bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cell proliferation patterns during cytodifferentiation in embryonic chick tissues: liver, heart and erythrocytes
Authors: Jeter James R. , Cameron Ivan L. 
Published: April 2021

ABSTRACT
Tritiated thymidine was administered to four groups of embryos at various stages of development. The first group was killed 45 min after isotope administration. The second group received the isotope three times over a 12 h period, the third group four times over a 24 h period, and the last group eight times over a 48 h period. Sagittal histological sections of the embryos were prepared for radioautography. In the radioautographs the percentage labeled nuclei were scored as an index of cell proliferation. The following observations were made.
From stage 10 to 23 (45 min series) there is a progressive increase in the proliferative index of the labeled erythrocytes. This was followed by a precipitous drop as embryonic age increased. At stage 23 of the .12 h series, 97 % of the cells were labeled. The 24 and 48 h series of embryos also exhibit a high labeling index, 97 % and 95 % respectively, by stages 20–24. This indicates that at these stages most of the cells were in the proliferative pool. In correlation with the demonstrated presence of hemoglobin as early as stage 10, it was concluded that cell proliferation and cytodifferentiation in chick primary erythrocytes are not mutually exclusive.
A random pattern of proliferative activity existed in the liver of the early embryos; however, at stage 29 the periphery began to show a higher labeling index than was found in the center. This indicates that liver growth was primarily appositional. From stage 29 through hatching there was a gradual decline in the labeling index. After hatching a burst of proliferative activity occurred but the appositional pattern of growth was not seen. The proliferative activity of the littoral cells remained relatively constant when compared to that of the hepatic parenchymal cells. This suggests that the control of their proliferative activity was somewhat different from that of the hepatic parenchymal cells. The relationship of cell proliferation and cytodifferentiation in the liver could not be established.
There was a progressive increase in the proliferative index of the heart ventricular myoblasts from stage 12 through stage 20–23. This was followed by a gradual decline in proliferation as embryonic age increased. An appositional growth of the heart was also demonstrated. Cytodifferentiation of heart myoblasts is known to occur as early as stage 10. Almost all of the myoblasts were labeled at stages 32 and 33 of the group exposed to the isotope for 48 h. This indicates that, in the heart, cytodifferentiation and cell proliferation are not mutually exclusive processes.
Etude par cytochimie ultrastructurale des corpuscules périnucléaires présents dans les jeunes oocytes de Ilyanassa obsoleta Say (Mollusca gastéropode)
Authors: Gerin Yves 
Published: April 2021

ABSTRACT
An ultrastructural cytochemical study of the perinuclear corpuscles found in young oocytes of Ilyanassa obsoleta Say (molluscan gastropod)
Ultrastructural study of the perinuclear region of young oocytes of Ilyanassa obsoleta shows the existence of numerous corpuscles which we have called ‘perinuclear corpuscles’.
These are composed of filaments, of variable thickness (15–45 nm) and frequently show contacts with the nuclear envelope. With the development of the oocyte, they scatter in the cytoplasm and then disappear.
Treatment of ultrathin sections by pronase or by pepsin provokes the disappearance of the main part of the perinuclear corpuscle. The residual structures of these corpuscles are not digested either by RNase or by DNase. However, if a digestion is carried out with DNase and pronase together, it increases the contrast of the residual structures. On the other hand, the contrast of the perinuclear corpuscles is not altered by specific techniques for polysaccharides.
The constitution and the role of the perinuclear corpuscles is discussed.
The relationship between cleavage and blastocoel formation in Xenopus laevis
Authors: Kalt Marvin R. 
Published: April 2021

