bluuebunny/crossref_metadata_2025 huggingface dataset:
Delayed appearance of ectodermal cell death as a mechanism of polydactyly induction
Authors: Scott William J , Ritter Edmond J. , Wilson James G.
Published: April 2021

The temporal program of cell death in the apical ectodermal ridge and mesoderm of rat embryo hindlimbs was documented using supravital staining with Nile blue sulfate. Dye uptake indicative of cell death began postaxially at about 290 h of development and was followed in a few hours by preaxial staining, which became more extensive and intense up to 313 h.

Two agents which cause preaxial polydactyly, cytosine arabinoside and 5-fluorodeoxy-uridine, postponed the onset of preaxial ectodermal cell death while at the same time having the expected cytotoxic effect on limb-bud mesoderm. In addition, a zone of deep preaxial mesodermal necrosis, thought to control the size of digit 1 in normal embryos, was usually absent in cytosine-arabinoside-treated embryos.

The results suggest that the prolonged survival of ectodermal cells effected an increased inductive activity on the underlying mesoderm, leading to the formation of excess digital tissue. The data further suggest that the rate at which mesodermal cells were killed affected the subsequent delay of ectodermal cell death.
Cartilage matrix deficiency (cmd) : a new autosomal recessive lethal mutation in the mouse
Authors: Rittenhouse E. , Dunn L. C. , Cookingham J. , Calo C. , Spiegelman M. , Dooher G. B. , Bennett D.
Published: April 2021

A new autosomal recessive lethal mutation in the mouse designated cartilage matrix deficiency (cmd) is described. Homozygotes are dwarfed, and have abnormally short trunk, limbs, tail and snout, as well as a protruding tongue and cleft palate. The abdomen is distended because the foreshortened rib cage and spinal column forces the liver ventrad from its normal location. Histological and electron microscopic study reveals a deficiency of cartilage matrix in tracheal cartilage and in all cartilagenous bones examined. The syndrome closely resembles the rare lethal condition achondrogenesis, found in human infants, which is also believed to be due to an autosomal recessive gene.
Functions of the Lymph Gland Cells during the Larval Period in Drosophila
Authors: El Shatoury H. H. , Waddington C. H.
Published: April 2021

In the latter half of the second instar the lymph glands of Drosophila larvae hypertrophy and release cells into the body-cavity, many of which move to the imaginal buds (Shatoury, 1955a). These cells have been referred to as oikocytes. The optic region of the cephalic disk becomes colonized by the large cells known as hexagons. During the first half of the third instar these increase considerably in number. At about the 85-hour stage, and simultaneously with similar changes in the cells still in the lymph glands, the oikocytes in the optic disk exhibit nuclear pycnosis and the deposition of melanin. Later the cells may become vacuolarized and disintegrate. The precursors of the ommatidia can be seen in the optic disk before the oikocytes become melanized. During the latter part of the first instar oikocytes are also released from the lymph glands, and hexagons accumulate around the end of the oesophagus where it enters the proventriculus. In the immediate neighbourhood of these oikocytes the radial layer of the proventriculus shows some cellular differentiation, forming an ‘upper ring’ of highly basophilic cells. It has usually been considered that this upper ring constitutes the primordia of the imaginal fore-gut, but it has been found that the lower radial cells will also contribute to this structure. The oikocytes of the proventriculus suffer melanization and degeneration at the same time as those of the optic disk and the lymph gland. In larvae aged between 85 and 96 hours two groups of degenerating cells can be found near the cephalic end of the testis and one group in the caudal end. These three groups of cells seem to be oikocytes, and can be traced back to the first instar, when they seem to enter the testis at the same time that the proventriculus is being colonized. Their appearance in the testis is followed by the first sign of the differentiation of spermatocytes. The appearances suggest that the oikocytes, when they arrive at the testis, the proventriculus and the optic disk, play some part in stimulating those processes of differentiation which bring these organs into the condition from which they can undergo metamorphosis. The simultaneous degeneration of these cells at the end of the third instar would seem to indicate that this stimulus is no longer needed after that time. Shatoury (1956) has suggested that the mechanism which brings about this degeneration involves the formation of auto-antibodies.
A Critical Period for the Turning of Hens’ Eggs
Authors: New D. A. T.
Published: April 2021

