bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pattern formation in 8-cell composite embryos of Xenopus laevis
Authors: Kageura H. , Yamana K. 
Published: April 2021

ABSTRACT
We have shown in defect experiments that an 8-cell embryo of Xenopus laevis consists of three kinds of cells, that is, animal, vegetal dorsal and vegetal ventral cells, and that cells of different kinds are distinctly different in their developmental capacity. Complete pattern formation occurs in any defect embryo which contains at least two animal, one vegetal dorsal and one vegetal ventral cell. In the present transplantation experiments, we replaced one or two cells of one 8-cell embryo by those of another to obtain 29 series of composite embryos, in which the cell composition of an embryo and/or the dorsoventral orientation of individual cells differed from those of a normal 8-cell embryo. The resulting embryos were examined macroscopically when controls reached stage 26 (tailbud stage) and later.
The results showed that both the two animal dorsal cells or one vegetal dorsal cell could be replaced by animal ventral cells or a vegetal ventral cell, respectively, without any detectable effect on pattern formation, irrespective of the ventrodorsal direction of the ventral cells. On the other hand, replacement of an animal ventral or a vegetal ventral cell by an animal dorsal or a vegetal dorsal cell, respectively, made most composite embryos twins. Twins were also formed when a left-handed vegetal dorsal cell was replaced by a right-handed counterpart and vice versa. In these composite embryos, the dorsoventral orientation of the transplanted cell was different from that of a resident dorsal cell or cells of a recipient, and several lines of evidence show that the dorsal cell transplanted in an off-axis orientation is responsible for twin formation. Thus, dorsal cells have the capacity to form dorsal axial structures at later stages and this capacity is localized on the dorsal side, and endows the cells with polarity. On the other hand, ventral cells did not have this capacity or polarity, judging from the fact that their orientation had no effect on pattern formation. One vegetal dorsal or ventral cell could be replaced by an animal dorsal or ventral cell, respectively, without any marked effect. However, replacement of two vegetal cells by animal ones and of one or two animal cells by vegetal ones resulted in deficiency of vegetal cells and oedema and in deficiency of animal cells and incomplete invagination, respectively.
Twin formation in composite embryos with animal dorsal cells in place of animal ventral ones is discussed in consideration of findings in recombination experiments by Nieuwkoop.
Pattern of skeletal muscle regeneration after reautotransplantation of regenerated muscle
Authors: Gulati Adarsh K. 
Published: April 2021

ABSTRACT
Autotransplantation of rat extensor digitorum longus muscle results in initial myofibre degeneration and subsequent regeneration from precursor myosatellite cells. To determine what effect a reinjury would have on the regenerative response, in the present.study, once transplanted and regenerated muscles were reinjured by reautotransplantion. In rats, four weeks after initial transplantation, when the regeneration was complete, the extensor digitorum longus muscle was transplanted again and the pattern of regeneration in reautotransplanted and once auto transplanted muscles was compared. Muscles were analysed 2, 4, 7, 14 and 30 days after autotransplantation and reautotransplantation. Both autotransplanted and reautotransplanted muscles underwent degeneration and regeneration; however, the pattern of regeneration in these two transplants was quite different. In autotransplants, a thin myogenic zone, marked by activated myoblasts, was first seen at 4 days. By 7 days the width of myogenic zone increased but still many degenerating myofibres were present in the central region of the muscle. By 14 days the muscle was filled with regenerated myotubes and myofibres. The reautotransplanted muscles underwent similar regenerative events; however, the rate of regeneration was considerably faster. The myogenic zone was apparent as early as 2 days and was much larger at 4 days, and by 7 days the entire muscle was filled with regenerated myotubes and myofibres which matured at later time intervals. Furthermore, the decrease in muscle weight in reautotransplanted muscles was not as much as that seen after autotransplantation. These findings reveal that not only is skeletal muscle capable of regeneration after a second injury, but the rate of this regeneration is much faster. This increased rate and recovery may be due to a conditioning effect of the first injury.
The growth of supernumerary legs in the cockroach
Authors: Truby Paul R. 
Published: April 2021

