bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in glycosaminoglycan content of healing rabbit tendon
Authors: Reid T. , Flint M. H. 
Published: April 2021

ABSTRACT
Changes in the concentration of the major glycosaminoglycan compounds were measured during healing of severed Achilles tendons in rabbits. Using zone electrophoresis for separation, and densitometry for quantitation of these compounds, their concentrations could be measured in each of several portions of the tendon and its associated muscle.
Immediately after injury, the concentration of hyaluronic acid in the healing area and those portions of the tendon closely associated with it increased dramatically. An increase in the concentration of dermatan sulphate accompanied the subsequent formation of repair tissue.
Increased concentrations of glycosaminoglycan compounds were also found in the musculotendinous area remote from the injury, probably in response to relaxation of the severed tendon.
Further evidence that enterochromaffin cells are not derived from the neural crest
Authors: Andrew Ann 
Published: April 2021

ABSTRACT
Recently, a previous finding that the enterochromaffin cells of chick embryos are not derived from the neural crest has been contested, and so further evidence has been sought. Presumptive gut, i.e. endoderm and adherent mesoderm, of embryos between the short headprocess stage and the 25-somite stage was grown on the chorio-allantoic membranes of host embryos. Whether the presumptive gut was excised before or after the probable time of arrival of neural crest cells in the gut, enterochromaffin cells occurred in the intestine in the grafts. The presence or absence of enteric ganglia indicated the presence or absence, respectively, of neural crest cells. Enterochromaffin cells were plentiful even if the donor had been at a stage preceding that at which cells of the neural crest start to migrate, or preceding that at which the crests themselves first appear. In a second experiment, presumptive gut of embryos at 10-to 21-somite stages was excised so as to exclude the portion underlying the somites. Enteric ganglia were lacking in the intestine of these grafts, but enterochromaffin cells were invariably present.
These experiments show that the precursors of enterochromaffin cells are present in the more lateral part of the presumptive gut before the neural crest precursors of enteric ganglia reach the region; and that they are present in the presumptive gut long before any crest cells could have arrived there. This evidence supports the view that enterochromaffin cells are not derived from the neural crest in chick embryos.
Artificial insemination of deermice(Peromyscus maniculatus)with sperm from other rodent species
Authors: Maddock Michael B. , Dawson Wallace D. 
Published: April 2021

ABSTRACTDeermice (Peromyscus maniculatus) were hormonally induced to ovulate and artificially inseminated with sperm of 13 other rodent species varying in taxonomic distinction from species to family level. These were compared with inter se and sham inseminated controls. Embryos were recovered at various stages from 5 h to 10 days. Hybrid embryos failed to develop fully in all crosses except those within the same species group. Closely allied interspecies group crosses produced implantation embryos, but intersubgeneric and intergeneric crosses did not develop beyond early cleavage. Interfamilial hybrid embryos could not be obtained.
Investigation of a substance of renal origin which inhibits the growth of renal cortex explant in vitro
Authors: Dicker S. E. , Morris Christine A. 
Published: April 2021

ABSTRACT
Explants of renal cortex from 7-day mice or 5-day rats were reared on plasma clots, in the presence or absence of chick embryo metanephros. The size of outgrowth, estimated after 48 h, was similar for renal cortex of both species. When reared in chick embryo extract in the presence or absence of metanephros, the outgrowth estimated after 48 h was 2·08 ± 0·092 greater than that of the initial explant. Addition of supernatant fluid from a homogenate of renal cortex of adult mouse, rat, guinea-pig, rabbit or pig inhibited the outgrowth of renal cortex explant from neonate mouse or rat. The supernatant fluid from a homogenate of adult renal medulla had no significant effect. The inhibitory activity of the supernatant fluid from a homogenate of renal cortex from adult animals was destroyed by heating at 99 °C. The compound with growth-inhibitory activity appeared to be cortex-specific but not species-specific. Extracts of liver, spleen, duodenum, and heart muscle of adult animals had no significant effect on the outgrowth of renal explants of neonate animals; and extracts from renal cortex of adult mammals had no significant effect on the growth of other tissues from neonate mice or rats. The degree of growth inhibition was related to the amount of protein in the extract of renal cortex. Maximum inhibition was observed with extracts of renal cortex containing 2·5 mg protein/0·5 ml. Immune serum samples were obtained from rabbits and guinea-pigs immunized against extracts of renal cortex and medulla and liver from rats and mice. Only the serum from either rabbit or guinea-pig immunized against extracts of renal cortex blocked the growth-inhibitory action of renal cortex extracts.
Transfilter induction of kidney tubules: correlation with cytoplasmic penetration into Nucleopore filters
Authors: Wartiovaara Jorma , Nordling Stig , Lehtonen Eero , Saxén Lauri 
Published: April 2021

