bluuebunny/crossref_metadata_2025 huggingface dataset:
Caractérisation et évolution des hémoglobines dans le cours du développement postembryonnaire chez la Poule
Authors: Godet Par J. , Schürch D. , Nigon V.
Published: April 2021

Un certain nombre de travaux ont déjà montré l’existence, dans le cours du développement embryonnaire et postembryonnaire de la Poule, de plusieurs hémoglobines se succédant dans le temps. Cependant une difficulté considérable provient du désaccord entre les auteurs au sujet des résultats que donne le fractionnement des hémolysats. Chez la poule adulte, le nombre des fractions obtenues va de deux à cinq selon les auteurs. Les hémoglobines de l’adulte servant de référence dans l’étude des hémoglobines de l’embryon et du poussin, l’insécurité de leur définition rend aléatoire toute conclusion concernant les changements qui peuvent intervenir sur ce point au cours du développement. Il nous a donc paru nécessaire de soumettre au recoupement d’un ensemble de techniques les fractions d’hémoglobine que l’on peut obtenir à partir d’un hémolysat de poule et de poussin. L’ensemble de ces techniques nous a conduit à admettre l’existence de quatre constituants dans les hémoglobines de poule adulte. Elles aboutissent également à une caractérisation d’hémoglobines propres au jeune poussin, apparemment distinctes des hémoglobines de l’embryon de 5 à 7 jours.
The development of rabbit eggs after culture in vitro for 1-4 days
Authors: Adams C. E.
Published: April 2021

Rabbit eggs recovered from the fallopian tube during the early stages of cleavage develop readily in culture up to the late morula stage (Lewis & Gregory, 1929; Pincus, 1930; Adams, 1956; Purshottam & Pincus, 1961; Onuma, Maurer & Foote, 1968). The transition from morula to blastocyst, which normally occurs 70–76 h post coitum (p.c.) coincident with entry into the uterus, may also take place in vitro, especially if culture begins at the late morula stage. However, growth of the blastocyst is generally limited, owing to failure of expansion of the zona pellucida which may rupture (Lewis & Gregory, 1929; Pincus & Werthessen, 1938). Under certain conditions, prolonged blastocyst growth even to the preimplantation stage ‘with typical expansion and little or no herniation’ has been observed, though very few eggs were involved (Pincus & Werthessen, 1938).
On the occurrence of specific adhesion between cells
Authors: Curtis A. S. G.
Published: April 2021

The idea that cells adhere to one another in a specific manner, such that cells of one type stick only to cells of the same type, appears to have had its origin from the work of Wilson (1907). He found that when cell suspensions from two species of marine sponge were mixed and allowed to aggregate, each individual aggregate body was composed of cells of one species alone. This conclusion has been supported by the results obtained by Humphreys (1963) amongst others, though some workers, who have used different species of sponge, have failed to detect signs of specific adhesion of the cells (Sara, Liaci & Melone, 1966). Until recently there has been little evidence in favour or against the idea that specific adhesion occurs between the cells of higher animals. Clearly it is of great interest to discover whether or not specific adhesion occurs, not only because such a phenomenon might be of great importance in the control of morphogenesis but also because its occurrence would have an important bearing on the mechanisms by which cells adhere to one another.
Trypan blue inhibition of yolk deposition—a clue to follicle cell function in the cecropia moth
Authors: Anderson Lucy M. , Telfer William H.
Published: April 2021

The yolk of insect eggs consists largely of proteins derived pinocytotically from the maternal blood (Telfer, 1965). Vitellogenic oocytes can also sequester the acidic colloid trypan blue: when injected into the blood, the dye, like the blood proteins, is deposited in yolk spheres in the cortex of the oocyte. This behavior of trypan blue was first described in the scorpian fly by Ramamurty (1964), and has since been confirmed in a cricket (Sander & Vollmar, 1967) and in the cecropia moth (Telfer & Anderson, 1968).
Etude des phénomènes de régénération après section d’antenne chez le Phasme Sipyloidea sipylus W.
Authors: Urvoy Par Jeanne
Published: April 2021

Dans une étude précédente sur la régénération des organes sensoriels antennaires chez Carausius morosus B. (Urvoy, 1958, 1959) nous avions donné la description d’un appendice hétéromorphe régénéré après section dans la zone distale du pédicelle. 11 nous semble nécessaire d’apporter quelques précisions à ce problème.
Differentiation potencies of the young chick blastoderm as revealed by different manipulations
Authors: Eyal-Giladi Hefzibah
Published: April 2021

Transversely folded chick blastoderms of unincubated to primitive streak stages were used in two different experimental series to check the following: (a) The effect of local damage (right corner) on the embryo-forming potencies of the blastoderm.(b) The effect of the removal of the hypoblast on the stability of the embryo-forming potencies of the primitive streak stage blastoderm.

The conclusions are: (a) Intact, transversely folded, primitive streak stage blastoderms put on the culture medium with their posterior half downwards are relatively stable and the embryo forms from their posterior side.(b) Younger blastoderms are less stable and reveal the inherent asymmetry of the blastoderm by the formation of left-side embryos.(c) Partial extirpation of the right corner in such blastoderms causes a remarkable local rise in the embryo-forming potencies of the right side in both age groups, but the rise is more pronounced in the unincubated group.(d) Removal of the hypoblast from a primitive streak stage blastoderm reduces its developmental potencies to the level of those of the unincubated stage.
Differentiation in small grafts of the median region of the presumptive prosencephalon
Authors: Boterenbrood Elze C.
Published: April 2021

In early neurulae of Triturus alpestris the cranio-caudal distribution of differentiation tendencies in the presumptive prosencephalon was tested.