Turning hens’ eggs between the 4th and 7th day of incubation gives a hatchability similar to that of eggs turned throughout incubation. Turning the eggs between the 8 th and 11th day gives a hatchability similar to that of unturned eggs. New evidence is presented that absence of turning leads to abnormal adhesion between the chorion and shell membranes. The mechanism by which turning effects development is discussed.
Embryological Development of Primordial Germ-cells in the Mouse: Influence of a New Mutation, Wj
Authors: Mintz Beatrice
Published: April 2021

Twenty-seven mouse embryos at days from matings of Wjw × Wjw were examined in order to establish the embryological basis of the germ-cell deficiency found in the WjWj genotype at birth. Elective staining of primordial germ-cells was obtained with the azo dye coupling histochemical technique for alkaline phosphatase. Numbers and locations of these cells were recorded in complete serial sections. Formation of germ-cells occurs, as in normals, in all members of the 8-day group. At 9 days and later, during gonial migration from yolk sac toward germinal ridges, two distinct populations of individuals are recognizable. In one, the number of germ-cells increases; in the other, totals remain very low. The latter would be expected to characterize the WjWj class. Observed incidence of such cases was close to the theoretical frequency of 25 per cent, defective offspring. These findings support the earlier proof (Mintz & Russell, 1955, 1957) that the cells observed are the primordial germ-cells and are of extra-gonadal origin. In defectives, migratory retardation of germ-cells accompanies their mitotic insufficiency. The effects of Wj are compared with those of the alleles W and Wv, and the significance of the study for the problem of pleiotropic gene action is considered.
Evidence for a positional memory in the development of the chick wing bud
Authors: Smith J. C.
Published: April 2021

Grafts of quail zones of polarizing activity (ZPA), treated with 10000 rad γ-radiation, tend to remain at the base of a limb. Their signalling ability is not passed on to more distal tissue, but the limb goes on to produce a reduplication. This suggests that the effect of a ZPA can be remembered in its absence, and explains why a normal limb can develop if its ZPA is removed.
Development of the chick embryo mesoblast: pronephros, lateral plate, and early vasculature
Authors: Meier Stephen
Published: April 2021

The early development of the mesoblast in the intermediate and lateral regions of the chick embryo was examined with the scanning and transmission electron microscope. It was found that primary mesenchyme here becomes condensed into epithelial structures that emerge in a metameric pattern. Viewed in developmental sequence, the intermediate mesoblast condenses into a narrowing cord of axially oriented cells which divert medially at regular intervals into the intersegmental interfaces of somitomeres and somites. These cells give rise to the vascular channels of the posterior cardinal vein as well as to tubular elements of the pronephros. Intermediate mesenchyme cells become epithelial, forming zonular junctional complexes apically and depositing patchy basal lamina over their basal surfaces. The lateral plate mesenchyme organizes similarly into somatic and splanchnic epithelial sheets that utilize the body coelom as their lumenal surface. Cells of the lateral plate extend filopodia basally that interweave with adjacent cells, fibrillar extracellular matrix, as well as with interstitial bodies. The pattern in the lateral plate is subtly ribbed as bands of mesoblast undulate along the axis. The central region of each band is raised while there are grooves created along lines of band abutment, corresponding to intersegmental clefts in the paraxial region and reflecting an underlying metameric pattern. These grooves are usually demarked medially by the protrusion of short segments of adjacent intermediate mesoblast. Most of the remaining primary mesenchyme develops into a non-metameric vascular epithelium, which forms a prominent anastamosing plexus between splanchnic mesoderm and endoderm. It is proposed that the emergence of primary mesenchyme into patterned epithelial anlage facilitates the distribution of neural crest cells introduced subsequently.
Nucleo-cytoplasmic interactions in cell hybrids between mouse oocytes, blastomeres and somatic cells
Authors: Tarkowski Andrzej K. , Bałakier Hanna
Published: April 2021