ABSTRACT
When the anteroposterior axis of a cockroach leg is reversed at a graft by exchanging a left leg for a right leg at the mid-tibia level, regeneration occurs in the region of the graft/host junction. This results in the formation of a pair of lateral supernumerary legs. In these experiments the patterns of cell division which take place during supernumerary leg formation were observed in sections of regenerating legs of the cockroach Leucophaea maderae. Early patterns of cell division resemble those seen in control grafts in which no axial reversal had been carried out during grafting. These cell divisions are associated with the process of wound healing. Later, a large area of the epidermis proximal to the graft/host junction becomes activated and shows a rapid rate of cell division. This area forms two outgrowths which grow by cell division throughout their epidermis to form the epidermis of the supernumerary legs.
The results are more consistent with the view that the formation of supernumerary legs involves dedifferentiation of the epidermis in the region of the graft/host junction to form a blastema, rather than being due to local cell division at the point of maximum pattern discontinuity. This conclusion is used to offer an explanation for the range of different types of outcome of left-right grafts that has been observed.
Proximal–distal sequence of development of the skeletal tissues in the penis of rat and the inductive effect of epithelium
Authors: Murakami Ryutaro , Mizuno Takeo 
Published: April 2021

SUMMARY
The penis of adult rats comprises the corpus cavernosum penis and the proximal and distal segments of os penis which are situated proximal–distally in this order. Androgens are necessary for the phenotypic differentiation of these tissues. In the present study, genital tubercular mesenchyme of foetal rats was recombined with or without homologous or heterologous epithelia and transplanted beneath the kidney capsule of syngeneic adult male rats, and the development of the corpus cavernosum penis and the os penis in the transplants was examined. Only in the presence of epithelia can the genital tubercular mesenchyme acquire the capacity for differentiation into the corpus cavernosum penis, the proximal segment of os penis, and the distal segment of os penis in this chronological order. The inductive effect of epithelium is a permissive step in the differentiation of the os penis of rat. The epithelium seems to be necessary for the process of rudiment formation of the os penis and the corpus cavernosum penis.
The effects of two retinoids on limb regeneration in Pleurodeles waltl and Triturus vulgaris
Authors: Lheureux Emile , Thoms Stephen D. , Carey Frederick 
Published: April 2021

ABSTRACT
The effects of two vitamin A analogues, retinol palmitate and retinoic acid, on pattern formation during limb regeneration in larvae of two European newts, P. waltl and T. vulgaris are described. The response of the regenerating limb to retinoid treatment differed according to the larval stage of development for P. waltl. Young larval limbs, which were anterior limb buds at the time of amputation, duplicated transversely while limbs of older larvae duplicated proximodistally. Proximodistal duplications were usually limited to the production of supernumerary carpals or a second zeugopod. Complete limbs regenerating from a distal amputation plane were rarely seen. T. vulgaris larvae regenerated limbs with either one or the other type of duplication, but never both on the same limb, at all larval stages tested.
When larval P. waltl were kept in normal laboratory light during the treatment with retinol palmitate suspended in the rearing water the percentage of limbs which duplicated was very small for young larvae and increased with the age of the larvae used. Keeping the animals in the dark during the treatment period greatly increased the percentage of duplicate limbs obtained on the young larvae but not on the older larvae. This result is discussed in terms of the photodegradation of the retinoid and the length of the sensitive period for the regenerating limb.
A dose–response relationship between the dose of retinol palmitate and either the percentage of limbs duplicated or the degree of duplication was not found. Such a relationship, however, was observed when retinoic acid was injected intraperitoneally into stage-54+ P. waltl larvae. Additionally, this technique revealed a peak of sensitivity to retinoic acid on the 6th day after amputation.
Limb regeneration in older larvae was temporarily blocked by retinoid treatment. The limbs showed little or no regression and began blastemal development shortly after the treatment ended. Limbs of young larvae, however, often regressed. Such regressions were followed by blastemal formation and middle- to late-bud blastemas were found at the end of 11 or 14 days treatments with retinol palmitate.
The effects of temporary ischaemia on rat muscle spindles
Authors: Diwan F. H. , Milburn Alice 
Published: April 2021

