bluuebunny/crossref_metadata_2025 huggingface dataset:
A structural analysis of congenital limb deformities in experimental hyperthyroid tadpoles
Authors: Sit K. H. , Kanagasuntheram R.
Published: April 2021

An experimental model for the study of hyperthyroidism in embryonic development was achieved in the local anuran larvae, Bufo melanostictus, by treatment with potassium perchlorate at a critical dose and time of embryogenesis.

Phocomely-hemimely and digital deformities of foreand hind limbs in high percentages of the population were found associated with such critically stimulated tadpoles. Similar deformities were reproduced by exogenous treatment with L-thyroxine sodium. The deformities were severely aggravated if the tadpoles had anti-thyroid treatment before critical stimulation with thyroxine in the sensitive phase of development.

Incoordinate cellular differentiation in the malformed limbs was indicated histologically by undifferentiated mesenchyme in the distal extremities although the overlying ectoderm had already formed mature epidermis with specialized skin glands. The differentiated mesodermal components (muscles, cartilages and connective tissues) more proximally were afflicted with degenerative changes. Lytic spinal motor neurones and involuted Mauthner’s neurones with precipitate metamorphosis were accompanying features. Embryonic thyrotoxicosis is discussed in relation to congenital deformities of limbs.
Elektrolytveränderungen in Amphibiengeweben während der Larvenentwicklung, Metamorphose und Regeneration (Xenopus laevisDaudin undTriturus cristatus carnifex)
Authors: Burkart Von T.
Published: April 2021

Changes of electrolyte content in amphibian tissues during larval development, metamorphosis and regeneration

Measurements of sodium-, potassium- and water-content were made in amphibian tissues during normal postembryonic development and during various regenerative processes, specifically: (a) of whole larvae of Xenopus laevis curing larval development and metamorphosis, (b) of normally-growing hindlimbs of Xenopus laevis during larval development and metamorphosis, (c) of trunk and the tail, respectively, of X. laevis during the metamorphic climax, (d) of regenerating hindlimbs of Xenopus larvae, (e) of regenerating forelimbs of adult Triturus cristatus carnifex and (f) of heteromorphically regenerating forelimbs of adult X. laevis.

Drastic changes in electrolyte concentration were observed for all developmental processes studied and characteristic changes for certain developmental subprocesses like cell accumulation, proliferation and differentiation (see Table 2).

The changes in growth-rate (as measured by increase in dry weight) are compared with the changes in K/Na ratio in Xenopus larvae during prometamorphic development and in normally-growing Xenopus hindlimbs. The changes in growth-rate are positively correlated with the changes in K/Na ratio (Figs. 2, 4).

Mitotic activity in the normally-growing hindlimbs of Xenopus larvae and in regenerating forelimbs of adult Triturus was studied and compared with the changes in K/Na ratio. It was found that with increasing K/Na ratio the mitotic rates also increased, but beyond a certain level the mitotic frequency decreased (Figs. 4, 11).

The beginning of cell differentiation in normally-growing hindlimbs of Xenopus (Figs. 3,4), in regenerating hindlimbs of Xenopus larvae (Figs. 8, 9) and regenerating forelimbs of adult Triturus (Figs. 10,11) is concomitant with an increase in the potassium concentration and the K/Na ratio.

The possibility that electrolytes serve as regulators of growth and differentiation processes is discussed.
A decolorant of the sulfhydryl reagent DTNB released from live blastulae of sea urchins in saline medium
Authors: Wolfson N.
Published: April 2021

Cleaving embryos of the sea urchin Paracentrotus lividus exposed briefly to buffered saline release materials into the medium which will bleach a yellow mixture of DTNB and DTT [5,5’ -dithiobis (2-nitrobenzoic acid) and dithiothreitol]. The decolorant activity is thermolabile and dialysable. The bleached mixture recolors rapidly on heating, suggesting the breakdown of a complex between the decolorant and the yellow DTNB ion.

The release of decolorants is maximal at the blastula stage, and in Ca-free saline, Tris-HCl pH 7. When various untreated embryonic stages are homogenized with DTNB, the assay for SH is lowest at blastula, suggesting that decolorants in the blastulae interfere with the assay.
Studies on self-differentiating and induction capacities of Hensen’s node using intracoelomic grafting technique
Authors: Viswanath J. R. , Mulherkar Leela
Published: April 2021

Living Hensen’s node of the definitive primitive streak of chick embryo was prepared into ‘sandwiches’ with the competent ectoderm and the sandwich grafts were transplated into the 2·5 day chick embryo using the intracoelomic grafting technique of Hamburger.

One hundred and twenty-four grafts were prepared and transplanted intracoelomically, 28 grafts were lost due to the death of the host embryos, 63 grafts did not differentiate at all, but 33 well-defined grafts were recovered, after cultivating the transplanted hosts for 12–14 days.

All kinds of tissues from feather germs to neural tissue were found to have differentiated in the grafts. The more frequently occurring tissues were feather germs, epidermal vesicle, neural tissue, kidney and muscle. Other differentiations were the cartilage notochord and gut. No definite combination pattern has emerged from the tissues. But when the tissues were traced to their germ-layer derivation, 22 of them belonged to the mesodermal complex, 11 to the ectodermal complex and 8 to the endodermal complex.

