bluuebunny/crossref_metadata_2025 huggingface dataset:
The measurement of cell adhesiveness by an absolute method
Authors: Curtis A. S. G.
Published: April 2021

The development of a quantitative method for measuring cell adhesion would allow tests to be made of a variety of hypotheses concerning the role of cell adhesiveness in many morphogenetic processes, such as segregation (Steinberg, 1963; Curtis, 1960, 1967), contact inhibition of movement (Abercrombie, 1961), malignancy, etc. Furthermore, the development of a quantitative method giving absolute measurements of cell adhesiveness would be of considerable value in that it would allow critical experiments to be made to test hypotheses about the mechanism of cell adhesion. Basically, two methods exist for the measurement of cellular adhesiveness: (i) a measure of the force or energy required to reseparate two cells or a group of cells from one another or from a non-cellular substrate; (ii) a measure of the forces or energies of interaction involved in bringing two cells or cell groups into adhesion. The first method was introduced as a qualitative test of adhesiveness by Dan (1936). Recently, Brooks, Millar, Seaman & Vassar (1967) have made ingenious calculations of the probable magnitude of the adhesive energies which have to be overcome in dispersing a tissue by mechanical means into single cells. Measurement of the forces that have to be used to disperse the tissue can be used to derive a value of the adhesiveness of the cells as Brooks et al. (1967) have done. But there are difficulties in this method since intercellular materials, such as collagen, may contribute to the average resistance of a tissue to dispersion by mechanical forces, and if the hypothesis advanced by Weiss (1961) is correct, the measurement is not of the adhesiveness of cells but of the mechanical resistance of the cells to being broken. With the first of these considerations chiefly in mind, it seemed desirable to develop a method for measurement of adhesiveness using the formation of adhesions between cells.
Etude comparative des effets de l’ypérite azotée sur les constituants, mésodermique et ectodermique, des bourgeons de membres de l’embryon de Poulet
Authors: Salzgeber Berthe
Published: April 2021

Des recherches récentes (Salzgeber & Pinot, 1968) ont montré que les ébau-ches de membres d’embryons de 3 à jours d’incubation (stades 18 à 20 de Hamburger & Hamilton, 1951) traitées in vitro à l’aide d’une solution d’ypérite azotée et de liquide de Tyrode, et greffées après lavage à l’embryon de Poulet, évoluent en membres micromèles, phocomèles ou ectromèles. Le type de mal-formation obtenue dépend de la durée du traitement et de la concentration de la solution. Ces expériences apportent la preuve d’une action directe de l’ypérite azotée sur les ébauches de membres.
The effect of trypan blue on the growth of the rat embryo in vivo
Authors: Berry Colin L.
Published: April 2021

In a previous paper (Berry, 1968) it has been demonstrated, by comparison of in vivo and in vitro growth of the rat foetus, that it is possible to dissociate growth and differentiation in the rat. In a series now exceeding 1000 embryos it is evident that for a given somite number the protein content of an animal developing in vitro might be less than half that of the normal control, suggesting that a considerable reduction in growth rate might be found without necessarily inducing death or malformation. The rate of somite formation is not reduced in vitro in the rat; it has been shown by Herrman & Schultz (1958) that the rate of somite formation is not interfered with by different explant conditions in the chick embryo. These findings suggest that the increase in somite number is more rigidly determined than the increase in growth rate.
Characteristics of five cell types appearing during in vitro culture of embryonic material from Drosophila melanogaster
Authors: Shields Glen , Sang James H.
Published: April 2021