ABSTRACT
Soleus muscle of adult rat is revascularized 5–8 days after sectioning the supplying blood vessels. The temporary ischaemia thus produced results in the rapid concomitant degeneration of extra- and intrafusal muscle fibres along with their nerve terminals and supplying axons.
The basal lamina of all muscle fibres usually remains intact throughout the degenerative phase. Necrotic sarcoplasm is removed by phagocytic cells. Satellite cells survive the temporary ischaemia and give rise to presumptive myoblasts which fill the basal-lamina tubes. These myoblasts fuse to form myotubes which, by the 14th day after devascularization, are maturing into muscle fibres in the absence of any innervation. Within the spindle, nuclear-bag fibres degenerate more rapidly than nuclear-chain fibres. Regeneration proceeds more rapidly within the basal-lamina tubes of the original bag fibres than within those of the chain fibres.
Reinnervation of regenerating extra- and intrafusal fibres begins 21 days after devascularization and is completed some 7 days later, during which time further equatorial differentiation of some reinnervated intrafusal fibres may occur.
Regenerated spindles vary considerably with respect to their innervation and equatorial nucleation. Most contain short, thin, additional muscle fibres as well as those that have regenerated within the basal-lamina tubes of the original fibres.
The pigmentary system of developing axolotls: III. An analysis of the albino phenotype
Authors: Frost S. K. , EPP L. G. , Robinson S. J. 
Published: April 2021

ABSTRACT
The albino mutant in the Mexican axolotl (Ambystoma mexicanum) is analysed with respect to the differentiation of pigment cells. Pigment cells were observed with the transmission electron microscope in order to determine any unusual structural characteristics and to determine what happens to each of the cell types as development proceeds. Chemical analyses of pteridine pigments were also carried out, and the pattern of pteridines in albino animals was found to be more complex than, and quantitatively enhanced (at all developmental stages examined) over, the pattern observed in comparable wild-type axolotls. The golden colour of albino axolotls is due primarily to sepiapterin (a yellow pteridine) and secondarily to riboflavin (and other flavins).
Coincident with enhanced levels of yellow pigments, xanthophore pigment organelles (pterinosomes) in albino skin reach a mature state earlier than they do in wild-type axolotl skin. This morphology is conserved throughout development in albino animals whereas it is gradually lost in the wild type. Unpigmented melanophores from albino axolotls are illustrated for the first time, and in larval albino axolotls the morphology of these cells is shown to be very similar to xanthophore morphology. In older albino animals xanthophores are easily distinguished from unpigmented melanophores. Iridophores seem to appear in albino skin at an earlier stage than they have been observed in wild-type skin. Morphologically, wild-type and albino iridophores are identical.
Albumin and transferrin synthesis in whole rat embryo cultures
Authors: Williams Carolyn L. , Priscott Paul K. , Oliver I. T. , Yeoh George C. T. 
Published: April 2021

ABSTRACT
The uptake of [3H]leucine by the rat yolk sac and embryo and the subsequent synthesis of albumin and transferrin have been studied in whole embryo culture. Rat embryos of 12 days gestation were used in all experiments. Isotopically labelled transferrin was detectable in yolk-sac and embryo tissue extracts. In contrast, [3H]albumin could not be found in either tissue extract. Levels of radioactive transferrin in the yolk sac of cultured whole conceptuses decreased during 12 h in cold media. Embryonic transferrin showed an opposite trend in that it increased over 12 h by nearly 30-fold. In view of these results experiments were conducted in embryos and yolk sacs cultured in separate bottles. Radioimmunoprecipitation for transferrin revealed that there was synthesized protein in the yolk sac which then decreased by approximately 30 % after 2h in normal cultured medium. There was no evidence of transferrin synthesis in embryo extracts over a 12 h period. These results present evidence that the visceral yolk sac is the primary site of transferrin synthesis in the rat and that the protein is thereafter transported, intact, to the embryo.
Pathways of regenerated retinotectal axons in goldfish I. Optic nerve, tract and tectal fascicle layer
Authors: Stuermer Claudia A. O. 
Published: April 2021