In the light of the above results, the probable existence of a mesodermal factor and an ectodermal factor independently responsible for the respective differentiations, as also the competence of the ectoderm, is discussed.
Re-evaluation of the presence of multiple haemoglobins during the ontogenesis of the chicken: Electrophoretic and chromatographic characterization, polypeptide composition and immunochemical properties
Authors: Schalekamp M. , Schalekamp M. , Goor D. Van , Slingerland R.
Published: April 2021

Haemolysates of red blood cells from embryos of several developmental stages ranging from 2 to 21 incubation days and from post-hatching chickens of various age groups were analysed by ion-exchange chromatography, agar-and starch-gel electrophoresis, immunoelectrophoresis with specific antisera and polypeptide chain electrophoresis.

With these methods two adult (A1 and A2) and six embryonic (E1–E6 haemoglobin types were identified. Antisera specific for the major adult haemoglobins (A1 and A2) as well as antisera specific for the major embryonic haemoglobins (E3, E4) could be prepared. Throughout embryogenesis the haemoglobin types contribute in varying amounts to the total haemoglobin pattern. Three periods of haemoglobin synthesis could be recognized, the transition between these periods occurred at the 6th and 12th incubation day. The first period is characterized by the presence of two major embryonic haemoglobins (E3 and E4) and two minor embryonic haemoglobins (E2 and E5). During the second period E3 and E4 are largely replaced by a major adult haemoglobin (A2) and a new embryonic haemoglobin (E1). The third period is characterized by the appearance of a second adult haemoglobin (A1) and a new minor embryonic haemoglobin (E6) with a concomitant decrease of E2 and E5. At the time of hatching two embryonic haemoglobins (E1 and E6) are still present.

Besides A1 and A2, several minor haemoglobin fractions were inconsistently found in adult chickens. Evidence has been obtained that these additional fractions are reflecting a so called minor heterogeneity or separation artifacts.

The haemoglobins A1, A2 and E1 –E6 show different polypeptide chain compositions. Three embryo-specific chains could be demonstrated (β E2E5, γE4 and δ E3). The production of the polypeptide chains appears to be correlated with the aforementioned periods of haemoglobin synthesis.

The genetic and morphological implications of the findings are discussed.
Study of yolk-sac endoderm organogenesis in the chick using a specific enzyme (cysteine lyase) as a marker of cell differentiation
Authors: Bennett Nelly
Published: April 2021

The detection of a specific enzyme (cysteine lyase) of the yolk-sac endoderm by a very sensitive method is employed to characterize cell differentiation during the early stages of endoderm organogenesis in the chick.

The first cells to contain active cysteine lyase are found in the germ wall at the primitive streak stage.

In vivo observations establish a relation between the morphological specialization and organization of endodermal cells, their loss of mitotic activity and the increase in cysteine lyase activity. They suggest an influence of the mesoderm on endoderm differentiation.

In vitro experiments confirm the existence in the yolk-sac endoderm of an incompatibility between cell proliferation and differentiation, as well as the action of the mesoderm on both the structural organization of the endoblast and the appearance of cysteine lyase; this last action seems to be due mainly to blood cells; chicken and rabbit blood cells are equally active.

The problems of the origin of the endoderm and of the interactions occurring during the organogenesis of the yolk-sac endoderm are discussed.
A histochemical study of sulphated glycosaminoglycans associated with the somites of the chick embryo
Authors: O’hare M. J.
Published: April 2021

A histochemical analysis has been made of sulphated glycosaminoglycans (mucopoly-saccharides) associated with chick embryo somites before and after the onset of overt cartilage differentiation. The sulphated glycosaminoglycans were distinguished and resolved into different types by the use of alcian blue at low pH and alcian blue ‘critical electrolyte con-centration’ staining combined with hyaluronidase digestion.

The newly formed somites are bounded on their dorsal, ventral, and medial surfaces by basement membrane material as they are delimited from the unsegmented paraxial mesoderm Such epithelial basement membrane material, which was first detected in association with the epiblast/mesoderm boundary in the stage-4 embryo, was found to contain a major chondroitin sulphate A/C fraction and a minor chondroitin sulphate B fraction. The notochord sheath contained similar sulphated glycosaminoglycans.

Sulphated glycosaminoglycans were first detected between cells of the somite ‘core’ at stage 14 and were subsequently seen to accumulate around the cells of the developing sclero-tome and later around cells of the dermatome; the myotome was devoid of such material at these stages (stage 14–20). These pre-cartilaginous sulphated glycosaminoglycans were also of the chondroitin sulphate A/C plus chondroitin sulphate B types.