With the help of the technique of Sendai virus-mediated cell fusion, hybrid cells were produced between two maturing oocytes, between maturing oocytes or mature secondary oocytes and interphase blastomeres from 2-cell embryos, and between secondary oocytes and follicle cells (FC). In the first case giant oocytes form and in these the two groups of condensing bivalents join on a common spindle, undergo a first meiotic division, and become arrested in metaphase II; these hybrids are heterozygous diploids. When blastomeres are fused with oocytes undergoing maturation, then the blastomere nucleus undergoes premature chromosome condensation (PCC), and two sets of chromosomes (meiotic and mitotic) come close to each other but the mitotic chromosomes are not fully incorporated into the meiotic spindle. The behaviour of the nuclei from blastomeres or from follicle cells fused with secondary ovulated oocytes, depends on whether or not the oocyte undergoes activation. When the oocyte is not activated, then the introduced nuclei undergo PCC but the chromosomes remain separate from the spindle of metaphase II. When the oocyte is activated, then the introduced nuclei remain in interphase; the FC nuclei may increase their volume eight times and undergo some other structural changes but during the 6 h period after fusion their appearance remains distinct from that of the female pronucleus. Since some oocytes are not activated after fusion has occurred, it follows that the fusion process itself is not sufficient to trigger egg activation.
Changes in the distribution of cortical myosin during the cellularization of the Drosophila embryo
Authors: Warn R. M. , Bullard B. , Magrath R.
Published: April 2021

Changes in the distribution of myosin during the formation of the cellular blastoderm of Drosophila melanogaster were followed by staining sections of embryos with antibodies to myosin. These were visualized with indirect immunofluorescence. Prior to the start of cell membrane extension myosin is distributed between the nuclear caps as a thin sub-plasmalemma layer. There is also myosin present beneath the surface of the caps. When plasmalemma growth occurs, myosin is associated with the furrow canals, the tips of the advancing membranes. The fluorescence is distributed in an approximately hexagonal pattern around the growth points of each cell. The hexagons are joined up forming a network. It is suggested that this myosin is associated with bundles of microfilaments, orientated parallel to the surface, to form many interlocking contractile rings. The simultaneous contraction of these rings causes the cleavage of the blastoderm. During the first phase of membrane growth, myosin is also associated with the apical surfaces of the forming cells. At this stage these surfaces are rich in microvilli. However, by the time the furrow canals have reached the bases of the cells much of this myosin has disappeared. At about this time the apical surface becomes taut with a loss of the microvilli.
Changes in cell dimensions and intercellular contacts during cleavage-stage cell cycles in mouse embryonic cells
Authors: Lehtonen E.
Published: April 2021

The cleavage behaviour of cells isolated from 1- to 8-cell-stage mouse embryos was studied with time-lapse video equipment; changes in cellular dimensions and their timing were recorded. The division of an isolated cell results in the formation of a twin-cell pair. The divisions of these two cells were always asynchronous. In each division the volume of a daughter cell was approximately half of that of the parental cell but its apparent surface area was 59–65 % of that of the parental cell. Consequently, the ratio of apparent surface area to volume increased in each division by 25–30%. The most noticeable changes were observed in the relationship between the two daughter cells of each division. After cytokinesis, the intercellular contact area gradually increased during the following cell cycle in the 2/8- and 2/16-cell pairs, whereas it hardly changed in the 2/2- and 2/4-cell pairs. The comparison of the behaviour of the daughter cells on different substrates suggested that the zona pellucida and the mid body might have a role in the contact development at the early stages. Scanning electron microscopy was used for studying changes in the density of cell surface microvilli in an attempt to explain how the cells regulate their intercellular contacts.
The in vitro culture of primitive-streak-stage mouse embryos
Authors: Tam P. P. L. , Snow M. H. L.
Published: April 2021

The in vitro growth and morphogenesis of mouse embryos from early primitive-streak stage to early-somite stage is described. The embryo culture method employs a static culture system, a conventional chemically defined medium (Dulbecco’s modified Eagle’s medium), supplemented with additional glucose, glutamine and suitably prepared serum. The method of serum preparation is important for successful culture. Both mouse serum and rat serum support good development of primitive-streak-stage mouse embryos. Over 60% of early-streak stage and about 90 % of late-streak stage grow and develop for 48 h in vitro. During the first 24 h in culture, total growth of the embryos, as reflected by protein content, size and morphology is the same as in vivo.
The Localization of β-Glucuronidase in the Early Chick Embryo
Authors: Billett F. , Mulherkar Leela
Published: April 2021

The technique for the localization of β-glucuronidase, based on the precipitation of ferric 8-hydroxyquinoline from quinolyl-8-glucuronide has been applied to explanted chick embryos. When the enzyme is first detectable, at the head-process stage, it appears to be widely diffused in the dorsal side of the embryo and in the adjacent area opaca. In later stages the histochemical reaction is confined to the region of the developing somites and neural tube.
Comparative Effects of Moni-, Di-, and Triphosphorylated Nucleosides on Amphibian Morphogenesis
Authors: Ambellan Elisabeth
Published: April 2021

