bluuebunny/crossref_metadata_2025 huggingface dataset:
Sexual differentiation of the urogenital tract in the chicken embryo: autoradiographic localization of sex-steroid target cells during development
Authors: Gasc Jean-Marie , Stumpf Walter E.
Published: April 2021

The determinant role ascribed to steroid hormones in sexual differentiation of the reproductive tract of the embryo implies the presence of target cells for sex steroids. An autoradiographic technique adapted for diffusible compounds was employed to characterize and localize cells which concentrate either [3H]oestradiol (E2) or [3H]dihydrotestosterone (DHT) in their nuclei. This paper describes the topographical distribution of cells containing receptor sites for oestrogen or androgen in various tissues of the reproductive tract of chicken embryos from day 6 to 15 of incubation. Receptor sites for oestradiol are present in the mesenchyme of the cloaca and in urodeum and vascular body. In the lower part of the Wolffian duct, only epithelial cells display nuclear labelling. In the Müllerian duct, nuclear receptor sites for [3H]oestradiol are observed not before day 15. Receptor sites for DHT are localized in the mesenchyme of the cloacal region from day 7 to 15. The Wolffian, but not the Müllerian duct contains receptor sites for DHT in the nuclei of epithelial and mesenchymal cells. Cross-competition experiments between [3H]E2 or [3H]DHT and unlabelled DHT or E2 respectively, show that 2 different types of receptor sites exist. The observations indicate: (a) complementary roles for oestrogenic and androgenic hormones in embryonic sexual differentiation; (b) precocity of receptors for sex hormones during embryonic development; (c) importance of mesenchyme in differentiation processes which are sex-steroid dependent.
A gradation of hyaluronate accumulation along the proximodistal axis of the embryonic chick limb bud
Authors: Kosher Robert A. , Savage Mary P. , Walker Kordasey H.
Published: April 2021

We are currently investigating the mechanism by which the apical ectodermal ridge (AER) of the embryonic chick limb bud exerts its negative effect on the cytodifferentiation of limb mesenchymal cells directly subjacent to it, and the mechanism by which cytodifferentiation is triggered when the cells leave the influence of the AER. Since there is a gradation of differentiation along the proximodistal axis of the limb bud, we have dissected limb buds into discrete segments along the proximodistal axis, and biochemically examined the accumulation of hyaluronate (HA) and other glycosaminoglycans (GAG) in each segment. The unspeciajized subridge region of stage-25 limb buds was separated into distal (segment 1) and proximal (segment 2) regions, and the remaining proximal portion of the limb was separated into four segments (segments 3, 4, 5 and 6) along the proximodistal axis. Stage-24 limb buds were separated into corresponding regions. Since in the proximal regions of the limb (segment 3 through 6), only the cells comprising the central cores of the limb are involved in chondrogenic differentiation, the central core tissue was surgically separated from the peripheral tissue. We have found that HA is by far the predominant GAG accumulated by cells comprising the distal subridge region (representing greater than 50% of the total GAG accumulated during a 90-min labelling period with [3H]glucosamine), and that there is a progressive decline in HA accumulation along the proximodistal axis. The relative and total amount of HA accumulated is highest in the distal subridge region (segment 1), intermediate in the proximal subridge region (segment 2) and lowest in the proximal central core regions Of the limb (segments 3 through 6). The striking decrease in HA accumulation in the central core of segment 3 is accompanied by a striking increase in the accumulation of chondroitin sulphate, one of the major constituents of cartilage matrix. In contrast to the central core regions of segments 3 through 6, the relative and total amount of HA accumulated by the peripheral non-chondrogenic regions of these segments remains relatively high, being similar to the accumulation observed in the proximal subridge region. These results indicate that there is a gradation of HA accumulation along the proximodistal axis of both stages-24 and -25 limb buds which correlates with distance of cells from the AER and the state of differentiation of the cells.
A SEM study of cell shedding during the formation of the area pellucida in the chick embryo
Authors: Fabian Barry , Eyal-Giladi Hefzibah
Published: April 2021

Intrauterine eggs at different stages of development were retrieved from hens and the blastodiscs were dissected out and prepared for scanning electron microscopy. Our observations trace the polarized shedding of cells from the central area of the lower layers of the blastodisc, which leads to the formation of the area pellucida. Prior to the shedding, single central blebs appear on the ventral side of the cells facing the sub-blastodermic cavity. We also noted the presence of lobopodia which establish contact with nearby cells. The possible function of the lobopodia is discussed. The cells of the blastodisc are at the same time (stages IV and V, E.-G.&K). also intimately interconnected via a profusion of threadlike cytoplasmic processes (filopodia). When shedding starts the blebs as well as the lobopodia disappear, and the filopodia undergo typical withdrawal steps such as showing a beaded stage and appearing drawn out or taut, before they finally disrupt to leave behind a smooth round cell which is detached from its neighbours. The beading phenomenon points to the possibility of a disassembly of the microtubular skeleton of the filopodia operated by some physical force influenced by gravity.
Secondary lens formation from the cornea following implantation of larval tissues between the inner and outer corneas of Xenopus laevis tadpoles
Authors: Reeve Julie G. , Wild Arthur E.
Published: April 2021

Secondary lens formation from the cornea of larval Xenopus laevis has been used as a measure of the lens-inducing capacities of various larval Xenopus tissues. The experimental design employed involved implantation of selected body tissues between the inner and outer corneas of stage-50 tadpole eyes, in such a way that the integrity of the inner cornea and eye cup was not disrupted.

