bluuebunny/crossref_metadata_2025_split huggingface dataset:
The role of the tissue environment in the expression of spotting genes in the mouse
Authors: Deol M. S. 
Published: April 2021

ABSTRACTGenes causing white spotting in the mouse act in two major ways: some affect the melano-blasts, while others affect the tissue environment of the melanoblasts. The question is whether the normal tissue environment plays any role in the origin of spots in those mutants in which the melanoblasts are believed to be the site of gene activity. An earlier study, using the genotypes + /mi, Miwhl+, s/s, Wv/ + and Wv/Wv(mi = microphthalmia; Miwh= white; s = piebald; Wv= viable dominant spotting), indicated that it probably does, the evidence largely consisting in the occurrence of extremely precise pigmentation patterns on a minute scale. It seemed that more direct evidence could be obtained by comparing the pigmentation of the iris with that of the choroid and the retina in the same eye in these and other genotypes. The outer and inner layers of the iris derive their pigment cells from the choroid and the retina respectively; therefore any clear and consistent differences between the behaviour of these cells in their original and their secondary place of activity would constitute evidence for the role of the tissue environment. Such differences were found.It was also found that in another genotype, Miwh/mi the retinal pigment cells, although unpigmented, are clearly distinguishable. This casts serious doubt on the widespread assumption that melanoblasts which do not differentiate always die.
Effects of nerve growth factor from the venom ofVipera russellion dispersed sensory ganglion cells from the embryonic chick
Authors: Banthorpe D. V. , Pearce F. L. , Vernon C. A. 
Published: April 2021

ABSTRACTA quantitative study has been made of the effects of nerve growth factor (NGF), isolated from the venom of Vipera russelli, on the growth of dispersed cells from the sensory ganglia of the embryonic chick. The main effects were to increase the viability of the sensory neurons in culture and to promote the regeneration of nerve fibres. In the presence of NGF a higher proportion of neurons produced fibres and the fibres were longer and slightly more branched than in control cultures. The number of fibres produced per neuron was unaltered. Supporting cells were unaffected by the presence of NGF. No stimulation of mitotic activity among either type of cell was observed. It is concluded that, under the stated conditions, NGF does not promote the differentiation of immature cells but acts, both in a maintenance and a stimulatory capacity, only on those cells recognizable as neurons.
Relationship between the amount of the ‘germinal plasm’ and the number of primordial germ cells in Xenopus laevis
Authors: Tanabe Kazuyuki , Kotani Minoru 
Published: April 2021

ABSTRACT
Tadpoles of Xenopus laevis completely lacking primordial germ cells were obtained by irradiating the vegetal hemisphere of early 2-cell eggs with u.v. (wavelength, 253·7 nm; dose, ca. 6000 ergs/mm2). An increasing number of primordial germ cells were observed as the stage at irradiation advanced from early 2-cell to early 4-cell stages. Furthermore, early 2-cell eggs irradiated with doses ranging from 750 to 6000 ergs/mm2 grew into tadpoles carrying a decreasing number of primordial germ cells in accord with the increase of the dose. On the other hand, tadpoles developed from eggs irradiated immediately after being centrifuged at 150 g for 1 min at early 2-cell stage to displace the ‘germinal plasm’ deeper into the cytoplasm, carried a considerable number of primordial germ cells. These facts were interpreted to suggest the presence of u.v.-sensitive germ cell determinant in the ‘germinal plasm’.
It was revealed by varying the area of irradiation that the number of primordial germ cells decreased in direct proportion to the increase of the area irradiated. It was concluded that the amount of the u.v.-sensitive material(s) contained in the ‘germinal plasm’ determined the number of primordial germ cells in tadpoles.
Surface coat on the epithelium of developing palatine shelves in the mouse as revealed by electron microscopy
Authors: Greene R. M. , Kochhar D. M. 
Published: April 2021