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

Experiments 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

The 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

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

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

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

‘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

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

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

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

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

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

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

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

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

The 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

The 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.
The early development of the primary sensory neurones in an amphibian embryo: a scanning electron microscope study
Authors: Taylor J. S. H. , Roberts Alan
Published: April 2021

We have described the development of the primary sensory system of the trunk region of Xenopus laevis embryos from larval stages 21 to 32. The system is based upon Rohon-Beard and extramedullary cells, which have central axons forming a dorsolateral spinal tract and peripheral neurites which innervate the skin. The pioneer axons of the central tract grow along the outer surface of the cord at stage 22. These pioneer axons may be used by secondary axons as a growth substrate. As the tract forms it is covered by the radially expanding distal processes, ‘end feet’, of the ependymal cells of the cord. Cell bodies of the extramedullary cells bulge out of the cord surface, and are first seen between the newly segmented myotomes, at stage 24. Peripheral neurites from these extramedullary cells grow out laterally from the cord. The Rohon-Beard cells, located within the cord, produce similar peripheral neurites which grow laterally with the extramedullary cell neurites, using them as a substrate. The neurites form bundles which coincide with the intermyotomes and are periodically spaced. The growth cones of these neurites contact the outer surface of the myotomes and proceed ventrally, first on the myotomes and then on the basal lamina of the skin. ‘Pioneer’ neurites are used by later neurites as a growth substrate, but not to the exclusion of all other substrates. The neurites form a plexus on the skin’s basal lamina and contact the underlying epidermal cells through holes in the basal lamina. These holes occur in positions over the intercellular boundaries of the epidermal cells.
Growth of 9·5-day rat embryos in human serum
Authors: Gupta M. , Beck F.
Published: April 2021

Rat embryos were explanted at 9·5 days and cultured for 48 h in human serum supplemented with glucose. The embryos were anaemic and frequently malformed. The haemoglobin and DNA content of these embryos was less than those grown in pure rat serum. Addition of 10 % rat serum improved the embryonic growth as well as the haemoglobin and DNA content. This suggests that rat serum provides essential growth factors required by the embryos which are not present in human serum.
A test of the predictions of the boundary model regarding supernumerary limb structure
Authors: Maden M.
Published: April 2021

The model proposed in the preceding paper (Meinhardt, 1983) makes specific predictions about the handedness of supernumerary limbs generated after 180° rotation of blastemas. These predictions are tested here by re-examining, in detail, the structure of 100 of these supernumeraries. Of the four predictions, only one was found not to hold. The other three are remarkably precise in their predictions and fit perfectly with the data. A possible reason for the failure of this one prediction is suggested.
Replacement of irradiated epidermis by migration of non-irradiated epidermis in the newt limb: the necessity of healthy epidermis for regeneration
Authors: Lheureux Emile
Published: April 2021

An X-irradiated newt limb is able to regenerate if non-irradiated skin as well as non-irradiated muscle is transplanted to the stump. Non-irradiated epidermis is brought to the stump with a skin graft but not with a muscle graft. In order to know whether limb regeneration required healthy epidermis or not, a triploid skin cuff was set at the most proximal level of an irradiated limb and muscle was transplanted to the level of the midforearm. The forearm was then amputated through the muscle graft. A cytophotometrical analysis of DNA content of the epidermis cell nuclei sampled from the skin of the regenerate was undertaken to detect a migration of triploid epidermal cells. The result was a complete replacement of diploid irradiated epidermis by triploid epidermis, during the six weeks necessary for regeneration. Another investigation consisted of detecting a possible migration of non-irradiated triploid epidermis along an irradiated limb which had not been amputated. Healthy epidermis was found to migrate distally and replace irradiated epidermis in three weeks. Previous experiments involving transplantation of a non-irradiated skin cuff or muscle to an irradiated limb stump were carried out again but on animals which had been entirely irradiated to prevent any extra healthy epidermis cells from contaminating the regenerating limb epidermis. A regenerate developed from the skin graft but not from muscle graft. It is concluded that healthy epidermis must be present on the limb stump to permit the blastema to develop.
Membrane changes in neural target cells studied with fluorescent lectin probes
Authors: Gualandris L. , Rougé P. , Duprat A. M.
Published: April 2021

The competent ectoderm of Pleurodeles waltl comprises two cell layers with characteristic differences in their morphology, their composition and the molecular arrangement of the various constituents.