In contrast, the matrix material of newly forming vertebral cartilage, which was first seen in the anterior region of stage 21 embryos, was distinguished by its lack of a hyaluronidase-resistant sulphated glycosaminoglycan component, and therefore presumably contained only chondroitin sulphates A/C. Much later in development (after stage 33) small amounts of sulphated glycosaminoglycan with the staining properties of keratan sulphate were found in the perichordal and subperichondrial regions of the vertebral cartilage.
An experimental study of eye development in the cephalopod Loligo vulgaris: determination and regulation during formation of the primary optic vesicle
Authors: Marthy H.-J.
Published: April 2021

By a series of explantation, transplantation (yolk syncytium left intact) and incision experiments done with the eye rudiment during the stages VI –IX (Naef, 1923) it is concluded that the yolk syncytium does not induce the differentiation of ‘the outer layer of cells’ from stage VI on as suggested by Arnold (1965 b). From the explantation and transplantation experiments the author draws the conclusion that there exists, from stage VI on, in the ‘outer layer of cells’ on each side of the embryo, an area which contains all factors necessary for eye formation and which manifests itself, under experimental conditions, in regulation. The explanted eye rudiment shows in vitro autonomous differentiation capacity only if nutritional conditions are sufficient. The incision experiments elucidate the role of ‘contractile elements’ in organogenesis. Arnold’s results are discussed.
Développement des organes lymphoïdes chez l’Amphibien UrodèleTriturus alpestrisLaur.; tolérance des allogreffes après la thymectomie larvaire
Authors: Tournefier Annick
Published: April 2021

The development of lymphoid organs in the urodele amphibian Triturus alpestris Laur.; skin allograft tolerance after larval thymectomy

The first part of this work is an attempt to extend anatomical knowledge of lymphoid organ differentiation: thymus, spleen and liver in Triturus alpestris Laur.

The purpose of the second part is to compare a first-set allograft reaction in normal adult newts (100% rejection) and the allograft reaction of larval-thymectomized adult newts. Thymectomy was performed on 39 newts in the tenth week of their life at a known stage of their splenic and thymic differentiation. These thymectomized newts were grafted 18 months later with two different adult skin grafts. A daily observation of the 78 grafts showed that larval thymectomy induced 72% of tolerance.

However, 11 newts rejected their grafts in the same way as normal adult newts, but with a longer median survival time (36 days instead of 23 or 27 days). In five of these newts, dissection showed one or two functional thymic nodules and the allograft rejection was due to an incomplete larval thymectomy.

In the six other newts, one thymic nodule was found, so the rejection was probably because the thymectomy was too late. Triturus alpestris Laur., like other urodeles, has no bonemarrow, and splenic lymphocytes are probably, for the most part, of thymic origin.

Lymphocytes first appear in the spleen during ths ninth week of larval life. If thymectomy is performed at the end of the tenth week, splenic differentiation is completed and the spleen may substitute for thymus function in allograft rejection.
Contribution expérimentale à l’étude de la formation de l’endoblaste chez les Oiseaux
Authors: Lutz par Hubert
Published: April 2021

The technique of marking the unincubated duck blastoderm with fine particles of Chinese ink leads to the following conclusions:

there exist superficial morphogenetic movements during the first few hours of incubation; surface material rolls round the posterior, lateral, and anterior margins; there is a direct continuity between extra-embryonic and embryonic endoblast.

The endoblastic layer forms therefore by surface material rolling round the posterior, lateral, and anterior margins.
Post-Partum Changes in the Uterus of the Rat
Authors: Warbrick James G.
Published: April 2021

Rats were killed at intervals from 0 hours to 5 days after littering. Some of the changes that occur in the uterus during this period were studied. The area of endometrium left devoid of epithelium by the separation of the placenta was re-epithelialized by cells which spread in from the existing marginal epithelium. There was no evidence of a transformation of stromal into epithelial cells. The migrating epithelial cells did not contain glycogen and their cytoplasmic content of ribonucleic acid was reduced. Re-epithelialization of the sites was completed within 36 hours. There was vacuolation of the epithelial cells which was most marked from between 24 to 36 hours after littering. The changes in the rats’ uterus are compared with those occurring in some other mammals.
The Reversibility of the Effect of Hypervitaminosis A on Embryonic Limb Bones Cultivated in vitro
Authors: Herbertson M. A.
Published: April 2021

Experiments were made to study the reversibility of the effects of hyper-vitaminosis A on embryonic long-bones in vitro. Limb-bone rudiments from 6-to 7-day chick embryos were cultivated by the watch-glass method, first in medium to which excess vitamin A had been added and then in normal medium. Suitable controls were also grown. The excess vitamin arrested the growth of the explants and caused the cartilage matrix to shrink and lose its basophilia and metachromasia. The extent of the damage depended upon the length of time spent in + A medium, the concentration of the vitamin, the stage of development of the rudiment when explanted, and the particular rudiment treated. The degree of recovery was related to the severity of the changes produced by the vitamin. In the shaft these changes were arrested but there was no restora-tion of lost matrix; the cells appeared healthy but resembled osteoblasts rather than normal hypertrophic chondroblasts. The epiphyses also partially recovered and began to enlarge again when transferred to normal medium; they had a high mitotic rate in comparison with the normal controls.
An ultrastructural study of germ plasm in spermatogenesis ofXenopus lœvis
Authors: Kerr J. B. , Dixon K. E.
Published: April 2021

