bluuebunny/crossref_metadata_2025_split huggingface dataset:
The development of monosomy 19 mouse embryos
Authors: Magnuson Terry , Smith Sandra , Epstein Charles J. 
Published: April 2021

ABSTRACTIn general, autosomal monosomy is lethal much earlier in mammalian development than autosomal trisomy. In an attempt to understand why monosomy is so deleterious, we have begun to characterize the development of mouse embryos monosomic for chromosome 19. A dramatic loss of monosomy 19 embryos was found to occur between days 3 and 4 of development. This loss occurred both in vivo and in vitro and with intact blastocysts or isolated inner cell masses. Experiments with inbred strains showed that this loss was not; due to the expression of recessive lethal genes. While monosomic embryos were found to have fewer cells than normal and trisomic litter-mates beginning at the early morula stage, the ability to form blastocysts is not interfered with. Electron microscopy revealed no difference in the cellular ultrastructure of monosomic when compared with diploid embryos” Furthermore, two-dimensional gel electrophoresis did not reveal any differences in the proteins synthesized by monosomie, trisomic or diploid litter-mates when examined at day 3 of development. These results indicate a lack of gross genomic disturbances in monosomic embryos. When monosomy&lt;-&gt; diploid chimaeras were made, viable monosomic cells were found in day-9 post-implantation embryos, well past the lethal period. Thus, in chimaerip embryos, the normal cells appear to be able to provide whatever is lacking, suggesting that monosomy 19 is not a cell lethal. Instead, death may be due to a dosage alteration in specific gene products needed during early development.
A scanning electron microscope study of the development of a peripheral sensory neurite network
Authors: Roberts Alan , Taylor J. S. H. 
Published: April 2021

ABSTRACT
The formation of the sensory neurite plexus on the basal lamina of trunk skin in Xenopus embryos has been examined using the scanning electron microscope. It is formed by Rohon-Beard and extramedullary neurons which provide the first sensory innervation of the skin. By observing the distribution of growth cones on the inside surface of the skin of embryos at different ages, the development of the plexus has been followed and related to the development of sensitivity to sensory stimulation. The general features of the plexus are illustrated using a photomontage taken at x 1100. Measurements on neurites from this, and of growth cone orientations demonstrate a general ventral growth pattern with some small regional variations. Interactions of neurites within the plexus are examined. Neurites meeting at shallow angles tend to fasciculate, while those meeting at close to 90° tend to cross each other. Angles of incidence and separation of neurites show few angles less than 30°, which suggests that active adjustments occur after a growth cone meets or leaves another neurite. The observations allow comparison of behaviour of growing neurites in vivo and in vitro. Our evidence suggests that adhesion between growth cones and neurites is stronger than that between growth cones and the basal lamina of the skin.
Control of pattern formation in urodele limb ontogeny: a review and a hypothesis
Authors: Stocum David L. , Fallon John F. 
Published: April 2021

ABSTRACTFrom a review of the literature, the hypothesis is advanced that the forelimb region of the urodele embryo acquires its transverse axial polarity and pattern by the action of posterior and dorsal polarizing regions. The anterior-posterior and dorsal-ventral axes are determined simultaneously and their determination is a prerequisite for proximal-distal outgrowth. Outgrowth of the limb bud is accompanied by the generation, between proximal and distal boundaries, of a set of positional values specifying proximal-distal axial polarity and pattern. The proximal boundary is the initial positional value carried by the cells of the limb area. The distal boundary is imposed upon the outermost layer of limb disc cells by the overlying ectoderm.
Studies in Embryonic and Larval Development in Amphibia : I. The Embryology ofEleutherodactylus ricordii, with Special Reference to the Spinal Cord
Authors: Hughes Arthur 
Published: April 2021

