bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative Effects of Moni-, Di-, and Triphosphorylated Nucleosides on Amphibian Morphogenesis
Authors: Ambellan Elisabeth 
Published: April 2021

ABSTRACT
Treatment of Rana pipiens embryos with adenosinetriphosphate (ATP), adenosinemonophosphate (AMP-3), adenosinediphosphate (ADP), and other diphosphorylated nucleosides, either under ‘optimum conditions’ or with an overdose, resulted in formation of neural tubes about 4 hours (at 18° C.) ahead of untreated controls. With overdoses specific side-reactions appeared that differed with the substance applied. The rate of neurulation was directly related to the number of phosphate groups of the nucleotides used; it was fastest with ATP, intermediate with ADP, and slowest with AMP-3. The other side-reactions varied specifically and consistently with the number of phosphate groups, but the intensity of these reactions was not directly proportional to the number of phosphate groups present. Overdose treatment with ATP blocked development of head and gill structures immediately following precocious neurulation. This effect was largely reversible by addition of equimolar AMP-3 to solutions. Overdose treatment with AMP-3 apparently enhanced formation of head and gill structures. Development was first blocked at the tail-bud stage. ADP, IDP, and other diphosphorylated nucleosides at similar concentrations had no adverse effects following precocious neurulation and apparently stimulated growth of the entire embryo. All of the mononucleotides specifically accelerated neural-tube formation whether applied at the 2-cell stage, during the blastula stage, or at the stage of the open neural plate.
Effects of Adrenal Transplants upon Forelimb Regeneration in Normal and in Hypophysectomized Adult Frogs
Authors: Schotté O. E. , Wilber J. F. 
Published: April 2021

ABSTRACTExperiments to test the proposition that systemic factors and not fixed properties of the cells within limbs determine loss of regeneration in frogs were performed upon the forelimbs of post-metamorphic R. clamitans and R. pipiens varying in body length from 4·4 to 5·7 cm. Control experiments consisting of simple amputations through the midradius ulnar or distal humeral regions showed that the frogs at this stage were incapable of detectable regeneration. The repeated removal of the cicatricial skin in another control series elicited regeneration, of an abortive type, in only one case among fourteen limbs tested. In twenty-five hypophysectomized R. clamitans adrenals from R. pipiens were transplanted heterotopically beneath the jaw concomitantly with amputation. Weak regenerative response was observed in eleven cases. It is concluded that the absence of the pituitary in the hosts lowers the activity of the transplanted adrenals. The transplantation of R. pipiens adrenals into normal R. clamitans hosts 7 and 14 days after amputation proved most effective, since among the twenty-one limbs examined only two did not show any regeneration. It is suggested that: (1) the transplanted adrenals were functional, although at a low level of activity; (2) the time of transplantation of the adrenals is critical, since in order to elicit regeneration it must coincide with a period in amputational wound repair that is most susceptible to corticoid activity; (3) the loss of regenerative potencies after metamorphosis in Anura is attributable to changes in the endocrine system of these organisms, rather than to changes in the properties of the cells of their limbs.
Morphogenetic Activities during Planarian Regeneration as influenced by Triethylene Melamine
Authors: Pedersen K. J. 
Published: April 2021

