bluuebunny/crossref_metadata_2025 huggingface dataset:
Facial formation in normal and cadmium-treated golden hamsters
Authors: Mulvihill James E. , Gamm Stephen H. , Ferm Vergil H.
Published: April 2021

In the golden hamster the critical days of palatal development occur between days 12 and 14 of gestation. During this period the shelves undergo transposition from vertical positions alongside the tongue to horizontal positions above it, and undergo fusion with each other. Palatal transposition, per se, probably takes place on or about day 12. Present data are in-sufficientto indicate in which direction this occurs. Although epithelial remnants arestill present in the midline of the palate on day 13, they have completely disappeared by day 14, thus signaling the completion of the fusion process. Preosteoblast areas are clearly visible on day 12 but actual ossification is first seen on day 13.

Cadmium apparently has a marked deleterious affect on the head mesoderm of golden hamsters, causing the production of numerous malformations, including unilateral and bilateral cleft lips and palates. It is suggested that the clefts found in cadmium-treated hamsters are due to a mesodermal deficiency rather than to a delay in shelf transposition. Marked abnormalities in cartilage formation and delays in ossification are also described.

The mechanism of action of cadmium—whether directly on the differentiating embryonic tissue, or indirectly through action on the maternal tissues—remains to be elucidated.
The origin and movement of prelung cells in the chick embryo as determined by radioautographic mapping
Authors: Rosenquist Glenn C.
Published: April 2021

The origin of the prelung cells was determined by tracing the movements of [3H]thymidine-labelled grafts excised from medium-streak to 4-somite stage chick embryos and transplanted to the epiblast, streak, and endoderm-mesoderm of similarly staged recipient embryos.

At the medium-streak stage the prelung endoderm cells are in the anterior third of the primitive streak; they shortly begin to migrate anteriorly and laterally into the endoderm layer. They are folded into the gut beginning at about the 4-somite stage, and begin to reach their definitive position in the ventrolateral gut wall at the 10-to 16-somite stage. At the ± 22-somite stage the prelung endoderm begins to burrow into the overlying splanchnic layer of mesoderm, pushing the prelung mesoderm ahead of it.

At the medium-streak stage the prelung mesoderm is in the epi blast (dorsal) layer about half-way to the lateral margin of the area pellucida on either side of the streak, at a level about half-way between the anterior and posterior ends of the streak. From this position the prelung mesoderm migrates medially to the streak and is invaginated into the mesoderm layer at a position about half-way between the anterior and posterior ends of the streak. As a section of the dorsal mesentery, it migrates anteriorly and laterally from the streak into the splanchnic mesoderm lateral to the somites. From the head process stage to the early somite stages, the prelung mesoderm is located posterior to the prelung endoderm. The prelung mesoderm continues to migrate with the splanchnic mesoderm into the mesentery dorsal to the heart, where it invests the prelung endoderm after the 16-to 19-somite stage. Beginning at about the 22-somite stage, the prelung endoderm penetrates the prelung mesoderm and the bilateral bronchi are formed.
Interactions morphogènes au cours de l’histogenèse du corpuscule de Herbst, étudiées à l’aide de transplantations hétérochrones
Authors: Saxod Raymond
Published: April 2021

Morphogenetic interactions during the histogenesis of Herbst’s corpuscle, as studied by heterochronic transplantations

Duck embryo frontal buds or bill fragments have been transplanted to the frontal bud or limb bud of early duck embryo hosts. Results show that : Somato-sensory nerve endings are able to participate in corpuscle histogenesis as soon as they reach 14 days of incubation.However, corpuscle histogenesis can take place only in dermis that is older than 20 days of incubation.The time at which the corpuscles form in a graft of a given age is independent of the total duration of graft innervation.

The results, which demonstrate the existence of morphogenetic interactions between the dermal mesenchyme and the nerve endings, are discussed in connexion with what is known about the origin of Herbst’s corpuscle and the role of nerve and cutaneous tissue in its development. A schematic model is proposed for the morphogenetic sequence of Herbst’s corpuscle.
Experimental study of the formation of the bulboventricular loop in the chick
Authors: Castro-Quezada Alfredo , Nadal-Ginard Bernardo , De La Cruz María V.
Published: April 2021

The formation of the normal bulboventricular loop (convex to the right) and the inverted loop (convex to the left) produced by the Lepori technique in chick embryos was studied. The development of the loops was recorded by means of diagrams, photographs and microscopic time-lapse photography. Electron-microscope studies were also made. The normal loop was studied by means of labelling and removal experiments on the heart tube. The results demonstrated that the fusion of both cardiac primordia is made in stage 9— in the mid-line of the embryo and that the first asymmetry of the heart tube appears in stage 10. The truncus region developed in situ directed towards the right after the fusion of both cardiac primordia, and in this region the electron-microscope study demonstrated a gradient of caudo-cephalic differentiation. In stage 10 the left caudal groove is the prospective interventricular groove, but the right caudal groove is not the right atrioventricular groove as had been stated by others. The asymmetric incorporation of both primordia begins in stage 11 —, when the curvature of the loop is already developing. In the removal experiments it was evident that the different portions of the cardiac tube in situ are orientated in space independently of the whole of the loop.