Spermatogonia and primary diplotene and zygotene spermatocytes contain an electron-dense, finely granular substance which is usually closely associated with mitochondria; small patches of this substance also occur close to the nuclear membrane, often in the nuclear pores, and within the nucleus of primary spermatogonia. The fine structure of this substance is very similar to the fine structure of germ plasm in other stages of development, and since an ontogenetic continuity with germ plasm can be demonstrated, it was concluded that this substance is also germ plasm. The substance disappears about pachytene, earlier than in oogenesis where it persists until mid-diplotene, a difference which may be due to the fact that the oocyte stores large quantities of germ plasm in its cortex for the next generation of primordial germ cells. If the presence of the substance in the nuclear pores and within the nucleus is an indicator of synthesis of germ plasm, then synthesis stops in the secondary spermatogonium, which correlates with the subsequent absence of germ plasm from the pachytene spermatocyte stages. It is suggested that the function of the germ plasm in specifying germ line cells is carried out between the gastrula stage and the beginning of meiosis. The three events which take place during this period are (i) the migration of the presumptive primordial germ cells from the endoderm to the genital ridges, (ii) mitosis of the primordial germ cells and subsequently of the oogonia and spermatogonia in the developing gonads and (iii) preparations for meiosis. It is suggested that the mechanism of action of the germ plasm may be in the control of one or more of these processes. Other types of granular cytoplasmic deposits are also described, and their possible relationship to germ plasm discussed.
Mise en évidence de glycogène et d’une activité de la glycogène synthétase dans l’ébauche hépatique aux stades précoces du développement embryonnaire chez le poulet
Authors: Houssaint Elisabeth , Douarin Nicole M. Le
Published: April 2021

Detection of glycogen and glycogen synthetase activity in the hepatic primordium of chick embryo at early developmental stages

Glycogen has been detected cytochemically in the chick hepatic primordium at early developmental stages. The cytochemical methods used are PAS according to Hotchkiss & MacManus after fixation by Gendre’s fluid at —20 °C and rapid dehydration at 4 °C and Thiery’s technique for polysaccharide detection at the electron microscopic level. Previous authors reported that glycogen appears in the hepatocytes during the sixth or seventh day of incubation in the chick embryo. In fact, the more sensitive methods used here show that this substance is present in the determined presumptive hepatic endoderm as early as the 20-somite stage, some hours before the formation of the primary hepatic bud. Glycogen is present in an approximately constant amount in the differentiating hepatic endoderm as β particles (according to Drochmans’ nomenclature) from the 20-somite stage to the sixth day of incubation. Then the hepatocyte glycogen content increases rapidly as had previously been shown by biochemical methods and a rosettes appear in the cell. A glycogen synthetase activity has been detected at the end of the fourth day of incubation (96 h). This activity increases sharply from the sixth day of incubation to reach a maximal value at .12 days and then decreases until hatching. The possible regulatory mechanisms of glycogen synthesis in differentiating liver cells of avian embryos are discussed.
Trophoblastic factors involved in lysis of the blastocyst coverings and in implantation in the rabbit: observations on inversely orientated blastocysts
Authors: Denker H.-W.
Published: April 2021

Lysis of the blastocyst coverings in the rabbit normally starts at the abembryonic hemisphere of the blastocyst facing the antimesometrial endometrium. Theoretically, this restricted effect could be caused by factors locally produced by abembryonic trophoblast, anti-mesometrial endometrium, or a combination of them. Blastocysts abnormally implanting with reversed orientation exhibit lysis of blastocyst coverings in the abembryonic hemisphere despite the absence of antimesometrial endometrium, and they do not show lysis in the embryonic hemisphere despite its contact with antimesometrial endometrium. Accordingly, it appears that lysis of blastocyst coverings is attributable to a factor localized in the abembryonic hemisphere of the blastocyst. Blastocyst protease activity was found to be maximal there in all blastocysts, whether oriented normally or reversed. The origin and role of this enzyme and other factors are discussed.
L’architecture des centres visuels diencéphaliques et pretectaux du poussin deGallus domesticusL. Etude expérimentale
Authors: Raffin J.-P.
Published: April 2021

The architecture of the diencephalic and pretectal visual centres in Gallus domesticus L. An experimental study

The effects of bilateral optic vesicle removal on the main diencephalic and pretectal visual centres have been studied from the 15th day of incubation till the 15th day after hatching.

Some centres (nucleus lateralis anterior, nucleus geniculatus lateralis dorsalis and ventralis, nucleus griseums tectalis and nucleus pretectalis principalis) show a variable degree of disorganisation and reduction in size. Others (nucleus ectomammillaris, nucleus superficialis synencephali) have already disappeared on the 15th day of incubation. The nucleus rotundus, though not recognized as an optic projection centre, is also affected by optic vesicle removal. No true neuronal degeneration could be observed in these structures.

