bluuebunny/crossref_metadata_2025 huggingface dataset:
Rôle des cellules mésectodermiques issues des crêtes neurales céphaliques dans laformation des arcs branchiaux et du squelette viscéral
Authors: Lievre C. Le
Published: April 2021

The participation of neural crest cells in the formation of the branchial arches and especially of the hypobranchial skeleton has been studied with heterospecific grafts of quail neural tube into the chick embryo. According to the labelling technique devised by Le Douarin, the differences between quail and chick interphase nuclei make it possible to use quail cells as cellular markers in this system.

The excision of the mesencephalo-rhombencephalic primordium of 4-to 12-somite chick embryos results in the atrophy of the branchial arches, and in important deficiencies of the hypobranchial skeleton. Nevertheless, the nearly complete absence of the branchial mesen-chyme does not prevent the visceral pouches and clefts from forming.

The isotopic and isochronic graft of quail neural primordium into the chick shows that the mesenchymal component of the branchial arches is of neurectodermal origin, except for the muscle plates and the endothelium of the aortic arches, which derive from the mesoderm. The mesencephalic neural crests give rise to the totality of the mesenchyme of the first branchial arch and partially to that of the second one, while the rhombencephalon con-tributes to the formation of the second, third and fourth arches.

The stability of the marker system produced by quail cells implanted into the chick makes it possible to follow the migrating cells until they have reached their definitive localization in the various structures of the hypobranchial skeleton, which thus appears to be entirely of neurecto-dermal origin. The cells arising from the mesencephalic neural primordium constitute the lower jaw skeleton (Meckel’s cartilage and bones) and are all still in the process of migration at the 6-somite stage. Cells originating from the rhombencephalon have left the neural axis at the 9-to 10-somite stage for the anterior part (in front of the first somite) and at the 11-to 12-somite stage for the posterior rhombencephalon.

Differentiation of mesectodermal cells into chondrocytes and osteocytes has been observed during the morphogenesis of the visceral skeleton.
A high frequency of fertilization in premature and mature coelomic toad eggs after enzymic removal of vitelline membrane
Authors: Katagiri Chiaki
Published: April 2021

The jelly-less coelomic eggs of the toad, Bufo bufo, even if chromosomally mature and reactive to parthenogenetic stimuli, are not fertilized or fertilized in a low frequency under the conditions which assure the sperm entry into dejellied uterine eggs. A high frequency of fertilization was obtained, however, when coelomic eggs from which the vitelline membrane had been digested away by pronase or hatching enzyme were inseminated in the presence of polyvinylpyrrolidone (PVP) or the diffusible egg-jelly component. Experimental evidence is presented to show that the conditions important for inducing this success in fertilization arc the complete removal of the vitelline membrane and insemination in the presence of one of the following sperm ‘capacitating’ substances: the diffusible jelly component, the non-dialysable jelly component, PVP, dextran, or Ficoll. Fertilization obtained by this method was monospermic, as defined both by cytological examination and by the mode of early cleavage. However, the eggs invariably ceased development at the gastrula stage, because of the lack of the mechanical support normally provided by the egg envelopes. These results indicate that toad eggs acquire the full ability, without any influences from the oviduct, both to react to a penetrating sperm and to prevent polyspermy.

When eggs undergoing maturation (premature eggs) were demembranated and inseminated in the presence of PVP, they did not show a genuine cleavage. Cytological examination proved the occurrence of highly polyspermie fertilization in these premature eggs, together with a tendency for the rate of pronucleus formation by the incorporated sperm to increase as the eggs were closer to the stage of full nuclear maturity.

On the basis of these results, a possible role of the oviduct in affecting the vitelline membrane-egg surface interrelationship is discussed, as well as the changing reactivity of maturing oocytes to spermatozoa, and vice versa.
Behavioural transformation in chick yolk-sac cells
Authors: Downie J. Roger
Published: April 2021

During the first 3 to 4 days of development in the chick, the extraembryonic part, the yolk-sac, expands to encompass the yolk mass. The yolk-sac, initially a two-layered epithelial sheet, is pulled out by the action of a specialized band of cells at its periphery. These attach to the overlying vitelline membrane and move out over it.

However, unincubated blastoderms are not attached to the vitelline membrane, and each comprises a loose assemblage of rounded cells, not an epithelial sheet.