Implantation of retina, pituitary, limb blastema or limb bud resulted in secondary lens formation from the outer cornea. Such lenses were similar in appearance to stage-5 lens regenerates described by Freeman (1963). No secondary lenses were observed in eyes receiving either heart or hind brain implants or in eyes which underwent corneal separation but which received no implant.

It is concluded that the retina is the natural source of a stimulatory factor which initiates and maintains corneal transformation to lens during lens regeneration following lensectomy. Influences emanating from pituitary, limb blastema and limb bud, but apparently not from heart or hind brain, are able to act on cornea in a way similar to the retinal factor. Furthermore, our findings support the contention that in the normal eye, the inner cornea is a barrier to the passage of retinal factor and so maintains the single lens structure of the eye. When this barrier is by-passed by lens-inducing tissue, as in the present experimental design, lens formation from the cornea is able to take place. Electronmicroscopical studies have shown that the inner cornea, in the stage-50 tadpole eye, consists of a dense meshwork of collagen fibrils and a basal layer of cohesive elongated mesenchymal cells well suited for this barrier function.
Proliferation and migration of primordial germ cells during compensatory growth in mouse embryos
Authors: Tam P. P. L. , Snow M. H. L.
Published: April 2021

Primitive-streak-stage mouse embryos were treated with Mitomycin C injected intraperitoneally into pregnant females at 6·75–7·0 days post coitum. The newborn mice developed poorly and mortality was high during the suckling period. Many weaned survivors showed impaired fertility and poor breeding performance. Histological examination revealed a paucity of germ cells in the adult gonads. The deficiency was mainly caused by a severe reduction of the primordial germ cell population in early embryonic life, which was not fully compensated for during the compensatory growth phase of the Mitomycin C-treated embryo. Also contributing to such impaired fertility were retarded migration of the primordial germ cells into the genital ridges, poor development of the foetal gonad and secondary loss of the germ cells during gametogenesis in males.
Cytoplasmic regulation of the duration of cleavage in amphibian eggs
Authors: Aimar Christian , Delarue Michel , Vilain Claude
Published: April 2021

Relations between a cytoplasmic species specificity and the duration of cleavage cycles were investigated by reciprocal injections of egg cytoplasm. Xenogenic cytoplasm induces an early or delayed cleavage of the recipient egg depending on the chronological specificity of the injected cell cytoplasm. Activity of the so-called cleavage timing system (CTS) was first detected in the cytoplasm of maturing oocytes at the stage of germinal vesicle breakdown (GVBD). This specific cytoplasmic property was not dependent on the maturation promoting factor (MPF). Relations between the CTS and other cytoplasmic components which are known to induce cleavage are discussed.
On the ‘clock’ mechanism determining the time of tissue-specific enzyme development during ascidian embryogenesis II. Evidence for association of the clock with the cycle of DNA replication
Authors: Satoh Noriyuki , Ikegami Susumu
Published: April 2021

Acetylcholinesterase (AChE) is a tissue-specific enzyme of the muscle cells of ascidian embryos and its synthesis begins at the neurula stage. Embryos which had been permanently cleavage-arrested with cytochalasin B could develop AChE activity. The time of first AChE occurrence in embryos which had been arrested in the 32-cell stage with cytochalasin was about the same as in normal embryos. The nucleus in the cell of cytochalasin-arrested embryos divided in good synchrony with that of normal embryos. Embryos which had been continuously arrested with colchicine could also produce AChE activity at nearly the same time as did normal embryos. In the cell of colchicine-arrested embryos normal nuclear divisions did not occur, but the cell showed repeated cycles of nuclear envelope breakdown and nuclear envelope reformation in almost parallel with cell cycles of normal embryos. The cell of colchicine-arrested embryos incorporated [3H]thymidine. Aphidicolin, a specific inhibitor of DNA synthesis, prevented cleavages of ascidian eggs. Embryos which had been permanently arrested with aphidicolin in the cleavage stages up to the 64-cell stage did not develop AChE activity, while embryos which had been treated with it from the 76-cell stage onwards were found to be able to differentiate AChE activity. Based on these findings it was proposed that DNA replication is prerequisite for development of the histospecific protein and that the cycle of DNA replication is closely associated with the clock mechanism which is determining the time of initiation of the enzyme development.
Avian primordial germ cells are of epiblastic origin
Authors: Eyal-Giladi Hefzibah , Ginsburg Malka , Farbarov Aharon
Published: April 2021

We have demonstrated that quail PGCs possess a characteristic heterochromatin nuclear marker demonstrable already at stage 6 H & H with Feulgen staining. Chimaeras of stage-XIII E. G & K. chick epiblast and quail hypoblast and vice versa have been made. The chimaeras were incubated up to stage 7−8 H & H and checked histologically with Feulgen staining for the presence of the heterochromatin marker in every detectable PGC. It was found that the PGCs are of epiblastic origin, contrary to previous data and speculations concerning avian PGCs.
Factors involved in the development of ipsilateral retinothalamic projections inXenopus laevis
Authors: Kennard C.
Published: April 2021

The extent, and the development, of the ipsilateral retinothalamic projection in the frog Xenopus laevis have been studied using terminal degeneration and autoradiographic techniques. This ipsilateral projection derives only from those retinal areas receiving visual information from the binocular portion of the visual field. In Xenopus, the ipsilateral retinothalamic projection arises from a larger area of the retina than was found to be the case in earlier studies on Rana. This correlates with the fact that Xenopus has a larger binocular visual field than does Rana.