ABSTRACTThe action of an anti-neoplastic substance, triethylene melamine (TEM) on the morphogenetic processes of head regeneration in the planarian Planaria vitta has been studied. A description of the normal regeneration is first given. TEM in very low concentrations strongly retards or blocks regeneration of two eyes. Administered continuously, a high toxicity is observed. Exposure to high concentrations for a short time involves severe retardation of regeneration without any mortality. A phase-specificity is observed. TEM in low concentrations only acts in the first phase of regeneration, in higher concentrations in the middle phase too, but no action is encountered in the late phase of regeneration. The phase specificity is not due to a failure of penetration of the substance. TEM strongly affects mitosis of neoblasts, and this is its primary action on the regenerative process. No action on cellular migration was observed. A dissociation between epimorphosis and morphallactic regeneration is possible following treatment with TEM. Differentiation and induction are not directly influenced by TEM, but may be modified as a result of depletion of neoblasts. A competition of the two symmetrical lateral halves for neoblasts is encountered, resulting in animals with only one lateral eye. The phenomenon is quite distinct from cyclopia. Fission as such is unaffected by TEM. The regeneration of the posterior fragments follows the same pattern as the head-pieces. Histological changes following TEM treatment are described. The PAS reaction is depressed after intense treatment with TEM, the intestine being first depleted of PAS-positive material. Respiratory intensity is unaffected by TEM. A partial protection is obtained by pretreatment of the animals with BAL (2:3-dimercaptopropanol). The free amino acids were studied after TEM treatment. Only one change is observed, a highly elevated glutamine reaction. The significance of epimorphosis and morphallaxis, and the respective role played by mitosis and neoblasts in these two modes of regeneration are discussed. Competition and inhibition phenomena during regeneration are briefly discussed.
Genetical Studies on the Skeleton of the Mouse
Authors: Grüneberg Hans 
Published: April 2021

ABSTRACT
The notochord of T / + mouse embryos is of normal length. In young embryos it tends to be retained to a varying extent in the dorsal wall of the hind-gut and/or the cloaca. Often, its separation from the primitive streak and/or the overlying neural plate is also delayed. In older embryos the notochord tends to become incorporated either in the neural tube or in the tail-gut in the distal region of the tail. The notochord of T/ + embryos often has a central lumen and tends to branch. In the majority of T/T embryos there is either no evidence, or ambiguous evidence, for the existence of a notochord as a separate structure. Some T/T embryos, however, show clear evidence of a notochord though this tends to be retained in the gut or to become incorporated in the neural tube. In T / t6 and T/t1 tailless embryos the caudal notochord is of normal length; however, it soon becomes incorporated in the neural tube. It is suggested that the action of the T gene in all these genotypes may be a change in some of the surface properties of the notochord. The possibility is considered that the notochord may be involved as part of a more general disturbance of the primitive streak.
The Development of the Adrenals and Sympathetic Paraganglia in certain Madagascar Insectivores
Authors: Adams W. E. 
Published: April 2021

ABSTRACT
The development of the adrenal gland in the insectivores has not been extensively studied, Aichel (1900) and Soulié (1903) having described it in the mole (Talpa) and Celestino da Costa (1920, 1926) in the hedgehog (Erinaceus euro-paeus). Both Soulié and Celestino da Costa agree that in these animals the adrenal develops basically much as in other mammals, i.e. the cortical primordium comes from the coelomic epithelium, and is later invaded by migrating elements (phaeochromoblasts) from the adjacent sympathetic anlage (Aichel, however, regards the two as having a common origin, from remains of nephrostomal canals of the upper part of the mesonephros).
Congenital Malformations in Mouse Embryos Induced by 8-Azaguanine
Authors: Nishimura Hideo , Nimura Hiroaki 
Published: April 2021

ABSTRACT
The effect of 8-azaguanine on the development of offspring of mice was investigated by injecting mothers once intraperitoneally with 0·08 to 0·4 mg. / g. of body-weight on a day between the 7th and 15th of gestation. The principal teratogenic effect was on the skeletal system. Among the malformations found were cleft palates and various abnormalities of the extremities; abnormally directed digits due to deviation of interphalangeal joints were most frequently encountered. When administered between the 7th and 14th days of gestation, this compound is frequently lethal to embryos, causing death immediately or a few days after injection.
Selective bilateral motor innervation in Xenopus tadpoles with one hind limb
Authors: Lamb Alan H. 
Published: April 2021

ABSTRACT
‘Bilateral innervation of a single hindlimb bud was induced by amputating the other limb bud and disrupting the barriers between the two sides. Though the routes of the crossed nerves were necessarily abnormal, the motor projections that developed subsequently were normal as determined by horseradish peroxidase tracing. The limb therefore appears to be innervated selectively, each region being invaded and/or synapsed with only by motoneurones at particular locations. The numbers of motoneurones surviving after metamorphosis were almost normal on both sides provided the operation was done before motor invasion of the limb bud begins. From this it is argued that the axons were probably guided actively to their correct destinations. Without such guidance, axons would probably not have been able to find their correct termination sites and motoneurone survival would therefore have been depressed. The normal motoneurone numbers also imply that the single limb was supporting twice its usual quota of motoneurones. The hypothesis that motoneurones compete in the limb for survival is therefore not supported.
Projections from sensory neurons developing at ectopic sites in insects
Authors: Anderson Hilary 
Published: April 2021