ABSTRACTThe presence of cell contacts in transfilter mouse kidney tubule induction by spinal cord was investigated. The interacting tissues were separated by Nucleopore® membrane filters of various pore sizes.Filters with a mean pore size of 0·2 μm or more allowed tubule formation, whereas 0·13 μm pore filters prevented it. There was an inverse correlation between pore size and minimum time of transfilter culture required for induction to occur. The differences in the diffusion rates through these filters do not support long range diffusion as a mechanism for induction. Electron microscopy of the cultures showed abundant cytoplasmic penetration deep into filters with 0·2 μm or larger pores. Processes from mesenchymal and spinal cord cells were closely apposed within the filter channels. No extracellular matrix or membrane vesicles were seen between the processes. In a few instances shallow penetration was seen in 0·1 μm type filters, but no contacts were observed.The presence of close cell appositions in those filters which allow kidney tubulogenesis suggests that close cellular interactions, rather than long range diffusion of signal substances, is the most likely communicative mechanism in this transfilter induction.
Susceptible stages and abnormal morphogenesis in the developing mouse limb, analysed in organ culture after transplacental exposure to vitamin A (retinoic acid)
Authors: Kochhar D. M. , Aydelotte M. B. 
Published: April 2021

ABSTRACT
The development of form and morphology of cartilage in limbs from control and retinoic acid-treated DBA/2J mice were studied in organ culture. Somite number at explantation (SE) ranged from 29 to 56. All cartilage segments except digits developed in cultures of 29-somite control limb-buds; digits developed well only from limb-buds of SE45 and older stages. Maternal treatment with retinoic acid specifically inhibited the growth of limbs rather than that of the whole embryo; the percentage reduction in limb length in culture ranged between 20 and 40 %, depending on the length of in utero exposure. The teratogenic effects of retinoic acid were expressed in culture even if the limb was explanted after only 1 h of in utero exposure. However, for a complete expression of the teratogenic effects, resulting in phocomelia, 24 h exposure was necessary. Limb-buds of 29 to 32-somite embryos were only mildly responsive to the teratogen. Embryos with 33–38 somites demonstrated the full extent of teratogenic effects. Embryos with more than 40 somites at the time of first exposure to retinoic acid escaped severe limb malformations except digital defects. Correlation between the developmental stage of the limb at the time of treatment and the final limb defect is attempted.
A scanning electron microscope study of the early limb-bud in normal andtalpid3mutant chick embryos
Authors: Ede D. A. , Bellairs R. , Bancroft M. 
Published: April 2021