The ipsilateral retinothalamic projection is just detectable at about stage 56 of larval life, considerably later than its contralateral counterpart. Experimental manipulation of the developing eye vesicle at early larval stages followed by histological studies of the ipsilateral retinothalamic projections showed, however, that the retinal areas which give rise to this projection are determined by stage 32 of larval life. Further studies, in which monocular enucleation was performed at different larval stages with subsequent examination of the retinothalamic projections from the remaining eye, indicated that the selective pattern of decussation and non-decussation of retinothalamic fibres at the optic chiasma does not require interactions, at the chiasma, between optic fibres from the two eyes.
Distribution of endogenous β-galactoside-specific lectin, fibronectin and type I and III collagens during dermal condensation in chick embryos
Authors: Kitamura Kunio
Published: April 2021

The distribution of endogenous β-galactoside-specific lectin, fibronectin, type I and III collagens was studied by the indirect immunofluorescence method during the formation of dermal condensation in the feathered region (dorsal skin) of a chick embryo. Endogenous β-galactoside specific lectin was concentrated in the condensed dermal region, coinciding with the formation of condensation of dermal cells. It was also detected in epidermal placodes. Fibronectin was weakly stained in dermis prior to the formation of dermal condensation but not in epidermis. Condensation of dermal cells resulted in the formation of thicker fibrils of fibronectin in the condensed region. Distribution of type I collagen was found to be very different from that of endogenous β-galactoside-specific lectin and fibronectin. Type I collagen in dermis decreased along with the formation of dermal condensation. Epidermis had no type I collagen. Type Ill collagen was not found in dorsal skin. Relationship found between these distribution patterns and dermal condensation in the embryonic chick skin is discussed.
Culture of mouse embryos during neurulation
Authors: Sadler T. W. , New D. A. T.
Published: April 2021

A comparison between static versus rotator culture systems and a variety of media (rat serum, new born calf serum, DMEM and Waymouth’s) was made in an attempt to promote in vitro growth of mouse embryos from the beginning of neurulation (headfold stage) to the closure of the neural tube and formation of the limb buds (48 h). The results demonstrate that good development can be achieved for 48 h using a rotator system and that 80 % of embryos cultured on rotators show growth and differentiation similar to that obtained for the same time period in vivo. Static cultures are less successful and embryos grown in this system show lower protein content and somite numbers than those maintained on rotators. Undiluted rat serum is superior to all other media tested and supports better growth and development as monitored by total protein and developmental abnormalities.
Accumulation, spatial distribution and partial characterization of poly(A)+RNA in the developing oocytes of Xenopus laevis
Authors: Wakahara M.
Published: April 2021

In situ hybridization using [3H]poly(U) was applied to developing oocytes of Xenopus laevis, which had been fixed in Bouin’s solution. Tissue sections were pretreated with DNase I, annealed with [3H]poly(U) and post-treated with RNase A and TCA. After the autoradiographical processing, silver grains over the oocyte were counted. As a result of the control experiments which included RNase A, RNase T2, DNase I and Pronase E hydrolysis and Cordycepin (3’-deoxyadenosine) incubation before in situ hybridization, it was concluded that the poly(U)-binding activity detected upon the oocytes was due to the possible presence of poly(A)+RNAs. Spatial distribution of the poly(U)-binding sites changed during the development of the oocytes; in a small oocyte before the pachytene stage, silver grains developed over the nucleus, while in a larger oocyte after the diplotene the grains were concentrated over the cytoplasm. After yolk platelets were deposited in the cytoplasm, two types of poly(U)-binding activities were noted; a bound-type activity which was firmly associated with the cytoplasm, so that the positions of the silver grains were not influenced by fixation, and an unbound type which did not bind so firmly to the cytoplasm and was therefore easily influenced by inflow of fixative. The bound-type activity persisted in the cytoplasm throughout the oogenesis, but the unbound type appeared only after the vitellogenesis, especially in the yolky cytoplasm. The total poly(U)-binding activity per oocyte increased continuously with the growth of the oocyte.
Specificity in the differentiation and morphogenesis of neural crest-derived scleral ossicles and of epithelial scleral papillae in the eye of the embryonic chick
Authors: Hall Brian K.
Published: April 2021

