bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of mouse−bank vole interspecific chimaeric embryos
Authors: Mystkowska Ewa T. 
Published: April 2021

ABSTRACT
One bank vole (Clethrionomys glareolus) embryo and two mouse embryos were combined at the 8-to 16-blastomere stage and cultured in vitro for 33–47 h. In 66% of cases single regular blastocysts were formed. The chimaeric composition of blastocysts was confirmed karyologically. Out of the 222 blastocysts transplanted to 49 pseudopregnant mouse recipients, a total of 52 implantations were found in 20 recipients. Among the 52 implantations, 14 contained embryos and the remaining were resorptions. The majority of embryos were abnormal and fell into two categories : (1) groups of cells surrounded by Reichert’s membrane and lying freely in a cavity filled with giant trophoblastic cells, (2) small and retarded eggcylinders usually composed of endoderm and ectoderm only, and containing a proamniotic cavity. The ectoplacental cone of these embryos was poorly developed or lacking altogether.
Two normal-looking embryos were recovered on the 9th and 10th day (4-somite and ca. 12-somite stage). Chimaerism of the younger embryo was confirmed karyologically. No evidence of chimaerism was available in the case of older embryo which was examined histologically. Thirteen implantations examined between 11th and 17th day contained only resorptions. It is suggested that the main cause of the heavy mortality of chimaeric embryos is the profound difference in the course of embryogenesis of these two species immediately following implantation.
Skull growth in achondroplasic (cn) mice ; a craniometric study
Authors: Jolly Rosemary J. , Moore W. J. 
Published: April 2021

ABSTRACT
Skull morphology in achondroplasic (cn/cn) mice was compared with that of normal siblings in order to determine the effects of this chondrodystrophy on skull growth, particular attention being given to dimensions reflecting growth at the synchondroses of the cranial base, the nasal septal cartilage and the condylar cartilage of the mandible. The central section of the cranial base (basicranial axis) was reduced by 25 %, the length of the viscerocranium by 18 % and the length of the condylar process by 11 %. The evidence indicates that these reductions are due to diminished growth at respectively the spheno-occipital and midsphenoidal synchondroses, the nasal septal cartilage and the condylar cartilage. The relative sizes of the reductions in cranial base, viscerocranium and condylar process suggest that the growth of synchondrotic and septal cartilages is diminished to a greater extent than that of condylar cartilage. This finding is in agreement with the observations that condylar cartilage, unlike synchondrotic and septal cartilage, grows by surface apposition and that the principal defect in enjen mice is a disturbance of interstitial cartilaginous growth. The posterior extension of the basicranial axis of the cn/cn mice was reduced by 14 % and the anterior extension by 2 %. The width of the cranial base was decreased by 9 % and the angle between the basicranial axis and its anterior extension was decreased by 3 %. The length of the neurocranium was reduced by 19 % in the cn/cn animals while the volume of the endocranial cavity was diminished by only 18 %. The latter reduction is less than would be expected from the cube relationship between volume and linear dimensions but is readily accounted for by the lack of reduction in the height or width of the neurocranium, the slight flattening of the cranial base and the doming of the neurocranial vault.
Neurulation et migration nucléaire intercinétique chez des embryons de poulet
Authors: Messier Paul-Emil , Auclair C. 
Published: April 2021

ABSTRACT

Neurulation and interkinetic nuclear migration in the chick embryo
Neurulation and interkinetic nuclear migration were studied in cells of the forming neural tube of chick embryos submitted to a variety of treatments. Our results show that cytochalasin B (5 μg/ml) does not protect microtubules against disruption occurring after 3h at 2 °C nor does it prevent their repolymerization once they are cold-disrupted. However, db-cAMP protects microtubules against such cold disruption. We indicate that the inhibitory effect of cytochalasin B on interkinetic nuclear migration cannot be ascribed to an effect on microtubules.
Les premiers stades de la formation de I’ébauche de nageoire pelvienne de Truite(Salmo farioetSalmo gairdneri): III—Capacités de régulation
Authors: Geraudie Jacqueline 
Published: April 2021