The formation of the experimentally inverted loop is a mirror-image of the normal loop and appears to be originated through mechanic traction of the cardiac tube by the left splachnopleure and not by a faster displacement of the right cardiac primordia.
Uterine protease activities and lysis of the blastocyst covering in the rabbit
Authors: Kirchner C.
Published: April 2021

Protease activity in rabbit uterine secretion and blastocyst between 5 days 18 hours and 7 days 18 hours after mating was studied histologically and electrophoretically by film gelatin lysis. At definite times after the beginning of implantation, the uterine secretion contains two and the blastocyst covering at least one protease, all with different electrophoretic mobility. Digestion of the blastocyst covering begins on the seventh day post coitum in the area of the embryonic disc. The function of the proteases, origin of the blastocyst protease, and possible activation mechanisms of these enzymes are discussed.
The development of rabbit eggs in the ligated oviduct and their viability after re-transfer to recipient rabbits
Authors: Adams C. E.
Published: April 2021

The development of fertilized rabbit eggs trapped in the oviduct by ligation was examined at 84, 96, 108 and 120 h p.c. in ten animals, five of which were superovulated. Out of 210 eggs recovered, only two failed to develop into early blastocysts. The proportion of blastocysts undergoing some expansion increased from 66% at 84 h to 100% from 96 h onwards, when a high proportion, 66-89%, had ruptured zonae pellucidae. The viability of the blastocysts was assessed by transfer to the uteri of recipient rabbits, in which the proportion developing to term fell from 62% at 84 h to 3% at 108 h.

A total of 643, 2- and 4-cell eggs recovered 30 hp.c. was transferred to the ligated oviducts of oestrous, early or mid-luteal does for periods of 24, 48 or 72 h. Development to the early blastocyst stage appeared to be faster in the luteal phase than in oestrous does. Of the eggs recovered after either 48 h or 72 h, 20-40% and 3-17% respectively were capable of developing to term. In general, the less advanced blastocysts survived better.

Three hundred and twenty-one 60 h morulae were transferred to the ligated oviducts of oestrous or mid-luteal does for 24,48 or 60 h. Neither the rate of egg development nor viability was significantly affected by the endocrine status of the temporary recipient. The proportions of eggs developing to term after transfer to recipients were 50%, 20% and 0%.

It is concluded that the rabbit egg cannot develop beyond the early blastocyst stage in the oviduct, irrespective of the host’s endocrine status. If development is interrupted, the life-span of the blastocyst is very short. The rabbit blastocyst requires to undergo almost continuous development to differentiate normally.
Le système nerveux périphérique crânien de l’embryon humain de 9 mm
Authors: Masy par Simone
Published: April 2021

With the help of silver impregnation, an accurate description of the distribution of the cranial nerves of a 9-mm. human embryo is given. The earlier description by Streeter (1908) appears to be incomplete. Numerous anastomoses have been found between the oculomotor and the ophthalmic nerves, between the fifth and the seventh, between the ninth and the tenth, and between the tenth, eleventh, and twelfth nerves. Collateral branches of the various nerves are described. Placodal contributions are found to the olfactory and the acoustic nerves. Cranial autonomic ganglia have not been observed.
In vitro studies on the control of trophoblast outgrowth in the mouse
Authors: Jenkinson E. J. , Wilson I. B.
Published: April 2021

When placed in serum-free medium on reconstituted collagen surfaces re-implantation mouse embryos are capable of producing characteristic trophoblast outgrowths. Previously this pattern of differentiation has been considered to be essentially dependent on the presence of serum macromolecules. Such activity is expressed only at the late blastocyst stage and is qualitatively different from the adhesive interactions between blastomeres earlier in development. The development of the properties responsible for outgrowth is intrinsic to the blastocyst, being independent of stimulation by exposure either to the uterine environment or to whole serum. The significance of these observations related to implantation control in vivo is discussed.
Genetic effects on the timing of early development in the mouse
Authors: Mclaren Anne , Bowman Patricia
Published: April 2021

On the 4th day of gestation, embryos were recovered from mice of the C57BL, RIII, JU, C3H and Q strains, and cell counts were carried out. Significant differences between strains were seen, both in the percentage of embryos which had reached the blastocyst stage, and in the mean number of cells per embryo. C57BL embryos had most cells, and C3H embryos fewest. Examination of earlier stages of C57BL and C3H development showed that the proportionate difference in cell number remained constant, so that the difference involved the time at which cleavage began, and not the rate of cleavage. Activation of the eggs and the formation of pronuclei also occurred earlier in C57BL than in C3H females. The difference in cell number between C57BL and C3H embryos did not depend on a difference in time of mating, nor on the genotype of the male, since reciprocal crosses were similar to the maternal strain. The difference was maintained in culture from the two-cell stage.
A re-examination of two skeletal mutants of the mouse, vestigial-tail (rt) and congenital hydrocephalus (ch)
Authors: Grüneberg H. , Wickramaratne G. A. De S.
Published: April 2021