Small grafts made from a median strip excised from the region of the neural plate and transverse neural fold were transplanted to a pocket made under the cranio-ventral ectoderm of early neurulae.

Grafts made from the middle portion of the strip showed almost exclusively eye differentiation, whereas more cranial as well as more caudal grafts showed relatively more telencephalic differentiation, and only little diencephalic differentiation.

The results indicate that the process of pattern formation in the central region of the prospective prosencephalon is advanced with respect to the surrounding areas.
The origin of the acoustic ganglion and effects of the gene dominant spotting (W
v
) in the mouse
Authors: Deol M. S.
Published: April 2021

The gene dominant spotting in the mouse affects coat colour. The heterozygotes for the viable allele (Wv) have one or two white spots and a general greying of the coat. The homozygotes are entirely white. There is evidence that the gene causes abnormalities of pigmentation by affecting the neural crest.

The inner ears of 33 Wv/ Wv, 23 Wv/+ and 6 + /+ mice were examined. Marked abnormalities were found in the cochlea of all mice and in the saccule of many. They also occurred, though in a restricted form, in a small part of the cochlea of a few old Wv/ + mice. The +/+ animals were all normal.

These findings may be interpreted as follows. The neural crest contributes to the formation of the acoustic ganglion, and as it is abnormal in WV/WV mice in its undifferentiated state, both the melanoblasts and the ganglionic primordia are affected. The abnormality of the primordium of the acoustic ganglion manifests itself as pathological changes in the inner ear.

This interpretation is supported by the results of an earlier study on the mutant piebald- lethal (S1). But as there is considerable evidence that the otic placode also contributes to the formation of this ganglion, it probably has a dual origin. Since the vestibular part of the inner ear in both WVIWV and sl/sl mice appears to be unaffected, it may be assumed that the placodal moiety innervates this region, and the neural crest moiety the cochlea and the saccule.

The mode of formation of the acoustic ganglion suggested here should also be applicable to man, the dog, the cat, the mink and the deer mouse, if not to all mammals. In the species named above inner ear abnormalities have either been observed or been inferred from the behaviour, and when examined they have been found to be extraordinarily similar to those discovered in the mouse mutants.
Action de la puromycine et d’une substance analogue sur la différenciation de cellules embryonnaires d’amphibiens, cultivées in vitro
Authors: Duprat Par A. M.
Published: April 2021

Des cellules embryonnaires de Pteurodeles waltlii et (d’Ambystoma mexicanum (Amphibiens, Urodèles) ont été cultivées in vitro en présence de diverses concentrations de puromycine, inhibiteur des synthèses protéiques, ou d’aminonucléoside de la puromycine, substance analogue n’agissant pas sur les synthèses protéiques. Lorsque le puromycine est introduite dans le milieu de culture (0,15 μg/ml) avant que la différenciation morphologique des cellules ne se manifeste, on constate:

L’apparition sur le vivant d’anomalies affectant divers organites cellulaires (nucléoles, chromatine, chondriome…). L’inhibition de la différenciation morphologique des cellules, bien que d’autres fonctions cellulaires continuent à se dérouler. La réversibilité de ce phénomène de blocage, à condition que la durée du traitement n’excède pas trois jours, même en présence d’actinomycine D (troisième lot, Fig. 5).

Ces résultats sont comparables à ceux obtenus avec la cycloheximide, autre inhibiteur des synthèses protéiques.

Une étude autoradiographique nous a permis de constater que la puromycine inhibe l’incorporation de [ 3H]uridine dans le nucléole mais ne perturbe apparemment pas celle qui se fait dans le nucléoplasme. De plus, le passage du RNA du noyau au cytoplasme ne paraît pas affecté par l’antibiotique. La puromycine (0,15μg/ml) a une action inhibitrice plus ou moins marquée sur l’incorporation de deux acides aminés selon la sensibilité de la ponte utilisée. Cette inhibition des synthèses protéiques semble en corrélation avec celle de la différenciation morphologique. En effet, l’aminonucléoside de la puromycine qui n’est pas un inhibiteur des synthèses protéiques aux concentrations utilisées, n’affecte pas la différenciation morphologique des cellules.

On conclut que l’effet de la puromycine est lié à son action inhibitrice des synthèses protéiques.
Succinate, glycerophosphate and ascorbate as sources of cellular energy and as antiteratogens
Authors: Landauer Walter , Sopher Dinah
Published: April 2021

Our experimental findings show that succinate and ascorbate greatly reduce the teratogenic effects of 3-acetylpyridine, 6-aminonicotinamide and sulfanilamide. Glycerophosphate led to similar alleviating results when used in combination with 3-acetylpyridine and 6-amino-nicotinamide, but not with sulfanilamide. With certain other teratogens the high-energy intermediates failed to alleviate; in some instances (acetazolamide, insulin) they even led to potentiation of teratogen-induced defects.