ABSTRACT
This study investigates the order of regenerating retinal axons in the goldfish. The spatiotemporal pattern of axon regrowth was assessed by applying horseradish peroxidase (HRP) to regenerating axons in the optic tract at various times after optic nerve section and by analysing the distribution of retrogradely labelled ganglion cells in retina. At all regeneration stages labelled ganglion cells were widely distributed over the retina. There was no hint that axons from central (older) ganglion cells might regrow earlier, and peripheral (younger) ganglion cells later, as occurs in normal development.
The absence of an age-related ordering in the regenerated optic nerve was demonstrated by labelling a few axon bundles intraorbitally with HRP (Easter, Rusoff & Kish, 1981) caudal to the previous cut. The retrogradely labelled cells in retina were randomly distributed in regenerates and not clustered in annuli as in normals. Tracing regenerating axons which were stained anterogradely from intraretinal HRP applications or retrogradely from single labelled tectal fascicles illustrated the fact that the regenerating axons coursed in abnormal routes in the optic nerve and tract.
On the surface of the tectum regenerated fibres re-established a fascicle fan. The retinal origin of tectal fascicles was assessed by labelling individual peripheral, intermediate and rostral fascicles with HRP. The retrogradely labelled ganglion cells in the retina were often more widely distributed than in normals, but were mostly found in peripheral, intermediate and central retina, respectively.
The order of fibre departure from each tectal fascicle was revealed by placing HRP either on the fascicle’s proximal or on its distal half. With proximal labelling sites labelled ganglion cells were found in the temporal and nasal retina, and with distal labelling sites labelled ganglion cells were confined to nasal retina only. Further, the axonal trajectories of anterogradely labelled dorsotemporal retinal ganglion cells were compared to those of dorsonasal retinal ganglion cells in tectal whole mounts. Dorsotemporal axons were confined to the rostral tectal half, whereas dorsonasal axons followed fascicular routes into the fascicles’ distal end and reached into caudal tectum. This suggests that the fibres exited along their fascicle’s course in a temporonasal sequence.
Thus in the tectum, fibres in fascicles restore a gross spatial and age-related order and tend to follow their normal temporonasal sequence of exit.
The preliminary characterization of mitogens secreted by embryonic chick wing bud tissues in vitro
Authors: Bell K. M. 
Published: April 2021

ABSTRACT
Embryonic chick wing bud tissues secrete diffusible mitogens when cultured in vitro (Bell & McLachlan, 1985). These molecules may play an important role in limb development since media conditioned by morphogenetically active regions of the wing bud possess greater mitogenic activity than media conditioned by non-morphogenetic regions. These studies show that while the chick-derived growth factors were mitogenic for mouse-derived NIH 3T3,10T1/2 and NR6 cells and chick limb bud cells, they did not stimulate DNA synthesis in 3B11, PC13 END, normal rat kidney or bovine endothelial cells. Furthermore, the effects of the chick-derived mitogens were synergistically enhanced by insulin and PGF2α but remained unaffected by ECDGF, EGF, FGF and MSA. These findings indicate that embryonic chick limb bud cells synthesize and secrete growth factors which resemble in function other well-characterized growth factors and in particular PDGF.
Clonal analysis of chimaeric patterns in aortic endothelium
Authors: Schmidt Günter H. , Wilkinson Maureen M. , Ponder Bruce A. J. 
Published: April 2021

ABSTRACT
The mosaicism in aortic endothelium of mouse aggregation chimaeras is demonstrated using the lectin Dolichos biflorus agglutinin as a strain-specific marker. The general fragmentary appearance and considerable size range of patches suggests that endothelial cells do not proliferate in a highly coherent manner. The developmental significance of the observed patterns is investigated by means of a quantitative statistical analysis -the Greig-Smith analysis of variance. This method examines the spatial distribution of patches and is able to detect and characterize pattern at various scales. The results show that (1) patches are non-randomly distributed at all scales examined and (2) ‘clusters of clusters’ occur at one small and one large scale, defining territories of ‘primary’ and ‘secondary’ descendent clones, which arose respectively during early and late periods in the development of the endothelium. We conclude from this analysis that (1) cell mixing is never complete, even in the early embryo and (2) cell mingling is not uniform during development. A different pattern was previously demonstrated for intestinal epithelium (Schmidt, Wilkinson & Ponder, 1985c) indicating the potential value of the method for quantitative comparison of mosaicism between tissues and also different developmental stages. Our results suggest that the analysis of patch sizes is likely to be less informative in terms of developmental mechanisms, than the analysis of the spatial arrangement of patches.
Comparison of microfilament patterns in nurse cells of different insects with polytrophic and telotrophic ovarioles
Authors: Gutzeit Herwig O. , Huebner Erwin 
Published: April 2021