The development of two skeletal mutants in the mouse has been re-investigated. In vestigial-tail (vt), a simple syndrome is traceable to an anomaly of the primitive streak. In congenital hydrocephalus (ch), the complicated events have been followed to a level at which the most fundamental gene action detected (or, more accurately, postulated) is no longer demonstrable by conventional histological methods. It involves the mesenchyme and some of its direct derivatives (meninges, skeletal blastemata, mesonephros), but also organs of different origin (nasal glands, ureteric bud, certain ganglia) for which the mesenchyme is the environment. Failure of the meningeal mesenchyme to form the subarachnoid drainage system for the cerebrospinal fluid leads to hydrocephalus which, by essentially mechanical means, is responsible for a multitude of subordinated effects.
Effects of cytochalasin B on meiosis and development of fertilized and activated eggs of Sabellaria alveolata L. (Polychaete Annelid)
Authors: Peaucellier G. , Guerrier P. , Bergerard J.
Published: April 2021

Unfertilized, fertilized and activated eggs of Sabellaria alveolata were submitted to cytochalasin B concentrations ranging from 0·1 to 20 μg/ml. Their behaviour was studied either in vivo or in acetocarmine squash preparations. Polar body extrusion, cytokinesis and polar lobe formation are completely inhibited by cytochalasin B concentrations as low as 0·3–0·5 μg/ml. Caryotype determinations demonstrate that chromosomal meiotic and mitotic processes are not affected by the drug. Thus, polyploid embryos usually developed from fertilized eggs whilst they did not from activated ones. This is related to the contrasting behaviour of meiotic and cleavage centres. While the latter duplicates at each cycle, the former cannot replicate at the end of meiosis. This leads to an abortive monastral stage even if inhibition of polar body extrusion has provided the egg with two or four centres. These observations suggest the existence of an internal mechanism regulating the number of effective centrioles at the end of meiosis. They demonstrate also that the main cause of developmental failure in activated eggs cannot be related to ploidy. Eggs treated throughout meiosis with moderate drug concentrations developed into swimming larvae. However, frequent developmental abnormalities affecting lobe dependent structures were obtained even if polar lobe formation was unimpaired. This suggests either that cytochalasin B has irreversibly affected some decisive cortical element or that previously described activating processes, which begin with polar lobe formation, are actually exerted on specific materials segregated during meiosis.
Embryonic defects in Drosophila eggs after partial u.v. irradiation at different wavelengths
Authors: Bownes Mary , Kalthoff Klaus
Published: April 2021

Drosophila eggs at nuclear multiplication or blastoderm stages were regionally irradiated with monochromatic u.v. Twenty-four hours after irradiation, the results were classified as normal larvae, undifferentiated eggs, or defective embryos; the latter were subdivided into embryos with anterior or posterior defects, or embryos without anterior and posterior specificity. The irradiation of anterior (posterior) egg regions and the occurrence of anterior (posterior) defects were strongly correlated. These correlations were found using eggs of both stages. The size of the irradiated area did not obviously influence the types of defect.

Dose-response curves were established irradiating anterior quarters of eggs at 245, 265, 285, or 305 nm wavelength. The frequency of embryonic defects increased with increasing u.v. doses, whereas the dosages applied did not increase the frequency of undifferentiated eggs over the control level. In eggs during nuclear multiplication 285 nm radiation was most effective in producing embryonic defects. After blastoderm formation, the efficiency of irradiation was generally increased but similar at all wavelengths employed. The induction of embryonic defects was photoreversible after u.v.-irradiation at the blastoderm stage. The data reported also include transmittance spectra of chorion and egg membrane preparations from Droso-phila eggs.
Changes in glycosaminoglycan content of healing rabbit tendon
Authors: Reid T. , Flint M. H.
Published: April 2021

Changes in the concentration of the major glycosaminoglycan compounds were measured during healing of severed Achilles tendons in rabbits. Using zone electrophoresis for separation, and densitometry for quantitation of these compounds, their concentrations could be measured in each of several portions of the tendon and its associated muscle.

Immediately after injury, the concentration of hyaluronic acid in the healing area and those portions of the tendon closely associated with it increased dramatically. An increase in the concentration of dermatan sulphate accompanied the subsequent formation of repair tissue.

Increased concentrations of glycosaminoglycan compounds were also found in the musculotendinous area remote from the injury, probably in response to relaxation of the severed tendon.
Further evidence that enterochromaffin cells are not derived from the neural crest
Authors: Andrew Ann
Published: April 2021

Recently, a previous finding that the enterochromaffin cells of chick embryos are not derived from the neural crest has been contested, and so further evidence has been sought. Presumptive gut, i.e. endoderm and adherent mesoderm, of embryos between the short headprocess stage and the 25-somite stage was grown on the chorio-allantoic membranes of host embryos. Whether the presumptive gut was excised before or after the probable time of arrival of neural crest cells in the gut, enterochromaffin cells occurred in the intestine in the grafts. The presence or absence of enteric ganglia indicated the presence or absence, respectively, of neural crest cells. Enterochromaffin cells were plentiful even if the donor had been at a stage preceding that at which cells of the neural crest start to migrate, or preceding that at which the crests themselves first appear. In a second experiment, presumptive gut of embryos at 10-to 21-somite stages was excised so as to exclude the portion underlying the somites. Enteric ganglia were lacking in the intestine of these grafts, but enterochromaffin cells were invariably present.