The transformation of the unincubated blastoderm into an actively expanding epithelial sheet has been followed in culture, using hanging-drop cultures of fragments to observe large-scale behaviour, and disaggregated blastoderms to observe individual cell behaviour. The timing of events in culture accords well with related events in ovo, and the possibility that in vitro changes are merely a response to culture conditions has been largely excluded.

0–6 h in ovo. No cells attached to the vitelline membrane. All cells loosely attached to one another.

0–6 h in vitro. Cells do not attach to the glass. The cells of disaggregated blastoderms are rounded and stationary.

6–10 h in ovo. Cells at the blastoderm periphery attach to the vitelline membrane inner surface, but expansion does not start. The cells remain loosely attached to one another.

6–10 h in vitro. Cells begin to stick to the glass surface. Cells from disaggregated cultures move around as individuals. They remain rounded with long, narrow filopodia. If two cells collide, the adhesion tends to be brief.

10+h in ovo. The blastoderm starts to expand rapidly as a cohesive epithelial sheet, pulled by its specialized ‘edge’ cells. All yolk-sac cells become tightly attached to one another.

10+h in vitro. Blastoderm fragments start to spread rapidly as flattened epithelial sheets. There is no sign of specialized ‘edge’ cells. Cells at the periphery of any fragment take on the role of the edge. Cells from disaggregated cultures flatten out on the glass with wide lamellae all round. When two cells collide, they now tend to stick permanently together.

The role of these changes in the mechanics of blastoderm expansion is briefly discussed.
‘Spontaneous’ sex reversal in organ cultures of the embryonic male gonad of the bird
Authors: Erickson Gregory F.
Published: April 2021

The left embryonic testis of the bird (4–8 days of incubation) was organ cultured in medium that contained 10% foetal calf serum. Under these conditions, the germinal epithelium (GE) of the 4-day gonad differentiates into an ovarian cortex and the male primordial germ cells (PGCs) complete a developmental sequence similar to normal oocytes, i.e. they divide mitotically, develop a Balbiani body, divide synchronously in groups of two, four, and eight germ cells, and some enter pre-leptotene. No medullary tissue develops in the 4-day explants. The pieces of 6-and 8-day gonad differentiate into true ovotestes in which the GE develops into a cortex and the medulla develops into seminiferous cords. The PGCs in the cortex differentiate as oocytes and those in the seminiferous cords differentiate as spermatogonia. The possibility that biologically active oestrogens are present in the growth medium is discussed.
Diploid and haploid mouse parthenogenetic development following in vitro activation and embryo transfer
Authors: Kaufman M. H. , Gardner R. L.
Published: April 2021

Parthenogenetic mouse embryos were selected following in vitro activation, and transferred to the oviducts of pseudopregnant recipients. Decidua was evoked by 50–56 % of diploid parthenogenones compared to 35·1 % of haploid embryos with a single pronucleus, 37·5 % of immediate cleavage eggs and 77 % of fertilized eggs (controls). On day 4, 58·7 % of diploid parthenogenones were morphologically normal morulae or blastocysts; over 90 % of these ‘normal’ embryos evoked decidua when retransferred to recipients compared to 8·9 % of abnormal embryos flushed from the ‘transfer’ sides, suggesting that only ‘normal’ embryos could evoke decidua. Potentially diploid parthenogenones remained diploid on chromosomal examination on day 4.
Serum variants causing the formation of double hearts and other abnormalities in explanted rat embryos
Authors: Steele C. E. , New D. A. T.
Published: April 2021

Rat embryos explanted before organogenesis ( days gestation) were grown in culture in homologous serum. When the serum was prepared from blood centrifuged after clotting, the embryos developed double hearts. In serum prepared from blood centrifuged before clotting had occurred, and in plasma, the embryos developed normal single hearts. The delayed-centrifuged (D.C.) serum also supported less growth of older embryos than the immediately-centrifuged (I.C.) serum. The harmful properties of D.C. serum appeared rapidly in contact with a normal blood clot but did not develop in contact with separated blood cells and fibrin clot. Mixtures of D.C. and I.C. sera gave results intermediate between those from the two sera alone. No significant differences were found between D.C. and I.C. serum in calcium or complement content but both supported better embryonic development after pre-heating.
Induction de la maturation sexuelle chez la Planaire scissipare Dugesia gonocephala (Turbellarié, Triclade)
Authors: Lender Th. , Briançon C.
Published: April 2021

Induction of sexual maturity in a fissiparous Planarian, Dugesia gonocephala

The planarian Dugesia gonocephala reproduces either sexually, or asexually by fission, according to the presence or absence of a genital apparatus.