Although attempts have been made over a number of decades to achieve successful tissue culture of Drosophila material (see Schneider, 1964), progress has been held back until recently by a lack of basic information on the chemical and physiological characteristics of the haemolymph of the organism necessary for a reasoned formulation of a culture medium. In 1963, Begg & Cruickshank published details of the mineral composition, osmotic pressure and pH of the haemolymph of third instar larvae, and this has provided the basis for a more satisfactory approach, as reflected in an increasing amount of fruitful work since reported. Much of this work has been done with embryonic material. Horikawa & Fox (1964) claimed continuous multiplication of a small type of early embryonic cell; Lesseps (1965) described re-aggregation of dissociated embryonic cells in culture, with possible development of muscle cells, nerve cells and oenocytes in the aggregates; in the same year, Echalier, Ohanessian & Brun (1965) noted the emergence of free contractile elements and a polygonal type of cell in embryonic cultures, with the later development of a fibroblastic type of cell; Gvozdev & Kakpakov (1968) reported the appearance of a small type of cell growing in multilayer clumps as well as of fibroblast-and epithelial-type cells, and Seecof & Unanue (1968) reported the development of free neuron-like cells and muscle cells. Results are presented below of a further investigation into the behaviour of Drosophila melanogaster embryonic cells in culture, and the characteristics of five distinct cell types are described. These comprehend the types mentioned above (and to some extent there is necessarily repetition of the earlier work) but, as well as bringing the previously isolated observations into a single study, greater detail is given of the form and mode of development of the elements, and some account of the dynamic activities of some of them is included.
An inverse relation between the rate of cell division and RNA synthesis per cell in developing frog embryos
Authors: Flickinger R. A. , Lauth M. R. , Stambrook P. J.
Published: April 2021

Previous work has shown that endoderm cells synthesize more RNA per cell, including nuclear d-RNA, than do dorsal ectoderm-mesoderm cells (Flickinger, Miyagi, Moser & Rollins, 1967; Woodland & Gurdon, 1968). Both groups found lower levels of DNA synthesis in endoderm cells compared to dorsal ectoderm-mesoderm cells. It has also been found that in developing frog embryos both LiCl and cytosine arabinoside inhibit DNA synthesis and also inhibit RNA synthesis. Since RNA synthesis is inhibited less than DNA synthesis, the levels of RNA synthesis relative to total DNA increase (Flickinger, Miyagi, Moser & Rollins, 1967). A number of investigators have demonstrated that LiCl can cause isolated amphibian gastrula ectoderm to form endoderm and mesoderm (Barth & Barth, 1962; Gebhardt & Nieuwkoop, 1964; Masui, 1966; Ogi, 1961). Such compounds as NaHCO3 (Barth & Barth, 1963) and NaCl (Barth, 1966) can induce isolated frog gastrula ectoderm to form neural tissue.
Growth and metabolism in snake embryos
Authors: Dmi’el Razi
Published: April 2021

Since the early papers of Bohr & Hasselbalch (1900, 1903) and Murray (1925), considerable information concerning the growth and metabolic processes in the avian embryo has been accumulated (Romanoff, 1967). Respiratory and growth processes during embryonic life in many species of fishes, amphibians and mammals are also fairly well known. Only a few studies have been reported, however, on the metabolism and growth of the reptilian embryo. Lynn & Brand (1945) presented a detailed description of these processes in four species of turtles. Some data on respiration in the egg of the snake Coluber natrix are given by Bohr (1904). The respiration of four eggs a few days prior to hatching in the snake Liopeltis vernalis was studied by Zarrow & Pomerat (1937). Scattered information on the embryonic growth of snakes may also be obtained from papers dealing with the development of certain anatomical systems in the embryo, such as venom glands and the musculature related to them (cf. Fukada, 1958; Kochva, 1963, 1965). Growth or metabolic curves are not available for snake embryos, however.
Isolation and partial characterization of amphibian tyrosine oxidase polysomes
Authors: Triplett E. L. , Herzog R. , Russell L. P.
Published: April 2021

A population of polysomes isolated from frog skin is capable of supporting protein synthesis in a cell-free system containing an energy generating system, ‘soluble components and amino acids.

These polysomes catalyse the oxidation of DOPA after gentle trypsinization, and they also have antigenic determinants attributable to tyrosine oxidase.

Skin polysomes sedimented in 10–30% sucrose gradients contain tyrosine oxidase peaks of enzymic activity at the bottom and top of the tube and in the 250 S regions. A peak of tyrosine oxidase antigenic acitvity is found in the 250–350S region of the gradient.

Polysomes resolved on the gradient retain the ability to support protein synthesis in a cell-free system. All 250–350 S particles capable of supporting the incorporation of [14C]amino acid into tyrosine oxidase are precipitable with tyrosine oxidase antibodies. It is probable that 25O–35OS tyrosine oxidase antibody precipitates contain only polysomes for this protein.
Immunochemical analysis of the water-soluble fraction of the chick embryo yolk
Authors: Grossi C. E. , Carinci P. , Manzoli-Guidotti L.
Published: April 2021

By means of immunochemical techniques, the protein components of the water-soluble fraction (WSF) of the egg yolk have been examined in the unincubated egg and during incubation.