ABSTRACT
The development of the blastocoel in Xenopus laevis was studied by electron microscopy. Two major morphological specializations were associated both with blastocoel formation and with cleavage. The first specialization was the formation of close junctions at specific points along cleavage furrows, starting as early as the first division. The second was the secretion of material into the blastocoel and extracellular spaces. Secretion occurred by three processes, one merocrine, the other two apocrine. The main secretory product released was β-glycogen, although other products were also liberated. The membrane added to the cell surface during secretion contributed to the growth of both the blastocoel and the furrows. Filaments 80 Å in diameter were found to be present at some, but not all, furrow tips during embryogenesis, but the filaments apparently played no direct role in the formation of the blastocoel.
Early limb development of Xenopus laevis
Authors: Tarin D. , Sturdee A. P. 
Published: April 2021

ABSTRACT
This investigation has used histological techniques and the scanning electron microscope to establish the presence of an apical ectodermal ridge in the developing limbs of Xenopus laevis.
The ridge appeared at stage 50, reached its maximal size at stage 51, and subsequently disappeared by stage 53.
The course of the ridge was consistently related to a marginal sinus in the underlying mesenchyme.
The other features of limb morphogenesis, such as the formation of a paddle and the sequence of condensation of skeletal rudiments in the mesenchyme, corresponded closely to those seen in other vertebrates.
It remains to be seen whether the ridge we have demonstrated in Xenopus exercises a similar function to that claimed for its counterpart in the chick.
Ascorbic acid in the normal and regenerating tail of the house lizard, Hemidactylus flaviviridis
Authors: Shah R. V. , Hiradhar P. K. , Magon D. K. 
Published: April 2021

ABSTRACT
The concentration of ascorbic acid (AA) and the histochemical distribution of the vitamin in the normal and regenerating tail of the gekkonid lizard, Hemidactylus flaviviridis, have been investigated.
In the regenerating tail of the lizard the AA concentration almost doubles during wound healing and becomes fivefold during differentiation. However, it falls almost to the normal level during the blastema phase (i.e. period between wound healing and differentiation). Again, during the growth period (i.e. after differentiation) the AA concentration gradually becomes reduced, reaching the normal mark as the regenerate regains the full length of the original tail. Nevertheless, the vitamin level does not fall below the normal mark at any stage of regeneration. Increase of ascorbic acid during wound healing is thought to be mainly due to increased demand for the vitamin at the broken ends of the stump tissues, for their repair and formation of wound epithelium; the vitamin is known to help these processes. A fivefold increase of the vitamin during the differentiation period corresponds to an increased pace of laying down of the matrix material for the connective tissues, suggesting the role of ascorbic acid in the formation of collagen and mucopolysaccharides. Besides, the role of ascorbic acid in lipid and carbohydrate metabolism is also important during tail regeneration. Fluctuations in the vitamin level during different phases of tail regeneration are correlated with various states of metabolic activities of the corresponding phases.
Control of protein synthesis during the development of Acetabularia
Authors: Ceron Gabriel , Johnson E. Marshall 
Published: April 2021

ABSTRACT
Proteins from the soluble, chloroplastic and cell membrane fractions of axenically grown /lce/fl6zz/orza were analysed by zone electrophoresis. Incorporation of 14C] leuci ne intodifferent proteins was measured by autoradiographic analysis of the electrophoretic patterns. The protein patterns from the soluble fraction remain constant with respect to the number of detectable bands but change with respect to the relative synthetic rates at various developmental stages. The protein patterns from the membrane fraction change with respect to both the number of protein species and the relative synthetic rates. The analysis of the synthetic performance of enucleated cells revealed that most of the proteins from the soluble and the membrane fractions continue to be synthesized in the absence of the nucleus and that the changes that normally occur in the protein patterns of the membrane fraction at the time of cap formation also take place in enucleated cells. This is taken as an indication that the control of the synthesis of the proteins studied is of extranuclear nature.
It was also found that chloroplasts are capable of synthesizing all the components of the chloroplastic protein spectrum at least 4 weeks after enucleation. Some of the chloroplastio proteins can also be synthesized by purified chloroplasts in extracellular conditions.
The possibility of extranuclear control of protein synthesis being a rather general phenomenon during the development of Acetabularia is discussed.
Cell death in the ‘opaque patch’ in the central mesenchyme of the developing chick limb: a cytological, cytochemical and electron microscopic analysis
Authors: Dawd D. S. , Hinchliffe J. R. 
Published: April 2021