ABSTRACTThe fine structure of the surface epithelium of developing palatine shelves in the mouse was studied from days 11 through 14 of gestation. Ruthenium red, a cationic stain used as an ultrastructural indicator of acid mucopolysaccharides, was employed to detect the presence of any surface coat.Positive staining was first observed on day 12 of gestation and was seen to be present throughout the period of shelf elevation and fusion. Tt was seen over medial and lateral surfaces as well as the inferior to of vertical shelves. The surface coat was found to be present along the entire length of the shelf, extending superiorly up the medial and lateral epithelial borders until it abruptly disappeared.Since this surface coat first appeared approximately 48 h prior to shelf elevation, it is suggested that its appearance may be associated with the ability of palatine shelves to undergo fusion as shown by previous in vitro experiments. The time of acquisition by the shelves of this ‘fusing potential’ is also in the range of 48 h before shelf elevation.
Cellular aspects of regeneration hormone influence inNereis diversicolor
Authors: Olive P. J. W. 
Published: April 2021

ABSTRACTThe histology of caudal regeneration in Nereis diversicolor is described with special reference to the role of the cerebral ‘regeneration’ hormone. Wound healing is complete after 8 days; the regenerated stump of tissue then consists of the pygidium, associated anal cirri and a prepygidial region between the pygidium and the posterior margin of the last intact segment. The term segment blastema is used to refer to the cells from which all segmental structures are derived. The segment blastema is situated in the ventral posterior margin of the prepygidial region, and consists of transverse bands of cells with large nuclei (12 μm diameter) and prominent nucleoli. Segment anlagen are formed immediately in front of the segment blastema; the development of the anlagen is described, and six stages of development are defined.The extent of caudal regeneration in different animals is best compared with reference to the total number and stage of development reached by the segment anlagen. During normal regeneration at 18 °C, segment anlagen are first formed after 8 days, and they continue to be formed at the same rate until at least the 21st day after caudal ablation. The oldest segments reach stage 6 after about 15 days of regeneration.Wound healing, pygidium formation, and cirrus development and establishment of the segment blastema all occur in decerebrate animals following the loss of caudal segments, but segment anlagen formation is almost completely inhibited. Implantation of ganglia taken from intact donor animals into the coelom of decerebrate animals which have lost caudal segments initiates segment anlagen formation. The segment blastema of decerebrate animals remains competent to respond in this way for at least 15 days.The regeneration hormone produced by the cerebral ganglion is essential for continued segment anlagen production throughout the 2nd and 3rd weeks of regeneration at 18 °C. Delayed decerebration leads to an arrest of anlagen production, and anlagen younger than stage 3 fail to develop further. Older anlagen (stages 4 and 5) are independent of the regeneration hormone and can continue to differentiate in its absence.
Tissue differentiation in ectopic grafts after cultivation of rat embryonic shieldsin vitro
Authors: Škreb N. , Crnek V. 
Published: April 2021

ABSTRACTDifferentiation of rat embryonic shields in vitro is inferior to that obtained in grafts under the kidney capsule. To see whether the in vitro differentiation is stable or whether it can be improved in a better environment, rat embryonic shields, isolated on gestation days 8 and 9, were transplanted under the kidney capsule after a period of 7 or 14 days in vitro.After transfer, some tissues appear in the kidney that never appear in vitro. Many but not all tissues appear more frequently in grafts than in vitro. Most tissues differentiate further in grafts than in vitro, though skeletal muscle, when cultivated for 14 days before transplantation, is an exception.Thus the effect on differentiation of imperfect culture conditions can be counteracted, for some tissues but not all, by grafting to the kidney. The effect depends partly on the time spent in vitro before transfer.
Morphogenesis and growth of the definitive opisthonephros during metamorphosis of anadromous sea lamprey,Petromyzon marinusL
Authors: Ooi E. C. , Youson J. H. 
Published: April 2021

ABSTRACTThe definitive opisthonephros of the adult lamprey, Petromyzon marinus L., develops during metamorphosis from the nephrogenic cord confined within a nephric fold and extending from the posterior tip of the larval opisthonephros to the cloaca. This development is initiated prior to the first signs of external metamorphosis and begins with the simultaneous appearance of clusters of cells scattered along the entire length of the cord. Proliferation of these cell clusters and their elongation to connect to the closely associated archinephric duct results in the formation of rudimentary nephron units. Subsequent development involves the formation of tubular lumina, branching of the tubules, and the participation of the proximal ends of the newly formed tubules in the formation of the single renal corpuscle. Growth in size of the kidney is the result of lengthening of the existing tubules through cell proliferation rather than through the addition of new nephrons. This growth appears to be at the expense of adipose tissue within the nephric fold. During later stages of metamorphosis, cell proliferation is more prevalent in the ventral part of the nephric fold where a parallel system of tubules develops.The development of the definitive opisthonephros during metamorphosis of lamprey may prove to be a useful model for further studies of tissue differentiation and interaction during kidney development in vertebrates.
Proportional control of organelle position by a mechanism which similarly monitors cell size of wild type and conical form-mutantTetrahymena
Authors: Lynn Denis H. 
Published: April 2021