Enzymatic digestion followed by recombination of epithelia and ectomesenchyme from embryonic sclera and mandibles has been used to demonstrate that isolated scleral ectomesenchyme is only able to form scleral ossicles if in prior contact with scleral epithelium until H.H. stage 36 (10 days of incubation); that this induction by epithelial scleral papillae is a prolonged one, commencing as early as H.H. stage 30 (6·5–7 days); that scleral ectomesenchyme can respond to mandibular epithelium by forming bony ossicles and that mandibular ectomesenchyme can respond to scleral epithelium by forming bony rods, i.e. these interactions are not site, time or tissue specific. Scleral epithelia did not form scleral papillae when maintained alone in vitro or when recombined with scleral ectomesenchyme and maintained in vitro. Nor did papillae form when mandibular epithelia were cultured with scleral ectomesenchyme. These results, coupled with data from the literature, are used to argue that papillae will only form when scleral epithelia are under the tension generated by normal intraocular pressure of the growing eye.
In vivoandin vitrodevelopment of mouse embryos homozygous for the embryonic lethal velvet coat (Ve) mutation
Authors: Rossant J. , Vijh K. M.
Published: April 2021

Embryos homozygous for the velvet coat mutation, Ve/Ve, were recognized at 6·5 days post coitum by the reduced size of the ectodermal portions of the egg cylinder and the loose, columnar nature of the overlying endoderm. Later in development ectoderm tissues were sometimes entirely absent. Abnormalities appeared in the ectoplacental cone at 8-5 days but trophoblast giant cells and parietal endoderm appeared unaffected. Homozygotes could not be unequivocally identified at 5·5 days nor at the blastocyst stage but were recognized in blastocyst outgrowths by poor development of the inner cell mass derivatives, It has previously been suggested that Ve may exert its action at the blastocyst stage by reducing the size of the inner cell mass, but no evidence for such a reduction was found. Most of the observations on Ve/Ve homozygotes are, however, consistent with the hypothesis that Ve exerts its action primarily on later primitive ectoderm development.
Partial characterization of a morphogenetic factor in the developing chick limb
Authors: Maccabe Jeffrey A. , Richardson Kathryn E. Y.
Published: April 2021

A morphogenetic substance from the posterior region of the developing chick limb appears to be a glycoprotein with a molecular weight in the range of 370000–415000. This morphogen is capable of maintaining the apical ectodermal ridge of the limb in culture and is probably related to the previously hypothesized polarizing or maintenance factors in limb mesoderm.
Cell interactions in the developing somite: in vitro comparisons between amputated (am/am) and normal mouse embryos
Authors: Flint O. P. , Ede D. A.
Published: April 2021

Facial, axial and limb development are all abnormal in the homozygous mutant mouse embryo (amputated). An interpretation of cell behaviour in vivo based on sectioned material which may explain these abnormalities has been previously suggested. In this study, somite cells cultured in vitro were found to behave exactly as predicted in this interpretation: they clump together, forming extensive areas of cell contact, and this has a profound effect on their mobility as measured by time-lapse cinemicrography. The similarity of cell behaviour in vitro and in vivo under two distinct sets of environmental conditions suggests that the abnormal cell behaviour is intrinsic to the cell, and directly linked to the mutation. The more extensive areas of cell contact formed between mutant cells suggests that the mutation changes the adhesive properties of the cell surface, but it cannot be excluded that the cells’ motile apparatus is also affected.
Cell shapes on the surface of the Drosophila wing imaginal disc
Authors: Brower Danny L. , Smith R. J. , Wilcox Michael
Published: April 2021

Antibodies that bind to antigens on the surfaces of imaginal disc cells can be used to visualize the cellular morphology of the disc exterior. Using this technique, we have examined wing imaginal discs at various times during the third larval instar, paying particular attention to those areas where the anteroposterior and dorsoventral compartment borders are located. We have been unable to detect any distinguishing feature in the shapes of the cells at the anteroposterior compartment border. However, there is a line of unusually shaped cells extending across the disc, from anterior to posterior and which, in the central region of the disc, takes the form of a shallow groove in the epithelium. A number of observations suggest that this line is coincident with the dorsoventral compartment border.
Formation of viable chimaeras by aggregation between teratocarcinomas and preimplantation mouse embryos
Authors: Stewart C. L.
Published: April 2021

The formation of viable teratocarcinoma-adult chimaeras, by aggregation rather than by microinjection, is described. Aggregation chimaeras were produced using two pluripotential EC cell lines, PSA-l/NG-2 and PSA-4/TG12. The frequency and distribution of chimaerism were assessed, for the EC cells, in conceptuses recovered from in utero and in adults. In utero 37% of the morphologically normal conceptuses formed from PSA-l/NG-2 aggregations and 73 % of the morphologically normal conceptuses produced from PSA-4/TG12 aggregations were found to be chimaeric. However, the frequency of chimaeric adults formed from both cell lines was lower. The reason for this discrepancy appeared to be that in the chimaeric conceptuses, the predominant tissues colonized by the EC cells were the extraembryonic membranes.
Scanning electron microscopy of gastrulation in a sea urchin (Anthocidaris crassispina)
Authors: Amemiya Shonan , Akasaka Koji , Terayama Hiroshi
Published: April 2021

Gastrulation in Anthocidaris was investigated by observing the inside and the outside of embryos by scanning electron microscopy.