ABSTRACTScanning electron microscope studies, supported by transmission electron microscope and light microscope observations, have been made of the wing-bud apex in the region of the apical ectodermal ridge (AER) in both normal and talpid3 mutant embryos.Ln normal embryos: the ectoderm consists of two layers, the periderm and the basal layer, resting upon a basal lamina. The external surface of the periderm cells bears numerous villi, especially numerous at the cell boundaries. In the AER the cells of the basal layer are compacted into a fan-shaped form, remaining as a single layer, though displacement of their nuclei gives the appearance of a stratified epithelium; the periderm cells tend to round up and many are necrotic. Microfilaments and microtubules are present in greater numbers in the AER than in other ectoderm cells and are orientated along the long axis in the very narrow elongated cells which comprise the middle of the ridge. The mesenchymal cells of the mesoderm tend to be flattened, with extensive flattened surface areas separated from each other by long edges of lamellar cytoplasm, from which many long filopodial extensions arise. Often the cells are elongated, with the filopodia arising predominantly at the anterior and posterior ends.In talpid3 embryos : when these were compared with normals no differences were detected in the general ectoderm or in the AER, but in the mesoderm a statistical analysis revealed significant differences in the occurrence of sections through very fine cytoplasmic processes in transmission electron microscope micrographs. Taken in conjunction with visual examination of scanning electron microscope pictures the differences suggested that talpid3 cells have filopodia distributed more extensively around the cell, but that these extensions do not extend so far through the intercellular spaces or produce such fine terminal arborizations as in normal mesenchyme.At the ectodermal/mesodermal boundary there is a web of extracellular material under the basal lamina, separated from the underlying mesoderm by a very narrow gap in normal embryos. Fine cytoplasmic extensions from the mesenchyme cells extend across the gap towards the basal lamina and many are in contact with it. The gap is wider in talpid3 wing-buds and a statistical analysis confirmed that far fewer filopodia approach closely to the basal lamina or make contact with it.The significance of these findings in relation to problems of AER formation and activity and motility of mesenchymal cells in the wing-bud is discussed.
Mise en évidence du rôle, dans la régénération des Amphibiens, d’une glycoprotéine sécrétée par la cape apicale: étude cytochimique et autoradiographique en microscopie électronique
Authors: Chapron Claude 
Published: April 2021

ABSTRACT

Evidence for the role of an apical cap glycoprotein in amphibian regeneration : cytochemical and autoradiographic electron-microscopic studies
Early during limb regeneration in the newt, an ectodermal apical cap covering a mesodermal blastema is formed. High-resolution autoradiography of these tissues has been carried out after incorporation of [3H]fucose, which is a precursor of glycoproteins. Autoradiography shows that silver particles are located at first on epithelial cells, then on mesenchymatous cells. This observation is consistent with a hypothesis in which the apical cap would elaborate a glycoprotein acting on the blastema. Substructural autoradiography and cytochemistry also show the importance of cellular surfaces for both cells producing glycoprotein and those which are target cells.
Experimental manipulations of early Drosophila embryos : I. Adult and embryonic defects resulting from microcautery at nuclear multiplication and blastoderm stages
Authors: Bownes Mary , Sang J. H. 
Published: April 2021

ABSTRACT
Localized regions of Drosophila eggs were damaged at both nuclear multiplication and blastoderm stages, using the technique of microcautery. The resulting defects in embryos and adults were recorded in order to study the effects of microcautery on determination of larval and adult structures. Using 70 °C microcautery, few specific defects were found in either embryos or adults. Sensitivity maps relating embryonic mortality to sites of damage were prepared for both egg stages and compared. Microcautery at 75 °C was used to check experimentally the putative localization in the egg of adult disc cells, as indicated by genetic mosaic studies. Although some of the expected adult defects were found, there was also evidence for regulation. Localized embryonic defects were found using this higher temperature, such that anterior damage produced anterior defects and posterior damage led to posterior defects. Mid-region microcautery resulted in both anterior and mid-region defects, the latter being most common after damage to the blastoderm. Comparisons are made with results obtained using other experimental manipulations and with the development of some embryonic lethal mutants.
The RNA polymerase activity of the preimplantation mouse embryo
Authors: Moore G. P. M. 
Published: April 2021

ABSTRACT
The activation of the mouse embryo genome has been studied during early cleavage, in vivo. Individual embryos, prepared as whole mounts, were assayed for endogenous RNA polymerase activity. RNA synthesis was detected by autoradiography as the incorporation of [3H]UMP into an acid-insoluble product.
No RNA polymerase activity could be detected in the pronuclei of one-cell embryos. Radioactive incorporation was first evident in the nuclei of two-cell embryos. This appeared to be confined to the nucleoplasm and could be abolished by a-amanitin but not by low concentrations of actinomycin D. Polymerase activity which was not affected by α-amanitin was first detected in the four-cell embryo, predominantly at the peripheries of the nucleoli. Nucleolar labelling increased markedly between subsequent cleavages, reaching a peak in early morulae. In one- and two-cell embryos, label incorporation could be found in the nucleus of the persisting polar body.
Effects of bromodeoxyuridine, cytosine arabinoside and Colcemid uponin vitrodevelopment of mouse blastocysts
Authors: Sherman Michael I. , Atienza Sui Bi 
Published: April 2021

