bluuebunny/crossref_metadata_2025_split huggingface dataset:
The behaviour of the egg pigment in wild-type and ‘rusty’ tadpoles of Xenopus laevis
Authors: Uehlinger V. , Beauchemin M. L. , Droin A. 
Published: April 2021

ABSTRACT
The behaviour of the egg pigment was studied by histological analysis of wild-type and ‘rusty’ embryos and tadpoles of Xenopus laevis as well as by experimental procedures.
The histological analysis of the wild-type animals showed that the various tissues, notably the skin, neural tube, alimentary system and cement gland go through progressive stages of egg pigment migration and concentration at the apical ends of the cells. In the ‘rusty’ mutants the migration and concentration of pigment occur to a slight extent only, the majority of the pigment granules remaining dispersed.
The experiments (tail cultures, squashes of cement gland mucus and of meconium) showed that in wild-type animals the pigment, after migration and concentration, is eliminated from the cells by expulsion. In ‘rusty’ animals, this expulsion does not take place.
Parabiotic tadpoles of a ‘rusty’ wild-type combination possess a coloration corresponding to their genotype. Ectodermal grafts performed at the neurula stage between ‘rusty’ and wild-type embryos develop according to their origin.
The amount of egg pigment found in wild-type and ‘rusty’ tadpoles, and the exceptional case of the cement gland are discussed.
It is concluded that the behaviour of the egg pigment is an active cell-specific process, and that the pigment is eliminated by expulsion. The non-elimination of the egg pigment in the ‘rusty’ mutant, accounting for its characteristic colour, appears to be due to a failure of the expulsion mechanism.
Cytological and cytochemical studies of centrifuged eggs of the slug Avion ater rufus L.
Authors: Sathananthan A. H. 
Published: April 2021

ABSTRACT
The stratification of various cell organelles and of important chemical substances have been studied in the eggs of the slug, after moderate centrifugation.
As in other molluscs the egg contents stratify typically into three well-defined zones - lipid, hyaline and yolky zones - but a distinct equatorial band of inclusions consisting mainly of phagosomes and associated lysosomes was detected in the most centrifugal region of the hyaline zone.
The sub-stratification of various cell inclusions in their respective zones was determined in some detail.
The role of the cell membrane and egg cortex in the redistribution of these inclusions and the nature of the ergastoplasm are discussed in the light of electron-microscope studies of eggs of this slug and of the sea urchin.
Les relations épithélio-mésenchymateuses au cours de l’organogenèse gastrique du fœtus de Lapin
Authors: David Par Danielle 
Published: April 2021

ABSTRACT
The epithelio-mesenchymal relations during the gastric organogenesis of the rabbit foetus
The experimental study of the epithelio-mesenchymal relations during the gastric organogenesis shows the following facts:
Completely deprived of mesenchyme, the cultured or grafted isolated epithelium cannot develop. On the other hand the mesenchyme free of epithelium can survive and differentiate its muscular layer. Isolated after the 18th day, it possesses sufficient autonomy to form chorionic villi when covered only by vitelline membrane. The epithelium and the mesenchyme, dissociated by treatment with trypsin, then reassociated in culture (with or without subsequent grafting), develop identically to those of untreated controls. From the 19th day the mesenchyme shows a polarity and only the zone normally adjacent to the epithelium can form chorionic villi. The heterochronic associations of gastric epithelium and mesenchyme demonstrate the existence of two types of mesenchymal inductors: (a) a primary inductor, responsible for the epithelial morphogenesis, elaborated early in embryonic life (10th day); it acts till about the 21st day. (b) A secondary inductor, produced at a later time (15th day), provokes the epithelial cytodifferentiation; its activity is still strong at the 23rd day.
These experiments again show the early competence of the epithelium to react to the two mesenchymal inductors. The presumptive gastric endoderm of the 10-day-old rabbit foetus has a developmental potential such that it can respond as well to the stimuli elaborated by a young mesenchyme as to those of an older mesenchyme.
Aspects of spinal cord induction of chondrogenesis in chick embryo somites
Authors: O’hare M. J. 
Published: April 2021