ABSTRACTIn the West Indian Anuran genus Eleutherodactylus the larval stage is wholly suppressed. As in other systems of organs there are features in the spinal cord which are correlated with this embryonic type of development. The cord in the trunk region resembles more that of a chick embryo than that of a larval Amphibian. Within the thick neuroepithelium mitoses in the ependymal zone persist much longer than in larval forms. There is a relatively thin layer of white matter. The Rohon-Beard system of sensory neurones persists, but does not precede the development of the dorsal root ganglia. In the trunk there are no conspicuous primary motor-cells as in larval Amphibia. The numbers of cells within the dorsal root ganglia and ventral motor horns have been counted both in the embryo and in the adult. From the first, the numbers of cells present in both are similar to those in the adult. During development, increase by mitosis is opposed by cell degeneration. Pycnotic nuclei are conspicuous in both spinal ganglia and ventral horns in the embryo. As soon as the spinal ganglia are recognizable, their relative sizes are similar to those of the adult. The ganglia at limb levels are already larger than those elsewhere a day before nerve fibres first enter the limb-buds.
Protein Accumulation in Early Chick Embryos Grown under Different Conditions of Explantation
Authors: Britt L. Gwen , Herrmann Heinz 
Published: April 2021

ABSTRACT
Chick embryos were explanted at the 11 – 13 somite stage to an agar medium and the protein content of the embryos was measured after 8, 18, and 24 hours of explantation. An increase in the concentration of yolk-albumen in the medium as well as an increased extra-embryonic area was found to increase the protein contents of the explants. In the presence of a large extra-embryonic area and a high concentration of yolk-albumen in the medium, the protein content of the explant was found to approach, during the first 18 hours of explantation, the protein content of the embryo developing in the egg.
Experiments on the ‘Overgrowth’ Phenomenon in the Brain of Chick Embryos
Authors: Bergquist Harry 
Published: April 2021

ABSTRACT
A pathologic phenomenon consisting of complex folding of the brain-wall has been obtained in living chick embryos after operations upon the rhombencephalon in early stages. The operation consisted of the extirpation of the tip of the notochord and the overlying neuromere. Its results mainly appear in the hemispheres and tectum opticum region, but sometimes also extend to other evaginated brain parts, viz. the optic évaginations, the epiphyseal region, and possibly also the caudal parts of the hypothalamus. The pathologic phenomenon is identical with certain abnormal foldings, described in human embryonic brains by Patten (1952) and called by him ‘overgrowth’. It may be combined with encephaloschisis in the mesencephalic roof.
Recherches sur quelques aspects de l’hétéroploïdie expérimentale chez le Triton Pleurodeles waltlii Michah
Authors: Gallien L. 
Published: April 2021

ABSTRACT
Experimental conditions and methods of rearing which make it possible to obtain heteroploidy in Pleurodeles waltlii are described. A method based on silver impregnation of the tail of young larvae permits the diagnosis of haploidy, diploidy, or triploidy. This method, by outlining the cell borders, makes possible planimetric measurement in any area of the epithelial sheet of the tail skin. The general structural organization of the ectodermal layers is described for the whole of the tail skin, and the alterations and adjustments resulting from an aneuploid make-up are analysed. In aneuploid chimaeras, micro- and macrocells are formed as a result of mitotic anomalies, corresponding respectively to groups of chromosomes lost from the mitotic spindle and to highly polyploid cells. The disappearance of the most atypical cells is followed by movements and reorientations of neighbouring cells producing characteristic rosette formations. Various teratogenic effects of thermal shock to the eggs, compatible with life, are described. Strongly hypomorphic or aneuploid larvae and haploid individuals, which usually have a brief survival, may be reared by means of parabiotic grafting to a normal individual. Amongst triploid males and females, fertile individuals have been obtained.
Recherches sur I’animalisation de l’œuf d’Oursin par les ions Zinc
Authors: Lallier R. 
Published: April 2021