ABSTRACTMouse blastocysts in culture have been treated with increasing concentrations of cytosine arabinoside, bromodeoxyuridine or Colcemid. Concentrations of all three antimetabolites have been found which interfere with neither hatching of the blastocysts from their zona pellucidae nor subsequent attachment of the blastocysts to the culture dish, but which eventually result in death of the inner cell mass (ICM) and its derivatives. The effect upon the ICM is selective at these antimetabolite concentrations since many or, in some cases, all trophoblast cells continue to survive, and by a number of criteria, undergo normal patterns of differentiation and development.
Stage-sensitivity and dose-response curve of u.v. effect on germ cell formation in embryos of Xenopus laevis
Authors: Ijiri Ken-Ichi 
Published: April 2021

ABSTRACT
Ultraviolet light (u.v.) irradiation of the vegetal hemisphere of Xenopus laevis eggs resulted in the elimination of primordial germ cells in tadpoles. Quantitative studies were performed on this phenomenon. The stage sensitivity to u.v. inactivation of germ cell formation was obtained for the early developmental stages ranging from immediately after fertilization to small-cell blastula. It was found that u.v. irradiation at the stage immediately after fertilization was more injurious than irradiation at the beginning of the first cleavage. After deciding optimal conditions for this u.v. irradiation experiment, a dose-response curve of the phenomenon was obtained. It showed a good agreement with the theoretical expectation, which the authors had previously presented.
An autoradiographic analysis of nucleic acid synthesis in the presumptive primordial germ cells of Xenopus laevis
Authors: Dziadek Marie , Dixon K. E. 
Published: April 2021

ABSTRACT
Microinjection of [3H]thymidine into Xenopus laevis embryos between late blastula (stage 10) and early tadpole (stage 44) showed that the presumptive primordial germ cells synthesise DNA between stages 10-33. The percentage of labelled cells was highest between stages 10 and 16, declined sharply between stages 22 and 26 and rose again between stages 26 and 33. The fluctuations in the labelling patterns together with increase in the number of presumptive primordial germ cells and direct observation of germ cells in mitosis suggested that the germ cells divide three times between stages 10 and 44. The first divisions probably take place during gastrulation (stages 10-12), the second relatively synchronously at about stages 22-24 and the third series again relatively synchronously about stages 37-39. This period of proliferative activity is distinguishable on the one hand from the cleavage divisions in which the number of germ cells does not increase and on the other hand from the next proliferative phase by a period of mitotic inactivity. Microinjection of [3H]uridine showed that the presumptive primordial germ cells synthesize RNA only in mid-gastrula to early tail-bud-stage embryos. There is no obvious simple causal relationship between RNA synthesis and the movement of the germ plasm to the nucleus, or with division of the germ cells or with their migration out of the endoderm.
Experiments on Neuromery in Ambystoma punctatum Embryos
Authors: Källén Bengt 
Published: April 2021

ABSTRACT
When the substratum was removed from under the archencephalic or rhombencephalic anlagen of the neural plate of Ambystoma punctatum embryos, the neuromeres in these regions developed normally. When the rhombencephalic part of the neural plate was transplanted to the ventral ectoderm of an older host together with substratum, neuromeres developed in the transplant. When the transplantation was made without the substratum, no distinct neuromeres appeared. When the neural plate was explanted together with the substratum, neuromeres were formed in the explant. When the explantation was made without the substratum, neuromery was either absent or, when some mesoderm had been left behind, very irregular. It is concluded that the substratum plays an important role in the formation of the neuromeres. The latter are not secondary to a mesodermal segmentation. The influence from the substratum is probably a general mitotic stimulation.
Selective Inhibition of Cleavage in Different Regions of the Frog Egg by Sulphydryl Inhibitors
Authors: Barth Lucena J. 
Published: April 2021