Anti-ovalbumin and anti-total adult chicken serum antisera have been employed.

Ovalbumin can be detected in the unincubated WSF as well as during incubation; its concentration seems to increase during incubation.

In the WSF of the unincubated egg, six proteins immunologically related to adult serum proteins can be detected. They correspond to α-livetin, α1-globulin, β-livetin, ovotransferrin (conalbumin) and γ-livetin (two components). β-Livetin disappears after the 14th day of incubation while the other components can be demonstrated till hatching.

The findings are discussed in relation to the data available in the literature.
Tissue interactions in embryonic mouse tooth germs: I. Reorganization of the dental epithelium during tooth-germ reconstruction
Authors: Kollar Edward J. , Baird Grace R.
Published: April 2021

The ability of fragments of incisor enamel organ and lip-furrow epithelium from 15-and 16-day old embryonic mice to regulate into harmonious tooth constructions is described. The cervical loop and upper half portions of the incisor enamel organ were confronted with incisor or molar dental papillae. Similar combinations were made from lip-furrow epithelium and incisor or molar papillae. The cultures were grown in the anterior chambers of homologous host eyes.

The epithelial fragments from the incisor enamel organ when associated with the dental papillae reconstruct teeth typical in all respects; enamel and dentin matrices are deposited.

Lip-furrow epithelium arises from the oral epithelium and is temporally and spatially related to the incisor dental epithelium proper. This ectopic epithelium was confronted by incisor and molar papillae. Harmonious teeth developed in these explants.

It is concluded that the ability of the dental papillae to elicit new cytodifferentiative and biochemical syntheses from the lip-furrow epithelium indicates that the dental papillae act inductively during tooth ontogeny.

The shape of the teeth reconstructed from enamel organ fragments and lip-furrow epithelium were incisiform or molariform in response to the incisor or molar dental papillae. These data confirm the conclusion that the structural specificity for tooth shape resides in the dental papilla.
Interspecific relationships of oviducal materials as related to fertilization in Amphibia
Authors: Shaver John R. , Barch Stephanie H. , Umpierre Carmen C.
Published: April 2021

Experiments are described in which eggs of Rana species were treated prior to insemination with antisera prepared against oviducal materials of Rana, Bufo, and Ambystoma species. Three types of treatment with antisera were employed.

Eggs of Rana pipiens and R. clamitans were treated with antisera against materials prepared from whole oviducts, or from upper and lower segments of oviducts, of R. pipiens, R. clamitans, R. sylvatica, R. catesbeiana, Bufo americanus, B. marinus and Ambystoma mexicanum.

Eggs of R. pipiens were treated with antisera against materials from whole oviducts, or from upper, middle or lower oviducal regions, of R. pipiens, which had been absorbed with materials from whole oviducts of the species named above.

Eggs of R. pipiens were treated with antisera against materials from whole oviducts, or from upper, middle or lower oviducal segments of R. pipiens, which antisera had each been absorbed with material from whole, upper, middle or lower oviducts of Rana species.

The results indicated that treatment with antisera against oviducal materials of Rana origin was inhibitory to fertilization of Rana eggs, while treatment with antisera against oviducal materials from other amphibian genera was not.

The experiments with absorbed antisera indicated that the secretion by the oviducts of R. pipiens of components also occurring in other Rana species is regionally localized in the oviduct.

The relationships of secretions of amphibian oviducts to fertilization is discussed in connexion with the histochemically demonstrable complexity of the jelly envelopes around eggs.
Morphogenesis in hydra:II Peduncle and basal disc formation at the distal end of regenerating hydra after exposure to low temperatures
Authors: Corff Sondra C. , Burnett Allison L.
Published: April 2021

When Hydra oligactis is excised below the tentacles and incubated for a short time in concentrations of colchicine that inhibit spindle formation in dividing cells, a peduncle and basal disc subsequently form at the cut distal end, where hypostome and tentacles normally form (Corff & Burnett, 1969). Since recent reports suggest a similarity in the action of colchicine and low temperature, in this study the effects of low temperatures on regenerating hydra were investigated. High hydrostatic pressure and low temperature have been shown to act synergistically with colchicine to inhibit the first mitotic division in sea urchin eggs (Marsland, 1968). Colchicine and cooling have also been shown to cause disintegration of the microtubule system in Actinosphaerium (Tilney, 1965).
The transplantation of nuclei from single cultured cells into enucleate frogs’ eggs
Authors: Gurdon J. B. , Laskey R. A.
Published: April 2021

Nuclei from a monolayer of cultured epithelial cells have been transplanted singly to enucleated unfertilized eggs of Xenopus laevis.