ABSTRACTDistance between mouthparts of dividing cells of wild type and conical form-mutant Tetrahymena thermophila (formerly T. pyriformis syngen 1) is directly proportional to cell size. This distance is related to cell length in both wild type and conical cells although the proportionality is different in each cell type. However, for both wild type and conical cells the distance between mouthparts is directly and similarly proportional to the product of cell length and cell width which is an estimate of cell size. Evidence has been obtained which suggests that the new mouthparts are positioned with reference to the anterior mouthparts rather than to either pole of the cell. Determination of the site of the new mouthparts is not related to the number of basal bodies between the two sets of mouthparts.
Re-evaluation of the presence of multiple haemoglobins during the ontogeny of the mouse
Authors: Shimizu Koji , Watanabe Tomomasa 
Published: April 2021

ABSTRACT
In mice, three alleles, Hbbs, Hbbd and Hbbp, have been found at the β-chain locus of haemoglobin. Analytical polyacrylamide gel electrophoresis revealed the presence of almost the same four haemoglobin bands (E-I, E-II, E-III and X) in all of the lysates of peripheral blood cells from 12-day-old foetuses of C57BL/6J (Hbbs), A/He (Hbbd) and PON (Hbbp). All were embryonic-type haemoglobins; the most anodal band (X) seemed to be a product of polymerization of E-I. Electrophoretic patterns of the haemolysates from 12-day-old foetuses were not affected by alkylation with iodoacetamide or maleic anhydride. Almost the same electrophoretic patterns in subunit analysis, using acid starch and acid-urea polyacrylamide gels, were obtained in 12-day-old foetuses of C57BL/6J, A/He and PON. E-I comprised α-and x-chains, E-Il, α-and y-chains, and E-III, α-and z-chains.
In adults, two haemoglobin bands, s and Y, were present in the haemolysate of C57BL/6J, while three, dmaj, dmin and Y, existed in A/He, and three, pmaj, pmin and Y, in PON. All were adult-type haemoglobins. Haemoglobin Y, which was not demonstrable after alkylation of the haemolysates, seemed to be a product of polymerization of major haemoglobins (s, dmaj and pmaj). Each haemoglobin possessed common a-chains, while the β-chains of major haemoglobins were different from those of minor haemoglobins.
Developmental changes of the haemolysates from foetuses of C57BL/6J, A/He and PON were similar to each other. Haemolysates of the liver cells of developing foetuses contained only adult-type haemoglobins. Our techniques used here were not able to demonstrate the presence of foetal-type haemoglobins.
Feather-forming capacities of the avian extra-embryonic somatopleure
Authors: Dhouailly Danielle 
Published: April 2021

ABSTRACT
Blocks of 12·5- or 13·5-day embryonic mouse upper-lip dermis were introduced under the ectoderm of the extra-embryonic area of 2-to 3-day chick or duck embryos. Two kinds of ectopic cutaneous appendages were produced : either arrested feathers alone, or arrested feathers and full-grown feathers. The former developed in the ectoderm overlying the implanted mouse dermal cells, the latter formed in their close vicinity, but contained host dermal cells exclusively.
Thus, avian extra-embryonic somatopleure, both ectoderm and mesoderm, possesses the information for feather development: the extra-embryonic ectoderm, if it is brought in contact with an appendage-forming dermis, is able to respond to the dermal induction by initiating feather morphogenesis; the extra-embryonic mesoderm, if it is experimentally transformed into a dense dermis, can express its feather-forming capacity by specifying feather tract morphology and barb-ridge number, thus leading to the achievement of feather morphogenesis.
Production of erythropoietic colony-forming units and erythrocytes during chick embryo development: an attempt at modelization of chick embryo erythropoiesis
Authors: Samarut J. , Jurdic P. , Nigon V. 
Published: April 2021

