bluuebunny/crossref_metadata_2025_split huggingface dataset:
Osteogenesis in transplants of bone marrow cells
Authors: Friedenstein A. J. , Piatetzky-Shapiro I. I. , Petrakova K. V. 
Published: April 2021

ABSTRACT
After heterotopic (e.g. subcutaneous) transplantation of bone marrow, haemopoiesis in the graft ceases; reticular tissue develops instead, and later bone is formed (Denis, 1958). The result can be achieved by grafting either free pieces of bone marrow or those placed in diffusion chambers (Petrakova, Tolmacheva & Friedenstein, 1963; Rosin, Freiberg & Sajnek, 1963). In the case of free transplantation the bone formed is later filled with bone marrow. After transplantation in diffusion chambers haemopoiesis does not recur despite the development of a considerable mass of bone in the chambers (Friedenstein, 1965).
The development of the chick embryo diencephalon and mesencephalon during the initial phases of neuroblast differentiation
Authors: Lyser Katherine M. 
Published: April 2021

ABSTRACTThe development of the nervous system presents many interesting problems as a developing system with numerous parameters of differentiation as well as from the point of view of the establishment of adult structure and function. With our growing understanding of developmental processes in general, and interactions at various stages of development in particular, it should be profitable to study more closely events of each period in a developing system, looking for information concerning their immediate control and their relation to events of other periods. In the nervous system, one phase which should be investigated much more thoroughly—especially from the point of view of the control of cellular differentiation—is that of the initial appearance of neuroblast cells and formation of the first nerve processes. Most studies of normal embryos which have included the period of initial differentiation have been primarily concerned with tracing the origins of definitive nuclei and fiber tracts, though possible mechanisms controlling various aspects of their development have of course been discussed.
The influence of the area opaca on the development of the young chick embryo
Authors: Bellairs Ruth , Bromham D. R. , Wylie C. C. 
Published: April 2021

ABSTRACT
The effects exerted by the area opaca upon the area pellucida have been tested experimentally by interfering with the normal relationships between them and then growing the blastoderm in tissue culture by the technique of New. If the entire area opaca was removed from a blastoderm at the full-length primitive streak stage, the embryo that formed was smaller than the controls and poorly differentiated. New evidence supporting the hypothesis that the area opaca influences the development of the embryo by exerting a tension upon the area pellucida is presented. Estimates of the mitotic rates provided no evidence to support the idea that this centrifugal tension promoted a high rate of cell division. With reduction in tension, however, cell death increased. No evidence could be found to suggest that the isolated area pellucida failed to grow and differentiate because its cell population was inadequate. When three area pellucidae were cultured in close contact with one another, growth and differentiation were no better than when one was cultured alone. The hypothesis that the proximal part of the area opaca exerted a nutritive effect on the area pellucida was tested. This was supported by the fact that when the area pellucida was explanted on top of the area opaca, differentiation of the embryo was good. Furthermore, some digestion of the area opaca endoderm appeared to take place. On the other hand, such a relationship cannot be essential for development at this stage, since equally good development could occur when the proximal part of the area opaca had been removed.
Somite segmentation in amphibian embryos: is there a transmitted control mechanism?
Authors: Deuchar E. M. , Burgess A. M. C. 
Published: April 2021

ABSTRACTIn all vertebrate embryos, somite segmentation begins in the occipital region and proceeds from here caudally with remarkable regularity. The segmentation pattern and the shape, size and number of somites formed are constant for each species, and it appears as if some quite complex mechanism must control their development. That this control mechanism must be versatile as well as precise is shown, for instance, by the fact that haploid newts have a larger number of cells per somite than the normal diploid, while polyploids have smaller numbers of somite cells than normal, so that the somite sizes are very nearly the same in all cases: the number of somites per embryo is also always the same as in the diploid (Fankhauser, 1945). Further, when mesoderm is either added to or excised from the somite region of the archenteron roof experimentally (Waddington & Deuchar, 1953), there is regulation so that the overall shape of the somites remains nearly normal, and again, their number per embryo is unchanged from that typical of the species.
Extra-toes:a new mutant gene causing multiple abnormalities in the mouse
Authors: Johnson D. R. 
Published: April 2021