These experiments show that the precursors of enterochromaffin cells are present in the more lateral part of the presumptive gut before the neural crest precursors of enteric ganglia reach the region; and that they are present in the presumptive gut long before any crest cells could have arrived there. This evidence supports the view that enterochromaffin cells are not derived from the neural crest in chick embryos.
Artificial insemination of deermice(Peromyscus maniculatus)with sperm from other rodent species
Authors: Maddock Michael B. , Dawson Wallace D.
Published: April 2021

Deermice (Peromyscus maniculatus) were hormonally induced to ovulate and artificially inseminated with sperm of 13 other rodent species varying in taxonomic distinction from species to family level. These were compared with inter se and sham inseminated controls. Embryos were recovered at various stages from 5 h to 10 days. Hybrid embryos failed to develop fully in all crosses except those within the same species group. Closely allied interspecies group crosses produced implantation embryos, but intersubgeneric and intergeneric crosses did not develop beyond early cleavage. Interfamilial hybrid embryos could not be obtained.
Investigation of a substance of renal origin which inhibits the growth of renal cortex explant in vitro
Authors: Dicker S. E. , Morris Christine A.
Published: April 2021

Explants of renal cortex from 7-day mice or 5-day rats were reared on plasma clots, in the presence or absence of chick embryo metanephros. The size of outgrowth, estimated after 48 h, was similar for renal cortex of both species. When reared in chick embryo extract in the presence or absence of metanephros, the outgrowth estimated after 48 h was 2·08 ± 0·092 greater than that of the initial explant. Addition of supernatant fluid from a homogenate of renal cortex of adult mouse, rat, guinea-pig, rabbit or pig inhibited the outgrowth of renal cortex explant from neonate mouse or rat. The supernatant fluid from a homogenate of adult renal medulla had no significant effect. The inhibitory activity of the supernatant fluid from a homogenate of renal cortex from adult animals was destroyed by heating at 99 °C. The compound with growth-inhibitory activity appeared to be cortex-specific but not species-specific. Extracts of liver, spleen, duodenum, and heart muscle of adult animals had no significant effect on the outgrowth of renal explants of neonate animals; and extracts from renal cortex of adult mammals had no significant effect on the growth of other tissues from neonate mice or rats. The degree of growth inhibition was related to the amount of protein in the extract of renal cortex. Maximum inhibition was observed with extracts of renal cortex containing 2·5 mg protein/0·5 ml. Immune serum samples were obtained from rabbits and guinea-pigs immunized against extracts of renal cortex and medulla and liver from rats and mice. Only the serum from either rabbit or guinea-pig immunized against extracts of renal cortex blocked the growth-inhibitory action of renal cortex extracts.
Transfilter induction of kidney tubules: correlation with cytoplasmic penetration into Nucleopore filters
Authors: Wartiovaara Jorma , Nordling Stig , Lehtonen Eero , Saxén Lauri
Published: April 2021

The presence of cell contacts in transfilter mouse kidney tubule induction by spinal cord was investigated. The interacting tissues were separated by Nucleopore® membrane filters of various pore sizes.

Filters with a mean pore size of 0·2 μm or more allowed tubule formation, whereas 0·13 μm pore filters prevented it. There was an inverse correlation between pore size and minimum time of transfilter culture required for induction to occur. The differences in the diffusion rates through these filters do not support long range diffusion as a mechanism for induction. Electron microscopy of the cultures showed abundant cytoplasmic penetration deep into filters with 0·2 μm or larger pores. Processes from mesenchymal and spinal cord cells were closely apposed within the filter channels. No extracellular matrix or membrane vesicles were seen between the processes. In a few instances shallow penetration was seen in 0·1 μm type filters, but no contacts were observed.

The presence of close cell appositions in those filters which allow kidney tubulogenesis suggests that close cellular interactions, rather than long range diffusion of signal substances, is the most likely communicative mechanism in this transfilter induction.
Susceptible stages and abnormal morphogenesis in the developing mouse limb, analysed in organ culture after transplacental exposure to vitamin A (retinoic acid)
Authors: Kochhar D. M. , Aydelotte M. B.
Published: April 2021

The development of form and morphology of cartilage in limbs from control and retinoic acid-treated DBA/2J mice were studied in organ culture. Somite number at explantation (SE) ranged from 29 to 56. All cartilage segments except digits developed in cultures of 29-somite control limb-buds; digits developed well only from limb-buds of SE45 and older stages. Maternal treatment with retinoic acid specifically inhibited the growth of limbs rather than that of the whole embryo; the percentage reduction in limb length in culture ranged between 20 and 40 %, depending on the length of in utero exposure. The teratogenic effects of retinoic acid were expressed in culture even if the limb was explanted after only 1 h of in utero exposure. However, for a complete expression of the teratogenic effects, resulting in phocomelia, 24 h exposure was necessary. Limb-buds of 29 to 32-somite embryos were only mildly responsive to the teratogen. Embryos with 33–38 somites demonstrated the full extent of teratogenic effects. Embryos with more than 40 somites at the time of first exposure to retinoic acid escaped severe limb malformations except digital defects. Correlation between the developmental stage of the limb at the time of treatment and the final limb defect is attempted.
A scanning electron microscope study of the early limb-bud in normal andtalpid3mutant chick embryos
Authors: Ede D. A. , Bellairs R. , Bancroft M.
Published: April 2021

Scanning electron microscope studies, supported by transmission electron microscope and light microscope observations, have been made of the wing-bud apex in the region of the apical ectodermal ridge (AER) in both normal and talpid3 mutant embryos.