The experimental induction of sexual maturity in a fissiparous planarian can be obtained by grafting a piece of a planarian with a genital pore containing mature testes, whether they are testes existing in the graft before the operation (grafts of testes) or testes differentiated in the piece after grafting (grafts of ovaries). Grafts of cephalic or caudal region, and pieces of a planarian without genital pore, cannot induce this maturation and cannot differentiate testes.

The induction of testicular structures seems to be dependent on hormones.

The development of a genital apparatus in a planarian without genital pore is accompanied by the disappearance of fission.
An ultrastructural study of sex differentiation in the teleostOryzias latipes
Authors: Satoh Noriyuki
Published: April 2021

Electron-microscopic observations on sex differentiation during normal development in the medaka, Oryzias latipes, are presented in this report.

Primordial germ cells in embryos 6-10 days after fertilization are clearly distinguishable from somatic cells by the presence in the cytoplasm of the former of germinal dense bodies, closely associated with large aggregations of mitochondria. The gonadal primordium is composed of the primordial germ cells and the enveloping somatic cells; no special ultrastructural relationships have been detected between these two cell types. The sex of an embryo cannot be decided by means of the electron microscope.

The newly formed ovary is distinguishable in newly hatched fry of about 5 mm total body length. In the ovary, a layer of cells forming the ovarian wall encloses the ovarian matrix, consisting of oogonia and their surrounding follicle cells. There are often observable desmosomes between two neighbouring follicle cells. Although marked rearrangement of somatic cells takes place during sex differentiation of the gonad, few visible changes are observed in the ultrastructure of the primordial germ cells during their transition to oogonia. The transition from the oogonium to the oocyte is, however, characterized by a distinctive change in the nucleus, associated with the onset of meiosis. In the young ovary of 5-day-old fry, ooctye chromatin is visibly organized into electron-dense axial elements at the leptotene stage of meiotic prophase. But in the ovary of 10-day-old fry (about 6 mm body length), many oocytes at zygotene or pachytene stages are found, with synaptonemal complex configurations essentially the same as those described in numerous other meiosing plant and animal cells.

In contrast, the testis of newly hatched male fry remains in an undifferentiated state, with the somatic cells simply enveloping the spermatogonia.

No cells with the ultrastructural characteristics of Leydig cells (as observed in adult testis) can be distinguished in the young ovary or in the undifferentiated testis 10 days after hatching. Cells with the ultrastructural characteristics of adult Leydig cells are detectable for the first time in the matrix of the testis of 25-day-old young, about 8 mm in total length. When proliferation of spermatogonia has occurred, to form the typical testis of 45-day-old (about 15 mm), young, these cells appear in the interstitial region of the testis.

Observations from the present study indicate that sex differentiation of germ cells and somatic cells in the gonad precedes the differentiation of steroid-secreting cells. Therefore, the hypothesis that sex hormones are natural sex-inducers is not supported by the present results. The possibility is emphasized that some intracellular mechanisms may be involved in the natural course of sex differentiation of the germ cells and the gonad in this fish.
X-inactivation pattern in the epididymis of sex-reversed mice heterozygous for testicular feminization
Authors: Drews Ulrich , Alonso-Lozano Valentin
Published: April 2021

Female mice heterozygous for testicular feminization were sex-reversed by means of the autosomal sex reversal mutation (Sxr). Due to X-inactivation, the blastemata for male sex organs in these animals are composed of a mixture of cells, carrying either the wildtype X chromosome or the X chromosome affected with Tfm in an active state. Thus, the two types of cells are sensitive to androgens or insensitive to androgens, respectively. This mosaic could be demonstrated in the epididymis on a cellular level. Segments of undifferentiated Tfm cells were found alternating with normally differentiated wild-type cells. The ultras truc tura] appearance of the mosaic is described.
Mesenchyme specificity in rodent salivary gland development: the response of salivary epithelium to lung mesenchyme in vitro
Authors: Lawson Kirstie A.
Published: April 2021

Lung mesenchyme is able to support budding and cytodifferentiation of salivary epithelial rudiments in vitro. No difference in response was found between submandibular and parotid epithelium from mouse or rat.