Furrows which possibly reflect changes in intercellular interactions were observed on the outer surface (hyaline layer side) of embryos twice in development: firstly at the time of primary mesenchyme cell formation, and secondly at the time of vegetal plate indentation. In the latter case, the cells within and surrounding the vegetal plate appeared to change their shapes differently; the former (within the plate) having broader surfaces on the blasto-coel side whereas the latter (surrounding the plate) having broader surfaces on the hyaline layer side. This suggests that the first phase of indentation may be mediated by the autonomous change of cell shape and intercellular adhesiveness, accompanied by an autonomous cell movement in the vegetal pole region.

Although some pseudopodial linkages were observed between secondary mesenchyme cells on the top of the invaginating archenteron and the animal pole in the mid-gastrula and later stage embryos, they were thinner and smaller in number as compared to those in the Pseudocentrotus embryos. The rate of invagination appeared rather constant throughout gastrulation in contrast to the accelerated invagination in other embryos with larger blasto-coel cavities. Moreover, the number of columnar cells on the dissected surface of embryos remained unaltered.

These findings suggest that the secondary mesenchyme cells may act as a linker between the archenteron tip and the animal pole, but they may not generate major motive forces for archenteron invagination at least in the Anthocidaris embryos.
Developmental effects of some newly inducedUltrabithoraxalleles ofDrosophila
Authors: Kerridge Stephen , Morata Gines
Published: April 2021

Nine X-ray-induced mutations of the bithorax complex (BX-C) have been isolated and characterized. They all show the typical features of the Ultrabithorax mutations. They are homozygous lethal, produce a slight enlargement of the haltere in heterozygous condition and fail to complement the mutations at the bx, bxd and pbx loci. Some of them are associated with chromosomal aberrations in the regions 89E 1-4, where the BX-C lies, while others appear normal cytologically.

The effect of six of these mutants in the adult cuticle has been studied, producing mutant marked clones in heterozygous individuals. The clones were generated by X-radiation at two points in development: the blastoderm stage and the second larval period. In all cases mutant clones showed the same phenotype: clones appearing in the dorsal structures transform metathorax and first abdominal segment towards mesothorax. That is the additive effect of bx, bxd and pbx mutations. Clones in the legs, if induced during the larval period, show an effect homologous to that seen in the dorsal structures. However, when produced at blastoderm they show in addition a transformation of the posterior second (mesothoracic) and third (metathoracic) legs into the posterior first (prothoracic) leg. This transformation, named postprothorax (ppx) has been recently described for the alleles Ubx130 and Ubx1 (Morata & Kerridge, 1981) and appears to be general for the Ubx mutations.

It is concluded that the realm of action of the Ubx gene is defined by part of the meso-thoracic segment (posterior second leg compartment) and the entire metathoracic and first abdominal segments.
Cell membrane regionalization in early mouse embryos as demonstrated by 5′ -nucleotidase activity
Authors: Izquierdo L. , Ebensperger C.
Published: April 2021

The distribution of 5’-nucleotidase activity in pre-implantation mouse embryos is studied by means of a cytochemical method adapted from Uusitalo & Karnovsky (1977). The enzyme activity is detected, from the 4-cell stage up to the morula stage, on discrete patches of the cell membane between blastomeres. Appropriate controls show that this distribution is not a localization artifact due to selective retention of the enzyme reaction product in the narrow interblastomeric spaces. In early blastocysts, as the blastocoel expands the enzyme activity on its lining disappears. The external surface of the trophectoderm in early blastocysts lacks any enzyme activity, whereas in late blastocysts a strong enzyme activity is detected at the embryonic trophectoderm, decreasing in intensity towards the opposite pole of the embryo.

These results are compared to previous observations by other authors and the differences are mainly ascribed to differences in the cytochemical procedure employed.

We conclude that during cleavage a gradual cell membrane regionalization unfolds, revealing a pattern that may be related to morphogenesis; in particular, to the localization of zonular tight junctions around the peripheral blastomeres of the morula (Izquierdo, 1977; Izquierdo, López & Marticorena, 1980).
Neural tube development in mutant(curly tail)and normal mouse embryos: the timing of posterior neuropore closurein vivoandin vitro
Authors: Copp A. J. , Seller M. J. , Polani P. E.
Published: April 2021

A dye-injection technique has been used to determine the developmental stage at which posterior neuropore (PNP) closure occurs in normal and mutant curly tail mouse embryos. In vivo, the majority of non-mutant embryos undergo PNP closure between 30 and 34 somites whereas approximately 50% of all mutant embryos show delayed closure, and around 20% maintain an open PNP even at advanced stages of development. A similar result has been found for embryos developing in vitro from the headfold stage. Later in development, 50-60% of mutant embryos in vivo develop tail flexion defects, and 15-20% lumbosacral myeloschisis. This supports the view that delayed PNP closure is the mftin developmental lesion leading to the appearance of caudal neural tube defects in curly tail mice. The neural tube is closed in the region of tail flexion defects, but it is locally over-expanded and abnormal in position. The significance of these observations is discussed in relation to possible mechanisms of development of lumbosacral and caudal neural tube defects. This paper constitutes the first demonstration of the development of a genetically induced malformation in vitro.
The effects of chlorcyclizine-induced alterations of glycosaminoglycans on mouse palatal shelf elevation in vivo and in vitro
Authors: Brinkley Linda L. , Vickerman Mary M.
Published: April 2021

To define whether glycosaminoglycans play a role in palatal shelf movement, we studied the morphology and elevation behaviour of chlorcyclizine-treated mouse palatal shelves. Chlorcyclizine treatment was used because this agent enhances degradation of the palatal glycosaminoglycans, hyaluronate and chondroitin sulphates, with little or no effect on their synthesis. Use of in vitro and in vivo experiments enabled us to control the complicating effects of other factors on elevation.