The results of our experiments demonstrate clearly that high-energy intermediates, by being fed into the respiratory chain of the mitochondria, can alleviate incidence and degree of expression of malformations produced by specific teratogens. In concert with earlier evidence on the nature of antiteratogenic compounds it can further be concluded that the particular teratogens in question exert their effects by interference with mitochondrial energy production in the tissues for which they have specific affinity.
Organogenèse de l’estomac de l’embryon de Poulet: Evolution de F épithélium du proventricule au contact de surfaces conditionnées par des mésencliymes
Authors: Sigot Par Michel , Marin Lea
Published: April 2021

Lorsque des cellules vivantes séjournent, en culture, au contact d’un support solide, elles laissent en place, une fois détachées de leur support, une certaine quantité de matériel organique acellulaire. Cette propriété a permis de conditionner des lamelles de plexiglas par une culture préalable de tissus inducteurs (mésenchymes de proventricule ou de gésier) qui laissent sur les lamelles un matériel résiduel. Nous avons analysé les propriétés de ce matériel résiduel sur la différenciation de l’épithélium de l’estomac de Poulet.

Le matériel résiduel possède des propriétés inductrices analogues à celles du tissu dont il provient: au contact de lamelles ayant porté du mésenchyme de proventricule, l’épithélium de proventricule tend à évoluer suivant le type proventricule; au contact de lamelles ayant porté du mésenchyme de gésier, l’épithélium de proventricule tend à évoluer suivant le type gésier. Le tissu inducteur, cultivé au contact d’un support solide, a donc laissé sur celui-ci une substance inductrice capable d’agir sur l’épithélium.

Le matériel résiduel du mésenchyme de gésier a des propriétés stabilisatrices capables d’arrêter la différenciation normale de l’épithélium de proventricule en le maintenant dans la forme gésier. Remis au contact avec le mésenchyme de proventricule, l’épithélium, qui a subi l’influence du matériel résiduel du mésenchyme de gésier, n’est plus capable de donner des structures de proventricule normales. Par contre, lorsque l’épithélium a séjourné au contact de lamelles vierges, sa compétence reste intacte et il reprend son évolution normale lorsqu’on le réassocie à du mésenchyme homologue.

Le facteur stabilisant a pu être mis en solution, à partir de lamelles porteuses de matériel résiduel de mésenchyme de gésier. Cette solution, recueillie sur des lamelles, est éprouvée sur des épithéliums de proventricules. Ses effets sont les mêmes que ceux du matériel résiduel dont elle provient: l’épithélium qui a subi l’influence de cette solution n’est plus capable de donner des structures proventriculaires normales lorsqu’il est réassocié à du mésenchyme homologue.
Déterminisme de la différenciationspécifique des plumes néoptiles et téléoptiles chez le Poulet et le Canard
Authors: Dhouailly Par Danielle
Published: April 2021

Des expériences précédentes ont montré que les facteurs de la différenciation épidermique plumaire spécifique sont localisés dans le derme pour les uns, dans l’épiderme pour les autres, à 7–9 jours d’incubation (peau dorsale). Les premiers fixent l’architecture générale de la plume; les seconds déterminent la structure des cellules barbulaires.

De nouveaux types d’associations hétérospécifiques Canard/Poulet ont été réalisés: épiderme tarso-métatarsien de 11–12 jours/derme dorsal de 7–9 jours; épiderme dorsal de 7–9 jours/derme tarso-métatarsien de 11–12 jours; ectoderme alaire/mésoderme alaire de 3–4 jours d’incubation.

Les résultats obtenus montrent que l’information nécessaire à la morphogenèse spécifique des barbules (présence ou non de barbicelles) est déjà présente à 3–4 jours dans l’ectoderme alaire. De plus, elle n’est pas limitée aux seules régions plumigènes, le futur épiderme scutellaire de 11–12 jours la possédant à l’état potentiel.

D’autre part, le derme (y compris celui du tarso-métatarse) possède l’information nécessaire au développement du rachis, déterminant ainsi l’architecture spécifique de la plume. Le mésoderme alaire de Canard impose de plus la différenciation de praeplumidae, caractéristiques du plumage néoptile des Ansériformes.

L’apparition plus ou moins précoce des plumes téléoptiles ainsi que le mode de remplacement des plumes néoptiles par les plumes téléoptiles juvéniles est sous la dépendance des tissus mésodermiques de l’aile. L’espèce de l’hôte a cependant une influence limitée sur la date d’apparition du plumage téléoptile.
Expansion of the area vasculosa of the chick after removal of the ectoderm
Authors: Augustine J. M.
Published: April 2021

The role of the ectoderm in the expansion of the mesoderm in the area vasculosa of the chicken embryo was studied.

The basement membrane of the ectoderm was found to constitute a substratum for the expansion of both layers of mesoderm, since (a) the somatic mesoderm, particularly at its margin, adheres to the basement membrane, and (b) the somatic and splanchnic mesoderm adhere to each other throughout most of the area opaca.

Following removal of the ectoderm from the outer surface of the basement membrane, movement of the underlying mesoderm along its inner surface stopped. Mean expansion of the mesoderm in these cases was zero.

Following removal of both ectoderm and basement membrane, expansion of the underlying mesoderm was normal in amount.