ABSTRACT
The specificity of the chondrogenic inductive activity of chick embryonic spinal cord has been examined in chorioallantoic culture. It has been found that the 2-day spinal cord is capable of inducing somites to chondrify even after lethal X-irradiation (5000 rads, i.e. 50 J/l kg); this dose of X-radiation resultingin the inhibition of mitosis in the spinal cord and its complete necrosis within 48 h of irradiation.
The unirradiated spinal cord is capable of promoting the chondrogenesis of stage 9 –12 posterior lateral mesoderm, but to a lesser extent than when it is combined with stage 9 –12 posterior somite mesoderm. Irradiated spinal cord, however, possesses no chondrogenic activity with respect to lateral mesoderm. Thus it would appear that the 2-day spinal cord possesses a general cartilage-promoting activity dependent on its continued viability and proliferation, in addition to a somite-specific chondrogenic activity that survives a lethal dose of X-radiation.
The inclusion of enzymes in the Millipore filter used as a graft vehicle has been used to demonstrate that collagenase and hyaluronidase when combined, but not individually, are capable of interfering in the induction of somite chondrogenesis by irradiated spinal cord. Grafts of somites with unirradiated spinal cord show that these enzymes do not directly reduce the chondrogenic potential of the somites or interfere in the subsequent deposition of cartilage matrix. The activity of the spinal cord in inducing somite chondrogenesis appears to be associated with the synthesis of basement membrane materials by either or both of the interacting tissues during the first 24 h of the interaction.
No influence of the 2-day spinal cord on the morphogenesis of non-somitic cartilage could be detected.
Patterns of cell division, cell death and chondrogenesis in cultured aggregates of normal and talpid3 mutant chick limb mesenchyme cells
Authors: Ede D. A. , Flint O. P. 
Published: April 2021

ABSTRACT
Aggregates were prepared from dissociated mesenchyme cells obtained from normal and talpid3 mutant chick limb buds at stage 26 and were maintained for 4 days in culture. They were shown by autoradiographic techniques to consist initially of populations of uniformly dedifferentiated cells within which chondrogenesis was initiated between 1 and 2 days, leading to the formation of areas of precartilage in the interior of the aggregates.
Measurements of cell population density, cell death and cell division were made in precartilage and non-cartilage regions on sections prepared from normal and mutant aggregates fixed at 1-day intervals and were related to the pattern of chondrogenesis.
Non-cartilage areas consisted of cells surrounding the precartilage areas and extended to the surface of the aggregate; these cells showed no special pattern or histochemical reaction. Precartilage areas consisted of one or more ‘condensations’, comprising cells arranged in concentric rings around a central cell or group of cells, characterized by uptake of [35S]sulphate and taking up alcian blue stain in the intercellular matrix. Chondrogenesis was initiated at the condensation foci and spread centrifugally.
Condensations were arranged in a simple pattern, roughly equidistantly from each other and never at the surface of the aggregate. The shape and arrangement of the cells comprising them suggested that they were formed by a process of aggregation towards the condensation foci. The relation of these observations to events in the intact limb bud developing in vivo is discussed.
Budding in hydra: the role of cell multiplication and cell movement in bud initiation
Authors: Webster Gerald , Hamilton Susan 
Published: April 2021

ABSTRACT
The work described in this paper is concerned with the role of cell multiplication and cell movement in relation to the initiation of buds in hydra. .
Hydra starved for 6 days do not initiate new buds ; in such animals the mean mitotic index is only 10% of that in well-fed animals. When starved animals are re-fed, there is a rapid rise in mitotic index which reaches a maximum 12 h after feeding and thereafter declines. This cell division causes an increase in the cell population of about 30% in the 24 h following the meal. New buds are initiated at 24–72 h, i.e. at some time after the major part of the cell multiplication.
Cell division occurs in all parts of the axis to more or less the same extent and there is no sign of a growth zone in the budding region. However, the cell population in the budding zone of re-fed animals shows a significantly greater increase than in other parts of the axis and this can only be accounted for if it is assumed that cells have moved into this region from other parts of the axis.
Some cell multiplication is a necessary prerequisite for bud initiation, but grafting experiments with starved animals suggest that division per se is not necessary; the important factor seems to be the increase in size resulting from division.
The mechanics and causes of the cell movement which results in bud initiation are briefly discussed. It is suggested that changes in intercellular adhesion may be important.
The innervation of the hind limb of Eleutherodactylus martinicensis : further comparison of cell and fiber numbers during development
Authors: Hughes Arthur , Egar Margaret 
Published: April 2021