A survey of chicken optic projections suggests that some may be only transitory, disappearing in the adult. A comparison of these results with those of other authors leads one to consider the morphogenetic influence of the optic pathways on the visual centres.
Studies on the gastrulation of amphibian embryos : pseudopodia in the gastrula ofBufo bufojaponicus and their significance to gastrulation
Authors: Nakatsuji Norio
Published: April 2021

The course of gastrulation in embryos of Bufo bufo japonicus was studied by use of 1 μm Epon sections. It was observed that the cells of the presumptive pharyngeal endoderm and mesoderm form pseudopodia coinciding with their invagination. Some of the inner cells of the ectodermal layer also form pseudopodia. The cells of the endodermal mass and the surface of the embryo rarely form such structures. The observed pseudopodia seem to correspond to the hitherto reported pseudopodia formed by the dissociated cells from the gastrula of amphibians. Formation of the pseudopodia seems to suggest that the invagination of the presumptive pharyngeal endoderm and mesoderm is brought about by active migration of the individual cells along the inner surface of the ectodermal layer.
Induction de la tolérance aux allogreffes de peau dans les chimères de l’amphibien modèle,Pleurodeles waltliiMichah.
Authors: Goujon P.
Published: April 2021

Induction of skin allograft tolerance in chimaeras of urodele amphibian, Pleurodeles waltlii Michah

Allogenic chimaeras were produced in Pleurodeles waltlii (Amphibian, Urodele) by associating the anterior and the posterior parts of two different embryos. A reciprocal exchange between two homologue embryos gave rise to reciprocal allogenic chimaeras.

Skin grafts performed in the adult stage between two reciprocal chimaeras are always tolerated. On the other hand, when two skin grafts coming from the anterior and the posterior part of one chimaera are grafted on a common host, one of them may be tolerated and the other rejected : each part of a chimaera keeps its own antigenicity.

In allogenic chimaeras, the average natural tolerance for skin allografts is 30 % higher than in sibling controls.
Differentiation in vitro of larval cell types from early embryonic cells of Drosophila melanogaster
Authors: Shields Glen , Dübendorfer Andreas , Sang James H.
Published: April 2021

A variety of cell types develop when cells of h Drosophila embryos are cultured in an improved medium. Nerve, muscle, fat-body, chitin-secreting, and macrophage-like cells (possibly haemocytes) appear in the first 24 h and mature over the next week. Tracheal, imaginai disc, a second stage of the macrophage-like, and a number of unidentified fibroblastic and epithelial cells appear in the 2nd and 3rd week, following a resumption of cell multiplication. There is some organization of some of the cell types into higher structures.
Structural basis of the functional development of the retina in the cichlid Tilapia leucosticta (teleostei)
Authors: Grün Gerd
Published: April 2021

The differentiation of retinal cells has been studied with special reference to the formation of functionally important structures. Three phases could be revealed: from day 3 to day 6 retinal cells in the mostly advanced central part show signs of general cell differentiation (formation of ribosomes, endoplasmic reticulum, mitochondria). In the second phase from day 6 to day 9 characteristic nerve cell structures appear (neurites, dendrites, synapses, receptor outer and inner segments). In the last phase from day 9 to day 12 these special structures attain their final, mature appearance, synapses seem ready for function, dendritic invaginations and synaptic ribbons are formed, twin cones become arranged in mosaic patterns. This developmental order conforms to a gradient running from the ganglion cells to the receptors. Neurites and dendrites appear in the ganglion cells on day 3, in the intermediate neuron layer not before day 4. The horizontal cells are the last ones to differentiate out of the intermediate neurons. The inner plexiform layer synapses are structurally mature before those from the outer plexiform layer. The receptor inner and outer segments differentiate from the 5th day up to the time the young fish is able to see (day 13). The last structures to appear are dendritic invaginations and synaptic ribbons in the receptor terminals, and the twin cone mosaic. It is assumed that the ability to see is achieved only when these structures have been formed.
Differentiation of photoreceptors in cultured optic vesicles from embryos of Rana esculenta
Authors: Caravita S. , Cataldi E.
Published: April 2021

Optic vesicles from embryos of Rana esculenta at a stage corresponding to stage 19 in the development of Ranapipiens were cultured for 15 days. The eyes which differentiated in vitro were much smaller than controls of the same age, due partly to the absence of the vitreous body. In many specimens a well-stratified retina surrounded by a layer of pigmented cells was found. The features of all the components of the retinal layers are described.

The complete differentiation of photoreceptors, including their outer segments, is the most interesting result obtained in these organ cultures, and is in contrast with the observations previously reported for retinal tissue cultures. The authors suggest that the source of the material (amphibia instead of birds or mammals) is the main reason for this discrepancy. Frog embryo cells are practically self-sufficient since they are endowed with nutritional substances, amongst which Vit. A and antioxidative agents (Vit. E and ascorbic acid) have been indicated as the most important factors for the structural organization and integrity of the outer segments. The role played by the pigment epithelium is also discussed.
Autoradiographic studies of t
n
/t
nmouse embryos
Authors: Nadijcka Mary , Hillman Nina
Published: April 2021

High-resolution autoradiographic studies were used to determine whether t12/t12 and tw32/tw32 mouse embryos synthesize the excessive lipid which distinguishes these embryos prior to their death. The studies show that the tn homozygotes synthesize neutral lipid which is stored in intracellular lipid droplets. Cholesterol and phospholipid precursors are not incorporated into these droplets.
Development of mouse−bank vole interspecific chimaeric embryos
Authors: Mystkowska Ewa T.
Published: April 2021

One bank vole (Clethrionomys glareolus) embryo and two mouse embryos were combined at the 8-to 16-blastomere stage and cultured in vitro for 33–47 h. In 66% of cases single regular blastocysts were formed. The chimaeric composition of blastocysts was confirmed karyologically. Out of the 222 blastocysts transplanted to 49 pseudopregnant mouse recipients, a total of 52 implantations were found in 20 recipients. Among the 52 implantations, 14 contained embryos and the remaining were resorptions. The majority of embryos were abnormal and fell into two categories : (1) groups of cells surrounded by Reichert’s membrane and lying freely in a cavity filled with giant trophoblastic cells, (2) small and retarded eggcylinders usually composed of endoderm and ectoderm only, and containing a proamniotic cavity. The ectoplacental cone of these embryos was poorly developed or lacking altogether.