Experimental changes in the ectodermal substratum can thus stop movement of the associated mesoderm, but the role which the substratum normally plays in mesodermal expansion remains unclear.
Coincidence of embryonic growth and uterine protein in the ferret
Authors: Daniel Joseph C.
Published: April 2021

The protein content of fluids isolated from the lumen of the uterus of the ferret was correlated with growth of the pre-implantation embryo. Similar observations were made with mink for comparative purposes. It is concluded that in the ferret :

Protein content rises coincidentally with blastocyst expansion, becoming especially high when the embryo is implanting.

The proteins present early in the period are of types that diffuse easily in electrophoresis; they become more like those of serum near the time of implantation.

There is no evidence of an embryonic diapause. Mitotic activity in cells of the blastocyst is maintained at a high rate (about 5 %).

The prolonged pre-implantation period results from a relatively long mitotic duration in blastocyst cells (80+ min).

The protein content found during the pre-blastocyst period is similar to that of mink uterine fluids collected during the period of embryonic diapause. This observation provides additional circumstantial evidence that the embryonic diapause accompanying delayed implantation is related to limited protein availability.
Stimulation of cell division in pronephros of embryonic grafts following partial nephrectomy in the host (Xenopus laevis)
Authors: Chopra D. P. , Simnett J. D.
Published: April 2021

Following partial nephrectomy in juvenile metamorphosed Xenopus laevis the mitotic activity in the regenerating kidney reached its maximum on the 6th day and returned to its normal level by the 16th day.

The mitotic activity was measured in the pronephros and epidermis of prefeeding Xenopus larvae (stage 38) at different intervals after their implantation into the lymph sacs of partially nephrectomized and control metamorphosed hosts.

Ten days after partial nephrectomy, during the period of increased mitotic activity in the regenerating kidney of the host, the mitotic activity in the implant pronephros was twice as high as that in the implant pronephros of the control hosts.

Eighteen days after partial nephrectomy when the mitotic activity in the regenerating host kidney had returned to normal, there was no difference between the mitotic activity of pronephros of implants in nephrectomized and control hosts.

There was no significant difference between the mitotic activity of epidermis of the implants in nephrectomized and control hosts, nor was there any difference between the epidermal mitotic activity in implants examined 10 and 18 days after host nephrectomy.

It was concluded that a circulating factor (or factors) responsible for the control of mitotic activity in the regenerating host kidney enters the implant through its vascular supply and influences the mitotic activity in the homologous embryonic tissue. It is possible that this factor is a tissue-specific mitotic inhibitor synthesized by the host kidney.
Behaviour of mouse primordial germ cells in the chick embryo
Authors: Rogulska Teresa , Ożdżeński Wacław , Komar Aldona
Published: April 2021

Hind guts of -day mouse embryos were transplanted into the posterior part of the coelomic cavity of -day chick embryos. The hosts were sacrificed after 1–7 days and the mouse primordial germ cells (PGCs) in the graft and in the surrounding host tissues were searched for by means of the histochemical technique for alkaline phosphatase. Altogether 94 grafts were examined.

During the first 3 days of intracoelomic development of the graft accumulations of mouse PGCs close to the mesonephros, the mesentery or the gonad of a chick embryo were observed in 26 out of 51 cases. In 12 grafts single PGCs crossed the boundary between the host and the graft and settled in host tissues such as the mesonephros, the mesentery or the gonad.

After 3 days mouse PGCs are no longer visible in the chick tissues. However, the number of PGCs in the grafts also gradually decreases and from the 4th day onwards many of the grafts contain no PGCs. The ability of mouse PGCs to survive extragonadally, even in the embryonic hind gut, is thus limited.

In some of the 4-to 7-day-old grafts PGCs occur on the periphery of the graft in the form of single aggregations. From the 6th day the only PGCs which survive are those in aggregations.

The experiments indicate that the gonads, together with adjacent tissues (mesonephros, mesentery) of a chick embryo are attractive to mouse primordial germ cells and that the hypothetical attractive substance is not species specific.
The mechanism of axial rotation in the rat embryo: an experimental study in vitro
Authors: Deuchar E. M.
Published: April 2021

Axial rotation has been studied in 9- to 11-day rat embryos grown in culture by New’s watch-glass technique.

Unlike the mouse, the rat embryo rotates towards its right side and rotation starts with the head end only. The twist then passes caudalwards until the whole axis has reversed its dorsoventral orientation and curvature. Contractions in cervical and cardiac regions appear to initiate the rotation.

Posterior parts of 9- and 10-day embryos, isolated by transections at mid-trunk or cervical levels, show much less ability to rotate than unoperated controls: the frequencies of fully turned, partially turned and unturned embryos have been compared between control and experimental groups and show significant differences. There is more marked inhibition of rotation when the operation is performed at 9 days than at 10 days, and more with cervical than with mid-trunk transections. In all, 67 % of embryos transected at the mid-trunk level and 98 % transected at the cervical level were unable to rotate the posterior parts. Extrusion of embryos from the amniotic cavity also resulted in abnormal or incomplete axial rotation. The role of the membranes in facilitating rotation is discussed briefly.
The effects of an antiserum to the contractile proteins of the heart on the developing rat embryo
Authors: Berry Colin L.
Published: April 2021

An antiserum with specific reactivity against the contractile proteins of the rat heart has been raised in the rabbit. Fractions of the serum have been shown to enter the isolated rat embryo by electron-microscopic studies with ferritin, where they bind to the myocardium, producing degenerative changes. Both IgG and IgM fractions are toxic, producing foetal death in a large proportion of explanted embryos.
Development of the secretory capacity of the chick embryo adrenal glands
Authors: Pedernera Enrique A.
Published: April 2021

The secretory capacity of the chick embryo adrenal was investigated at different stages of its development employing a sensitive bioassay for corticosteroids based upon the modifications produced in vitro by these hormones on the height of the chick embryo duodenal mucosa.