ABSTRACTLa différenciation de l’embryon d’oursin peut être modifiée expérimentalement par des agents chimiques. On peut obtenir ainsi la végétativisation des embryons, c’est à dire l’extension des régions entomésoderrniques, en traitant les œufs par le chlorure de lithium (Herbst, 1893; Lindahl, 1936), L’animalisation ou extension des territoires ectodermiques est provoquée par les ions sulfocyanure (Lindahl, 1936), l’acide iodosobenzoïque (Runnström & Kriszat, 1952) et l’acide thiomalique (Lallier, 1952). Nous avons montré au cours de recherches antérieures que l’animalisation peut être obtenue aisément en traitant les œufs par les ions zinc (Lallier, 1955 a,b) ou par certains dérivés organiques acides (Lallier, 1956, 1957, 1958a). L’animalisation obtenue dans ces conditions est particulièrement forte et homogène.
Embryonic Growth relative to the Vitelline Membrane, and its Role in Determining the Level of Post-operative Abnormalities, as Measured in the Chick
Authors: Silver P. H. S. 
Published: April 2021

ABSTRACT
The changing relationship between a point on the vitelline membrane and the 1st somite or Hensen’s node has been investigated in the chick embryo, between stages of about 6 somites to about 40 somites. A puncture in the V.M. opposite the 1st somite at the six-somite stage lies opposite a point between the 10th—14th somites about 24 hours later, and between the 15th-20th somites about 48 hours later. The anterior intestinal portal maintains its orientation approximately relative to such an opening in normal development. Attention is drawn to the significance of these observations regarding embryos experimented on at an early stage, and which show abnormalities far caudal to the region of operative interference.
Correlation between ventral surface structures and local degeneration of cilia during conjugation inParamecium
Authors: Watanabe Tsuyoshi 
Published: April 2021

ABSTRACTCorrelation between cortical structures, such as the suture lines and the oral apparatus, and local degeneration of cilia during conjugation was investigated using aberrantly shaped cells which were produced by treating normal cells with 2 mM adenine for 24 h. Three types of aberrantly shaped cells were obtained: (1) proters, in which the oral apparatus is located at or near the posterior end of the cell and the preoral suture is much longer than that of a normally shaped cell ; (2) opisthes, in which the oral apparatus is located extremely anteriorly, the preoral suture is very short and bent to the left, and the postoral suture and cytoproct are much longer than those of normally shaped cells; and (3) L-shaped cells, which are cells that have not separated at division and contain two buccal openings. The anterior member of the L-shaped cell (AML) has a long preoral suture and the posterior member of the L-shaped cell (PML) has a long postoral suture and cytoproct. The postoral field of AML and the preoral field of PML are missing. When these cells were mixed with normally shaped cells of the opposite mating type, the mating reaction took place between them. Scanning electron microscopic observation showed that, in all abnormally shaped cells, the degeneration of cilia always occurred along the full length of the preoral suture, regardless of its total length, and along the posterior right field of the buccal vestibulum, regardless of its location in the cell cortex. The localization of the degeneration of cilia, therefore, coincided with the position of the preoral suture and the buccal opening.
Cellular events during early formation of yolk-sac-derived teratomas
Authors: Sobis H. , Hove L. Van , Vandeputte M. 
Published: April 2021

ABSTRACTA sequential morphological study of the initial cellular events in teratoma induction by displaced visceral yolk sac after foetectomy in rats was undertaken. This study led to the observation that apart from proliferation of cells displaying definite endodermal or mesodermal characteristics, a population of poorly differentiated cells appeared some days after the surgical procedure. It is very likely that these poorly differentiated cells are stem cells from which differentiated structures originate afterwards by a process of redifferentiation. The development of granulation tissue rich in capillaries seems to enhance this process. Similarities and differences with blastema formation are discussed.
Cosegregation of monoclonal antibody reactivity and cell behaviour in the mouse preimplantation embryo
Authors: Randle Beverley J. 
Published: April 2021

