bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical stresses and morphological patterns in amphibian embryos
Authors: Beloussov L. V. , Dorfman J. G. , Cherdantzev V. G. 
Published: April 2021

ABSTRACT
Embryos of Rana temporaria have been dissected and shape alterations of different parts of the embryo, taking place within 1 h of separation, have been studied. Two categories of deformation have been revealed. The first category comprises those deformations which take place immediately after separation. They are insensitive to cooling, cyanide and Cytochalasin B treatment. These deformations, which consist of a shortening of initially elongated cells, are considered to be the passive relaxations of previously established elastic tensile stresses. Deformations of the second category proceed more slowly. They are inhibited by cooling, cyanide and Cytochalasin B treatment, are accompanied by elongation and migration of cells and occasionally lead to rather complex morphodifferentiations of isolated fragments. These processes are considered to be the result of the active work of intracellular contractile systems, either pre-existing or induced de novo. By analysing the arrangement of the passive deformations we have constructed maps of mechanical stresses in embryos from late blastula up to the early tail-bud stage. At several embryonic stages drastic transformations of the stress pattern occur, these transformations being separated by periods during which the pattern of stress distribution remains topologically constant. A correlation between the arrangement of stress lines and the presumptive morphological pattern of the embryo is pointed out. Some possible relations between tensile tissue stresses and active mechanochemical processes are discussed.
Pattern formation in early developmental stages of amphibian embryos
Authors: Tiedemann H. 
Published: April 2021

ABSTRACT
The causal morphological analysis of the determination and differentiation processes in early developmental stages has been successfully carried out, especially in insects, sea urchins, amphibians and mammals. In all these investigations the final outcome of isolation and transplantation experiments has been evaluated by histological analysis of the differentiated tissues. In such experiments the term determination, which has been used in several ways, can be defined as follows: A certain region of a cleaving egg or an embryo is said to be determined if after isolation it forms the same tissues as in the intact embryo.
Clonal development of the retinal epithelium in mouse chimaeras and X-inactivation mosaics
Authors: West J. D. 
Published: April 2021

ABSTRACT
A comparative study of coherent clones in the retinal epithelium is presented for mouse aggregation chimaeras and X-inactivation mosaics. There is a basic similarity in the number of coherent clones and the pattern of clonal development between mosaics and chimaeras. While this similarity is compatible with the difference in mean patch size reported by other authors this is at variance with some interpretations of previous work and suggests that no conclusive evidence on the timing of X-inactivation is provided by comparisons of patch sizes between chimaeras and mosaics.
The present clonal analysis also suggests that at days post coitum the cells in the retinal epithelium are distributed almost randomly while, in the adult, the cells are grouped into small coherent clones, which comprise an average of five or six nuclei. However, these data could also be explained by larger, irregular coherent clones.
Etude chez les oiseaux de 1’influence du mésenchyme néphrogène sur le canal de Wolff à l’aide d’associations hétérospécifiques
Authors: Martin C. 
Published: April 2021

ABSTRACT
A study of the influence of mesonephric mesenchyme on the Wolffian duct in birds using heterospecific associations
An in ovo experimental study of mesonephric mesenchyme-Wolffian duct relationships has been performed with special reference to the progression and the ramification of the Wolffian duct in quail-chick and quail-duck associations. Two methods are used to obtain chimaeric mesonephros in ovo. First, a piece of a quail blastoderm containing the tip of the Wolffian duct is grafted on to a chick blastoderm behind an obstacle. The obstacle is a small piece of shell membrane and it prevents the migration of the chick Wolffian duct. Second, chimaeric blastoderms are made by associating in ovo halves of quail blastoderm (anterior or posterior) with the complementary halves of chick or of duck blastoderms. The experiments are performed in such a way that the Wolffian ducts are in the anterior part and the nephrogenic blastemas in the posterior part. In those experiments in which a Wolffian duct of one species is associated with the mesonephric mesenchyme of another, the Wolffian duct grows backward above the intermediate cell mass without any participation of the heterospecific cells. In quail-duck associations, the Wolffian duct reaches the cloaca and buds off the ureteric diverticulum later than it does in quail-chick associations.
The mesonephric mesenchymal area induces the Wolffian duct to branch out into a collecing system. Quail Wolffian duct gives rise to more numerous collecting tubules than does the chick Wolffian duct. In quail mesenchyme-chick Wolffian duct mesonephros, the collecting tubules are not always present and often the tubules derived from the mesenchyme invade the wall of the Wolffian duct. In all cases only very short collecting tubules are derived from the Wolffian duct.
Immunological studies on the incorporation of radioactive leucine into sea urchin embryonic proteins: extractability and turn-over of newly synthesized proteins
Authors: Westin Monica 
Published: April 2021