The adrenal gland cultivated in contact with explants of duodenum and stimulated with increasing doses of ACTH exhibited a mucosal response similar to that produced by corticosterone, both in the slope of the bioassay dose-response curve and in the histological pattern.

It has been found that the chick embryo adrenal glands can secrete corticoids from the 5th day onwards by adding ACTH to the culture medium. The basal (unstimulated) secretory capacity of the gland (registered from the 8th day on) is significantly correlated with the total protein content of the adrenals in the different stages of development studied.

The maximal secretory capacity of the gland (measured with the dose of ACTH which produces the maximal response) increases steadily up to the 10th day.

The rate of increase of corticosteroid secretion due to ACTH is a constant within the interval of development investigated.
Hop-sterile, a mutant gene affecting sperm tail development in the mouse
Authors: Johnson D. R. , Hunt D. M.
Published: April 2021

Hop-sterile (hop) is a new mutation in the mouse, the effects of which include complete male sterility, a ‘hopping’ gait and preaxial polydactyly of all feet. Ultrastructural studies of spermiogenesis show that sperm tails are absent or highly modified. Second meiotic division is frequently abnormal or incomplete, often with four centrioles per cell. These centrioles usually fail to form flagella and sperm tail development is arrested.
Influence of the RNA content on oogenesis in the bobbed mutants of Drosophila melanogaster
Authors: Mohan Jag
Published: April 2021

Developing egg chambers of Drosophila melanogaster (wild-type and bobbed mutants) have been examined for their nucleic acid content by cytophotometric methods. No differences were observed in the total DNA and RNA content of the egg chambers at all stages between the bobbed mutants and the wild type. It is shown that the process of oogenesis in bobbed females is prolonged, and that this prolongation occurs at all the stages of oocyte development. Since the ovaries of the bobbed females synthesize less rRNA per unit time, it is likely that this prolongation allows the egg chambers of the bobbed females to normalize their RNA content. When they achieve a given RNA content, they proceed to the next stage of development.
La formation des somites chez l’embryon d’oiseau: étude expérimentale
Authors: Lanot Par R.
Published: April 2021

Somitogenesis in the avian embryo: an experimental study

The determinism of somitogenesis has been studied.

A complete segmental plate can form somites even when isolated from cord, neural tube and somites. Somites are always formed if the segmental plate remains in continuity with the somites which have just formed.

When the segmental plate is separated from the axis and deprived of its apical end, it undergoes no differentiation or differentiates incompletely. In the latter case the quality of differentiation decreases in a cephalo-caudal direction.

When the segmental plate, without its apical end, is left in contact with neural tissue or chorda, it forms somites normally.

The growth of the segmental plate is reduced whenever it has been isolated from neural tube and chorda altogether.

Behind its apical end the segmental plate can regulate excesses as well as deficiencies.

It appears, then, that the intersomitic fissures are determined at the apical ends of the segmental plates, but not behind them.

This determination is progressively established backwards. It can be transmitted by the last differentiated as well as the differentiating somites. However, the neural tube, and possibly the cord, play the leading role in this process, for the intersomitic clefts are fixed at their proper place in connexion with them.
An electrosurgical technique for the production of localized tissue ablations in the early chick embryo
Authors: Jordan R. K.
Published: April 2021

The passage of low-frequency alternating current was found superior to other methods considered for the production of small, discrete, electrolytic ablations in young chick embryos.

Active electrodes of tungsten metal less than 5 μm in diameter were prepared by controlled electrolytic corrosion. These gave reproducible, discrete foci of destruction of the required size, with currents less than 2 mA. The identification of destroyed tissue areas was immediately apparent under the operating microscope and confirmed histologically. Preliminary studies on bilateral extirpation of the ultimobranchial primordia show the absence of the ultimo-branchial bodies 6 days after destruction of the primordia at 96 h of incubation.
Ultrastructure of diploid and haploid cells of Xenopus laevis larvae
Authors: Fox H. , Hamilton Louie
Published: April 2021

A study was made of tissues of diploid and haploid Xenopus laevis larvae by electron microscopy. The comparison of the two types of larvae was both quantitative and qualitative. Haploid cells contain fewer similarly sized mitochondria and/or cilia (compared with the diploid), commensurate with their smaller cell size. Cellular differentiation is retarded in haploids and the degree of retardation is reflected in the retention of cellular lipid and yolk. It is suggested that the failure to differentiate adequately is an important component in the development of the haploid syndrome.
A biochemical and ultrastructural study of RNA in yolk platelets of Xenopus gastrulae
Authors: Kelley Robert O. , Nakai George S. , Guganig Marlene E.
Published: April 2021

Yolk platelets from Xenopus gastrulae were isolated in a sucrose-polyvinyl pyrrolidone medium, washed, centrifuged four times, and portions of each pellet were prepared for electron microscopy.