ABSTRACT
This paper reviews recent experiments which attempt to gain more understanding about the recognition processes involved in the formation of neuronal connexions by studying the degree of specificity with which sensory neurons form their central connexions. This is done by generating ectopic neurons (either by transplantation or by genetic mutation) whose axons grow into novel regions of the central nervous system, and then examining their projections and synapses.
The sensory systems reviewed are: the Antennapedia, spineless-aristapedia, proboscipedia, and bithorax homeotic mutants of Drosphila melanogaster; the cercus-to-giant interneuron system of crickets, and the wind-sensitive hair system of locusts.
The results show that ectopic neurons form projections that are discrete and characteristic, not random and chaotic. In those cases where single classes of sensilla have been studied, they follow either their normal CNS pathways or those pathways normally used by their segmental homologues.
Ectopic sensory neurons can also form appropriate functional connexions in some cases but not in others. Possible reasons are discussed, but detailed understanding of the underlying events requires further experimentation.
The role of morphogenetic cell death during abnormal limb-bud outgrowth in mice heterozygous for the dominant mutation Hemimelia-extra toe (Hm
x
)
Authors: Knudsen T. B. , Kochhar D. M. 
Published: April 2021

ABSTRACT
A dominant mutation in the mouse, Hemimelia-extra toe (Hmx), induces congenital limb malformations in heterozygotes. Typical expression includes axial shortening of the radius, tibia and talus (‘hemimelia’), with supernumerary metacarpals, metatarsals, and digits (‘polydactyly’). Pathogenesis was investigated during developmental stages 16 through 22 (11th through 15th days of gestation). Full expression was apparent during stage 20 when the limb pattern was comprised of pre-cartilaginous anlagen. Formation of a pre-axial protrusion on the autopod during stage 17 or 18 was the earliest gross abnormality, and foreshadowed the development of supernumerary digits. Microscopically, there was an alteration in the pattern of physiologic cellular degeneration (PCD) programmed to occur within the zeugopod and autopod. The ‘opaque patch’ (mesodermal necrotic zone normally occurring between tibial and fibular anlagen) was overextended pre-axially causing resorption of the tibial precartilage. Additionally, PCD normally occurring within the basal cell layer of the apical ectodermal ridge (AER) and the ‘foyer primaire préaxial’ was not expressed in the mutant autopod. This occurred in association with outgrowth of the protrusion. The pre-axial portion of the AER remained in an abnormally thickened, viable, proliferative state, and did not undergo scheduled degression. This may have been the basis for prolonged induction of pre-axial outgrowth. Paucity of mesenchymal cell filopodial processes extended along the basal lamina, as well as a rarefaction of the filamentous material normally associated with the mesodermal face of the basal lamina, was detected at the pre-axial AER-mesenchymal interface on stage 18. A potential involvement of epithelial-mesenchymal interactions in the induction of epithelial PCD is discussed.
Growth and cell competition in Drosophila
Authors: Simpson Pat 
Published: April 2021

ABSTRACT
The process of cell competition, whereby slowly dividing Minute cells are eliminated by faster-growing Minute+ cells in mosaic compartments of the Imaginal wing disc, is discussed. Evidence is presented suggesting that after completion of growth of the Imaginal discs, Minute+ cells no longer continue overgrowing and eliminating the Minute cells. The process of competition thus appears to be restricted to discs that are actively growing.
No cell competition can be detected in the histoblast cells that give rise to the adult abdomen. This observation, however, has been interpreted to be the result of an extremely long perdurance effect for the Minute+ product in these cells.
Mesenchymal control over elongating and branching morphogenesis in salivary gland development
Authors: Nogawa Hiroyuki , Mizuno Takeo 
Published: April 2021