There are several further features of this result, which is contradictory to previous findings. (1) Lung mesenchyme is quantitatively less effective than submandibular mesenchyme for supporting submandibular morphogenesis. At least part of this difference is attributed to the inability of submandibular epithelium to replace lung epithelium in supporting the growth of lung mesenchyme. (2) Rat lung mesenchyme is quantitatively more effective than mouse lung mesenchyme when recombined with mouse submandibular epithelium. This may be at least partly due to mouse lung being more easily damaged by the procedures used. (3) Whereas the response of submandibular epithelium to submandibular mesenchyme is equally good on an agar or Millipore filter (MF) substratum, the response to lung mesenchyme is severely reduced or eliminated on MF. This difference is interpreted in terms of different mesenchymal cell densities necessary for submandibular or lung mesenchyme to support branching morphogenesis.

Salivary buds formed in lung mesenchyme after 6 days are smaller and more closely packed than in salivary mesenchyme. In these heterotypic recombinates, the accumulation of amylase-resistant, PAS-positive material in the buds is initially accelerated and the tubular epithelium accumulates glycogen.
Protein synthesis in the early Drosophila embryo; analysis of the protein species synthesized
Authors: Roberts David B. , Graziosi Giorgio
Published: April 2021

The soluble proteins were extracted from Drosophila eggs which had been permeabilized and incubated in medium containing [35S]methionine. These proteins were analysed on immunoelectrophoresis plates and on SDS polyacrylamide gels both by staining for total protein and by autoradiography. The radioactive proteins must have been synthesized during the period of incubation with [35S]methionine. In the period covered by this study (0–3 h) there was much protein synthesis but no new proteins were synthesized which had not already been synthesized during oogenesis. We conclude that the considerable protein synthesis that occurs in early Drosophila development is translated from maternal mRNA which is activated both by egg deposition and fertilization. Translation of protein from either masked maternal mRNA, which had not been previously translated, or from mRNA transcribed from the zygote genome must occur after blastoderm formation.
Etablissement de l’axe dorso-ventral dans le pied de l’embryon de poulet
Authors: Pautou Marie-Paule
Published: April 2021

Establishment of the dorso-ventral axis in the foot of the chick embryo

The experiments were performed on 3·5-day and 5·5-day chick embryo leg-buds. Homo-and heterochronic heteropolar ecto-mesodermal recombinants were prepared in which the dorso-ventral (d-v) axis of the ectoderm was rotated by 180° with respect to that of the mesoderm. The mesodermal component of the associations consisted either of the intact mesodermal core or of a reaggregate of dissociated mesodermal cells. Recombinants were grafted onto a host wing stump and grown to day 16–20 of incubation.

The resulting feet display a d-v polarity in their integument and skeleton. This polarity conforms to that of the mesoderm in the proximal part of the foot (roughly basipod and metapod) and to that of the ectoderm in its distal part (roughly acropod) in the case of recombinants containing 3·5-day mesoderm. With 5·5-day undisrupted mesoderm, the polarity conforms entirely to that of the mesoderm.

In the recombinants containing 3·5-day or 5·5-day disrupted reaggregated mesoderm, the d-v polarity of the resulting feet, on the whole, conforms to that of the ectoderm. However, a high frequency of unpolarized integumentary and skeletal abnormalities occurs with 5·5-day disrupted mesoderm.