ABSTRACTThe first stages of genesis of the pelvic fin aniage in the trout (Salmo fario and Salmo gairdneri). III. Regulation capacitiesIn S. fario and S. gairdneri, microsurgical excisions of parts of pelvic fin-buds showed the important regulation capacities of the fin anlage. At the stages studied, a complete unilateral excision is generally not followed by a regulatory response. On the contrary, a unilateral partial excision performed at the same developmental stages is followed by a regulatory response. Bilateral excisions of the fin-buds, performed at earlier developmental stages than unilateral ones (and at a slightly different level for mesoderm) are followed by regulation.The results are discussed in this article. It appears that the mesoderm is a determining factor in the development of the fin-buds; the epidermis does not appear influential -at least in the first stages of regulation.We noticed a higher percentage of regulation in S. gairdneri than in S. fario’, the results obtained are analysed with regard to histoenzymological data.
The relationship between erythropoietin-dependent cellular differentiation and colony-forming ability in prenatal haemopoietic tissues
Authors: Cole R. J. , Regan T. , White S. L. , Cheek E. M. 
Published: April 2021

ABSTRACT
Levels of haem synthesis achieved by foetal liver erythroblasts responding to erythropoietin in vitro are similar in dissociated cell cultures and in cultures of organized tissues. Erythroid colony-forming cells reach maximum numbers on the sixteenth day of gestation. Their presence in foetal liver is associated with the period of most rapid production of erythrocytes, and with in vitro sensitivity to erythropoietin measured as enhanced haem synthesis. It is concluded that at least a proportion of erythroid colony-forming cells in the foetal liver are dependent on erythropoietin in situ and that these cells are separated from the earliest recognizable pro-erythroblast by 1 –2 cell divisions. Populations of granulocyte-macrophage colony-forming cells change independently of erythroid colony-forming cell numbers.
Effets de la vinblastine sur la morphogenèse du pied de l’embryon de poulet. Aspects histologiques
Authors: Kieny Madeleine 
Published: April 2021

ABSTRACT
Vinblastine was injected into the amniotic cavity of 6·5-day-old chick embryos. Acropods were fixed 0,2, 3·5, 6,12,18,24, 36 and 48 h after treatment and 1 μm thick sections were prepared from the region of digit IV and interdigit III-IV. Cell counts were mainly performed in a distal zone (see Fig. 2) comprising the ectodermal apical ridge, the distal non-ridge ectoderm and the distal underlying mesoderm.
In control non-treated embryos, the mitotic index does not vary significantly in either of the three tissues between 6·5 and 8 days except for a temporary increase at 7 days in the mesoderm. In treated embryos, the mitotic index increases rapidly in the non-ridge ectoderm and in the mesoderm to a maximum of 44 and 35% respectively, 18 h after injection, after which it decreases almost as rapidly to a level of about 15% 36 h after injection. In the apical ridge ectoderm, the increase of the mitotic index is much slower and reaches its maximum value of about 30% only 36 h after injection. This suggests that most of the cells participating in the AER do not arise within the ridge but are generated in more proximal zones of the ectoderm.
Due to mitotic arrest, the number of mesodermal cells is thus decreased to approximately half the normal value within 36 h and the AER disappears earlier than normal. These alterations are the direct cause of the hypophalangy observed at the morphological level.
A particular distribution pattern of arrested mitoses is revealed: in the digital as well as in the interdigital mesoderm, the majority of blocked metaphases is located in a dorsal and a ventral wing-shaped subectodermal 500 μm long area whose thickness is maximal at the level of the marginal sinus and gradually decreases in proximal direction. In the central-part of the mesoderm blocked mitoses are relatively rare.
The present results are discussed in view of the recent literature on the morphogenetic processes of limb development.
In vitrostudy of chorionic and ectoplacental trophoblast differentiation in the mouse
Authors: Hernandez-Verdun Danièle , Legrand Chantal 
Published: April 2021