ABSTRACT
Cell death in the ‘opaque patch’ of central mesenchyme of the developing chick forelimb was investigated by a variety of light and electron-microscope cytological and cytochemical techniques. Cell death appears first at stage 23/4 (4 days) and reaches its maximum extent at stages 24 and 25 ( and 5 days), at which it separates the ulnar and radial mesenchymal condensations. I t then decreases in size to a small area separating the proximal parts of radius and ulna and disappears at stage 28.
Cytological studies show the presence of a few isolated dead cells, of mesenchymal cells containing 1–3 ingested dead cells and of macrophages containing up to 18 dead cells in various stages of digestion. These findings are interpreted as showing that isolated dead cells are ingested by neighbouring mesenchymal cells which thus become transformed into macrophages, first ingesting and then digesting further dead cells.
Histochemical studies show that isolated dead cells and recently ingested dead cells contain no more acid phosphatase activity, either discrete or diffuse, than either neighbouring living mesenchymal cells, or mesenchymal cells which have ingested 1–3 dead cells.
Increased acid phosphatase activity is found within the macrophages, where activity is localized within the digestive vacuoles (‘secondary lysosomes’) containing the dead cells, and within the Golgi apparatus and Golgi vesicles (‘primary lysosomes’) of macrophage cytoplasm. Loss of staining capacity by the dead cell is correlated with high acid phosphatase activity: this is interpreted as indicating the digestion of dead cells within the macrophage by acid hydrolases.
There is circumstantial evidence that viable mesenchyme cells in the ‘opaque patch’ area autophagocytose part of their own cytoplasm in secondary lysosomes (1·2–2μm).
The role of the ‘opaque patch’ in relation to the pattern of limb chondrogenesis is discussed. It is suggested that cell death may play a role in separation of radius and ulna, and that autophagocytosis may indicate a change in the pathway of differentiation of the mesenchyme cells lying between radius and ulna.
The reactions to carcinogens in the axolotl (Ambystoma mexicanum) in relation to the ‘regeneration field control’ hypothesis
Authors: Ingram Andrew J. 
Published: April 2021

ABSTRACT
About 200 axolotls, between 5 and 21 months old, were treated in the body wall with carcinogens or control substances, by subcutaneous or intradermal injection, or by sub-cutaneous implantation.
In response to an injection of dibenzanthracene in olive oil an initial reaction appeared within 13 days. This consisted of an epidermal proliferation and a subcutaneous infiltration of macrophages. The epidermis returned to normal after several weeks, but the subcutaneous response took 6 months to disappear. The initial reaction appeared to be, at least partially, a wound healing response; its regression could not have been due to regeneration field control as it occurred in the posterior body region.
Following the disappearance of the initial reaction a secondary reaction of papilloma-like outgrowths arose between 7 and 20 months after injection. Of the axolotls surviving for a sufficient length of time, outgrowths arose in 14 out of 54 animals injected with dibenz-anthracene and in 18 out of 57 sites injected with methylcholanthrene. These outgrowths had some features in common with the papillomata of mice, but none have yet progressed to carcinomata. In a group of axolotls injected in three different regions the frequency of out-growths varied according to the sites; however, this was thought to be due to differences in the difficulty of injecting the three regions.
Two tumours, a sarcoma and a hepatoma, arose in the course of these experiments, 3 and 2 years respectively after carcinogen treatment. From this it is suggested tentatively that tumour induction by polycyclic hydrocarbons in the axolotl may require a long latent period and involve a low tumour incidence; however, it is possible that at least one of the tumours was not induced by the treatment.
Reproduction of Dugesia tigrina under short-day and long-day conditions at different temperatures
Authors: Vowinckel C. , Marsden J. R. 
Published: April 2021

