the ventral body, followed by growth on the ventral flap and dorsal body. The length of hair produced on both rotated grafts and transposed flaps was consistent with the origin of the follicles and not in accordance with their new positions. In intact rats it was demonstrated that follicular activity precedes vascularization. Vascularization of follicles in grafts or transposed flaps was always consequent upon follicular activity, even when this was out of phase with the normal waves of hair-growth on the adjacent body. The evidence suggests that follicular activity depends mainly on an inherent rhythm, and that the hyperaemia which accompanies hair-growth is consequent upon an innate demand of the follicles and is not itself the cause of their activity.
The Differentiation Centre Inducing the Development from Larval to Adult Leg in Pieris brassicae (Lepidoptera)
Authors: Kim Chang-Whan
Published: April 2021

It is generally supposed that the imaginal bud of the leg in Lepidoptera, which Bodenstein (1935, 1937) reported to be visible in the second segment during the last larval instar of Vanessa urticae, develops to produce the adult leg by histogenesis.
Study on the participation of neoplastic cells in the development of mouse embryos
Authors: Calef Enrico , Crimi Corrado , Fruscalzo Alberto , Jucker Richard
Published: April 2021

To test the ability of cloned committed erythroleukemic cells to participate in development we have injected Friend leukemia cells (FLC) into C57B1/6 mouse blastocysts together with Friend leukemia virus (FLV) and we have examined the newborn individuals derived from them. Five animals out of 32 born have FLC-derived neoplasia. The incidence of neoplasia is increased as compared with other similar experiments without the virus. In two of the animals with the FLC neoplasia the disease manifestation is an erythroid leukemia similar to the one obtained directly with the virus in normal DBA/2 mice.
The effect of tail skin on the morphology and morphogenesis of limb regenerates in the red-backed salamander, Plethodon cinereus
Authors: Dinsmore Charles E.
Published: April 2021

Tail skin cuffs have been grafted to the upper forelimb of red-backed salamanders in either normal or 180°-rotated dorsoventral orientation. Subsequent amputation through the graft region resulted in arrested regeneration, distally deficient or typical four-digit regenerates. Distribution was not substantially influenced by graft orientation nor were there any supernumerary limbs induced by the axially dislocated tail skin on the limb stumps. Furthermore, regenerates bore no indication of tail-like structures other than large granular skin glands proximally. These data indicate that, unlike limb skin, tail skin is not morphogenetically active in the epimorphic process of limb regeneration. In addition, the species used in this study is a fin-less, round-tailed salamander. It is therefore suggested that the previously reported morphogenetic effects of tail skin on limb regeneration may be related to the presence of tail fins on the species studied.