ABSTRACT
This study was undertaken in order to investigate the turn-over of newly synthesized sea urchin embryonic proteins, the distribution of these proteins in the cell and their changes in solubility with time. Refined immunological methods providing unique possibilities for studies of individual proteins were utilized. The proteins were obtained in two soluble fractions: a concentrate of proteins from the cytosol was obtained by homogenization in a hypotonic medium and another fraction constituting membrane-associated proteins was solubilized by detergent treatment of the residual pellet; 75 °/0 of the total protein content in early and 60 % in later developmental stages was thus solubilized. The proteins solubilized by these mild methods retained their antigenicity and could be analyzed by immunodiffusion methods.
The fate of newly synthesized embryonic proteins was studied by incorporation of a radioactive amino acid using two different incubation procedures. The results of these studies indicated that newly synthesized proteins changed their solubility properties with time. Proteins were thus transfered from the soluble to the insoluble fraction. The findings that more proteins became insoluble during development mentioned above also supports such an interpretation.
The synthesis of individual proteins was studied by immunodiffusion and autoradiography. Most of the antigens in the two soluble fractions were identical. Experiments with absorbed antisera revealed that only two to four antigens were present exclusively in one of the two soluble fractions. Three groups of antigens differing in regard to their metabolic activities were distinguished. Some antigens were labeled after both procedures without substantially increasing in concentration during development. Thus, their labeling was probably sustained by turn-over. Other antigens were labeled only after one of the two incubation procedures indicating large variations in regard to synthesizing rates of individual proteins.
Aspects quantitatifs du peuplement des gonades par les cellules germinales chez l’embryon de Caille (Coturnix coturnix japonica)
Authors: Didier Eliane , Fargeix Noël 
Published: April 2021

ABSTRACT
Quantitative aspects of the colonization of the gonads by germ cells in the quail embryo (Coturnix coturnix japonica)
A quantitative analysis made on quail embryos coming from 13 isolated parent-couples reveals some significative variations of a genetic origin, between some of the offspring studied : the differences observed concern both the quantitative importance of the colonization of gonads by germ cells and the asymmetrical distribution of PGCs (primordial germ cells) between the two genital ridges.
The chronological study of the colonization in the quail shows, as in both the duck and the chick, two periods of rapid and regular increase of the number of gonadic PGC, at stages from 13 to 18 and from 24 to 30 of Hamburger & Hamilton.
The distribution of germ cells between the two genital ridges is, at the beginning of the colonization, not very asymmetrical. Between stages 18 and 24 the asymmetry increases and remains stable so that the mean value of D % (percentage of the number of PGC contained in the right gonad) from that moment on is equal to 29 ·34 %. This value is specific for the quail embryo.
The Distribution of Placental Scars of First and Second Pregnancies in the Rat
Authors: Momberg Harold , Conaway Clinton 
Published: April 2021

ABSTRACT
In albino rats placental scars of a second pregnancy partially or completely overlapped 32 of 312 old placental scars from a previous pregnancy in 61 uterine horns. Gross recognition of the superposed scars was often impossible. Microscopic recognition of the superposed sites was possible under the conditions of the experiment. The major changes in the distribution pattern of second pregnancy scars as compared to those of the first pregnancy are (a) the intervals between second pregnancy scars are more variable; (b) the most posterior new scar tends to be further from the cervix than the last first pregnancy scar; (c) the most anterior new scar tends to be closer to the oviduct than the corresponding first pregnancy scar; and (d) although the oviducal scar-free segment is longer than the cervical scar-free segment in both pregnancies, the difference is less in the second pregnancy.
Cell division, cell elongation and the co-ordination of crystallin gene expression during lens morphogenesis in the rat
Authors: McAvoy J. W. 
Published: April 2021