ABSTRACT
Dugesia tigrina was reared under various combinations of long- or short-day length with three temperature levels, 20, 23 and 26 °C. The resulting asexual and sexual reproduction was recorded.
Animals reared under short days exhibited shorter generation length and a higher number of worms hatching per cocoon than animals reared under long days.
Changes from short to long day or vice versa, experienced by animals during development, resulted in retardation or complete absence of sexual reproduction. Cocoons laid by these individuals showed a high degree of infertility.
D. tigrina was also collected in cocoons from the natural habitat shortly before hatching. When exposed to completely different light regimes they responded with a uniform generation length.
It is concluded that generation length, apart from temperature influences, is governed by photoperiod during early development of individuals, probably already in the maternal body. The number of worms hatching from one cocoon, likewise, is under photoperiod influence which acts at some time after hatching of the parent.
Vitamin E as an extrinsic and intrinsic signal controlling development in the rotifer Asplanchna: uptake, transmission and localization of [3H]α-tocopherol
Authors: Birky C. W. , Gilbert John. J. 
Published: April 2021

ABSTRACT
An increase in the level of vitamin E in the diet of saccate, amictic female Asplanchna modifies the development of their parthenogenetic female embryos developing in utero. The offspring develop prominent outgrowths of the body wall (BWO response), and some mature as mictic females which produce male progeny by haploid parthenogenesis. We have followed the fate of [3H] α-tocopheroI fed to immature females. In each generation, females lose about 50% of their α-tocopherol; the remaining material, which is 76–100 % undegraded, is transmitted almost entirely to their male or female offspring. The α-tocopherol content of a female is proportional to the degree of her BWO response. The results support the hypotheses that vitamin E acts directly on embryos to control development, i.e. that it serves as both an intrinsic and extrinsic control signal.
Interrelationships of mucopolysaccharide and collagen in connective tissue remodelling
Authors: Flint Michael 
Published: April 2021

ABSTRACT
The effects of the release of normal distractive forces from the rabbit’s tendo-achilles by distal tenotomy and proximal sciatic neurectomy alone, and in combination, have been studied. The results demonstrate that: Complete release of distractive forces from the tendon is followed by changes in collagenous architecture and an increase in cell size and cell population, particularly at the musculotendinous junction.The changes in the resident cell population and the cells migrating into the tendon from the musculo-tendinous junction and perivascular spaces are associated with the production of increased quantities of mucopolysaccharide and the disaggregation of collagen fibres in the vicinity.In the initial stages this increased mucopolysaccharide appears to be predominantly unsulphated material – probably hyaluronic acid, but with the reapplication of tension which follows spontaneous repair of the divided tendon, this is replaced by a sulphated polymer which appears to be associated with the reaggregation of collagen fibres at this stage.The implications of this biphasic production of mucopolysaccharide, and its effect on the stability and integration of collagen, are discussed.During this study it was found that the Masson’s trichrome stain appears to be a precise indicator of the state of tension of collagen fibres within the tendon, and other connective tissues.
The role of mesenchyme in the morphogenesis and functional differentiation of rat salivary epithelium
Authors: Lawson Kirstie A. 
Published: April 2021

ABSTRACTThe ability of foetal rat salivary epithelium, particularly from the parotid gland, to develop morphogenetically and functionally (amylase activity) in various mesenchymes, and the quantitative effects of altering mesenchymal mass on the development of the parotid epithelium, have been studied in vitro.Both parotid and submandibular epithelial rudiments were able to undergo morphogenesis and subsequent cytodifferentiation in their own and in the reciprocal mesenchyme. The growth of the explant and the arrangement of the acini were governed by the mesenchyme, submandibular mesenchyme supporting the development of more acini, which were more closely packed, than parotid mesenchyme. The functional product of the epithelium was not qualitatively affected, amylase activity being developed only by parotid epithelium, whether in its own or in submandibular mesenchyme.Amylase activity was greater when the epithelium from a single parotid rudiment was recombined with submandibular mesenchyme than with its own mesenchyme. Increasing the initial mass of either salivary mesenchyme also led to the development of more amylase activity.Parotid epithelium was able to develop in lung mesenchyme, but not so well as in its own mesenchyme. Stomach and pancreatic mesenchyme could support only limited histogenesis of parotid epithelium.The results are interpreted in terms of morphogenetic and growth control of salivary epithelium by mesenchyme, the subsequent cytodifferentiation of the terminal buds being typical of the organ from which the epithelium was derived.
Properties of the primary organization field in the embryo ofXenopus laevis: II. Positional information for axial organization in embryos with two head organizers
Authors: Cooke J. 
Published: April 2021