ABSTRACT
Recombination of the epithelium and mesenchyme between quail anterior submaxillary gland (elongating type) and quail anterior lingual or mouse submaxillary gland (branching type) was effected in vitro to clarify whether the elongating morphogenesis was directed by the epithelial or the mesenchymal component. Quail anterior submaxillary epithelium recombined with quail anterior lingual or mouse submaxillary mesenchyme came to branch. Conversely, quail anterior lingual or 12-day mouse submaxillary epithelium recombined with quail anterior submaxillary mesenchyme came to elongate, though the mesenchyme was less effective with 13-day mouse submaxillary epithelium. These results suggest that the elongating or branching morphogenesis of quail salivary glands is controlled by the mesenchyme.
Tetraploidy and early development: effects on developmental timing and embryonic metabolism
Authors: Eglitis Martin A. , Wiley Lynn M. 
Published: April 2021

ABSTRACT
The effect of balanced gene dosage changes on the timing of cavitation and on the timing of appearance of a stage-specific embryonic cell surface antigen was studied in preimplantation mouse embryos. Gene dosage was increased by creating tetraploid embryos at the 4-cell stage, either by blastomere fusion with polyethylene glycol (PEG) or by incubation in cytochalasin B (cytB) to block cell division. Removal of the zona pellucida with Pronase from diploid embryos caused a 7 h delay in cavitation. Further manipulations, either with PEG or cytB to induce tetraploidy, did not produce a statistically significant additional delay in cavitation timing. Likewise, PEG-induced tetraploidy did not affect the timing of appearance or disappearance of the embryonic cell surface antigen as compared with diploid control embryos. In analysing the metabolic effects of tetraploidy, we found that in tetraploid embryos with cell number equivalent to intact diploid embryos, MDH activity did not double with the doubling of the genome, being only 50 % greater than diploid levels in cytB-induced tetraploid embryos and only 20 % greater than diploid levels in PEG-induced tetraploid embryos. However, in tetraploid embryos with one-half normal cell number, enzyme activity was equal to that in whole diploid embryos, suggesting that in such embryos, MDH activity increased in parallel with increases in gene dosage. Further studies showed that levels of RNA synthesis in PEG-induced tetraploid embryos also did not increase in parallel with the doubling of the genome. Rather, these results suggested that in tetraploid embryos, compensation was made for at least part of the excess genetic material.
The Effects of Chorioallantoic Grafts on the Developing Chick Embryo:I. Studies on Weight and Histology of Homologous and Heterologous Tissues
Authors: Alten Pierson J. Van , Fennell R. A. 
Published: April 2021

ABSTRACT
It was observed that following CAM grafts of adult chicken duodenum there was a marked decrease in the absolute weight of the host, a marked increase in the weight of the spleen, liver, and heart, and a relative weight increase in the duodenum. Further, following grafts of adult skin and brain the spleen and liver were significantly heavier. Following liver grafts the liver and heart showed a significant increase in weight. Adult chicken spleen grafts caused a marked increase in the weight of the spleen and heart. Further, it was observed that, regardless of what tissue was used for grafting, 9 days later the morphological integrity of the graft was destroyed and the area was replaced by a myeloid metaplastic centre. On the other hand, embryonic duodena retained their integrity and continued to differentiate. Grafting of adult duodenum caused acceleration of tissue differentiation of the host duodenum. The polysaccharides in the connective tissue and goblet cells of the duodenum differentiated at least 24 hours earlier than in control chicks. Following grafting of duodenum, spleen, and skin, the host spleen exhibited a marked increase in granuloblasts and granulocytes. The heart and liver following grafts were essentially like those in control embryos. Treatment of the adult duodenum prior to grafting with either 95 per cent, alcohol for 24 hours at —20°C., lyophilization, or heating at 80° C. for 20 minutes, resulted in inactivation, the host not being affected. When duodena of 15-, 16-, 17-, 18-, and 20-day embryos were grafted to the CAM, no changes in the weight of host spleen, liver, or heart were found. Following 20-day duodenal grafts the weight of the duodenum was significantly decreased. All embryos receiving adult duodenum, liver, and heart extracts into the yolk sac at 4 days of incubation, died within 72 hours after inoculation. The results are discussed in the light of organ-specific growth stimulation and graft-versus-host reaction, both of which fail to adequately explain all the results observed.
Action of Triethanomelamine (TEM) on Early and Later Stages of Mouse Embryos
Authors: Jurand A. 
Published: April 2021