Drug-administration resulted in a reduction in shelf size, as measured by cross-sectional surface area, in the posterior two-thirds of the palatal shelf. In vivo shelf reorientation was also inhibited. When elevation behaviour was observed in vitro, pronounced regional variation was noted. The anterior third of the shelf was able to reorient, the posterior two-thirds was not. This region also showed distinct histological changes as compared to controls. Mesenchymal cells were rounded with prominent nuclei and nucleoli and were more densely packed than in controls.

These results suggest that for at least the posterior two-thirds of the palatal shelf, the intrinsic reorientation ability may in large part be linked to the acquisition of a specific temporal and spatial distribution of hyaluronate and possibly other matrix components.
Mutations affecting the indirect flight muscles ofDrosophila melanogaster
Authors: Deak Ilan I. , Bellamy Paul R. , Bienz Marianne , Dubuis Yvonne , Fenner Elke , Gollin Michael , Rähmi Andreas , Ramp Theodor , Reinhardt Christoph A. , Cotton Beata
Published: April 2021

The development of the indirect flight muscles of Drosophila melanogaster was studied by analysing mutations that cause flightlessness. Twenty-five mutations on the X-chromosome and two on the third chromosome were examined. The X-chromosomal mutations form ten complementation units. The ten loci were assigned preliminary map positions by meiotic recombination and deficiencies and duplications. The two autosomal mutations represent two genes. Gynandromorph analyses suggest that many of these mutations have their primary effect in the presumptive thoracic muscle region of the embryo. The mutations cause a variety of characteristic defects, such as absence of the bulk of the thoracic muscle mass, or absence of only one of the two fibrillar muscle groups. Electronmicroscopic studies of sixteen mutants representing all twelve loci reveal abnormal myofibrillar organization in some of these mutants, e.g. aberrant or missing Z-bands, or absence of the thin filaments. Mutant protein patterns, obtained by SDS-polyacrylamide gel electrophoresis, show the following differences from wild type: ten mutants are characterized by absence or reduction of the 54 K protein, and most mutants exhibit a reduction and modification of the 80 and 90 K proteins. The absence or reduction of the 54 K protein was strongly correlated with aberrant Z-bands.
Genetical and Developmental Studies on Droopy-eared Mice
Authors: Curry G. A.
Published: April 2021

Droopy-ear is a single, recessive, autosomal gene with full penetrance. Droopy-ear is linked to Varitint p27 ± 3·2, but segregates independently of the other genes tested. In adult droopy-eared mice the areas of specific abnormalities are the occiput and the shoulder girdle. The rest of the skeleton shows immaturity of form, and disproportionate shortening of the limb bones. The anomalies of the adult skeleton are traced back, through a delay in ossification, to a delay in chondrification and localized areas of abnormal cartilage, and thus back to disturbed mesenchymal condensations, which in some cases are also thin. Certain of the abnormalities, in particular the splitting of the dens epistrophei into two parts, one of which may be attached to the basioccipital, strongly recall the anatomical situation in the more primitive vertebrates. Some anomalies of the internal bone structure are described. The droopy-ear syndrome is considered in relation to the syndromes of the other mouse mutants whose mesenchymal condensations are disturbed. The similarities of the droopy-ear syndrome with some conditions in other chondrodystrophic disorders is noted. The theories concerning the localization of specific abnormalities are discussed in relation to droopy-ear.
Dimensions of the Notochord and Somites in Embryos of Xenopus laevis Treated with Thiocyanate
Authors: Ranzi Silvio , Gavarosi Gianna
Published: April 2021

As a result of previous research, Ranzi & Tamini (1939) pointed out that the notochord of Amphibian embryos of several species treated with sodium thiocyanate (NaSCN) solutions is larger than the notochord of control embryos. Later, several substances were identified which cause enlargement of the notochord: full data and a complete review of the literature on this subject are given by Ranzi & Citterio (1954) and Ranzi (1957). A careful statistical study on the number of nuclei in Rana escalenta embryos was carried out by Corti (1950). In embryos which had been treated for 24 hours with 0·05 M NaSCN, from the late blastula stage onwards, she found 1233 ±28 nuclei at the tail-bud stage, whereas the controls reared in spring-water had only 1107 ± 24 nuclei: these two sets of data are significantly different (standard error of the difference ±37).
The First Appearance of Specific Antigens during the Induction of the Lens1
Authors: Langman Jan
Published: April 2021