Ln normal embryos: the ectoderm consists of two layers, the periderm and the basal layer, resting upon a basal lamina. The external surface of the periderm cells bears numerous villi, especially numerous at the cell boundaries. In the AER the cells of the basal layer are compacted into a fan-shaped form, remaining as a single layer, though displacement of their nuclei gives the appearance of a stratified epithelium; the periderm cells tend to round up and many are necrotic. Microfilaments and microtubules are present in greater numbers in the AER than in other ectoderm cells and are orientated along the long axis in the very narrow elongated cells which comprise the middle of the ridge. The mesenchymal cells of the mesoderm tend to be flattened, with extensive flattened surface areas separated from each other by long edges of lamellar cytoplasm, from which many long filopodial extensions arise. Often the cells are elongated, with the filopodia arising predominantly at the anterior and posterior ends.

In talpid3 embryos : when these were compared with normals no differences were detected in the general ectoderm or in the AER, but in the mesoderm a statistical analysis revealed significant differences in the occurrence of sections through very fine cytoplasmic processes in transmission electron microscope micrographs. Taken in conjunction with visual examination of scanning electron microscope pictures the differences suggested that talpid3 cells have filopodia distributed more extensively around the cell, but that these extensions do not extend so far through the intercellular spaces or produce such fine terminal arborizations as in normal mesenchyme.

At the ectodermal/mesodermal boundary there is a web of extracellular material under the basal lamina, separated from the underlying mesoderm by a very narrow gap in normal embryos. Fine cytoplasmic extensions from the mesenchyme cells extend across the gap towards the basal lamina and many are in contact with it. The gap is wider in talpid3 wing-buds and a statistical analysis confirmed that far fewer filopodia approach closely to the basal lamina or make contact with it.

The significance of these findings in relation to problems of AER formation and activity and motility of mesenchymal cells in the wing-bud is discussed.
Mise en évidence du rôle, dans la régénération des Amphibiens, d’une glycoprotéine sécrétée par la cape apicale: étude cytochimique et autoradiographique en microscopie électronique
Authors: Chapron Claude
Published: April 2021

Evidence for the role of an apical cap glycoprotein in amphibian regeneration : cytochemical and autoradiographic electron-microscopic studies

Early during limb regeneration in the newt, an ectodermal apical cap covering a mesodermal blastema is formed. High-resolution autoradiography of these tissues has been carried out after incorporation of [3H]fucose, which is a precursor of glycoproteins. Autoradiography shows that silver particles are located at first on epithelial cells, then on mesenchymatous cells. This observation is consistent with a hypothesis in which the apical cap would elaborate a glycoprotein acting on the blastema. Substructural autoradiography and cytochemistry also show the importance of cellular surfaces for both cells producing glycoprotein and those which are target cells.
Experimental manipulations of early Drosophila embryos : I. Adult and embryonic defects resulting from microcautery at nuclear multiplication and blastoderm stages
Authors: Bownes Mary , Sang J. H.
Published: April 2021

Localized regions of Drosophila eggs were damaged at both nuclear multiplication and blastoderm stages, using the technique of microcautery. The resulting defects in embryos and adults were recorded in order to study the effects of microcautery on determination of larval and adult structures. Using 70 °C microcautery, few specific defects were found in either embryos or adults. Sensitivity maps relating embryonic mortality to sites of damage were prepared for both egg stages and compared. Microcautery at 75 °C was used to check experimentally the putative localization in the egg of adult disc cells, as indicated by genetic mosaic studies. Although some of the expected adult defects were found, there was also evidence for regulation. Localized embryonic defects were found using this higher temperature, such that anterior damage produced anterior defects and posterior damage led to posterior defects. Mid-region microcautery resulted in both anterior and mid-region defects, the latter being most common after damage to the blastoderm. Comparisons are made with results obtained using other experimental manipulations and with the development of some embryonic lethal mutants.
The RNA polymerase activity of the preimplantation mouse embryo
Authors: Moore G. P. M.
Published: April 2021

The activation of the mouse embryo genome has been studied during early cleavage, in vivo. Individual embryos, prepared as whole mounts, were assayed for endogenous RNA polymerase activity. RNA synthesis was detected by autoradiography as the incorporation of [3H]UMP into an acid-insoluble product.