ABSTRACTExtra-toes (Xt) is a new semi-dominant gene in the mouse. Xt/Xt animals die in utero or at birth. They have multiple abnormalities including paddle-shaped feet with up to eight or nine digits, hemimelia, disturbed spinal cord and brain, nose, eye and ear, and oedema. The heterozygote has pre- and post-axial polydactylism of all four feet. The Extra-toes homozygote can first be recognized as a 9-day embryo by excessively large pharyngeal arches and persistently open neural tube. Many abnormalities of the brain and sense organs can be traced back to malformation of the neural tube. Malformations of the upper jaw region and limbs can be traced back to overgrowth from the 9-day stage onwards. A third series of malformations due to oedema (first seen at 13 days) is described. The possible interrelations of these three groups of abnormalities to each other, and the relationship of the Xt syndrome to other gene effects in the mouse, chicken and guinea-pig are discussed.
Les facteurs de polarisation dans les premiers stades du développement chezParascaris equorum
Authors: Guerrier Par Pierre 
Published: April 2021

ABSTRACTLe développement de Parascaris equorum comporte une détermination très stricte ainsi que de faibles capacités de régulation. Celles-ci s’éteignent dès l’achèvement du premier clivage (Nigon, 1965). Il ressortait d’une étude antérieure (Nigon, Guerrier & Monin, 1960) que ces caractères pourraient être mis en rapport avec l’établissement, peu avant la première division de segmentation, d’une structuration corticale relativement stable. Le présent travail a été entrepris afin de tester cette hypothèse. Un bref rappel permettra de situer les circonstances dans lesquelles se dessinent les déterminations étudiées.
Recherches sur l'inhibition de la régénération du pharynx chez les planaires
Authors: Ziller-Sengel Catherine 
Published: April 2021

ABSTRACTL’idée que toute morphogenèse doit son accomplissement harmonieux non seulement à des facteurs positifs, les inductions, mais également à des facteurs négatifs, les actions inhibitrices, est relativement ancienne et très répandue. Elle s’appuie sur des données expérimentales aussi nombreuses que variées, tant dans le domaine de l’embryogenèse que dans celui de la régénération et chez des espèces animales très variées.
A quantitative study of the number and distribution of neoblasts in Dugesia lugubris (Planaria) with reference to size and ploidy
Authors: Lange C. S. 
Published: April 2021

ABSTRACT
This paper reports observations on the number of neoblasts in diploid and triploid planarian biotypes, the relation of this number to the size of the animal and the distribution of neoblasts with respect to the long axis of the animal. The number of neoblasts is a function of animal length for both diploid and triploid biotypes, but no significant difference was found between the biotypes. The combined data yield a regression equation of log. (number of neoblasts) = 1·90 log. (length) + 3·47. The distribution of neoblasts with respect to the long axis of the planarian was found to have two relative maxima, one anterior and one posterior to the intercalary minimum associated with the pharyngeal region of the animal. The relative position of the pharynx remains unchanged with growth in the triploid animal, in contradistinction to the progressive shift cephalad in the diploid. As statistical analysis showed no significant difference in the effects of the histological methods employed on the two biotypes, this observation is interpreted as a demonstration of different modes of growth in the diploid and the triploid. The volume of the planarian (in the fixed state) was correlated with the animal’s length (when alive) to yield a regression equation of log. (volume) = 2·62 log. (length) + 5·70. The slope of this regression equation is highly significantly different from that of the neoblast regression line. Thus larger animals have a lower density of neoblasts, although more of them. It is suggested that this latter observation may have some bearing on the problem of senescence in planarians. Counts of objects in serial sections are subject to an overestimate which can be corrected by the method of Abercrombie. This method, however, is based on an assumption which is not always valid. Therefore a more rigorous correction formula has been derived. This formula was then applied to the measurement of neoblast nuclear diameters (in the fixed state). No significant difference was found for nuclear diameters of diploid and triploid neoblasts.
Hox genes and growth: early and late roles in limb bud morphogenesis
Authors: Morgan Bruce A. , Tabin Cliff 
Published: April 2021