ABSTRACT
In montages of electron micrographs of the sciatic nerve of Eleutherodactylus martinicensis, the numbers of fibers of all classes have been counted, from the 8·5 day embryo, through the early juvenile to the adult. These counts have been compared with the total numbers of cells in the lumbar ventral horn plus those in the lumbar spinal ganglia 8, 9 and 10.
In the embryo, both sets of counts rise to a peak on the 13th day, and fall early in the 14th day. In the embryo, the cell count is 600–1000 more than the fiber count, while in the 6-day juvenile onwards, the fiber count is the greater.
These differences are held to arise from the play of two independent factors, namely production of axons in the embryo by only a minority of cells in ganglia and ventral horns, and secondly, the extent to which axons branch between spinal roots and sciatic nerve at all stages.
In the embryo, numbers of cells and fibers maintain a parallel course up and down the 13-day peak, indicating that many cells which are lost by degeneration had already sent axons into the nerve.
Myelinated fibers first appear in the limb nerves at 8-5 days, when limb motility is first seen. The course of formation of the earliest myelin in the sciatic nerve resembles that of fibers in the central nervous system.
In spinal roots there are both myelinated and unmyelinated fibers, the proportion of the latter in ventral roots being the greater.
Malformations des membres dues à des lésions vasculaires chez le fœtus de rat déficient en acide pantothénique
Authors: Giroud par A. , Lefebvres J. , Prost H. , Dupuis R. 
Published: April 2021

ABSTRACT
Female rats were given a synthetic diet devoid of pantothenic acid. They were then mated and the foetuses were examined on the 21st, 18th, 16th, and 15th days of gestation. Many foetuses were malformed. They exhibited exencephaly, anophthalmia, oedema, and alterations of the limbs. The extremities of the limbs on the 21st day were red and irregularly swollen. Histological examination on the 16th day showed that an arrest of blood circulation in the dilated marginal veins had occurred. The vascular endothelium had then disappeared, and the coagulated blood had come in direct contact with the tissues. Some skeletal elements may be distorted by the resulting pressure. Above all, there is a degeneration of the tissues in contact with the blood. The skele-togenous tissues of the digits degenerate and this results in ectrodactyly. The epidermis in some areas degenerates and the accumulated fluids and blood may be eliminated. These data are compared with other data concerning embryonic hemorrhagic processes, especially those producing limb amputation. Travail facilité par une aide de la Sécurité Sociale.
Foetal Death in the Rat
Authors: Frazer J. F. D. 
Published: April 2021

ABSTRACT
Pregnant rats were laparotomized 9 days after mating, and the number of implantation sites and conceptuses noted. These rats were killed at the end of pregnancy, and the numbers of foetuses noted. From these findings assessments were made of the degree of death before and after the 9th day of pregnancy. Different factors were found to be associated with loss of whole litters and of individual foetuses from litters. Different factors were associated with loss before and after the 9th day of pregnancy. Factors associated with loss of whole litters before the 9th day of pregnancy were the number of ova implanted and (in one strain of rat only) the time of year. Loss of part litters before the 9th day was associated with high numbers of ova implanted, with older mothers, and with the time of year. Loss of whole litters after the 9th day was associated with implantation of abnormal numbers of ova and with some previous loss of foetuses. Loss of part litters after the 9th day was associated with some previous loss of foetuses and with maternal coat colour. These findings are discussed.
The Uptake of Methionine-S35 by the Chick Embryo and its Inhibition by Ethionine
Authors: Feldman M. , Waddington C. H. 
Published: April 2021

ABSTRACT
The distribution of S35 in the proteins of the chick embryo was studied with labelled methionine. The various tissues were found to differ significantly from each other in their incorporated S35. Ethionine inhibited the uptake of methionine and higher dosages of ethionine retarded differentiation, and caused abnormalities. Methionine was shown to alleviate the effect of ethionine. Glycine did not. The specificity of the morphogenetic processes affected by ethionine, and the biochemical aspects of this inhibition, are briefly discussed.
Factors Affecting Vertebral Variation in Mice
Authors: Mclaren Anne , Michie Donald 
Published: April 2021