ABSTRACT
A quantitative analysis of cell division and cell elongation was carried out during lens morphogenesis in the rat. At 13 days of development elongating cells in the posterior part of the lens vesicle (presumptive fibre cells) have a lower mitotic activity than cells in the anterior vesicle. By 14 days these elongating cells do not divide. Thus at 14 days of development the lens can be separated into two compartments; a proliferation compartment in the anterior lens and an elongation compartment in the posterior lens.
The three main groups of lens-specific proteins, α- β- and γ-crystallins, were localized by immunofluorescence. Alpha-crystallin is the first crystallin to be detected and is localized in some lens pit cells at 12 days of development. By 14 days all lens cells contain α-crystallin. Beta- and γ-crystallins are detected later at days and are localized in some cells situated primarily in the posterior part of the lens vesicle. At later stages of development these crystallins are restricted to cells of the elongation compartment, i.e. presumptive fibre and fibre cells. Possible mechanisms that govern the temporal and spatial distribution of crystal-lins are discussed
On the Regulation of Bilateral Symmetry in Plutei with Exchanged Meridional Halves and in Giant Plutei
Authors: Hörstadius Sven 
Published: April 2021

ABSTRACT
After exchange of meridional halves between two eggs typical plutei were obtained in nearly all pairs (Text-fig. 2).
Two 32-cell stages were split along a meridian, flattened, and fused (Text-fig. 3). There resulted typical giant plutei (Text-fig. 4); plutei with a supernumerary rod at the dorsal pole (Text-fig. 6); plutei with a supernumerary dorsal strip of ciliated band (Text-fig. 7D); plutei with both supernumerary rod and a ciliated band in the dorsal part (Text-figs. 7 A-C, 8A); joined twins (Text-fig. 9); and plutei with two ventral sides (Text-figs. 8B, 10).
The results are interpreted in the light of the hypothesis that there is a dominating presumptive ventral centre capable of subduing the tendencies toward formation of a ventral side which are located in other parts of the egg.
The Effect of Maternal Immunization against Organ Tissues on Embryonic Differentiation in the Mouse
Authors: Gluecksohn-Waelsch Salome 
Published: April 2021

ABSTRACT
The response of embryonic differentiation to injection of organ-tissue-emulsion into female mice prior to conception was studied. The injection of brain-emulsion into females of the DBA/I strain was followed by abnormalities of the developing nervous system in 8–9 per cent, of subsequently conceived embryos. Such abnormalities consisted of suppression of nervous-tissue differentiation, microcephaly, and abnormalities of closure of neural folds. As controls, female sibs of brain-injected mothers were injected with a heart-emulsion. No nervous-system abnormalities were observed in the subsequently conceived embryos of these mothers. The possible mechanism of the effect described here is discussed. It seems most likely that maternal antibodies are responsible for the nervous-system abnormalities of the embryos. Problems of the transmission of these antibodies to the embryo and of the mechanism of their effect on embryonic differentiation are discussed.
‘Matted’, a New Hair-mutant in the House-mouse: Genetics and Morphology
Authors: Searle A. G. , Spearman R. I. 
Published: April 2021

ABSTRACT
Three types of hereditary hairlessness are known in the house-mouse. With Naked (Fraser, 1946) and Alopecia (Dickie, 1955), baldness results from the breaking of hairs; with hairless and its allele rhino, from the shedding of entire hairs (Fraser, 1946). The crinkled (Falconer, Fraser, & King, 1951) and ragged (Carter & Phillips, 1954) genes, however, lead to a complete absence of certain hair-types, due to delayed or imperfect follicle development (agenesis). In rough (Falconer & Snell, 1952) the fur is greasy and looks unkempt but no baldness occurs.
The Pluripotency of the Pharyngeal Primordium in Urodelan Neurulæ
Authors: Okada Tokindo S. 
Published: April 2021