It is concluded that the ectoderm is polarized along its d-v axis. It exerts a d-v polarizing activity on the mesoderm during the 48 h period necessary for the segregation of the presumptive territories of the autopod. The ectodermal polarizing effect is expressed in the morphology of the integument and skeleton. At the end of the 48 h period, the d-v axis of the mesoderm is irreversibly laid down.
Effect of the brachypod mutation on cell adhesion and chondrogenesis in aggregates of mouse limb mesenchyme
Authors: Duke Jackie , Elmer William A.
Published: April 2021

Twelve-day normal and brachypod mouse limb mesenchyme was studied in rotation culture. Over a h period the rate of decline of single cells was significantly greater in mutant than in normal cultures, probably because the brachypod cells were more adhesive. However, the final size of the aggregates and their cell densities were the same by 24 h of incubation. On the other hand their pattern of chondrogenesis was different. Normal aggregates contained condensations with typical histotypic cartilage by 24 h of incubation, and were entirely chondrified by 4 days in culture. The condensations in brachypod aggregates were fewer, smaller, and delayed in their chondrogenesis. Never more than 50% of the brachypod aggregate exhibited chondrogenesis. The importance of cell contact and cell density to the chondrogenic process are discussed.
La cinétique cellulaire au cours de la segmentation du germe d’Axolotl: proposition d’un modèle statistique
Authors: Signoret J.
Published: April 2021

The present work is based on the study of individual cell cycle times for a given category of cells. The material considered in detail is the Axolotl embryo during the eleventh cleavage cycle. In spite of the exceptional homogeneity of this population, individual cycle times show a remarkable variation from cell to cell, coinciding with a characteristic statistical distribution.

To describe the kinetics of cell proliferation, we propose a model for which the theoretical distribution of cycle times fits with the distribution observed in our material. Numerous observations allow us to generalize the model to other types of populations. According to this concept the notion of cell cycle time disappears in favour of the notion of a statistical distribution of individual cycle times.

This variability is integral to the cell division process itself. We suggest that in the cycle there is a particular event the probability of occurrence of which is constant beginning with a critical state. The cells would therefore remain a certain time in this state, overcoming it at a characteristic rate.

To this exponential distribution variability would be added the variability of other events whose cumulative effects would result in a normal distribution. The resultant of both factors conforms to the frequency distribution implicated in our kinetic model.

Discussing in a more general way the distributions of the cycle times of each cell division during cleavage, we propose the following interpretation of this development. The introduction of new events in the cyclic process would imply the switching on of certain essential genetic activities. The final consequences would be the desynchronization and the lengthening of the cycles observed at the blastula stage.

Thus considered, this period of embryonic development would be eminently suitable for the study of the factors of cell division control.
Anomalous ipsilateral optic fibre projection in Xenopus induced by larval tectal ablation
Authors: Straznicky Charles , Glastonbury John
Published: April 2021

Unilateral left tectal ablation was carried out in Xenopus between stage 48 and 1 month after metamorphosis. Six to 12 weeks after metamorphosis the retinal projection from the right eye was examined with the use of [3H]proline autoradiography. The autoradiographs indicated that optic fibres whose tectal target was destroyed recrossed to the ipsilateral tectum and basal optic nucleus via the posterior and pretectal commissures. No anomalous recrossing occurred if the tectal ablation was carried out at stage 58 or later. The aberrant optic fibres were restricted to the rostrolateral and central parts of the ipsilateral tectum and they terminated in a discontinuous manner. It is concluded that available surfaces serving as contact guidance cues are needed to direct aberrant optic fibres to the ipsilateral tectum.
The role of irradiated tissue during pattern formation in the regenerating limb
Authors: Maden M.
Published: April 2021

The amphibian limb regeneration blastema is used here to examine whether irradiated, non-dividing tissue can participate in the development of new patterns of morphogenesis. Irradiated blastemas were rotated 180° on normal stumps and normal blastemas rotated on irradiated stumps. In both cases supernumerary elements developed from the unirradiated tissue. The supernumeraries were defective but this did not seem to be due to a lack of tissue. Rather it suggested that this could be a realization of compartments in vertebrate development or simply reflect the limited regulative ability of the blastema. The results are also discussed in relation to a recent model of pattern formation.
Differentiation capacity of unincubated chick blastoderm in culture
Authors: Zagris Nicholas
Published: April 2021

Unincubated (stage X) chick blastoderms cultured in plain Dulbecco’s modified Eagle medium in the absence of serum, synthesize haemoglobin and melanin 2·5−3·0 and 607·0 days, respectively, after the beginning of culture. The capacity of unincubated blastoderm to form haemoglobin and melanin is a response to intrinsic genotypic instructions rather than to the active intervention of substances continuously supplied by the yolk. 5-Bromo-deoxyridine, applied during the first and second days of unincubated blastoderm in culture, is incorporated into DNA and perturbs the formation of haemoglobin and melanin, perhaps, by modifying gene expression.
An analysis of the aggregation and morphogenesis of area opaca endoderm cells from the primitivestreak chick embryo
Authors: Milos Nadine , Zalik Sara E. , Phillips Robert
Published: April 2021