Electron microscopy revealed isolated platelets to be free of cytoplasmic contamination with progressive disruption of the superficial layer after each washing.

Each washing and the final pellet were extracted with phenol and precipitated with ethanol.

Orcinol analysis indicated that 50–60 μg of RNA were present in yolk platelets isolated from 1000 gastrulae.

Autoradiography of yolk platelets from cells incubated in [5-3H]uridine revealed label in superficial and main body components after treatment with DNase but not after incubation in RNase.

Acrylamide-gel electrophoresis suggests that yolk platelet RNA is of both high and low molecular weight.
The effect of early thymectomy on histogenesis of the lymphoid organs in Xenopus laevis
Authors: Manning Margaret J.
Published: April 2021

The role of the thymus in the ontogenetic development of the lymphoid system of the clawed toad, Xenopus laevis, was investigated by removing the organ at stage 49 of Nieuwkoop & Faber (1967), a stage when small lymphocytes are present in the thymus but have not yet appeared in the peripheral lymphoid organs.

Complete thymectomy, confirmed histologically, was achieved in nine larvae killed at stage 56 and in 23 larvae killed at stage 59.

The spleen was smaller in thymectomized larvae than in sham-thymectomized controls in the series killed at stage 56, but the difference was no longer significant at stage 59. In both series, thymectomized larvae showed a fall in the number of extra-follicular lymphocytes and an increase in the reticulo-myeloid elements of the splenic red pulp.

The pharyngeal ventral cavity bodies were moderately or severely depleted of lymphocytes.

In other areas, histogenesis proceeded normally in the absence of the thymus. In the splenic white pulp, the follicles, which comprised immature cells of the lymphoblast type at the time of thymectomy, developed their normal complement of lymphocytes. All larvae grew and developed at the normal rate.
Transmission and spread of embryonic induction
Authors: Nordling Stig , Miettinen Heikki , Wartiovaara Jorma , Saxén Lauri
Published: April 2021

The question of whether inductive tissue interactions involve factors transmitted by long-range diffusion was investigated. In transfilter experiments with spinal cord as the inductor and metanephric mesenchyme as the responding tissue it was established that interposition of a second TA Millipore filter (pore size 0·8 μm, thickness 25 μm) prolongs the induction time by about 12 h. The prolongation of the induction time was concluded to be due to the time taken by the inductor to pass through the second filter. It was also demonstrated that metanephric mesenchyme partially lost its competence if precultivation lasted more than 12 h. This explains why 100% induction never was achieved in the double-filter experiments.

In order to rule out the possibility that the filters, owing to their inhomogeneous structure and negative surface charge, seriously restricted diffusion, the diffusion of several substances through the filter was measured under conditions as closely similar as possible to those in the transfilter experiments. Although there was some restriction of diffusion, the calculated diffusion constants were of the same order of magnitude as those reported in the literature, indicating that the filter is no major obstacle.

Calculations based on four different hypotheses that the inductor is transmitted by diffusion, indicate that diffusion can hardly explain the long transmission time.
Tentacular and oral-disc regeneration in the sea anemone, Aiptasia diaphana
Authors: Singer Irwin I.
Published: April 2021

Autoradiography with [3H]thymidine and electron microscopy were used to determine (a) the patterns of cellular division exhibited by intact anemones, (b) if measurable increases in cellular proliferation accompany oral-disc regeneration, (c) whether interstitial cells are present in Aiptasia, and (d) if these cells could be responsible for the latter proliferative patterns.

An oral-aboral gradient in cellular proliferation was exhibited by the epidermis of uncut anemones, with the highest levels in the tentacles.

Wound healing did not require cell proliferation and did not immediately stimulate cellular division which was associated with subsequent morphogenetic events.

Indices of presumptive oral-disc [3H]thymidine uptake into nuclei increased tenfold with the outgrowth of the new tentacles. This increase occurred in the epidermis, while only small amounts of gastrodermal proliferation were detected, it is hypothesized that the epidermis contributes new cells to the expanding gastrodermis during tentacle budding.

Most of the [3H]thymidine-labeled nuclei were localized in the basal portions of the epidermis of intact anemones and 1-to 2-day-old regenerates; very few gastrodermal nuclei accumulated the label.

Nests of interstitial cells and transforming interstitial cells were localized in the exact epidermal regions where nuclear labeling took place, suggesting that the proliferative patterns of intact and regenerating Aiptasia are a function of their interstitial cell distribution.
Timing of the phases of the cell cycle with tritiated thymidine and Feulgen cytophotometry during the period of synchronous division in Lymnaea
Authors: van den Biggelaar J. A. M.
Published: April 2021

The duration of the phases of the cell cycle during the 1–, the 2– and the 4–cell stage of the Lymnaea egg were determined with [3H]thymidine and with Feulgen cytophotometry. The M, S and G2 phases occupy 48, 27 and 25% of the first three cell cycles. A G1 phase cannot be observed. Only from the 4-cell stage was [3H]thymidine readily incorporated into DNA. The theory that an increase in respiration during the S phase of the 4-cell stage is connected with the energy requirements of DNA synthesis is discussed.
Timing of the phases of the cell cycle during the period of asynchronous division up to the 49-cell stage in Lymnaea
Authors: van den Biggelaar J. A. M.
Published: April 2021