Presumptive lens ectoderm with associated eye-cup from 5 – 17-somite chick embryos was explanted in ‘normal’ medium, ‘anti-myosin’ medium, and a medium containing lens antibodies. The control explants in ‘normal’ and ‘anti-myosin’ medium showed lens formation in 80-100 per cent, of the cases (Text-fig. 1); the explants in ‘anti-lens’ medium showed degeneration and necrosis of the future lens area, indicating the presence of substances (lens antigens) capable of reacting with lens antibodies (Text-fig. 1). Explants from embryos with 18 or more somites in ‘anti-lens’ medium formed lenses as the controls. Presumptive lens ectoderm without the associated eye-cup from 7 – 20-somite embryos was cultured on a ‘normal’ and ‘anti-lens’ medium. The controls showed epithelial membranous outgrowth in 80 –100 per cent, of the explants (Text-fig. 3; Table 1). Explants on ‘anti-lens’ medium showed outgrowth similar to controls when obtained from embryos younger than 11 and older than 17 somites, but showed degeneration when obtained from 11-to 17-somite embryos, indicating the formation of the first reacting substances (lens antigens) at the 11-somite stage (Text-fig. 3; Table 1). The ‘first-stage’ lens antigens are formed at the 11-somite stage, shortly after the adhesion between eye-cup and presumptive lens ectoderm has been established (9 somites) and shortly before the morphological changes characterized by loss of vacuolization, nuclear orientation, and palisade phenomenon appear (13 – 19 somites).
The Passage of Urea and Creatinine across the Placenta of the Pig
Authors: Zweymüller E. , Widdowson E. M. , Mccance R. A.
Published: April 2021

The concentration of ‘creatinine chromogens’ in the serum of the foetal pig at term may be over three times that in the maternal serum. The concentrations of urea were always about the same. The values for these chromogens in piglet sera fell to the adult level in the day following birth. Fructose was the only chromogen other than creatinine found in piglet serum by chromatography. Pyruvic acid was not the cause of the difference. It is concluded, therefore, that the chromogens were mostly true creatinine, and that the pig’s placenta is less ‘permeable’ to it than to urea.
Morphogenetic Events in Normal and Synchronously Dividing Tetrahymena
Authors: Williams Norman E. , Scherbaum Otto H.
Published: April 2021

A study of differentiation in the ectoplasmic cortex of T. pyriformis GL subjected to the standard temperature cycling for the induction of synchronous binary fission has demonstrated an arrest in development which occurs in all cells at a characteristic point in the cell cycle. After treatment all cells were found to possess anarchic fields of kinetosomes in the stomatogenic region, indicating 100 per cent, synchrony. The cells remain in this condition for a period of 50 –55 minutes after the last heat shock. During this time no changes other than in increase in the size of the macronuclear chromatin granules could be detected. At the end of the period of arrested development morphogenesis resumes and binary fission continues in synchrony. The degree of synchrony is somewhat reduced as development proceeds, resulting in about 85 per cent, synchrony at the time of cytoplasmic constriction. In order to facilitate analysis of morphogenesis in synchronously dividing Tetrahymena, a series of four developmental stages has been defined. Based on work which has confirmed available descriptions of stomatogenesis and macronuclear fission, the sequence includes new data on development of the somatic ciliature. All observations, including quantitative consideration of the somatic kinetosomes, ciliary meridians, and contractile vacuole pores has indicated that, aside from synchrony and the period of arrested development, the morphogenetic events in synchronized organisms are fundamentally no different from these processes in untreated cultures. Growth of the organism, growth of the macronucleus, and morphogenesis are to some extent dissociated in synchronized cultures of Tetrahymena. During the heat treatment morphogenesis is blocked while cell and macronuclear growth continues. After treatment and prior to the synchronous cytoplasmic constriction there is a significant increase in mean nuclear volume with no significant increase in total cell volume. After resumption of development in synchronized cultures morphogenesis proceeds unaccompanied by any increase in cellular volume. In addition, it is believed that the nuclear increase occurs during the period of arrested development and not during the subsequent period of development. The use of protargol staining promises to be of value in studies of ciliate morphogenesis. Of those structures in and on the ciliate cortex, protargol appears to be highly specific for kinetosomes. In addition to this the cilia and ciliary membranes are revealed by this technique.
A Study of Environmental Influences on the Size of the Pronephros and Related Structures in Triturus helveticus
Authors: Fox H.
Published: April 2021

Triturus helveticus embryos were reared from a stage equivalent to Harrison stage 24–26 for Ambystoma punctatum, in a variety of media for 15 days, and the pronephric systems were quantitatively analysed. The lumen volumes and internal surface areas of the tubules of decapsulated embryos were smaller than those of capsulated embryos. The pronephric tissue volumes and glomus volumes of decapsulated embryos reared in full-strength Holtfreter solution were smaller than when they were reared in one-tenth-strength Holtfreter solution. All measurements of pronephric components (except nuclear length) were significantly and considerably greater in decapsulated specimens reared in distilled water than in decapsulated embryos reared in full-strength Holtfreter solution. Pronephroi of decapsulated embryos reared in calcium-free one-tenth strength Holtfreter solution had a significantly smaller lumen volume and internal surface area of the tubules than those of controls. Pronephroi of decapsulated embryos reared in 0·5 per cent, urea in one-tenth-strength Holtfreter solution had slight, but significant, superiority in length and cell volume, but a smaller lumen volume, than those of controls. Comparison of the pronephric measurements of two unrelated collections of T. helveticus showed significant intra-specific differences.
Appearance of Antigens during Development of the Lens
Authors: Langman Jan
Published: April 2021