ABSTRACT
In recent years, molecular analysis has led to the identification of some of the key genes that control the morphogenesis of the developing embryo. Detailed functional analysis of these genes is rapidly leading to a new level of understanding of how embryonic form is regulated. Understanding the roles that these genes play in development can additionally provide insights into the evolution of morphology.
The 5′ genes of the vertebrate Hox clusters are expressed in complex patterns during limb morphogenesis. Various models suggest that the Hoxd genes specify positional identity along the anteroposterior (A-P) axis of the limb. Close examination of the pattern of Hoxd gene expression in the limb suggests that a distinct combination of Hoxd gene expressed in different digit primordia is unlikely to specify each digit independently. The effects of altering the pattern of expression of the Hoxd-11 gene at different times during limb development indicate that the Hoxd genes have separable early and late roles in limb morphogenesis. In their early role, the Hoxd genes are involved in regulating the growth of the undifferentiated limb mesenchyme. Restriction of the expression of successive 5’ Hoxd genes to progressively more posterior regions of the bud results in the asymmetric outgrowth of the limb mesenchyme. Later in limb development, Hoxd genes also regulate the maturation of the nascent skeletal elements. The degree of overlap in function between different Hoxd genes may be different in these early and late roles. The combined action of many Hox genes on distinct developmental processes contribute to pattern asymmetry along the A-P axis.
The Effect of Cortisone on Cell Proliferation and Migration in Peripheral Nerves undergoing Wallerian degeneration
Authors: Thomas G. A. 
Published: April 2021

ABSTRACT
The administration of 10 mg. of cortisone per day to rabbits caused a depression in the proliferation of all the cells in nerves undergoing Wallerian degeneration. The increase in numbers of cells within Schwann tubes was most affected, that of the endoneurial connective tissue cells and of the cells of the blood-vessel wall less. A greater depression of population occurred at the 10th day of degeneration than at the 20th or 25th. In vitro fewer cells migrated from expiants of degenerating peripheral nerves from animals receiving cortisone than from degenerating nerves from control animals, but the difference is accounted for by different numbers of cells in the expiants.
The Embryology of the Telencephalic Fibre Systems in the Mouse
Authors: Källén Bengt 
Published: April 2021

ABSTRACT
The ontogeny of the fibres in the telencephalon of Mus musculus has been studied. Reconstructions have been made using seven different stages. The formation of some telencephalic and diencephalic fascicles is described. The agreement supposed by Shaner (1936) to exist between the phylogeny and ontogeny of the fascicles is not supported by the present investigation. The migration areas and migration layers can develop before the fibre fascicles are formed, and thus without any influence from them. The division of the migration layers into nuclei takes place simultaneously with the entrance of the fibres into the layers, and hence a causal relation may exist between these two processes. The fibre anatomy may be of some importance with regard to establishing the homologies of the late subdivisions of the migration layers. The spaces between the migration areas and layers seem to act as pathways for the outgrowing neurites. The migration areas, which are also proliferation centres, seem to attract the neurites.
Morphogénèse de Bipartition chez Urocentrum Turbo (Cilié Holotriche)
Authors: Fauré-Fremiet E. 
Published: April 2021