Two normal-looking embryos were recovered on the 9th and 10th day (4-somite and ca. 12-somite stage). Chimaerism of the younger embryo was confirmed karyologically. No evidence of chimaerism was available in the case of older embryo which was examined histologically. Thirteen implantations examined between 11th and 17th day contained only resorptions. It is suggested that the main cause of the heavy mortality of chimaeric embryos is the profound difference in the course of embryogenesis of these two species immediately following implantation.
Skull growth in achondroplasic (cn) mice ; a craniometric study
Authors: Jolly Rosemary J. , Moore W. J.
Published: April 2021

Skull morphology in achondroplasic (cn/cn) mice was compared with that of normal siblings in order to determine the effects of this chondrodystrophy on skull growth, particular attention being given to dimensions reflecting growth at the synchondroses of the cranial base, the nasal septal cartilage and the condylar cartilage of the mandible. The central section of the cranial base (basicranial axis) was reduced by 25 %, the length of the viscerocranium by 18 % and the length of the condylar process by 11 %. The evidence indicates that these reductions are due to diminished growth at respectively the spheno-occipital and midsphenoidal synchondroses, the nasal septal cartilage and the condylar cartilage. The relative sizes of the reductions in cranial base, viscerocranium and condylar process suggest that the growth of synchondrotic and septal cartilages is diminished to a greater extent than that of condylar cartilage. This finding is in agreement with the observations that condylar cartilage, unlike synchondrotic and septal cartilage, grows by surface apposition and that the principal defect in enjen mice is a disturbance of interstitial cartilaginous growth. The posterior extension of the basicranial axis of the cn/cn mice was reduced by 14 % and the anterior extension by 2 %. The width of the cranial base was decreased by 9 % and the angle between the basicranial axis and its anterior extension was decreased by 3 %. The length of the neurocranium was reduced by 19 % in the cn/cn animals while the volume of the endocranial cavity was diminished by only 18 %. The latter reduction is less than would be expected from the cube relationship between volume and linear dimensions but is readily accounted for by the lack of reduction in the height or width of the neurocranium, the slight flattening of the cranial base and the doming of the neurocranial vault.
Neurulation et migration nucléaire intercinétique chez des embryons de poulet
Authors: Messier Paul-Emil , Auclair C.
Published: April 2021

Neurulation and interkinetic nuclear migration in the chick embryo

Neurulation and interkinetic nuclear migration were studied in cells of the forming neural tube of chick embryos submitted to a variety of treatments. Our results show that cytochalasin B (5 μg/ml) does not protect microtubules against disruption occurring after 3h at 2 °C nor does it prevent their repolymerization once they are cold-disrupted. However, db-cAMP protects microtubules against such cold disruption. We indicate that the inhibitory effect of cytochalasin B on interkinetic nuclear migration cannot be ascribed to an effect on microtubules.
Les premiers stades de la formation de I’ébauche de nageoire pelvienne de Truite(Salmo farioetSalmo gairdneri): III—Capacités de régulation
Authors: Geraudie Jacqueline
Published: April 2021

The first stages of genesis of the pelvic fin aniage in the trout (Salmo fario and Salmo gairdneri). III. Regulation capacities

In S. fario and S. gairdneri, microsurgical excisions of parts of pelvic fin-buds showed the important regulation capacities of the fin anlage. At the stages studied, a complete unilateral excision is generally not followed by a regulatory response. On the contrary, a unilateral partial excision performed at the same developmental stages is followed by a regulatory response. Bilateral excisions of the fin-buds, performed at earlier developmental stages than unilateral ones (and at a slightly different level for mesoderm) are followed by regulation.

The results are discussed in this article. It appears that the mesoderm is a determining factor in the development of the fin-buds; the epidermis does not appear influential -at least in the first stages of regulation.

We noticed a higher percentage of regulation in S. gairdneri than in S. fario’, the results obtained are analysed with regard to histoenzymological data.
The relationship between erythropoietin-dependent cellular differentiation and colony-forming ability in prenatal haemopoietic tissues
Authors: Cole R. J. , Regan T. , White S. L. , Cheek E. M.
Published: April 2021

Levels of haem synthesis achieved by foetal liver erythroblasts responding to erythropoietin in vitro are similar in dissociated cell cultures and in cultures of organized tissues. Erythroid colony-forming cells reach maximum numbers on the sixteenth day of gestation. Their presence in foetal liver is associated with the period of most rapid production of erythrocytes, and with in vitro sensitivity to erythropoietin measured as enhanced haem synthesis. It is concluded that at least a proportion of erythroid colony-forming cells in the foetal liver are dependent on erythropoietin in situ and that these cells are separated from the earliest recognizable pro-erythroblast by 1 –2 cell divisions. Populations of granulocyte-macrophage colony-forming cells change independently of erythroid colony-forming cell numbers.
Effets de la vinblastine sur la morphogenèse du pied de l’embryon de poulet. Aspects histologiques
Authors: Kieny Madeleine
Published: April 2021

Vinblastine was injected into the amniotic cavity of 6·5-day-old chick embryos. Acropods were fixed 0,2, 3·5, 6,12,18,24, 36 and 48 h after treatment and 1 μm thick sections were prepared from the region of digit IV and interdigit III-IV. Cell counts were mainly performed in a distal zone (see Fig. 2) comprising the ectodermal apical ridge, the distal non-ridge ectoderm and the distal underlying mesoderm.