ABSTRACT
The enumeration of erythropoietic colony-forming cells in vitro has allowed us to complete previous data on changes in the various erythroid cell populations during chick embryogenesis.
Erythrocytic colony-forming units in culture (CFU-cE) which are sensitive to avian erythropoietin appear in the blastoderm as soon as the 24th hour of development. They represent most likely precursors of the megalocytic erythropoiesis, and do not seem to derive from stem cells common with normocytic erythropoiesis.
Data concerning vitelline normocytic erythropoiesis were analysed in a kinetic model based on stochastic change of the stem cells. From this model it appears that 17−20 cell divisions are required for differentiation of erythrocytes from stem cells.
The central pathways of optic fibres in Xenopus tadpoles
Authors: Steedman J. G. , Stirling R. V. , Gaze R. M. 
Published: April 2021

ABSTRACT
A cobalt chloride impregnation technique was applied to the optic nerve in Xenopus tadpoles and the central optic pathways were examined in cleared, whole-mounted preparations, and in thick sections. The overall plan of the optic input was visualized in relation to the outlines of the parts of the brain and details of the structure of the tectal optic neuropil, the neuropil of Bellonci and the basal optic neuropil were seen. The fibres in the main retinotectal tract maintained an orderly disposition with respect to each other, in contrast to the fibres of the basal optic tract, in which no order was apparent. Optic fibres were seen passing caudally from the region of the basal optic neuropil.
Effect of the T-mutation on histogenesis of the mouse embryo under the testis capsule
Authors: Fujimoto H. , YANAGISAWA K. O. 
Published: April 2021

ABSTRACT
Mouse embryos homozygous for the T-mutation show abnormalities, severer at the posterior embryonic regions, by day 9 of gestation and die before day .11 in utero.
To analyse developmental potentiality of the T/T embryos, fragments of their anterior and posterior portions were grafted into the testes of adult T/ + mice, and examined histologically for the tissues formed after 1 month.
The grafted tissues of the T/T embryos grew beyond the destined lethal stage and gave rise to benign teratomas composed of mature tissues. Although there were some different features of the tissues formed in the teratomas derived from different portions and stages of the embryos, their types were essentially identical between wild-type and the mutant teratomas. Statistical analysis showed that frequency of the cartilage and/or bone formation was significantly lower in the posterior mutant teratomas. It cannot be concluded, however, that this difference is essentially caused by T-mutation. The main conclusion of present experiments is that grafted portions of T/T embryos have the potentiality to develop into teratomas containing derivatives of all three germ layers.
Chemotactic cell sorting inDictyostelium discoideum
Authors: Matsukuma S. , Durston A. J. 
Published: April 2021

ABSTRACTWe made mixed mounds of vitally stained prestalk cells and unstained prespore cells, from Dictyostelium discoideum (Dd), and exposed these to external 3′,5′-cyclic-AMP (c-AMP) sources. We show that prestalk cells will sort out by moving directionally toward c-AMP sources held at &lt; 10−5 M C-AMP. This is evidence for cell sorting via chemotaxis. We present arguments that the natural cell sorting, observed during Dd development, is also chemotactic to c-AMP.
The ontogeny of erythropoiesis in the mouse detected by the erythroid colony-forming technique: I. Hepatic and maternal erythropoiesis
Authors: Rich Ivan N. , Kubanek Bernhard 
Published: April 2021

ABSTRACT
Employing the erythroid colony-forming technique, it is shown that throughout hepatic erythropoiesis in the mouse, the CFU-E population remains sensitive to erythropoietin. Maximum stimulation was achieved during this period using an erythropoietin concentration of 0·075 units/ml. The peak in the CFU-E concentration occurs between the 11th and 12th day while absolute values show a maximum on the 14th day of gestation. These results are discussed in terms of changing cell populations, both of erythropoietic precursors and hepatocytes from which it is concluded that at no time during foetal erythropoiesis does the CFU-E population change or become unresponsive to erythropoietin. The BFU-E population follows closely that of the CFU-E, but declines about 24 h earlier on the 16th day of gestation.
The effect of the foetus on the mother was also studied during the second half of pregnancy. During this period of natural perturbation both femoral and, in particular, splenic erythropoiesis are increased. However, during this time an erythropoietin concentration of 0-3 units/ml was required to maximally stimulate the CFU-E population derived from these tissues. The fact that both adult and foetal erythroid tissue maintain a rather constant requirement for erythropoietin for their growth in vitro, indicates that it is an intrinsic properly of the cells. It is concluded that increased maternal erythropoiesis is due to an increased oxygen requirement causing hypoxia due to the growing foetus.
Changes in protein synthesis during the development of Xenopus laevis
Authors: Ballantine J. E. M. , Woodland H. R. , Sturgess E. A. 
Published: April 2021