ABSTRACT
Different species of Ciliates are characterized by the relative positions of the meridional ciliary bands (somatic kineties) and the oral or peristomial ciliary bands. Division sees the formation of two homothetic ciliary systems, one defining the anterior individual (proter) and the other the posterior individual (opisthe). Urocentrum turbo is characterized by the secondary arrangement of its somatic kinetosomes on transverse annular lines forming a wide anterior girdle or fascia and a narrow equatorial girdle or cingula. At the first stage of division the cingula grows by the multiplication of its kinetosomes; the distribution of these along the somatic kineties then completes the morphogenesis of the proter and opisthe. The cingula of Urocentrum is a morphogenic zone which conforms in its actual structure to the provisional idea of a ‘division zone’ introduced by Calkins. The oral ciliation constitutes an autonomous system with its own morphogenic zone.
Fecundity and Embryonic Mortality in Pigs
Authors: Perry J. S. 
Published: April 2021

ABSTRACT
863 female pigs, mostly sows discarded from commercial herds in East Anglia and sold for slaughter, were examined when killed and the condition of the reproductive tract was related to the animal’s reproductive history when it was known. The most frequent number of corpora lutea was 20, the average 19·6. Nineteen pigs pregnant for the first time (gilts) had an average of 13·6 corpora lutea and 9·8 embryos; 83 in their second or subsequent pregnancies (sows) averaged 19·25 corpora lutea and 11·9 embryos. The average number of corpora lutea (ovulations) rose sharply after the first litter, continued to rise slightly until after the fourth litter, and rose again after the fifth. The initial rise and subsequent upward trend for several litters is similar to what has been recorded elsewhere for the litter size at birth, but the increasing number of ovulations in later life is in contrast with the falling off which has been observed in the size of the litter at birth. If both occur in the same population, as seems likely, there must be a substantial increase in embryonic mortality in the later litters. The percentage of ova lost between ovulation and the time of observation was greater in parous than in nulliparous animals, but the difference was found to be attributable to the greater initial size of litters in sows, large litters being found to lose proportionately more ova than small ones. Five of 19 gilts and 4 of 83 sows showed no loss of ova. At least 40 per cent, of all ova ovulated are lost before parturition. About 85 per cent, of the loss is incurred in the first half of gestation, and something like three-quarters of it is incurred before the 25th day of pregnancy. It is suggested that most of the embryonic loss probably occurs at or about the time of implantation between the 10th and 20th day. Even in the case of the largest litters there is no evidence of heavy loss in late stages of pregnancy that could be attributed to the sow’s inability to accommodate or nourish the foetuses.
The Incorporation of Labelled Amino-acids into Amphibian Embryos
Authors: Waddington C. H. , Sirlin J. L. 
Published: April 2021

ABSTRACT
The rate of incorporation of glycine-l-C14 into the tissues of X enopus tailbud embryos was estimated by counting grains in autoradiographs. The tissues differed significantly, the order of activity being epidermis &gt; somitic mesoderm &gt; neural tube &gt; notochord &gt; endoderm. Less precise data indicated that the incorporation both of glycine-l-C14 and methionine-S35 is more rapid into the nuclei than the cytoplasm, and that there may be some differential accumulation also in the cell membranes. The rate of accumulation of glycine-2-C14 in acid- and acetone-insoluble material, estimated by the Geiger counter, is reduced in the presence of the amino-acid analogue p-fluoro-phenyl-alanine. This effect is counteracted by L-phenyl-alanine.
Teratological studies with sulphonamides and their implications
Authors: Landauer Walter , Wakasugi Noboru 
Published: April 2021

ABSTRACTIt is one of the principal aims of teratological research to trace the manner in which particular chemical compounds give rise to abnormal phenotypes by interfering with well-defined metabolic events. Problems that seemed to lend themselves to investigations of this nature arose with the discovery that malformations can be produced by sulphonamides, which in clinical practice are or have been used as inhibitors of carbonic anhydrase and the activity of which was considered to be quite specific in that respect. We had earlier reported on the effects which one such compound has on developing chicken embryos and shall now describe results obtained with three further sulphonamides. We shall then attempt to discuss the meaning of these and related data in terms of general teratological problems.
Studies of the cleavage in the frog egg: II. On determination of the position of the furrow
Authors: Kubota T. 
Published: April 2021