ABSTRACTExpression of an antigen, recognized by a monoclonal antibody raised against PCI 3 embryonal carcinoma, is described in mouse preimplantation embryogenesis. The antigen is found in the cytoplasm of ovulated ova and is first noted on the cell surface of the 1-cell embryo 20 h post-ovulation. Surface labelling of blastomeres is uniform until the 8-cell stage when antigen expression becomes polarized along the radial axis of the embryo. Two major populations of blastomeres are distinguishable on division to the 16-cell morula. Dissociation of morulae in calcium-free medium yields large, polar, antigen-positive cells and small apolar cells with reduced levels of detectable antigen. A third, minor population of small, antigen-negative cells is also found in vivo. Large and small blastomeres differ in their ability to relocate within the embryo when aggregated with intact 16-cell-stage embryos. The small blastomeres of the 16-cell morula contribute significantly to the inner cell mass while the large antigen-positive cells are found only in the trophectoderm.
The effect of cathepsin inhibitor on rat embryos grownin vitro
Authors: Beck Felix , Lowy Adam 
Published: April 2021

ABSTRACTThe addition of leupeptin to New cultures of rat embryos produces growth retardation and abnormalities of embryonic development. The effect is probably due to inhibition of the maternal protein breakdown necessary for embryonic growth. This function is carried out by the visceral layer of the yolk sac which shows distinct morphological changes akin to storage disease when leupeptin is added to the culture medium. We have not found it possible to reverse the effects of leupeptin by addition of amino acids to the culture medium.
Timing of X-chromosome inactivation in postimplantation mouse embryos
Authors: Rastan Sohaila 
Published: April 2021

ABSTRACTThe onset of X-chromosome inactivation was investigated cytologically in postimplantation female mouse embryos of age , and days post-coitum (d.p.c.) and in the isolated epiblasts of 6 d.p.c. embryos before primitive streak formation using a heat/hypotonic technique to reveal the inactive X chromosome by differentially dark staining with Giemsa. The results indicate that X inactivation has taken place in all the cells of the so-called ‘un-differentiated’ epiblast by 6 d.p.c. before primitive streak formation. Further evidence is presented to suggest that X inactivation is complete in all cells of the mouse embryo by d.p.c.
The chromosome complement of single-pronuclear haploid mouse embryos following activation by ethanol treatment
Authors: Kaufman M. H. 
Published: April 2021

ABSTRACTA technique in which mouse eggs are stimulated to develop parthenogenetically following their brief incubation in 7 % ethanol in PBS is described. Very high rates of activation were achieved, and a detailed analysis presented of the class of parthenogenone which develops a single haploid pronucleus following second polar body extrusion.As preliminary studies on presumptive haploid morulae indicated that a proportion of the metaphase spreads examined had an aneuploid chromosome constitution, the incidence of aneuploidy at the first cleavage mitosis was investigated. In the control groups the level of aneuploidy was about 1 %, whereas in the ethanol-treated series the incidence ranged from 13·6–18·8%. Additional pre-treatment of ethanol-activated oocytes in low osmolar medium raised the incidence of aneuploidy to 28-3%. Metaphase groups with 18, 19, 21 and 22 chromosomes present were observed in addition to groups with a normal complement of 20 chromosomes. The possible mode of action of ethanol in inducing parthenogenetic activation of mouse oocytes, and a high incidence of aneuploidy, is discussed in relation to previous knowledge of the action of this agent. Preliminary studies using G-banding indicate that the aneuploidy observed appears to arise as a result of non-disjunction which may involve any of the chromosomes of the complement.
Determination of axial polarity in the urodele limb regeneration blastema
Authors: Stocum David L. 
Published: April 2021

ABSTRACTThe state of determination of the anterior-posterior, dorsal-ventral and proximal-distal axes of the undifferentiated limb regeneration blastema was evaluated by heterografting and autografting experiments in which these axes were reversed with respect to the limb stump. Species-specific size differences in skeletal elements were used as markers to trace the origin of regenerate tissues in the heterografting experiments, and differences in the skeletal patterns of hindlimbs and forelimbs were used as markers in the autografting experiments. The resulting primary regenerates fell into two categories, those composed wholly or partly of donor tissues, and those composed entirely of host tissues. Regenerate structures formed from donor tissues always maintained the handedness of origin, while regenerates formed from host tissues always displayed host-side handedness. These results demonstrate that the axes of the blastema are determined from the start of regeneration, and that previous claims of axial lability in reversal experiments are based on an illusion created by resorption of graft tissue, accompanied by regeneration from the host. Reversal of the transverse axes resulted in the formation of supernumerary limbs. Analysis of heterograft cases in which the anterior-posterior axis was reversed showed that 50 % of the supernumeraries were constructed partly of donor blastema tissue whose axial polarity was reversed with respect to the adjacent primary regenerate. The vast majority of the primary regenerates in these cases possessed the normal number of digits. It is thus likely that the reprogrammed donor blastema cells used to construct the supernumeraries are derived by division of a thin band of cells at the edge of the graft adjacent to the supernumerary.
A method for obtaining chimaeric mouse blastocysts with two separate inner cell masses: a preliminary report
Authors: Tarkowski Andrzej K. , Wojewodzka Marie 
Published: April 2021