The double diffusion technique of Ouchterlony, based on the differential diffusion of a mixture of antigens in an agar gel, was used to study the formation of lens antigens during development of the chick embryo and to correlate chemical and morphological differentiation. Aqueous extracts prepared from lenses of 50-, 60-, 72-, and 96-hour, and 10-day embryos, and from new-born and young adult chickens, were tested with antiserum prepared with 10 per cent, adult chicken lens extract. The gradual appearance of 1–7 precipitin bands, indicating the corresponding formation of substantial amounts of up to 7-lens antigens, was noted during embryonic development. The number of bands formed was dependent upon the age of the embryos providing the lens extracts. The first appearing lens antigen causing a precipitin band was found in 50-hour lens extract (18-24 somites). The appearance of new precipitin bands in the course of development, indicating the formation of new lens antigens, preceded or coincided with the appearance of morphological structures indicating synthesis of new protein. Precipitin bands formed during the first stages of development (bands 2, 3, and 4 in Plate 1, fig. 2a and Plate 2, fig. 3a) were caused by antigens identical to those present in the later stages (Plate 2, figs. 5a, 6a, 1a). The molecular weight of the first formed antigens appeared to be higher than that of the antigens formed later in development.
Mitotic Pattern in the Chick Pronephric Duct
Authors: Overton Jane
Published: April 2021

Studies carried out on the stage 14 chick embryo indicate that in normal and in colchicine-treated embryos mitotic frequency is greatest towards the posterior tip of the elongating pronephric duct. Although the mitotic frequency in the duct tip is high compared to that in the duct at more cephalic levels, it is similar to that in other mesodermal regions at the same level. Distortions of the embryo which occur with colchicine treatment suggest that migratory activity is prominent towards the duct tip, and emphasize the dependence of normal morphology of the duct on tensions in the blastoderm.
Recherches sur les malformations déterminées par le refroidissement temporaire de l’œuf de poule et compatibles avec la vie des Poussins
Authors: Ancel P.
Published: April 2021

Nous avons signalé dans un travail antérieur (Ancel, 1958) portant sur 699 œufs que le refroidissement de l’œuf de poule à différentes périodes de l’incubation pendant deux ou trois jours donnait naissance à des malformations des paupières, du bec et des membres. Un petit nombre d’embryons avaient été prélevés seulement après le 17ème jour de l’incubation. Dans le présent travail, nous avons cherché à savoir si certaines des malformations ainsi obtenues étaient compatibles avec la vie des poussins.
The Pigment Cell System in the Light Sussex Fowl
Authors: Cohen J.
Published: April 2021

The pigmentation pattern of the Light Sussex fowl is described and considered as a case of ‘partial pigmentation’. By the use of tissue-culture methods it has been demonstrated that a competent pigment cell system occurs in the white plumage of the Light Sussex embryo and adult. Papilla transplantation experiments were used to evaluate the role of the epidermis in determining the fate of these pigment cells. The results obtained indicate strongly that the epidermis determines whether or not the equipotential pigment cells shall or shall not produce pigment in vivo. It is concluded that the pigment cell system of the Light Sussex responds to certain conditions in vivo and in vitro by the production of sufficient pigment to colour feather, and to other conditions by the production of insufficient pigment.
Tolerance of Skin Grafts produced by Various Adult Cells, Soluble Extracts, and Embryonic Cells
Authors: Terasaki P. I.
Published: April 2021

Tolerance of skin homografts was studied after the injection of various adult cells and soluble tissue extracts into newly hatched or embryonic chicks. Tolerance (measured by the proportion of surviving skin homografts 30 days after transplantation) was induced in 50 per cent, or more of the chicks injected with diluted whole blood, blood lymphocytes, blood monocytes, and thymocytes. Since monocytes and thymocytes do not produce a ‘graft against host’ reaction it follows that tolerance to homografts can be induced by adult cells without the complications associated with runt disease. Tolerance could not be induced with cell-free extracts of known antigenic potency. Analysis by the tolerance test of the appearance of adult-type iso-antigens during embryonic development shows that they are detectable by the 4th day of embryonic life.
Compaction of the mouse embryo: an analysis of its components
Authors: Pratt H. P. M. , Ziomek C. A. , Reeve W. J. D. , Johnson M. H.
Published: April 2021

A variety of agents (viz.: cytochalasin D, colcemid, cytochalasin D + colcemid, Ca2+-free medium, 7-ketocholesterol, cholesterol, concanavalin A, anti-embryonal carcinoma antiserum and tunicamycin) which modify the cell membrane and/or cytoskeleton were used to investigate the molecular and cellular basis of the intercellular and intracellular components of compaction and analyse the relationships between them. It was found that the individual components could be selectively dissociated from one another. Cell flattening and close intercellular apposition were the most sensitive features and affected by the majority of agents. Tight junctions did not form in the absence of intercellular apposition, however an apparently normal degree of intercellular apposition did not necessarily lead to the assembly of these junctions. Polarization of individual blastomeres, as assessed by the reorganization of the cell surface, was the component most resistant to experimental intervention since it occurred in the presence of all agents used, though it was modified by some of them. The results are discussed in terms of the molecular and cellular events underlying polarization, intercellular apposition and tight junction formation as well as the significance of these events for normal blastocyst formation.