In control non-treated embryos, the mitotic index does not vary significantly in either of the three tissues between 6·5 and 8 days except for a temporary increase at 7 days in the mesoderm. In treated embryos, the mitotic index increases rapidly in the non-ridge ectoderm and in the mesoderm to a maximum of 44 and 35% respectively, 18 h after injection, after which it decreases almost as rapidly to a level of about 15% 36 h after injection. In the apical ridge ectoderm, the increase of the mitotic index is much slower and reaches its maximum value of about 30% only 36 h after injection. This suggests that most of the cells participating in the AER do not arise within the ridge but are generated in more proximal zones of the ectoderm.

Due to mitotic arrest, the number of mesodermal cells is thus decreased to approximately half the normal value within 36 h and the AER disappears earlier than normal. These alterations are the direct cause of the hypophalangy observed at the morphological level.

A particular distribution pattern of arrested mitoses is revealed: in the digital as well as in the interdigital mesoderm, the majority of blocked metaphases is located in a dorsal and a ventral wing-shaped subectodermal 500 μm long area whose thickness is maximal at the level of the marginal sinus and gradually decreases in proximal direction. In the central-part of the mesoderm blocked mitoses are relatively rare.

The present results are discussed in view of the recent literature on the morphogenetic processes of limb development.
In vitrostudy of chorionic and ectoplacental trophoblast differentiation in the mouse
Authors: Hernandez-Verdun Danièle , Legrand Chantal
Published: April 2021

Mouse chorioallantoic pre-placental structures alone or in association with the embryo were explanted during the 9th day of gestation (7-somite stage) and cultured in a static medium for 24 to 48 h. From the subsequent morphological study of trophoblast differentiation, using both light and electron microscopy, we draw the following conclusions.

The allantoic mesoderm cells migrate inside the trophoblastic population but they do not differentiate a capillary network and trophoblast cells phagocytose the existing foetal erythrocytes. In the absence of allantoic mesoderm, chorionic trophoblast cells remain undifferentiated. The development of the chorionic trophoblast is modified in that chorionic trophoblast cells fail to establish close junctions with ectoplacental trophoblast, and some chorionic cells initiate the formation of multinucleated syncytia. The genesis of these syncytia is discussed.
The effect of ablation of the olfactory pits on the development of the habenular nuclei inRana pipiens
Authors: Norris Byron K. , Eichler Victor B.
Published: April 2021

The habenular nuclei in the diencephalon of the frog, Rana pipiens, are asymmetrical structures: two discrete cell groups develop on the left side (as medial and lateral nuclei), while a single nucleus is formed on the right side. Experimental animals were subjected to bilateral removal of the olfactory pits at an early embryonic stage, and were maintained with normal control animals until metamorphosis was complete. The length, relative volume and cell number for each of the three nuclei were determined in the control and experimental animals at regular intervals during larval development. In the control animals, the left medial nucleus developed similarly to the right nucleus spatially and temporally; however, the left lateral nucleus was significantly different in its development in the three parameters measured. In the experimental animals the left medial and the right habenular nuclei were alone affected by the removal of the olfactory pits. The results provide experimental evidence that the right and left medial, but not the left lateral, habenular nuclei are centers receiving afferent olfactory fibers.
Studies on the gastrulation of amphibian embryos: Light and electron microscopic observation of a urodele Cynops pyrrhogaster
Authors: Nakatsuj1 Norio
Published: April 2021

The course of gastrulation in embryos of a urodele, Cynops pyrrhogaster, was studied with 1 μm Epon sections and transmission and scanning electron microscopy. During the initial period of gastrulation, the bottle cells and a groove are formed in the dorsal part. The outer ends of the bottle cells have many microvilli, an electron-dense layer and many small vesicles. Microtubules are present parallel to the long axis of the bottle cells, and a yolk-platelet-free region is observed at the inner end. Thereafter, the archenteric roof makes contact with the inner surface of the blastocoelic wall. Cells of the archenteric roof form lobopodia, filopodia and lamellipodia. These cells make many focal contacts, having gaps of less than 20 nm, with the blastocoelic wall. Invaginating mesodermal cells of the lateral and ventral parts also form pseudopodia, and are in contact with the blastocoelic wall. Some of these cells appear to flatten against the wall. These observations suggest that, after the bottle cells and the blastoporal groove are formed, the invaginating cells actively migrate along the inner surface of the blastocoelic wall, and that these locomotive forces have an important role in the morphogenetic movements during gastrulation.
Embryonic development of tetraploid mice during the second half of gestation
Authors: Snow M. H. L.
Published: April 2021