The use of labelled lectin probes for observations of ectoderm tissue in vitro with u.v. microscopy (epi-illumination) and the quantification of the results show the following:- Differences in labelling according to the nature of the lectins (SBA, PSA, LCA and Con A). These differences provide information on the nature of the carbohydrates which are present at this stage and on the number of receptors.Differences in fluorescence intensity of the surfaces studied. The internal surface of the ectoderm is labelled more densely than the external surface.Rearrangement of the lectin receptors with a new molecular configuration, stressing the fluidity of the membrane (by the mobility of the receptors throughout the membrane) and its importance for the occurrence of neural induction.Existence of membrane glycoconjugate turnover.A difference in behavioural characteristics between the internal and the external surfaces with respect to the lectins and the formation of an extracellular matrix on the internal surface alone. The extracellular matrix seems to have a role in morphogenetic movements.
Expression of differentiation markers by chick embryo neuroretinal cells in vivo and in culture
Authors: Pomerai D. I. De , Kotecha B. , Flor-Henry M. , Fullick C. , Young A. , Gali M. A. H.
Published: April 2021

Several markers of chick neuroretinal differentiation were monitored in vivo and in culture. All increase markedly between 7 and 20 days of embryonic development in vivo. In vitro, endogenous GABA levels decrease almost immediately, while other neuronal markers increase as in vivo for 2 to 5 days before declining (choline acetyltransferase, acetyl cholinesterase, glutamic acid decarboxylase). Neuronal cell surface markers (binding sites for tetanus toxin, α-bungarotoxin, muscimol), however, reach maximal levels only after 8 days in vitro. Glial markers such as carbonic anhydrase and hydrocortisone-induced glutamine synthetase activities are also expressed only transiently in culture.
Regeneration of adult newt skeletal muscle tissue in vitro
Authors: Schrag Joan A. , Cameron Jo Ann
Published: April 2021

Explants and cells of forelimb muscle from adult Notophthalmus viridescens were cultured for periods up to 160 days in MEM-based medium supplemented with serum, hormones, and antibiotics. Explants which were not minced prior to culture contained muscle fibres with healthy myonuclei and no evidence of dedifferentiation after four weeks. Exlants which were minced prior to culture contained degenerated muscle fibres after 1 day and no evidence of dedifferentiation after four weeks. Mononucleated cells from both minced and non-minced explants proliferated. Cell proliferation and myotube formation was greater in the minced muscle cultures. Proliferation and fusion of myoblasts and subsequent formation of myofibrils were observed on the plate in primary cultures. Secondarily transferred cells proliferated and fused into myotubes. Although adult newt muscle does not contain satellite cells, myogenesis in this amphibian followed the same course as all other vertebrate skeletal muscle: proliferation of mononucleated myogenic cells, fusion of the myoblasts to form syncytia, and eventual accumulation of myofibrils. The ultimate source of the myogenic cells was not identified; however, the absence of dedifferentiation of the mature fibres and the occurrence of myogenesis in cultures of minced muscle explants demonstrated that the regenerated muscle developed from a population of mononucleated cells whose origin did not depend upon dedifferentiation of intact fibres.
The positional coding system in the early eye rudiment of Xenopus laevis, and its modification after grafting operations
Authors: Cooke J. , Gaze R. M.
Published: April 2021

In a series of Xenopus embryos, 60–90 ° sectors at various positions distributed around the eye rudiment were replaced with sectors grafted from the opposite position in the rudiment on the same side of the head of a donor. The majority of the operations were carried out before stage 28 (Nieuwkoop & Faber, 1956), and many before stage 26. The patterns of retinotectal connectivity which then developed were assayed electrophysiologically soon after metamorphosis. The visuotectal maps were frequently compound, giving evidence that many parts of the rudiment had already been equipped with distinct tissue positional codes by the time operations were performed (i.e. before neurogenesis). Although graft-derived sectors of retina connected to tectal sectors that were more nearly appropriate for their original positions in the rudiment than for their translocated ones, the ‘handedness’ of these ectopic components of the compound maps tended to bear a mirror-image relation to the major map, rather than the point-symmetrical one to be expected from a complete autonomy of mapping functions in grafted tissue. The results are discussed in relation to possible modes of organization of the developing eye, considered as a pattern-forming system.