ABSTRACT
Explantation experiments of pharyngeal endoderm, alone or together with various ecto- or endomesodermal materials, within epidermal envelopes were performed, using the neurulae of Trituras pyrrhogaster and Hynobius nebulosus as materials. The piece of endoderm, when explanted alone within the envelope, did not differentiate into any definable structure, persisting as an amorphous mass of undifferentiated endodermal cells, even after a prolonged cultivation as long as 30-40 days. Typically differentiated endodermal structures were found only in the explants in which the endodermal piece was combined with the ecto- or endomesodermal materials. When the pharyngeal primordium was explanted together with the material of either neural fold or archenteric roof, irrespective of the regions from which these materials were removed, the production of pharynx always occurred. When combined with lateral plate mesoderm, the pharyngeal primordium generally developed into an intestinal vesicle. Oesophagus, stomach, liver, or pancreas was occasionally found in these combination explants. Some xenoplastic explantations, in which the pharyngeal rudiment of Hynobius was combined with ecto- or endomesodermal material from the neurula of Rana japónica, were also carried out. Hynobius endoderm showed differentiation into pharynx when combined with anterior neural material of Rana, but it produced an intestinal vesicle when lateral plate of Rana was included. In all the available specimens of the present experiments it was a rule that pharyngeal differentiation occurred within free mesenchyme, while intestinal structures were found to be surrounded by endothelial tissue. On the basis of above data it is concluded that the pharyngeal primordium is still pluripotent in the early neurula stage, and its future fate may be varied, depending mainly upon the sort of connective tissue which is present around it.
Evidence of prostaglandin involvement in blastocyst implantation
Authors: Holmes P. V. , Gordashko B. J. 
Published: April 2021

ABSTRACT
Delayed-implantation mice were used to test for local implantation induction effects of prostaglandins E2 and F2α. Evidence of implantation was gathered by microdissection of implantation sites and by scanning electron microscopy. Indomethacin was tested for the ability to interfere with the mechanisms of estrogen-induced, normal implantation. Both prostaglandins appear to have significant effect inducing implantation when applied locally in the uterine lumen, PGE2 being more effective than PGF2α. The indomethacin clearly has a blocking effect on normal implantation. However, indomethacin appears only partially able to prevent the morphological changes indicative of the trophoblast cell transformation.
Repair of Wounds of the Mucosa in the Rectum of the Cat
Authors: McMinn R. M. H. , Johnson F. R. 
Published: April 2021

ABSTRACT
Wound healing in the rectum of the cat has been studied following the creation of artificial ulcers by removing small areas of mucosa. During the first few days of the repair process epithelial cells migrated from the wound margins over the floor of the ulcer, in which granulation tissue began to accumulate. Mitotic figures were occasionally found in migrating epithelium. The striated borders of normal epithelial cells gave a strong reaction for alkaline phosphatase and were PAS-positive. These reactions were not present during migration in the early stages of repair. Glycogen granules, not normally detectable histochemically in this epithelium, were found in migrating cells at the end of the first week. The pattern of healing at later stages showed considerable variation, according to the amount of granulation tissue formed. Where the amount of such tissue was relatively small, increasing epithelialization occurred, with evidence of new crypt formation; where granulation tissue was exuberant, the margins of the original lesion may have been drawn together by the contraction of maturing connective tissue. Alkaline phosphatase was absent from the developing and maturing connective tissue.
Cell surface properties of amphibian embryonic cells
Authors: Matsuda Motoko 
Published: April 2021