ABSTRACTMouse chorioallantoic pre-placental structures alone or in association with the embryo were explanted during the 9th day of gestation (7-somite stage) and cultured in a static medium for 24 to 48 h. From the subsequent morphological study of trophoblast differentiation, using both light and electron microscopy, we draw the following conclusions.The allantoic mesoderm cells migrate inside the trophoblastic population but they do not differentiate a capillary network and trophoblast cells phagocytose the existing foetal erythrocytes. In the absence of allantoic mesoderm, chorionic trophoblast cells remain undifferentiated. The development of the chorionic trophoblast is modified in that chorionic trophoblast cells fail to establish close junctions with ectoplacental trophoblast, and some chorionic cells initiate the formation of multinucleated syncytia. The genesis of these syncytia is discussed.
The effect of ablation of the olfactory pits on the development of the habenular nuclei inRana pipiens
Authors: Norris Byron K. , Eichler Victor B. 
Published: April 2021

ABSTRACTThe habenular nuclei in the diencephalon of the frog, Rana pipiens, are asymmetrical structures: two discrete cell groups develop on the left side (as medial and lateral nuclei), while a single nucleus is formed on the right side. Experimental animals were subjected to bilateral removal of the olfactory pits at an early embryonic stage, and were maintained with normal control animals until metamorphosis was complete. The length, relative volume and cell number for each of the three nuclei were determined in the control and experimental animals at regular intervals during larval development. In the control animals, the left medial nucleus developed similarly to the right nucleus spatially and temporally; however, the left lateral nucleus was significantly different in its development in the three parameters measured. In the experimental animals the left medial and the right habenular nuclei were alone affected by the removal of the olfactory pits. The results provide experimental evidence that the right and left medial, but not the left lateral, habenular nuclei are centers receiving afferent olfactory fibers.
Studies on the gastrulation of amphibian embryos: Light and electron microscopic observation of a urodele Cynops pyrrhogaster
Authors: Nakatsuj1 Norio 
Published: April 2021

ABSTRACT
The course of gastrulation in embryos of a urodele, Cynops pyrrhogaster, was studied with 1 μm Epon sections and transmission and scanning electron microscopy. During the initial period of gastrulation, the bottle cells and a groove are formed in the dorsal part. The outer ends of the bottle cells have many microvilli, an electron-dense layer and many small vesicles. Microtubules are present parallel to the long axis of the bottle cells, and a yolk-platelet-free region is observed at the inner end. Thereafter, the archenteric roof makes contact with the inner surface of the blastocoelic wall. Cells of the archenteric roof form lobopodia, filopodia and lamellipodia. These cells make many focal contacts, having gaps of less than 20 nm, with the blastocoelic wall. Invaginating mesodermal cells of the lateral and ventral parts also form pseudopodia, and are in contact with the blastocoelic wall. Some of these cells appear to flatten against the wall. These observations suggest that, after the bottle cells and the blastoporal groove are formed, the invaginating cells actively migrate along the inner surface of the blastocoelic wall, and that these locomotive forces have an important role in the morphogenetic movements during gastrulation.
Embryonic development of tetraploid mice during the second half of gestation
Authors: Snow M. H. L. 
Published: April 2021

ABSTRACTA small proportion (about 17%) of experimentally produced tetraploid blastocysts are capable of postimplantation development in the randomly bred Q strain of mice. Four newborn mice, three of which were confirmed as tetraploid, were produced but all were eaten by their mother within a few hours of birth. Studies on the embryonic development of tetraploid mice reveal a variety of developmental abnormalities, especially during the later stages of gestation. At and days, tetraploid embryos weigh significantly Jess than corresponding stage diploids, especially so if litter size is taken into account. Histologically, aberrations are found in many different tissues with a clear hierarchy of susceptibility shown among the organs. For instance, yolk-sac-derived blood, and gonads, are invariably affected and the anterior end of the neural tube also seems to be particularly at risk. Possible explanations for the aberrant development are discussed and it is concluded that strictly genetic reasons can be ruled out and that physiological difficulties imposed by the increased size of tetraploid cells and/or problems produced by lack of cell numbers are instrumental in causing abnormal development. Using weight as a guide it is estimated that tetraploid embryos at and days gestation contain about one-quarter as many cells as similar stage diploids.
Morphogenesis of intestinal villi: II. Mechanism of formation of previllous ridges
Authors: Burgess David R. 
Published: April 2021