ABSTRACT
Tn sea-urchin eggs, once karyokinesis reaches metaphase or anaphase, the cleavage furrow can be formed even if the mitotic apparatus is destroyed (Swann & Mitchison, 1953) or removed (Hiramoto, 1956). A similar result was obtained in frog eggs (Kubota, 1966). In amphibian eggs a much longer time is available for performing experiments than in sea urchins as the furrow first appears at the animal pole and slowly travels toward the vegetal pole. Taking advantage of this situation, Waddington (1952) and Dan & Kuno-Kojima (1963) performed various kinds of operations to elucidate the roles of the egg cortex and the inner cytoplasm in furrow formation, and Selman & Waddington (1955) also made cytological observations of the process.
The induction of hair follicle formation in the adult hooded rat by vibrissa dermal papillae
Authors: Oliver R. F. 
Published: April 2021

ABSTRACT
Hair follicles are essentially composed of two tissues. The inner epidermal component, which gives rise to, among other products, the keratinized hair shaft, is confluent with the surface epidermis and is ensheathed by the dermal component which is confluent with the pars papillaris of the dermis.
Viability and growth of mouse embryos after in vitro culture and fusion
Authors: Bowman Patricia , McLaren Anne 
Published: April 2021

ABSTRACT
About 80 % of 8-cell mouse eggs developed to the blastocyst stage in culture, whether the zona pellucida was left intact, or removed with pronase (pre-incubated and dialysed) and the eggs then cultured singly or as fused pairs. When pronase was used without prior incubation and dialysis, the success rate was reduced to 50 %.
After transfer to uterine foster-mothers, 20–30 % of apparently normal blastocysts cultured with or without the zona, singly or fused, developed into live foetuses, compared with over 50 % of control blastocysts taken directly from the uterus. Some of the excess mortality of cultured embryos took place before implantation and some soon after.
The foetuses derived from cultured blastocysts averaged 0·1g lighter than those derived from control uterine blastocysts similarly transferred. No differences in the weights of the placentae were observed. Foetal and placental weights were unaffected by whether the eggs had been cultured singly or fused, implying that growth regulation of fused embryos is complete by the 17th day of gestation.
The longer the eggs were maintained in culture, the lower was their viability after transfer, and the lighter were the foetuses derived from them.
Tissue degeneration: an electron microscopic study of the pronephros of Rana temporaria
Authors: Fox H. 
Published: April 2021

ABSTRACT
The structure of the non-degenerate and degenerating pronephros, of larval Rana temporaria, at different stages of the metamorphic cycle, was examined by electron microscopy.
Extra-renal cellular components in the circulation were likewise investigated, and particular consideration was given to their relationships with the pronephric tubules whose regression would seem to be bound up with them.
The activity of lysosomes in pronephric tubule degeneration suggests that they are an important component of the degeneration process, which probably embraces autolysis and phagocytosis.
Tissue interactions in embryonic mouse tooth germs: II. The inductive role of the dental papilla
Authors: Kollar Edward J. , Baird Grace R. 
Published: April 2021

ABSTRACT
The response of embryonic mouse dental epithelium and mesoderm to tissues of ectopic origin was examined. Isolated molar or incisor mesoderm was confronted with epithelium isolated from the plantar surface of the embryonic mouse foot plate or from the snout.
Harmoniously structured teeth were formed from the foot epithelium and incisor or molar mesoderm. These data are interpreted as an unequivocal demonstration of the inductive role of the dental mesenchyme.
Teeth were absent in confrontations of dental mesenchyme and snout epithelium. The presence of hair follicles in these explants is described and discussed with reference to other integumental epithelio-mesenchymal interactions.
Dental epithelium forms keratinizing surface-like epithelium and invading bands of epithelium in association with foot mesoderm; definitive structures are not formed.
On the other hand, when incisor or molar epithelium is associated with snout mesoderm, hair follicles are seen in addition to keratinizing surface-like epithelial configurations.
The roles of the epithelial and mesenchymal tissues and the nature of epithelio-mesenchymal interactions in the developing mouse integument are discussed.