About three-quarters of the injected eggs failed to cleave or cleaved abortively. Most of the remainder formed partial blastulae. Less than 1 % reached postneurula stages of development.

Nuclei from first-transfer blastulae were used for serial transplantation. The nuclei of partial blastulae promoted normal or nearly normal development more often than those of complete blastulae. Several clones were obtained which included nearly normal tadpoles with apparently normal muscle, nerve, blood, and other specialized cell types. Three tadpoles commenced feeding and have completed metamorphosis into young frogs.

To prove that the donor- and not egg-nucleus participated in the formation of nuclear-transplant tadpoles, genetically marked 2-nu and l-nu diploid nuclei were transplanted to 2-nu eggs; the resulting tadpoles had the nucleolar number characteristic of donor, not egg, nuclei. Chromosome counts and nuclear diameter measurements on the epidermal cells of these tadpoles revealed the presence of diploid mitoses and the absence of haploid nuclei.

The behaviour of egg and donor nuclei immediately after nuclear transfer was determined by tracing the early cleavage pattern of individual eggs and by following, autoradiographically, the fate of donor nuclei whose DNA had been previously labelled with 3H-thymidine.

These experiments show that the serial transplantation of nuclei from monolayer cell cultures can lead to sufficiently normal nuclear-transplant embryo development to provide a useful test of the genetic properties of the donor cell line.
Protein transmission across the rabbit foetal membranes
Authors: Wild A. E.
Published: April 2021

Fluorescent protein tracing, involving F.I.T.C.-conjugated proteins and the fluorescent antibody technique, was employed to study the sites and mechanism of transport of a variety of proteins across the rabbit foetal membranes.

No evidence was found for an intercellular transmission of proteins across the yolk sac splanchnopleure to the exocoel, but all proteins were shown to become localized in absorptive vesicles in the yolk-sac endoderm.

Different proteins became similarly localized in absorptive vesicles having different sizes and profiles. Characteristic broken vesicles were present, and more than one protein was demonstrated in each absorptive vesicle.

The yolk-sac endoderm was confirmed as the selective site for transmission of proteins to the foetal circulation, since only proteins readily detected in the foetal serum were present in, and below, the basement membrane.

The paraplacental chorion was shown to be the site for transmission of proteins to the exocoel and the process to be one of diffusion.

Unlike normal proteins, F.LT.C. conjugates readily became localized within macrophages present in the paraplacental chorion and yolk-sac vascular mesenchyme.

These findings are discussed in the light of differences previously shown to occur between transmission of proteins to the foetal fluids and to the foetal blood, and in the light of a current hypothesis to account for selection of proteins by the yolk-sac endoderm.
Capacité de régulation des excédents dans la crête neurale d’Amphibien
Authors: Chibon Par P.
Published: April 2021

L’étude des possibilités de régulation des excédents dans la crête neurale, au moyen d’implantation de fragments de crête neurale surnuméraire marquée par la thymidine tritiée conduit aux résultats suivants:

L’implantation d’un fragment de crête neurale surnuméraire n’entraîne aucune anomalie grave.

La migration des cellules surnuméraires et leurs localisations finales sont identiques à celles des cellules de la même région de la crête neurale, dans les conditions normales. La régionalisation de la crête neurale est donc maintenue.

Le marquage issu de ces opérations est toujours unilatéral; de ce côté les cellules marquées et les cellules de l’hôte se mélangent pour former en commun des dérivés dont le nombre ou la taille sont identiques à ceux des témoins.

Une régulation parfaite se réalise donc du côté opéré, sans retentissement du côté opposé.

Du côté opéré, il se produit une modification du comportement mitotique des cellules des crêtes neurales mises en présence.
Studies on mitochondria in the early development of the slug Arion ater rufus L
Authors: Sathananthan A. H.
Published: April 2021

The structure, distribution, cytochemical nature and functional significance of mitochondria have been studied during the embryogenesis of the slug Arion, from the ovum to the postgastrula stage.