No RNA polymerase activity could be detected in the pronuclei of one-cell embryos. Radioactive incorporation was first evident in the nuclei of two-cell embryos. This appeared to be confined to the nucleoplasm and could be abolished by a-amanitin but not by low concentrations of actinomycin D. Polymerase activity which was not affected by α-amanitin was first detected in the four-cell embryo, predominantly at the peripheries of the nucleoli. Nucleolar labelling increased markedly between subsequent cleavages, reaching a peak in early morulae. In one- and two-cell embryos, label incorporation could be found in the nucleus of the persisting polar body.
Effects of bromodeoxyuridine, cytosine arabinoside and Colcemid uponin vitrodevelopment of mouse blastocysts
Authors: Sherman Michael I. , Atienza Sui Bi
Published: April 2021

Mouse blastocysts in culture have been treated with increasing concentrations of cytosine arabinoside, bromodeoxyuridine or Colcemid. Concentrations of all three antimetabolites have been found which interfere with neither hatching of the blastocysts from their zona pellucidae nor subsequent attachment of the blastocysts to the culture dish, but which eventually result in death of the inner cell mass (ICM) and its derivatives. The effect upon the ICM is selective at these antimetabolite concentrations since many or, in some cases, all trophoblast cells continue to survive, and by a number of criteria, undergo normal patterns of differentiation and development.
Stage-sensitivity and dose-response curve of u.v. effect on germ cell formation in embryos of Xenopus laevis
Authors: Ijiri Ken-Ichi
Published: April 2021

Ultraviolet light (u.v.) irradiation of the vegetal hemisphere of Xenopus laevis eggs resulted in the elimination of primordial germ cells in tadpoles. Quantitative studies were performed on this phenomenon. The stage sensitivity to u.v. inactivation of germ cell formation was obtained for the early developmental stages ranging from immediately after fertilization to small-cell blastula. It was found that u.v. irradiation at the stage immediately after fertilization was more injurious than irradiation at the beginning of the first cleavage. After deciding optimal conditions for this u.v. irradiation experiment, a dose-response curve of the phenomenon was obtained. It showed a good agreement with the theoretical expectation, which the authors had previously presented.
An autoradiographic analysis of nucleic acid synthesis in the presumptive primordial germ cells of Xenopus laevis
Authors: Dziadek Marie , Dixon K. E.
Published: April 2021

Microinjection of [3H]thymidine into Xenopus laevis embryos between late blastula (stage 10) and early tadpole (stage 44) showed that the presumptive primordial germ cells synthesise DNA between stages 10-33. The percentage of labelled cells was highest between stages 10 and 16, declined sharply between stages 22 and 26 and rose again between stages 26 and 33. The fluctuations in the labelling patterns together with increase in the number of presumptive primordial germ cells and direct observation of germ cells in mitosis suggested that the germ cells divide three times between stages 10 and 44. The first divisions probably take place during gastrulation (stages 10-12), the second relatively synchronously at about stages 22-24 and the third series again relatively synchronously about stages 37-39. This period of proliferative activity is distinguishable on the one hand from the cleavage divisions in which the number of germ cells does not increase and on the other hand from the next proliferative phase by a period of mitotic inactivity. Microinjection of [3H]uridine showed that the presumptive primordial germ cells synthesize RNA only in mid-gastrula to early tail-bud-stage embryos. There is no obvious simple causal relationship between RNA synthesis and the movement of the germ plasm to the nucleus, or with division of the germ cells or with their migration out of the endoderm.
Experiments on Neuromery in Ambystoma punctatum Embryos
Authors: Källén Bengt
Published: April 2021

When the substratum was removed from under the archencephalic or rhombencephalic anlagen of the neural plate of Ambystoma punctatum embryos, the neuromeres in these regions developed normally. When the rhombencephalic part of the neural plate was transplanted to the ventral ectoderm of an older host together with substratum, neuromeres developed in the transplant. When the transplantation was made without the substratum, no distinct neuromeres appeared. When the neural plate was explanted together with the substratum, neuromeres were formed in the explant. When the explantation was made without the substratum, neuromery was either absent or, when some mesoderm had been left behind, very irregular. It is concluded that the substratum plays an important role in the formation of the neuromeres. The latter are not secondary to a mesodermal segmentation. The influence from the substratum is probably a general mitotic stimulation.
Selective Inhibition of Cleavage in Different Regions of the Frog Egg by Sulphydryl Inhibitors
Authors: Barth Lucena J.
Published: April 2021