The duration of the phases of the cell cycle (M-G1-S-G2) has been determined from the 8-up to the 49-cell stage in eggs of Lymnaea, using autoradiography and cytophotometry of Feulgen-stained nuclei. Division asynchrony of corresponding cells in different quadrants is primarily caused by unequal lengthening of the G2 phases. In general it appeared that in the vegetative cells lengthening of the cell cycles is chiefly due to an extension of the G2 phases, whereas in the cells of the animal half the duration of both the S and the G2 phases are extended. DNA synthesis is not blocked in cells which stop dividing and start to differentiate. A conspicuous lengthening of the cell cycles is observed in the 16- and 24-cell embryo; this is accompanied with the reappearance of distinct nucleoli. Supporting evidence has been obtained for the assumption that bilateral symmetry at the animal pole of the embryo is induced by cells from the vegetative hemisphere, presumably by the macromere 3D, during the 24-cell stage.
Forelimb regeneration in hypophysectomized adult Diemictylus viridescens following organ culture and autoplastic implantation of the adenohypophysis
Authors: Liversage Richard A. , Liivamagi Luna
Published: April 2021

After autografting an organ-cultured anterior pituitary gland, maintained in culture for up to 27 days, into the tail or lower jaw of an hypophysectomized adult Diemictylus viridescens, the animals recovered and survived readily until fixation at 102 days (129 days post-hypophysectomy) and normal bilateral limb regeneration occurred. Also, restoration of normal skin colour, muscle tone, eating habits and behaviour was identical to control regenerate cases. In the sham control cases, a muscle fragment from the dismembered portion of the amputated left forelimb was placed in organ culture one day after hypophysectomy and then autografted into the host tail 7 days later. The majority of animals lived only up to 28 days post-hypophysectomy; they acquired the gross characteristics of adult hypophy-sectomized newts; and bilateral forelimb regeneration was thwarted. Newts that were hypophysectomized only, showed no gross signs of limb regeneration and died within 28 days.

Organ culture and autoplastic implantation of the adenohypophysis permitted a study of the inhibition and then the concurrent restoration (left forelimb = old amputee) and initiation (right forelimb) of regenerative activity as well as normal advanced limb regeneration.
Sur le comportement des mastocytes chez le rat en conditions d’hypo- et d’hypervitaminose A
Authors: Spreca Par A. , Modis L. , Conti G.
Published: April 2021

The behaviour of rat mast cells under conditions of high and low vitamin A

The authors have studied the mast cells in normal rats and in rats under hypo- and hyper-vitaminosis A. The main results of their studies are: (a) in the skin (dermis), in the case of A hypervitaminosis, there is a significant rise in the number of the mastocytes with swelling and dcgranulation; (b) in lung and bone marrow, the number of mastocytes is increased under hypovitaminosis A and there is also blood congestion and lipomatosis of bone marrow.

The authors give an interpretation of their results.
Mise en evidence d’un facteur tissulaire intervenant au cours de la morphogenèse du système trachéen chez les insectes diptères
Authors: Pihan Par Jean-Claude
Published: April 2021

Demonstration of a ‘tissue factor’ acting in the morphogenesis of the tracheal system in the dip ter an insects

In an attempt to examine the factors acting during the morphogenesis of the tracheal system in the Diptera (Calliphoridae), various experiments were performed in larvae and pupae so as to modify the relations between the organs and their tracheal supply.

The results are as follows :
The retinotectal projections after uncrossing the optic chiasma in Xenopus with one compound eye
Authors: Straznicky K. , Gaze R. M. , Keating M. J.
Published: April 2021

The nature of the retinotectal projection from a compound (NN or TT) eye in Xenopus raises certain problems concerning the mode of formation of connexions between the eye and the tectum. Each half of the compound eye appears to spread its connexions across the entire extent of the (apparently normal) contralateral tectum. This could indicate a certain plasticity in the way in which optic fibres can connect with the tectum. Alternatively, it is conceivable that each (similar) half of the compound eye is only able to innervate its corresponding half-tectum; in which case the uninnervated half-tectum could remain undeveloped and the innervated half-tectum could overgrow to resemble a normal tectum. This mechanism would preserve the idea of a rigidly fixed cell-to-cell specificity between retina and tectum.

In an attempt to distinguish between these two mechanisms (spreading or overgrown half-tectum) we have given each of a series of Xenopus embryos at stage 32 one compound eye (NN or TT). Then, shortly after metamorphosis, we uncrossed the optic chiasma and 6 months later recorded the retinotectal projections from each eye to the tecta. Thus by connecting up the normal eye to the suspect tectum, and the compound eye to the normal tectum, we used the normal side in each case to provide an indication of the degree of abnormality with which the other side was connected.

The results showed that a compound eye (NN or TT), connected to a normal tectum, gave a typical reduplicated map across the entire tectum, whereas the normal eye, when connected to the tectum which was previously innervated by the compound eye, gave an approximately normal projection across the whole of that tectum.