ABSTRACTThe results are reported of a series of experiments, the exact geometry of which has been presented in a previous paper. Late blastulae and early stage-10 gastrulae are supplied with a second head organizer region at varying angular distances, in the marginal zone, from the presumptive site of their own organizer. The configuration of positional information existing in the mesodermal mantle of the late gastrula or earliest neurula, as a final result of such operations, was recorded by observing the pattern of axial organ differentiation obtained by tailbud stages (26–28).The operational differences between various current theories as to the nature of embryonic differentiation fields are briefly discussed, as a framework within which to consider the results of experiments such as those reported here. It is suggested that in the future, and using the present results as a basis, experiments may be possible that are more critical in distinguishing between the various theoretical suppositions involved.Evidence is presented that the final configuration of positional information, achieved as a result of the implantation of a second head organizer at or before the onset of host gastrulation, becomes stable some time before it is irreversibly expressed in terms of a pattern of cell commitment in the mesodermal/endodermal mantle. It is insensitive both to relative ages of host and graft at the time of operation, over the range employed and, probably, to the ambient temperature of development between operation and the time of cell differentiation, being dependent only on the angular distance originally existing between graft and presumptive host organizer sites.Tn the discussion, a model is given for the visualization of positional information in partially double fields, produced in a two-dimensional sheet of cells where the normal endpoint of field formation is a bilateral symmetry of differentiation zones.
The development of the tectum inXenopus laevis: an autoradiographic study
Authors: Straznicky K. , Gaze R. M. 
Published: April 2021

ABSTRACTThe development of the optic tectum in Xenopus laevis has been studied by the use of autoradiography with tritiated thymidine. The first part of the adult tectum to form is the rostroventral pole; cells in this position undergo their final DNA synthesis between stages 35 and 45 or shortly thereafter. Next, the cells comprising the ventrolateral border of the tectum form. These cells undergo their final DNA synthesis at or shortly after stage 45. Finally the cells comprising the dorsal surface of the adult tectum form, mainly between stages 50–55. This part of the tectum originates from the serial addition of strips of cells medially, which displace the pre-existing tissue laterally and rostrally. The formation of the tectum is virtually complete by stage 58.The tectum in Xenopus thus forms in topographical order from rostroventral to caudomedial. The distribution of labelled cells, several stages after the time of injection of isotope, indicates that, at any one time, a segment of tectum is forming which runs normal to the tectal surface and includes all layers from the ventricular layer out to the surface. In Xenopus, therefore, the times of origin of tectal cells appear to be related not to cell type or tectal layer but to the topographical position of the cells across the surface of the tectum.
Metabolite utilization by isolated embryonic rat hearts in vitro
Authors: Cox Steven J. , Gunberg David L. 
Published: April 2021

ABSTRACT
Isolated hearts from 11-, 12- and 13-day rat embryos were incubated in a simple defined salt solution to which was added a variety of single substrates. Utilization of the added substrate was determined by comparing the contractile rates of the hearts in the presence and absence of the compound being tested. Of all the compounds tested only those involved in the Embden-Meyerhof glycolytic pathway were capable of maintaining cardiac contraction at a maximum rate in the 11-day heart. This was accomplished under both aerobic and anaerobic conditions. Although glycolysis remained important, the 12- and 13-day hearts exhibited a shift in dependence towards other metabolic pathways. This conclusion was based on the observations that anaerobic glycolysis could no longer maintain maximum heart rates and that a variety of non-glycolytic compounds could be utilized for contractile activity by the 12- and 13-day organs.