ABSTRACT
Gastrula and neurula embryos of Cynopspyrrhogaster were dissociated into cell suspensions with ethylenediaminetetraacetic acid (EDTA), trypsin, and alkali solution. The cells were cultured in Niu-Twitty’s balanced salt solution and their aggregates were examined histologically. The results indicated that the capacity of amphibian embryonic cells for aggregate formation, sorting out, and notochord differentiation was not suppressed by EDTA and alkali treatments. Trypsin treatment, however, virtually suppressed the cell’s capacity for aggregate formation. When aggregate formation resulted from trypsin-dissociated cells, the aggregates showed the sorting out and no differentiation of notochord.
Differential localization of [35S]sulfate within ectodermal basement membrane in relation to initiation of chick limb buds
Authors: Lunt Dennis M. , Seegmiller Robert E. 
Published: April 2021

ABSTRACT
This study examined the possible developmental relationship between differential amounts of glycosaminoglycans (GAG) within the ectodermal basement membrane and initiation of limb outgrowth. Chick embryos at stages 11-20 were labeled in ovo with 35SO4 and processed for autoradiography. After exposure to sulfate for 15 min, the label was localized within the surface ectoderm whereas after 3 h the label was localized within the subjacent basement membrane. The label was sensitive to chondroitinase ABC. These experiments suggest that the labeled material was ectodermally derived chondroitin sulfate. At all stages examined, intense labeling of the basement membrane was associated with relatively undifferentiated, mitotically active tissue, e.g. limb-bud mesoderm. The labeling was less intense in regions with decreased mitotic activity, e.g. the flank. Thus, the labeling pattern of the basement membrane correlated with differential mitotic rates presumed to be associated with limb outgrowth. These observations support the hypothesis that communication between tissues of different origin resulting in altered mitotic behavior of limb and flank mesenchymal cells is facilitated by the ectodermal basement membrane.
The time required for positional signalling in the chick wing bud
Authors: Smith J. C. 
Published: April 2021

ABSTRACT
An estimate of the time required for positional signalling in the chick wing bud was obtained by grafting irradiated quail polarizing regions to host wing buds and removing them at various times. Such polarizing regions must be present for at least 15 h to induce additional structures in the host wings. This result is discussed in terms of a diffusible morphogen model.
Distribution of microvilli on dissociated blastomeres from mouse embryos: evidence for surface polarization at compaction
Authors: Reeve W. J. D. , Ziomek C. A. 
Published: April 2021

ABSTRACT
Cells of mouse embryos develop a polarization of microvillous distribution at compaction. Cells of the 4-cell embryo show a uniform pattern of fluorescent-ligand binding and an even distribution of microvilli. Each cell of the early 8-cell embryo has a uniform distribution both of microvilli and of fluorescent ligand. During the 8-cell stage, there is a progressive increase in the incidence of cells which show microvilli restricted to a region normally on the exposed surface of the embryo. When late 8-cell embryos were disaggregated to single cells, and these sorted by pattern of fluorescent-ligand binding, each of the four patterns of staining related consistently to a characteristic distribution of microvilli as viewed by scanning electron microscopy. The 16-cell embryo possessed an inside population of uniformly labelled cells with a sparse microvillous distribution, and an outside population of cells, each of which had a microvillous pole.
Naturally occurring abnormalities (Bruchdreifachbildungen) in the chelae of three species of Crustacea (Decapoda) and a possible explanation
Authors: Shelton P. M. J. , Truby P. R. , Shelton R. G. J. 
Published: April 2021

ABSTRACT
Naturally occurring abnormalities (Bruchdreifachbildungen) in decapod crustacean appendages are described. They are similar to the range of structures experimentally produced by cutting notches in the sides of insect legs (Bohn, 1965). It is argued that they result from failure of wounds to heal. Regeneration from a free surface along the proximodistal axis is always in a distal direction. Surfaces regenerating circumferentially can regenerate in either direction around the circumference. Regeneration will proceed until the two surfaces of the wound meet. Then, where the two surfaces on either side are non-congruent, intervening tissues will be intercalated. This explanation accounts for the range of structures observed after notching experiments (Bohn, 1965) and seen in crustacean Bruchdreifachbildungen. The explanation says that regeneration will occur wherever wounds fail to heal. This avoids the difficulties of the complete circle rule (French, Bryant & Bryant, 1976) and explains why appendages with mirror-image symmetry are often capable of regeneration.