ABSTRACT
Villi lining the avian intestine originate from longitudinal folds (previllous ridges) running the length of the embryonic intestine. The morphogenetic events that occur in the epithelium during initial ridge formation in the chick embryo duodenum were examined by light and electron microscopy. The epithelium, in cross-section, undergoes three stages prior to the formation of ridges; termed the circle ( days), the ellipse ( days), and the triangle ( days). At about 9 days of development three ridges form with three more forming one day later. The mechanisms responsible for folding of the epithelium were examined. Microdissection followed by organ culture demonstrated that constriction by the surrounding circular smooth muscle cannot account for folding of the epithelium. Mitotic pressure within the epithelium also cannot account for folding since there is no difference in the number of epithelial cells per cross-section between the ellipse and the triangle stages and the epithelial tube is not restricted from expanding. Active constrictions in groups of epithelial cells, mediated by bands of microfilaments, are thought to cause folding. Bundles of microfilaments are localized in the apical region of all epithelial cells at all stages studied and are localized in the basal region of those cells occupying the crests of the forming ridges. Cytochalasin B-treatment prevented ridge formation and disrupted the bundles of microfilaments.
The immediate postimplantation development of tetraploid mouse blastocysts
Authors: Snow M. H. L. 
Published: April 2021

ABSTRACTThe development during and immediately after the implantation period of 143 tetraploid blastocysts was studied both in vitro and in vivo; 58·7 % in vitro and 38·8 % in vivo were found to exhibit the changes associated with the early implanting blastocyst, i.e. giant cell transformation of the trophoblast and induction of the decidual cell reaction in the uterus. Of these 38·7 % in vitro and 19·4% in vivo showed evidence of inner cell mass function during this time but only two in each system could be claimed as showing normal development. Examination of the developing blastocyst leads to the conclusion that lack of cell numbers in the inner cell mass is the most likely reason for the poor development of tetraploid embryos and suggests that the minimum number of ICM cells required to fulfil its role in embryogenesis is between four and eight.
Leg regeneration in the cockroach,Blatella germanica: II. Regeneration from a non-congruent tibial graft/host junction
Authors: French Vernon 
Published: April 2021

ABSTRACTThe interactions occurring between host and graft leg epidermis at a non-congruent junction were studied in the cockroach, Blatella germanica. Graft and host tibia were cut perpendicular to the proximal-distal axis and two heteropleural combinations were used to reverse separately the two transverse axes of the graft relative to the host. Use of dark and light cuticle colour mutants gave a good indication of the graft or host origin of regenerated structures.Graft/host junctions regenerated segmented structures in various spatial arrangements, always comprising two copies of all structures distal to the level of the junction.It is concluded that the categories - two separate laterals, double lateral, completely and partially autonomous regeneration - reflect two processes.If the graft tarsus is removed, graft and host may not heal together and interact, but form autonomous regenerates lying in mirror-image symmetry separating original graft and host levels. If interaction occurs between graft and host (or their developing autonomous regenerates) two laterals of dual origin are produced, one from each point of transverse axis incongruity. These laterals may secondarily fuse together to form a double structure originating from a point of congruity. The orientation and composition of the component tarsi of the double structure depend on the site of origin and the extent to which the two laterals fuse.It is argued that the four ‘faces’ and two ‘transverse axes’ of the leg are merely descriptive terms. A new model is developed whereby lateral regeneration arises directly from the circumferential organisation of the leg epidermis. Previous work has shown that position is specified continuously around the circumference, and that intercalary regeneration occurs by the shortest route between confronted positions. After reversal of one ‘transverse axis’ the shortest route between confronted graft and host positions is different on the two sides of each of the two points of ‘axis’ incongruity, and at these points the two halves of a complete circumference are formed. These lateral circumferences, like the terminal circumference exposed by amputation, cannot heal over by intercalary regeneration, and this leads to regeneration of distal structures.The model accounts for lateral regeneration after reversal of both ‘transverse axes’ by 180° rotation of a homopleural graft.The possibility is discussed that there may be clonal restrictions on the circumferential positions which the progeny of a cell may occupy.
Morphogenesis of the silkworm egg
Authors: Legay J. M. 
Published: April 2021