When frogs are exposed during early cleavage to low concentrations of the sulphydryl inhibitor, p-chloromercuribenzoic acid, cleavage is inhibited at the animal pole, while the marginal zone and yolk cleave normally. Eggs exposed before first cleavage cleave only at the animal pole, while blastulae and gastrulae are inhibited uniformly in all regions by the sulphydryl reagent. The selective inhibition of animal-pole cells by p-chloromercuribenzoic acid is not readily explained on the basis of regional permeability differences or variations in sensitivity of the surface coat to inhibitors, since exposure of eggs to iodoacetamide results in normal cleavage at the animal pole, together with inhibition of cleavage at the marginal zone and in the yolk. The inhibition produced by p-chloromercuribenzoic acid is mediated by sulphydryl groups, since the effects of the inhibitor are reversible by thioglycollate and cysteine. When various protein fractions are extracted from eggs or hatched embryos and tested for sulphydryl groups by means of the nitroprusside reaction, the soluble fractions are found to contain freely reactive sulphydryl groups, while the yolk proteins are entirely lacking in reactive protein-bound sulphydryl groups. When the yolk proteins are fractionated into phosphoprotein (S2) and non-phosphoprotein (Si), the latter alone is found to contain masked SH groups that become fully reactive only after denaturation plus reduction of disulphide groups. It is suggested that the protein-bound SH groups at the marginal zone are protected against p-chloromercuribenzoic acid inhibition by a high content of soluble thiols such as reduced glutathione, which are synthesized at the expense of sulphur-containing amino acids from the yolk protein Si, under the control of enzymes and nucleotides such as adenosine triphosphate present in the dorsal lip region and marginal zone.
Recherches expérimentales sur la nature et les propriétés de l’inducteur de la régénération des yeux de la planaire Polycelis nigra
Authors: Lender par Théodore
Published: April 2021

After excision of eyes and brain of the planarian Polycelis nigra (Ehrbg.), regeneration of eyes fails unless the brain is allowed to regenerate too. But regeneration of eyes in the absence of the brain occurs if the animals are kept in the presence of a mince of planarian heads, or of such a mince embedded in agar, or of the supernatant obtained after grinding heads with sand. The induction of eye regeneration is therefore performed by a chemical substance, an organisine. Regeneration of eyes in the absence of the brain is possible if the organisine is only allowed to act on alternate days, or only for two consecutive days in all. In the latter case, best results are obtained if the substance acts during the 3rd and 4th days after operation. Regeneration of eyes is favoured by increased concentration of organisine in the medium. Treating the inducing material with 70 per cent, alcohol does not inactivate the organisine, nor does warming to 60° for 2 minutes. Higher temperatures reduce its activity, and boiling for 30 minutes almost destroys it. The organisine is not species-specific. Its presence can be demonstrated in the brain region of Dugesia lugubris, D. gonocephala, and Dendrocoelum lacteum. A mince of the pharyngeal or caudal region does not produce regeneration of eyes. But a mince of the caudal region can be activated by treatment at 60° for 2 minutes. With stronger heating the inducing power diminishes, as with the mince of heads. A mince of caudal regions is also activated if it is treated with alcohol of 70 or 95 per cent. The supernatant obtained from grinding caudal regions with sand also contains the organisine. Such supernatants from the caudal regions are more active the greater the number of animals from which they are prepared; but they contain less organisine than the supernatant from an equivalent number of head regions. The regeneration of eyes of Polycelis nigra is therefore induced by a chemical substance, an organisine, present throughout the body of the planarian. Its concentration is stronger in the anterior than in the posterior region; in the latter it is furthermore immobilized within the cells. These results are comparable with those obtained in the study of amphibian embryonic induction.
A Remarkable Case of Animalization in a Batch of Eggs of Paracentrotus lividus
Authors: Hörstadius Sven , Gustafson Tryggve
Published: April 2021

Sea-urchin eggs generally develop quite normally after artificial fertilization. Sometimes it may be difficult to obtain good membrane elevation, but, after repeated washing in sea-water, fertilization and further development may be quite normal. In some batches of eggs abnormalities may, however, be observed in the pluteus stage, but these abnormalities, as a rule, do not change the pattern of the larvae profoundly. The defects are generally restricted to the arms and to the skeletal rods which, for example, may fail to grow out to their normal length, or may bend in an abnormal direction. Supernumerary rods may also appear, and rods may grow in an abnormal direction inside the larval body without causing a change in the exterior of the pluteus. During many years of experimental work with sea-urchin eggs, for the senior author dating thirty years back, we have never encountered, nor have we seen in the literature, examples of such an abnormal development as the one described in this paper.
Les ions de métaux lourds et le problème de la détermination embryonnaire chez les Échinodermes
Authors: Lallier R.
Published: April 2021

The animalizing effects of zinc on the development of eggs of the sea-urchin, Paracentrotus lividus, were studied and compared with the effects of other closely related metals: nickel, cobalt, manganese, and iron.

Nickel chloride (1/1,000) suppressed the formation of an archenteron. The blastulae were covered with short cilia. The apical tuft was not formed.

Nickel chloride (1 / 5,000 and 1110,000) induced the formation of radial larvae.

Cobalt chloride disturbed gastrulation and inhibited development.

Zinc was detected in the embryos at various stages of development by the formation of a deep red colour with dithizone. Zinc appeared to be distributed in the mesenchyme and entoderm of the young stages. In the pluteus, it appeared to be fixed in the pigment cells.

Nickel was located by the colour reactions with dimethylglyoxime and a-furil-dioxime. The colour was developed in the mesenchyme of the young blastula.

The colour reaction with dithizone was not modified by previous washings with Complexone (ethylene-diamine tetra-acetic acid) solution.

Zinc fixed in the embryos could be displaced by mercury ions.

With the addition of p-chloro-mercuribenzoic acid, the development of embryos in zinc chloride was blocked. The sulfhydryl groups do not appear to be essential for animalization by zinc ions.