ABSTRACTPairs of zona-free mouse blastocysts aggregated in the presence of inactivated Sendai virus and subsequently cultured in vitro will fuse to form a chimaeric blastocyst with one common blastocoelic cavity. Depending on the relative position of the inner cell masses in the apposed ‘parental’ blastocysts, the resulting chimaeric blastocyst contains either a single inner cell mass (ICM) of dual origin or two discrete ICMs each originating from one embryo. In the present experiments, fusion between the two aggregated blastocysts occurred in 23 % of the pairs and 64 % of these chimaeric blastocysts contained two ICMs. Blastocysts of the latter type could potentially give rise to pairs of embryos which as regards the topography of the foetal membrane would resemble spontaneous identical twins, although they would be genetically dissimilar. Possible applications of the described method are discussed.
Juvenoids cause some insects to form composite cuticles
Authors: Willis Judith H. , Rezaur Rahman , Sehnal Frantisek 
Published: April 2021

ABSTRACTMetamorphosing insects treated with juvenoids may secrete composite cuticles which combine morphological features of two metamorphic stages within the area secreted by an individual epidermal cell. Characters found combined were pigmentation, tanning, surface sculpturing, and microtrichiae. Neighbouring cells frequently form different types of cuticle. Composite cuticles should not be confused with the more common mosaic cuticles, which are composed of discrete areas with different stage-specific morphology (e.g. some larval patches set in an otherwise normal adult cuticle).Treatment of last instar nymphs of Pyrrhocoris apterus (Hemiptera) with a juvenoid induced secretion of composite cuticle which combined larval morphological features with imaginal pigmentation. Cells remained susceptible to composite cuticle induction over an extended period prior to the actual initiation of cuticle deposition.Composite cuticle which contained larval microtrichiae and pupal tanning were induced with juvenoids in the lepidopterans Hyponomeuta malinella, Hyphantria cunea, Spodoptera littoralis, Mamestra brassicae, Pieris brassicae, Aglais urticae, but not in Galleria mellonella. Composite cuticle possessing both pupal and imaginal morphological features was produced with juvenoids in Leptinotarsa decemlineata (Coleoptera). It is suggested that this type of cuticle reveals the secretory capacities of a single epidermal cell when the cellular reprogramming from one developmental stage to the next has been stabilized at an intermediate point by juvenoids.
The pattern of campaniform sensilla on the wing and haltere ofDrosophila melanogasterand several of its homeotic mutants
Authors: Cole Eric S. , Palka John 
Published: April 2021

ABSTRACTA detailed mapping and description of campaniform sensilla on the wing and haltere of Drosophila melanogaster is provided. Six types of sensilla are distinguished. Similarities in the pattern of their distribution on the dorsal and ventral surfaces of each appendage, as well as between the wing and haltere, are apparent. These data are used to assess the quality of homeotic transformation in several mutants of the bithorax complex in which the halteres are transformed into wings. Flies homozygous for abxbx3pbx produce a complete inventory of wing sensilla on the homeotic appendage. In abx, bx3 and bx3pbx homozygotes the transformation of haltere into wing is incomplete, and each mutant shows characteristic fields of haltere and wing sensilla. It appears that specific regions of the anterior haltere compartment require different combinations of mutant alleles to produce a distinct homeotic transformation. Furthermore, the pbx mutation appears to influence expression of the bx3 mutation within the anterior compartment.