ABSTRACTOvarian follicle development, which accompanies morphogenesis of the silkworm egg has three distinct phases: spheric, ellipsoidal and flattened-ellipsoid. Transitions between phases are rapid and form-stability (characterized by length/width ratio) is preserved from the beginning of the ellipsoidal phase. The geometric stability of the follicle-oocyte-ovariole system, the polarity of the egg and the determinism in form changes reveal strikingly coordinated spatial and temporal organization.
Target discrimination in regenerating insect sensory nerve
Authors: Mclean Miriam , Edwards John S. 
Published: April 2021

ABSTRACT
The paired abdominal cerci of the cricket Acheta domesticus are mechanosensory appendages which regenerate readily when amputated during larval life. Their peripherally-located sense cells form axons which project centrally as a purely sensory nerve to the terminal abdominal ganglion.
In an attempt to analyze some of the factors which guide a regenerating sensory nerve to correct central terminations, implants of homologous, supernumerary terminal ganglia were made in cricket larvae and the host cerci amputated. The possibility that implants with multiple nerve stumps might release an attracting substance was considered. Surgical procedures used were (1) implant in posterior abdomen; (2) implant in posterior abdomen, ipsilateral to chronic cereal deprivation; (3) implant in mesothoracic leg socket, adjacent to heterotopically-transplanted regenerated cercus; (4) implant in posterior abdomen, ipsilateral host cereal motor nerve sectioned; (5) implant in posterior abdomen, ipsilateral margin of host terminal ganglion wounded. Results were determined after the adult molt, by con-ventional histology or by cobalt chloride filling of regenerated cereal nerves.
In all procedures except (3) and (4), the regenerated afferent nerve bypassed the implant and terminated in the host terminal ganglion. In (3), the regenerated fibers from cereal grafts bypassed the implant; terminations were not found. In (4), some regenerated cereal axons connected with the implant and the majority terminated in the host ganglion.
It is suggested that regenerating cereal afferents may depend in a facultative way on the cereal motor nerve as a pathway guide but there is as yet no clear evidence for a trophic influence from the central nervous system.
Etude comparative de l’évolution des cellules de planaires d’eau douce Polycelis tenuis (lijima) dans des fragments dissociés en culture in vitro aspects ultrastructuraux, incorporations de leucine et d’uridine tritiée
Authors: Franquinet Raphaël 
Published: April 2021

ABSTRACT
Comparative study of the cells of the freshwater planarian Polycelis tenuis (lijima) using dissociated fragments cultivated in vitro: ultrastructural aspects and incorporation of [3H] leucine and [3H]uridine
Study of planaria cells, which are the result of dissociated fragments cultivated in vitro, allows the evolution of two cell groups to be followed:Differentiated cells, which do not divide, and do not dedifferentiate either, incorporate leucine and uridine at a rate which remains stable for the whole duration of the culture.Undifferentiated cells have a mitotic and incorporation rate of leucine and uridine which varies during the period of culture. After 10 days of culture they demonstrate the characteristics of cells undergoing differentiation.
These results are in agreement with those of other authors who attribute an essential role to undifferentiated cells during the regeneration of the adult planaria.
Role of karyoplasm in the emergence of capacity of egg cytoplasm to induce DNA synthesis in transplanted sperm nuclei
Authors: Skoblina M. N. 
Published: April 2021

ABSTRACT
The behaviour of sperm nuclei was studied both in the cytoplasm of intact toad oocytes undergoing maturation and the cytoplasm of oocytes matured without germinal vesicles. The behaviour of the nuclei of pronase-treated sperm injected in the mature egg cytoplasm was shown to be exactly similar to that of the sperm nucleus after fertilization, i.e. they swelled, synthesized DNA, and divided. No changes in such sperm nuclei could be detected in the cytoplasm of the oocytes matured without germinal vesicles.
The signal from fruiting body and conus tips ofDictyostelium discoideum
Authors: Rubin Jonathan 
Published: April 2021

ABSTRACTTips from fruiting bodies and conuses were transplanted into interphase fields of Dictyostelium discoideum amoebae. Progressively increasing concentrations of beef-heart phosphodiesterase added to the fields significantly decreased the chemotactic range of the responding amoebae. The findings suggest that the tip secretes c-AMP. We also find that the chemotactic range is independent of the size of the tip implying that the tip may produce a regulating gradient.