ABSTRACT
When frogs are exposed during early cleavage to low concentrations of the sulphydryl inhibitor, p-chloromercuribenzoic acid, cleavage is inhibited at the animal pole, while the marginal zone and yolk cleave normally. Eggs exposed before first cleavage cleave only at the animal pole, while blastulae and gastrulae are inhibited uniformly in all regions by the sulphydryl reagent. The selective inhibition of animal-pole cells by p-chloromercuribenzoic acid is not readily explained on the basis of regional permeability differences or variations in sensitivity of the surface coat to inhibitors, since exposure of eggs to iodoacetamide results in normal cleavage at the animal pole, together with inhibition of cleavage at the marginal zone and in the yolk. The inhibition produced by p-chloromercuribenzoic acid is mediated by sulphydryl groups, since the effects of the inhibitor are reversible by thioglycollate and cysteine. When various protein fractions are extracted from eggs or hatched embryos and tested for sulphydryl groups by means of the nitroprusside reaction, the soluble fractions are found to contain freely reactive sulphydryl groups, while the yolk proteins are entirely lacking in reactive protein-bound sulphydryl groups. When the yolk proteins are fractionated into phosphoprotein (S2) and non-phosphoprotein (Si), the latter alone is found to contain masked SH groups that become fully reactive only after denaturation plus reduction of disulphide groups. It is suggested that the protein-bound SH groups at the marginal zone are protected against p-chloromercuribenzoic acid inhibition by a high content of soluble thiols such as reduced glutathione, which are synthesized at the expense of sulphur-containing amino acids from the yolk protein Si, under the control of enzymes and nucleotides such as adenosine triphosphate present in the dorsal lip region and marginal zone.
Recherches expérimentales sur la nature et les propriétés de l’inducteur de la régénération des yeux de la planaire Polycelis nigra
Authors: Lender par Théodore 
Published: April 2021

ABSTRACT
After excision of eyes and brain of the planarian Polycelis nigra (Ehrbg.), regeneration of eyes fails unless the brain is allowed to regenerate too. But regeneration of eyes in the absence of the brain occurs if the animals are kept in the presence of a mince of planarian heads, or of such a mince embedded in agar, or of the supernatant obtained after grinding heads with sand. The induction of eye regeneration is therefore performed by a chemical substance, an organisine. Regeneration of eyes in the absence of the brain is possible if the organisine is only allowed to act on alternate days, or only for two consecutive days in all. In the latter case, best results are obtained if the substance acts during the 3rd and 4th days after operation. Regeneration of eyes is favoured by increased concentration of organisine in the medium. Treating the inducing material with 70 per cent, alcohol does not inactivate the organisine, nor does warming to 60° for 2 minutes. Higher temperatures reduce its activity, and boiling for 30 minutes almost destroys it. The organisine is not species-specific. Its presence can be demonstrated in the brain region of Dugesia lugubris, D. gonocephala, and Dendrocoelum lacteum. A mince of the pharyngeal or caudal region does not produce regeneration of eyes. But a mince of the caudal region can be activated by treatment at 60° for 2 minutes. With stronger heating the inducing power diminishes, as with the mince of heads. A mince of caudal regions is also activated if it is treated with alcohol of 70 or 95 per cent. The supernatant obtained from grinding caudal regions with sand also contains the organisine. Such supernatants from the caudal regions are more active the greater the number of animals from which they are prepared; but they contain less organisine than the supernatant from an equivalent number of head regions. The regeneration of eyes of Polycelis nigra is therefore induced by a chemical substance, an organisine, present throughout the body of the planarian. Its concentration is stronger in the anterior than in the posterior region; in the latter it is furthermore immobilized within the cells. These results are comparable with those obtained in the study of amphibian embryonic induction.