ABSTRACT
The localization of F-actin (microfilaments) in the nurse cells of ovarian follicles has been studied in 12 different insect species by fluorescence microscopy after specifically staining F-actin with rhodamine-conjugated phalloidin. In the analysed species with polytrophic ovaries (Apis mellifica, Pimpla turionellae, Bradysia tritici, Ephestia kuehniella, Protophormia terraenovae) a dense F-actin network was found to be associated with the nurse cell membranes. Only in Protophormia were microfilament bundles seen to extend from the cell membrane into the nurse cell cytoplasm and in a few cases appeared to make contact with the nuclear membrane. In the analysed coleopteran species with telotrophic ovarioles (Strangalia melanura, Leptinotarsa decemlineata, Oryzaephilus surinamensis) the fluorescence was also concentrated at the nurse cell membranes only. However, in all analysed hemipteran species (Lyguspratensis, Calocoris affinis, Graphosoma lineatum, Euscelis plebejus) the microfilament pattern was very different: while the nurse cells stained only weakly, we always found a characteristic (in some species massive) microfilament network surrounding the trophic core, a central area in the germarium from where material is transported through the trophic cords into the oocytes. The observed differences in the microfilament patterns are likely to reflect different mechanisms for transporting macromolecules and organelles within the ovariole.
Pattern discontinuity, polarity and directional intercalation in axolotl limbs
Authors: Muneoka Ken , Holler-Dinsmore Gregory V. , Bryant Susan V. 
Published: April 2021

ABSTRACT
Axolotl limb stumps with dorsal-ventral confrontations between digits 2 and 3 but with a normal anterior-posterior pattern were created by grafting between contralateral limbs. Graft and host differed in ploidy to permit a determination of the origin of cells in the regenerated limb. After regeneration, limbs were analysed for skeletal and muscle patterns and for the distribution of marked cells in the regenerate. Regenerated limbs showed varying degrees of abnormality in their dorsal-ventral organization. Following regeneration, the original dorsalventral discontinuities were in some cases maintained and in others resolved. The maintenance or resolution of pattern discontinuities occurred in a position-dependent manner. Cell marker analysis indicates a relationship between the resolution of discontinuities and the extent to which cells become displaced across the original graft-host interface. These data lend support to the suggestion that circumferential intercalation is directionally biased.
Developmentally regulated expression of insulin-like growth factors by differentiated murine teratocarcinomas and extraembryonic mesoderm
Authors: Heath John K. , Shi Wai-Kang 
Published: April 2021

ABSTRACT
The expression of plasma membrane receptors for insulin-like growth factors (IGFs) by PC13 embryonal carcinoma (EC) cells, and their immediate differentiated progeny PC13END was examined by binding radiolabelled IGF-I to cell monolayers. Both cell types express high-affinity IGF receptors, but the apparent number of unoccupied receptor sites falls by about 60 % upon differentiation. Crosslinking studies reveal that both type 1 and type 2 IGF receptors are expressed by PC13EC cells.
PC13END-cell-conditioned medium contains developmentally regulated, separable activities, one of which reacts directly with IGF-II, and the other with IGF for plasma membrane receptors. The former activity represents a soluble secreted IGF-binding protein. The latter activity is structurally and functionally similar to rat IGF-II.
Polyclonal antibodies raised against purified rat IGF-II specifically recognize multiple forms of IGF in radiolabelled culture supernatants and material which closely resembles the soluble IGF-binding protein. Immunoprecipitation of radiolabelled culture supernatants with anti-rat IGF-II reveals that the differentiation of PC13EC cells is accompanied by the coexpression of IGF-like molecules and the soluble binding protein, and that IGF-like molecules are expressed by extraembryonic tissues of mesodermal origin in the early postimplantation mouse embryo.
These findings show that IGF-like molecules are expressed in early mammalian development and may act in an autocrine fashion in vivo.