These results lead us to conclude that, in the Xenopus visual system, no strict cell-to-cell type specificity exists; rather, what is preserved throughout these experimental manoeuvres is the polarity and extent of the projection.
Histological features of neural induction in Xenopus laevis
Authors: Tarin D.
Published: April 2021

It was first established by grafting experiments that neural induction occurs in Xenopus laevis and that it is the mesoderm in the dorsal lip of the blastopore which normally exercises this function. The subsequent histological work provided the following information:

At stage mesodermal invagination was already well under way, in advance of the formation of the archenteric cavity. This confirms the earlier observations of Nieuwkoop & Florschutz (1950).

The first evidence of neural induction, thickening of the mid-dorsal ectoderm combined with the development of an inner tier of columnar cells, occurred at stage .

By stage .12 there was generalized thickening of the dorsal ectoderm and between stage and 13 the brain and spinal cord regions of the neural plate became distinguishable.

The dorsal mesoderm segregated into notochord rudiment and two lateral masses at stage 13 and the latter further subdivided into paraxial mesoderm and lateral plates by stage 14.

The margins of the neural plate were clearly distinguished from presumptive epidermis by stage 15 and the median neural groove was also well marked.

In the next two stages the folding of the neural plate in the line of this groove proceeded rapidly. The dorsoventral enlargement of the somites and the relative shrinkage of the noto-chord were considered to contribute to the mechanism of neurulation.

Regionalization of the brain into prosencephalon, mesencephalon and rhombencephalon was in progress at stages 18 and 19.

These results indicate that induction consists of an initial activation of dorsal ectoderm (generalized thickening) followed by gradual transformation of the neural plate to form the different parts of the central nervous system (regionalization).

Intercellular metachromatic material was noted in various parts of the embryo. This was most plentiful between stage and stage 13 and thereafter gradually decreased. It was the only feature which persisted long enough to represent a possible inductive agent.

At all stages the archenteron was lined with a continuous layer of endoderm. This indicates that the mode of formation of the gastro-intestinal tube in Xenopus is different to that in urodeles. It further implies that the mesoderm is not present on the blastular surface prior to gastrulation but lies in deeper layers.
Reproduction of Dugesia tigrina under short-day and long-day conditions at different temperatures
Authors: Vowinckel C. , Marsden J. R.
Published: April 2021

Five successive generations of asexually derived populations of D. tigrina and their sexually derived parental population were reared under each of six combinations of 20, 23 and 26 °C with 12 and 16 h of daylight. Asexual and sexual reproduction were recorded for each population.

Peaks of asexual reproduction occurred increasingly earlier in consecutive generations to finally disappear or occur later again.

Peaks of sexual reproduction likewise occurred increasingly earlier in consecutive generations to be retarded again or disappear in later generations. Retardation occurs in earlier generations under short-day conditions than under long-day conditions.

All generations later than the third, asexually derived, were sterile.

The implications of these results are discussed and it is suggested that the time of cocoon deposition of all asexually derived offsprings is determined regardless of intervening generations during early development of the sexually derived parent. Attention is drawn to the similarity between the suggested mechanism and environmental control of aphid reproduction.
Synthesis of nuclear and cytoplasmic proteins in the early development of fishes and echinoderms
Authors: Krigsgaber Maya R. , Kostomarova Alla A. , Terekhova Tamara A. , Burakova Tatiana A.
Published: April 2021

Synthesis of nuclear and cytoplasmic proteins was studied biochemically and autoradio-graphically in early loach (Misgurnus fossilis) and sea-urchin (Strongylocentrotus nudus) embryos.

After incubation with [14C]amino acids for 5–120 min the ratio of the specific activities of nuclear, mitochondrial and 12000g supernatant proteins was shown to be equal approxi-mately to 6:1:2 in loach embryos and to 8:4:3 in sea-urchin embryos independently of the duration of labelling.

After incubation with [3H]amino acids the number of silver grains per unit section was on the average 2·4 times higher for nuclei than it was for cytoplasm at mid-blastula and mid-gastrula stages. At the mid-gastrula the vegeto-animal gradient of protein synthesis was found.

A higher level of the synthesis of nuclear proteins as compared with that of cytoplasmic proteins appears to be related to an increase in the nuclear volume and the nucleo-cytoplasmic ratio during the early development of the loach and sea-urchin embryos.
Embryological effects of a minute deficiency in linkage group II of the mouse
Authors: Dunn G. R.
Published: April 2021

A minute deficiency in linkage group II of the mouse, involving the short-ear locus and at least one other functional unit, was found to be lethal by day 8 after coitus when homozygous. The earliest time at which mutants could be detected was 7 days 16 h after coitus. Histologically, the mutant embryos showed overgrowth of ectoderm and trophoblastic giant cells. The mesoderm was almost entirely lacking and the mutant embryos were smaller than their normal litter-mates.

It was concluded that the mutant was first expressed morphologically late on day 7 after coitus and that its primary effect was to stimulate growth of extra-embryonic ectoderm.
The oviduct as a barrier to exogenous thymidine in the early development of the mouse embryo
Authors: Dyban A. P. , Samoshkina Natalia A. , Mystkowska Ewa B.
Published: April 2021

Mouse embryos are able to use exogenous thymidine during cleavage stages in vivo if the thymidine is injected directly into the oviduct.

DNA synthesis during cleavage occurs asynchronously and the intensity of DNA synthesis in the blastomeres of the same embryo varies. At all stages, the label in some nuclei is distributed unevenly, suggesting that some chromosomes may be heterochromatinized very early in development.