The aggregative behaviour and subsequent morphogenesis of extra-embryonic endoderm cells from primitive-streak chick embryos have been investigated. A relatively pure population of area opaca endoderm cells was obtained by differential dissociation, which involves partial separation of epiblast and endoderm cell clumps by sieving through Nitex mesh. For aggregation studies cells were cultured in rotating flasks in Leibovitz (L-15) medium, in saline or in saline supplemented with glucose (1 mg/ml). Aggregation was monitored using the Coulter Counter. In these three media aggregation is rapid; by 10 min an average of 61% of the population had aggregated, to reach a plateau at 30 min when an average percent adhesion value of 83 % was obtained. The aggregates in L-15 medium were large and compact. After several days in culture, they cavitated and formed smooth hollow vesicles with thin walls composed of one or a few cell layers. Aggregates formed in PCS were smaller and looser in appearance; the addition of glucose resulted in a certain degree of compaction. Some morphogenesis occurred under these conditions with the aggregates developing numerous irregular cavities. These experiments suggest that some of the factors that affect cell adhesion in early embryonic cells can be studied in vitro. The results also indicate that the ability to cavitate is an intrinsic property of the endoderm cells of the area opaca since this occurs in the absence of epi blast or mesoderm.
Somite formation in the early chick embryo following grafts of Hensen’s node
Authors: Hornbruch Amata , Summerbell Dennis , Wolpert L.
Published: April 2021

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

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

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

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

Cyclic-AMP and ammonia have been previously identified as extracellular signals during Dictyostelium development. Both are important in controlling morphological movements and cyclic-AMP also in inducing gene expression. The work in this paper is concerned with their effects on developmental gene expression. Cyclic-AMP was found to act as an inducer during the aggregative (as exemplified by phosphodiesterase) and the post-aggregative (glycogen phosphorylase, UDP-galactose polysaccharide transferase, prespore vacuoles and stalk cells) phases of gene expression. Ammonia inhibited the appearance of each of the above markers and antagonized the inductive effects of cyclic-AMP on them. This inhibition by ammonia of cyclic-AMP inducible gene expression may involve a step linking elevated intracellular cyclic-AMP levels to gene activation.

It has been suggested that the specification of cells within the aggregate into the stalk and spore pathways of differentiation might be controlled by cyclic-AMP and ammonia. In this model for pattern formation cyclic-AMP would induce stalk cell differentiation and ammonia spore formation. The present results argue against this idea since cyclic-AMP induces and ammonia inhibits differentiation along both pathways. The function of these agents may rather be to coordinate the rates of biochemical differentiation of individual cells and link them to the overall morphological changes occurring during development.
Lethality of radioisotopes in early mouse embryos
Authors: Macqueen Hilary A.
Published: April 2021

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

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

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

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

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

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

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

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

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

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

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

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

This paper presents evidence that maternal mRNA is responsible for the early increase in HPRT activity in preimplantation mouse embryos. Increase of HPRT activity is demonstrable from as early as 6 h postfertilization when there is barely detectable synthesis of embryonic RNA. The increase is sensitive to cycloheximide and thus requires protein synthesis, whereas it is insensitive to α-amanitin and therefore independent of mRNA synthesis. These results suggest that translation of HPRT occurs on pre-existing maternal mRNA.

Embryo-coded HPRT activity is detectable by the 4- to 8-cell stage when the increase in HPRT activity becomes sensitive to a-amanitin. The transition from maternal- to embryo-coded enzyme activity is completed by the time of compaction. At this stage there is an unexplained yet reproducible loss of HPRT activity. Other maternally-inherited enzymes show a marked degradation occurring at a similar time. It is possible that the enzyme degradation observed reflects some common mechanism directing the changeover from maternally-derived to embryonically-derived enzymes.
Quantitative aspects of RNA synthesis and polyadenylation in 1-cell and 2-cell mouse embryos
Authors: Clegg Kerry B. , Pikó Lajos
Published: April 2021

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