ABSTRACT
Patterns of protein synthesis during the development of Xenopus were studied by twodimensional gel electrophoresis. Up to the end of the blastula stage we find no newly synthesized proteins which are not already made in the oocyte. The first new proteins are seen during gastrulation, and they increase in number during neurulation. Some of these are restricted to the ‘ectodermal’ region, and some to the ‘endodermal’ region of embryos divided into two parts. These new, region-specific proteins include a-actin. When the oocyte matures the number of detectable newly synthesized proteins decreases, reaching a minimum in the unfertilized egg. Some, such as β and γ-actin, re-appear at the end of cleavage. This could not be shown to be a recovery artifact. The relation of the total mRNA to these changes in protein synthesis was studied by translation in the lysed reticulocyte cell-free system. The mRNAs that code for oocyte proteins that cease synthesis in the unfertilized egg and re-appear in blastulae are nevertheless detectable in total RNA made from eggs. These proteins therefore seem to cease and resume synthesis through translational control. mRNAs for new proteins first appear after gastrulation, just when these proteins are first detected in vivo. This strongly suggests, though it does not prove, that new gene activity is involved. It is therefore likely that region-specific gene activity is already present by the gastrula stage of development, and has an impact on the most abundant kinds of proteins made in the embryo.
Cyclic changes in the cortical layer of non-nucleated fragments of the newt’s egg
Authors: Sawai Tsuyoshi 
Published: April 2021

ABSTRACT
Various changes in the cortical layer of the amphibian egg have been observed during cleavage; for example, rounding up in the animal hemisphere, increase in stiffness of the surface and reactivity of the cortex to furrow-inducing cytoplasmic components. The three kinds of change occur synchronously with the cleavage cycle.
The present experiments were aimed at determining whether the above changes in the cortical layer are caused exclusively by the nucleus or autonomously by the cytoplasm. Uncleaved fertilized eggs of the newt, Cynopspyrrhogaster, were divided into two parts, one nucleated and one non-nucleated, by cutting with a fine glass needle. Special attention was paid to the behaviour of the non-nucleated fragments, where the above-mentioned changes were also observed. The cycle of these changes did not necessarily start synchronously with the cleavage cycle of the nucleated partner, but, once started, the rhythm of both cycles had almost the same timing. These results suggest that some change in the cortex necessary for cleavage furrow formation in the amphibian egg is brought about by cyclic change in the cytoplasm, independently of the nucleus.
The mechanism of somite segmentation in the chick embryo
Authors: Bellairs Ruth 
Published: April 2021

ABSTRACT
The segmentation of somites in the chick embryo has been studied by transmission and scanning electron microscopy (stages 8–14). The segmental plate mesoderm consists of loosely arranged mesenchymal cells, whereas the newly formed somites are composed of elongated, spindle-shaped cells arranged radially around a lumen, the myocoele. The diameter of each somite is thus two cells plus the myocoele.
Two major factors appear to be responsible for the change in cell shape at segmentation: (1) Each prospective somite cell becomes anchored at one end to the adjacent epithelia (i.e. the neural tube, the notochord, the ectoderm, the endoderm or the aorta) by means of collagen fibrils. These fibrils are already present in the segmental plate before the somites begin to form.(2) A change in cell-to-cell adhesiveness causes the free ends of these cells to adhere to one another. (Bellairs, Curtis & Sanders, .1978). This adhesion is then supplemented by the development of tight junctions proximally in the somite.
Because it is anchored at both ends, each somite cell is under tension in much the same way as a fibroblast cell in tissue culture is under tension. Each somite cell therefore becomes elongated and the somite as a whole accommodates its general shape to that of the space available between the adjacent tissues. The arrangement of the cells in the more differentiated somites (stages 17–18) has also been examined and it has been found that the chick resembles Xenopus in that the myotome cells undergo rotation and become orientated in an anteroposterior direction.