A small proportion (about 17%) of experimentally produced tetraploid blastocysts are capable of postimplantation development in the randomly bred Q strain of mice. Four newborn mice, three of which were confirmed as tetraploid, were produced but all were eaten by their mother within a few hours of birth. Studies on the embryonic development of tetraploid mice reveal a variety of developmental abnormalities, especially during the later stages of gestation. At and days, tetraploid embryos weigh significantly Jess than corresponding stage diploids, especially so if litter size is taken into account. Histologically, aberrations are found in many different tissues with a clear hierarchy of susceptibility shown among the organs. For instance, yolk-sac-derived blood, and gonads, are invariably affected and the anterior end of the neural tube also seems to be particularly at risk. Possible explanations for the aberrant development are discussed and it is concluded that strictly genetic reasons can be ruled out and that physiological difficulties imposed by the increased size of tetraploid cells and/or problems produced by lack of cell numbers are instrumental in causing abnormal development. Using weight as a guide it is estimated that tetraploid embryos at and days gestation contain about one-quarter as many cells as similar stage diploids.
Morphogenesis of intestinal villi: II. Mechanism of formation of previllous ridges
Authors: Burgess David R.
Published: April 2021

Villi lining the avian intestine originate from longitudinal folds (previllous ridges) running the length of the embryonic intestine. The morphogenetic events that occur in the epithelium during initial ridge formation in the chick embryo duodenum were examined by light and electron microscopy. The epithelium, in cross-section, undergoes three stages prior to the formation of ridges; termed the circle ( days), the ellipse ( days), and the triangle ( days). At about 9 days of development three ridges form with three more forming one day later. The mechanisms responsible for folding of the epithelium were examined. Microdissection followed by organ culture demonstrated that constriction by the surrounding circular smooth muscle cannot account for folding of the epithelium. Mitotic pressure within the epithelium also cannot account for folding since there is no difference in the number of epithelial cells per cross-section between the ellipse and the triangle stages and the epithelial tube is not restricted from expanding. Active constrictions in groups of epithelial cells, mediated by bands of microfilaments, are thought to cause folding. Bundles of microfilaments are localized in the apical region of all epithelial cells at all stages studied and are localized in the basal region of those cells occupying the crests of the forming ridges. Cytochalasin B-treatment prevented ridge formation and disrupted the bundles of microfilaments.
The immediate postimplantation development of tetraploid mouse blastocysts
Authors: Snow M. H. L.
Published: April 2021

The development during and immediately after the implantation period of 143 tetraploid blastocysts was studied both in vitro and in vivo; 58·7 % in vitro and 38·8 % in vivo were found to exhibit the changes associated with the early implanting blastocyst, i.e. giant cell transformation of the trophoblast and induction of the decidual cell reaction in the uterus. Of these 38·7 % in vitro and 19·4% in vivo showed evidence of inner cell mass function during this time but only two in each system could be claimed as showing normal development. Examination of the developing blastocyst leads to the conclusion that lack of cell numbers in the inner cell mass is the most likely reason for the poor development of tetraploid embryos and suggests that the minimum number of ICM cells required to fulfil its role in embryogenesis is between four and eight.
Leg regeneration in the cockroach,Blatella germanica: II. Regeneration from a non-congruent tibial graft/host junction
Authors: French Vernon
Published: April 2021

The interactions occurring between host and graft leg epidermis at a non-congruent junction were studied in the cockroach, Blatella germanica. Graft and host tibia were cut perpendicular to the proximal-distal axis and two heteropleural combinations were used to reverse separately the two transverse axes of the graft relative to the host. Use of dark and light cuticle colour mutants gave a good indication of the graft or host origin of regenerated structures.

Graft/host junctions regenerated segmented structures in various spatial arrangements, always comprising two copies of all structures distal to the level of the junction.

It is concluded that the categories - two separate laterals, double lateral, completely and partially autonomous regeneration - reflect two processes.

If the graft tarsus is removed, graft and host may not heal together and interact, but form autonomous regenerates lying in mirror-image symmetry separating original graft and host levels. If interaction occurs between graft and host (or their developing autonomous regenerates) two laterals of dual origin are produced, one from each point of transverse axis incongruity. These laterals may secondarily fuse together to form a double structure originating from a point of congruity. The orientation and composition of the component tarsi of the double structure depend on the site of origin and the extent to which the two laterals fuse.

It is argued that the four ‘faces’ and two ‘transverse axes’ of the leg are merely descriptive terms. A new model is developed whereby lateral regeneration arises directly from the circumferential organisation of the leg epidermis. Previous work has shown that position is specified continuously around the circumference, and that intercalary regeneration occurs by the shortest route between confronted positions. After reversal of one ‘transverse axis’ the shortest route between confronted graft and host positions is different on the two sides of each of the two points of ‘axis’ incongruity, and at these points the two halves of a complete circumference are formed. These lateral circumferences, like the terminal circumference exposed by amputation, cannot heal over by intercalary regeneration, and this leads to regeneration of distal structures.

The model accounts for lateral regeneration after reversal of both ‘transverse axes’ by 180° rotation of a homopleural graft.

The possibility is discussed that there may be clonal restrictions on the circumferential positions which the progeny of a cell may occupy.