ABSTRACTAs a test for genetic differences within that part of the C3H inbred strain of mice which has predominantly 5 lumbar vertebrae, males from each of three C3H(5) colonies were crossed to C57BL females. The F 1 offspring differed in vertebral type according to paternal origin, showing that genetic divergences between colonies and substrains have occurred within that section of the C3H strain which has predominantly 5 lumbar vertebrae. These matings also gave further evidence, in the form of significant hetero-geneity between litters, that vertebral type is in part determined by a fluctuating variable of the mother’s physiological state. We have summarized published data on the variation of the number of lumbar vertebrae in mice in the C3H and C57BL inbred strains and their F1 and F2 hybrids. On certain assumptions we find that the inbreds are about twice as variable as the F1 hybrids.
The teratogenic effects of sugars on the chick embryo
Authors: Hughes A. F. , Freeman R. B. , Fadem T. 
Published: April 2021

ABSTRACTThe effect of treatment of chick embryos during the first day of incubation with a number of sugars is described. To some embryos solid sugars were applied in opened eggs; for others the substances were injected in solution. By both methods, all sugars tested were found to be teratogenic, but no apparent general differences between mono-, di-, and trisaccharides were found. Nor were there any correlations between those which can be metabolised at these stages and their teratogenicity.The range of defects produced is similar to those found when embryos of this age are treated with other substances. In embryos treated with [14C]sucrose, some of the label is retained within the tissues in a bound, insoluble form. Possible implications of this finding are suggested.
Experimental study of the formation of the heart tube in the chick embryo
Authors: Argüello Carlos , De La Cruz MaríA V. , Sánchez Gómez Concepción 
Published: April 2021

ABSTRACT
A study was made of the development of the heart tube beginning from Hamburger & Hamilton (1951) stage 8+ up to stage 12. We used labelling with particles of iron oxide followed with time-lapse cinemicrophotography, staining with methylene blue, serial section and cutting the embryo in two halves.
Our results led to the conclusion that the tubular heart is formed by the addition of precardiac material into its posterior end, but in addition it is necessary to consider the fusion of the myocardium in a cephalic direction, starting with the fusion of both heart primordia at the rostral end. By this fusion the most anterior part of the heart up to stage 12 is formed.
Experimental cardiac morphogenesis: I. Development of the ventricular septum in the chick
Authors: Harh Jung Y. , Paul Milton H. 
Published: April 2021

ABSTRACT
An experimental technique utilizing microfiber markers and radioautography was used to study the morphogenesis of the ventricular septum in the chick embryo heart from stages 22 to 33 of Hamburger & Hamilton (1951). Fibers placed in the myocardium of the primitive ventricles of 4-day-old embryos within 250 μm to each side of the future site of the ventricular septum resulted in shortening of the distance between the two fibers until both were found within the myocardium of the septum at 7 days. The fibers coated with tritiated thymidine labeled the myocytes of the trabeculae immediately adjacent to where the fibers were placed and showed that when trabeculae were labeled within the 400–500 μm width centered on the ventricular septum, they aggregated together. The labeled myocytes in the trabeculae were found from the smooth crest to the most apical portion of the septum. These findings suggest that the muscular ventricular septum is formed by aggregation and coaptation of trabeculae and is of a single developmental origin.
Local autonomy of gastrulation movements after dorsal lip removal in two anuran amphibians
Authors: Cooke Jonathan 
Published: April 2021

ABSTRACT
The time-course of the remaining gastrulation movements has been investigated after removal of the dorsal lip, the presumptive foregut endoderm and the anterior mid-dorsal mesoderm as a plug-shaped mass of cells from beginning gastrulae of Xenopus laevis and Bombina orientalis. This embryonic region has been previously studied in its role as an organizer, when grafted into a host gastrula marginal zone.
There is usually no effect of the removal of these cells, the first morphogenetically active ones, either upon rate of subsequent completion of the external aspects of gastrulation, or upon the internal evolution of the presumptive mesodermal mantle. This finding is discussed in connexion with results of a previous paper on pattern formation in early Xenopus development, since it may help to distinguish between possible types of explanation for those results.
Differentiation in vitro of sympathetic cells from chick embryo sensory ganglia
Authors: Newgreen D. F. , Jones R. O. 
Published: April 2021