The role of zinc in the animalization of sea-urchin eggs is discussed as a function of the formation of complexes between metal and proteins.
Action de la dicarnitine’ sur la croissance et l’ossification d’ébauches de tibias et de fémurs d’embryons de poulet cultivés in vitro
Authors: Lièbecq-Hutter Suzanne
Published: April 2021

Tibias and femurs of 7-day-old chick embryos were cultivated in the absence and in the presence of racemic dicarnitine on a solid medium (fowl plasma + embryo extract, the latter usually diluted 20-to 200-fold). The growth in length of the bones was increased by 1/3 to 2/3 in comparison with the controls, when 2·5 and 5 mg. / I. of dicarnitine was added and when the embryo extract was not diluted more than 100-fold. With embryo extract diluted 200-fold, the shape of the bone was abnormal. Dicarnitine in this case restored the normal shape without increasing the elongation. Dicarnitine in a medium containing embryo extract diluted 200-fold was found to increase the maximal thickness of the periosteal bone in comparison with the controls. This effect was statistically highly significant in the case of dicarnitine concentrations of 2·5 and 5 mg./l. The effect was not found with non-diluted embryo extract. Mitoses were counted in tibias and femurs cultivated in vitro for periods of 1 to 7 days. 2·5 mg./l. dicarnitine was shown to promote mitotic activity. In the periosteum, it maintained for 4 days a mitotic activity equal to 45 per cent, of the mitotic activity in vivo. In vitro controls retained only 6 per cent, of this activity. The usefulness of frequent transfers was demonstrated. The percentage of prophases was higher in the periosteum than in the epiphyses. The relative frequency of metaphases increased with the age of the cultures. The frequency distribution of the phases of mitosis was shown to be very little changed by dicarnitine. After 7 days of culture, the number of cells was more increased in the hypertrophic cartilage than in other tissues. Dicarnitine did not much increase the total number of cells; there was practically no effect on the number of cells of the epiphyses but a large increase in the number of cells of the periosteum and of the hypertrophic cartilage was observed.
Interdigital cell death during limb development of the turtle and lizard with an interpretation of evolutionary significance
Authors: Fallon John F. , Cameron Joann
Published: April 2021

Cell death accompanies the formation of free digits in birds and mammals. However, in species with webbing between the adult digits, little or no cell death occurs in the prospectively webbed region of the developing interdigit. Cell death does not occur during the formation of free digits in amphibians. In this paper we report that cell death accompanies the formation of the digits in snapping and painted turtles and in the skink (a lizard). We conclude that cell death accompanying the formation of free digits had its origin at the point of amniote emergence during evolution.
L’activité3β-hydroxystéroïde déshydrogénasique dans les gonades en différenciation dePleurodeles waltlii(Amphibien, Urodèle); visualisation sur coupes sériées à l’aide d’une nouvelle technique histochimique
Authors: Collenot G. , Collenot A.
Published: April 2021

3βHydroxysteroid dehydrogenase activity in the larval gonads of Pleurodeles waltlii (amphibian, urodele); a new histochemical technique for serial sections.

In order to detect a 3β-hydroxysteroid dehydrogenase (3β-HSDH) activity in the larval gonads of the newt Pleurodeles waltlii an original histochemical method has been derived from the cytochemical technique used by Bara & Anderson (1973) in their ultrastructural studies on the same enzyme activity. The new technique which is described here, allows the incubation in toto of the larval gonads, their paraffin embedding and their sectioning into serial sections of 7 /tm thickness. Unisexual, male and female, offsprings were used.

The 3β-HSDH activity could be detected, in the larval gonads, at the level of the inner cells which constitute the medulla inside the cavity of the genital ridge, as early as the end of the first third of the larval life, at a stage when the gonads are not yet differentiated. When an ovary differentiates, the enzyme activity remains at the level of the ovarian sac which will constitute the theca of the follicles in the mature ovary. When a testis differentiates, the medullary positive cells which associate with the germinal cells constitute the testicular ampullae or cysts and (later) become negative; but, at the level of the posterior part of the testis, several clusters of interstitial cells showed a 3β-HSDH activity in metamorphosed and juvenile animals.

The results are discussed in relation with former reports about the steroid-synthesizing cellular sites in the mature ovaries and testes of urodelean amphibians.
Application of a morphological time scale to hereditary differences in prenatal mouse development
Authors: Wahlsten Douglas , Wainwright Patricia
Published: April 2021

A standardized morphological time scale for prenatal mice is presented, which is useful from 13·0 to 17·0 days chronological age with an accuracy of 0·1 day. Morphological age for an embryo or fetus is shown to correlate highly with ages estimated from body weight and crown-rump length. The time scale is used to study the comparative development from 14 to 17 days prenatal age of an F2 and four inbred mouse strains. The F2 mice average 0-5 day ahead of C57BL/6 mice, and C57BL/6 mice average 0·5 day ahead of A, BALB/c, and, at some ages, DBA/2 mice. Using reciprocal F1 crosses and reciprocal backcrosses, it is also shown that both the fetal heredity and the maternal environment contribute significantly to the more advanced development of hybrid mice.