ABSTRACT
Several years ago triethanomelamine (2,4,6-tri(ethyleneimino)-l,3,5-triazine, or TEM) was introduced into clinical chemotherapy for its tumour-inhibiting property. It was found, in addition, that TEM is a strong mutagenic factor.
Pattern determination and pattern regulation in Paramecium tetraurelia
Authors: Kaczanowska Janina , Dubielecka Bożena 
Published: April 2021

ABSTRACT
Pattern regulation was investigated in the progeny of laterally fused cells of Paramecium tetraurelia. The immediate progeny of such fused cells (doublets) reveal two sets of cortical organelles arranged roughly symmetrically. Doublets tend to transform gradually into cells with only one set of organelles (singlets). At least two different and mutually exclusive pathways of doublet-to-singlet transformation are reported. In intermediate stages of regulation the cortical areas bearing different cortical landmarks may be brought into an abnormal neighbourhood. Differentiated cortical bands of cortex, bearing organellar landmarks, are faithfully propagated even if they are improperly and asymmetrically located on the cell. The confrontation of such cortical bands may lead to the transient appearance of additional duplicated organelles.
It is suggested that pattern regulation in Paramecium during doublet-to-singlet transformation results from at least three factors: the regression of some part of the cortical areas, the interaction of the juxtaposed parts remaining and the slow regulatory shift of positions of the cortical structures.
Histogenetic and neoplastic potential of different regions of the mouse embryonic egg cylinder
Authors: Beddington R. S. P. 
Published: April 2021

ABSTRACTThe histogenetic and neoplastic potentials of defined regions of the 8th day mouse embryonic egg cylinder were examined following ectopic transfer to beneath the testis capsule. No differences in histogenetic potential were detected between anterior and posterior slices of the embryo, either when composed of all three germ layers or of embryonic ectoderm alone. Small anterior and distal fragments of embryonic ectoderm also produced similar histogenetic profiles, although posterior fragments failed to grow in this ectopic site. The histogenetic potential of anterior and distal fragments exceeded the developmental fate ascribed to these two regions in the embryo (Beddington, 1981). There was some evidence for regionalization with respect to neoplastic potential, anterior slices of the embryo giving rise to a higher incidence of embryonal carcinoma cells than posterior slices.
Localization of messenger RNA in the cortex ofChaetopterus eggsand early embryos
Authors: Jeffery William R. , Wilson Linda J. 
Published: April 2021

ABSTRACTThe distribution of mRNA in Chaetopterus pergamentaceus eggs was examined by in situ hybridization with poly(U) and specific cloned DNA probes. Eggs contain three distinct regions; the cortical ectoplasm, endoplasm, and a plasm released from the germinal vesicle (GV) during maturation. The ectoplasm of the mature egg showed a 15-fold enrichment in poly(A) and in histone and actin mRNAs relative to the endoplasm and the GV plasm after in situ hybridization. More than 90 % of the total mass of egg poly (A)-I-RNA and histone and actin messages was estimated to be present in the ectoplasm. The mRNA molecules codistributed with ectoplasmic inclusion granules during ooplasmic segregation. During the extensive cytoplasmic rearrangements which occur at the time of the first cleavage the ectoplasm was divided into animal and vegetal portions. The animal portion was segregated evenly between the AB and CD blastomeres, whereas the vegetal portion entered the polar lobe and was preferentially segregated to the CD blastomere. Histone and actin mRNA entered both the AB and CD blastomeres of the 2-cell embryo. The results demonstrate that mRNA is quantitatively localized in the cortex of the Chaetopterus egg and early embryo.