ABSTRACT
This study was carried out in order to determine what factors control the differentiation of certain neural crest cells in the chick embryo. Emphasis was placed on the morphologically and biochemically divergent sensory and sympathetic pathways of differentiation. Embryos were precisely staged according to Hamburger & Hamilton (1951) and it was observed that sensory ganglia with somites, explanted at stages 21–24, gave rise to cells showing formaldehyde-induced fluorescence in more than 25% of explants. These cells were identical in properties to the fluorescent cells of the sympathetic system of embryos of similar age, and appeared by 12 days in vitro. These fluorescent cells did not appear when somites and sensory ganglia explants were maintained separately.
The incidence of fluorescent cells in combined explants was considerably reduced or absent when cultures were maintained for 7 days or less, or when the explants were obtained from stage 25–26 embryos. Furthermore, when neural tube was also included in the cultures, the appearance of fluorescent cells was markedly inhibited. The requirement for somitic tissue to induce fluorescent cells in combined explants can be replaced by forelimb-bud tissue.
The origin of these cells and the factors that control their differentiation in vitro are discussed with reference to the neural crest origin of the sensory ganglion, and the possible conditions pertaining in vivo in this region.
Determination in regenerating tissues of Dugesia dorotocephala: the influence of nerve cord grafts
Authors: Sperry Pamela J. , Ansevin Krystyna D. 
Published: April 2021

ABSTRACT
Lateral fragments which contained no nerve cord were isolated from the postpharyngeal body section of Dugesia dorotocephala and fused with nerve cord grafts soon after isolation and at daily intervals through 8 days of regeneration. Fragments fused soon after isolation formed ‘headless’ regenerates but had normal body proportions. If the lateral cordless fragment was allowed to regenerate for 1 day or longer before fusion with the nerve cord fragment, the head always developed and the body proportions were normal. Therefore, head structures become determined in the lateral fragment within the first 24 h of regeneration; during this time these tissues can also respond to the head-inhibiting influence of the nerve cord. The competence to form particular structures of the postcerebral body regions must emerge after head-forming competence is lost, that is about 24h after isolation; however, it persists at least through the first 8 days of regeneration. Normal body proportions can be induced by nerve cord grafts throughout the first 8 days of regeneration.
Lateral fragments fused at any time after isolation with another fragment containing no nerve cord developed head structures but failed to differentiate tissues of the postcerebral regions. This confirms that the nerve cord is responsible for inhibition of head structures and induction of differentiation of body regions and normal body proportions.
Fate maps and the pattern of cell division: a calculation for the chick wing-bud
Authors: Lewis J. H. 
Published: April 2021

ABSTRACT
Given the growth rate throughout an embryonic rudiment, one can calculate how its parts must shift as it gets bigger, and so plot fate maps showing their future positions. The calculation is done here for the chick wing-bud from stage 18 to stage 25, using published data for mitotic index and cell packing density, and new measurements of size and shape. Two main findings are: (1) the wing-bud in this period elongates almost uniformly along itsproximo-distal axis. (2) Each limb segment derives from the tissue generated by one cell division cycle in the ‘progress zone’ at the tip.
Time, place and positional value in the chick limb-bud
Authors: Summerbell D. , Lewis J. H. 
Published: April 2021

ABSTRACT
Quantitative experimental evidence is presented for the progress zone theory of limb development. The theory, here formulated mathematically, states that the parts of the limb are specified in proximo-distal succession by an autonomous timing mechanism operating in a ‘progress zone’ of undifferentiated growing mesenchyme under the influence of the apical ectodermal ridge. By the exchange of distal tips between young and old wing-buds, it is shown that there are no long-range morphogenetic signals from proximal to distal tissue. The width of the progress zone is calculated, and it is found autoradiographically that practically all its cells are dividing.