Mitochondria seem to undergo progressive but profound changes in form and fine structure during early development and their distribution conforms to a gradient pattern, which more or less resembles that of the sea urchin.

The most significant event in cyto-differentiation is the appearance of an extraordinary vegetal aggregation of mitochondria at the 8-cell stage which heralds a vegetalizing influence and undoubtedly has a precise morphogenetic function. This vegetal aggregation becomes involved in a remarkable series of morphogenetic movements and its mitochondria are later incorporated into the cells that differentiate into mesoderm and endoderm. Thus, apart from their energy-linked functions, mitochondria seem to play a dramatic directive role in development; mitochondrial segregation, in particular, seems to be the important factor in differentiation.

Certain aspects of their distribution and enzymic composition are discussed in relation to their normal metabolic functions.

The significance of mitochondrial RNA and DNA with reference to protein synthesis and self-duplication of mitochondria, and the possible roles played by mitochondria in inductive phenomena are also discussed in the light of recent work.
Effect of colcemid on the locomotory behaviour of fibroblasts
Authors: Vasiliev Ju. M. , Gelfand I. M. , Domnina L. V. , Ivanova O. Y. , Komm S. G. , Olshevskaja L. V.
Published: April 2021

Effects of metaphase inhibitors (colcemid, colchicine, vinblastine) on mouse and human embryonic, fibroblast-like cells growing on glass and on an oriented substrate (fish scale) were studied. All three inhibitors caused similar changes in the form of interphase cells and inhibited their directional locomotion. The effects of two inhibitors (colcemid and vinblastine) were found to be completely reversible. Microcinematographic studies have shown that the most conspicuous change of locomotory behaviour induced by colcemid was the disappearance of non-active stable parts of the cell edge; in normal cells only the leading part of the edge was actively moving, while in colcemid-treated cells all parts of the edge eventually became active. Activation of the whole edge made these cells unable to perform directional translocation.

It is suggested that colcemid and other metaphase inhibitors prevent stabilization of the non-active state of the cell surface. The possible role of this suggested colcemid-sensitive stabilization mechanism in the normal locomotory behaviour of fibroblasts is discussed.

Electron-microscopic examination has shown that microtubules disappeared from the cytoplasm of colcemid-treated, mouse, fibroblast-like cells. The formation of microtubules as the possible structural basis of the stabilization of the non-active state of the cell surface is discussed.
Le canal de Wolff induit la formation de l’ostium müllérien: démonstration expérimentale chez l’embryon de Poulet
Authors: Didier Par Eliane
Published: April 2021

The Wolffian duct induces the formation of the ostium of the Müllerian duct: demonstration in the chick embryo

An experimental analysis of the part played by the Wolffian duct in the formation of the ostium of the Müllerian duct has been made by blocking the Wolffian duct in front of and at different levels of the presumptive ostial area.

If the Wolffian duct is blocked between somites 13 and 19, the ostium and a short Müllerian duct always arise beside the developed part of the Wolffian duct.

If the blocking is performed between somites 9 and 13 there is no development of the ostium or Müllerian duct.
The influence of mesenchyme on the epithelial glycogen and budding activity in mouse embryonic lung developingin vitro
Authors: Alescio T. , Dani A. M.
Published: April 2021

Experiments have been performed to show the association of epithelial glycogen with budding activity, and their dependence on the nature of the associated mesenchyme.

The bronchial mesenchyme associated with the tracheal epithelium induces the appearance of a tracheal bud where glycogen remains present after its removal from the rest of the trachea.

The bronchial mesenchyme associated with the tracheal epithelium after the normal disappearance of glycogen, still induces the formation of an epithelial bud where glycogen is clearly demonstrable.

The primary left bronchus completely ceases its budding activity when brought in association with metanephrogenic mesenchyme ; glycogen is totally absent from the resting epithelium.

The reassociation of the morphogenetically quiescent primary left bronchus with bronchial mesenchyme brings about resumption of budding activity and reappearance of the epithelial glycogen, showing normal bronchial distribution.
Différenciation du trophoblaste au cours du développement in vitro d’embryon de Souris
Authors: Hernandez-Verdun Par D. , Legrand C.
Published: April 2021

Differentiation of the trophoblast during in vitro development of the mouse embryo

Mouse embryos obtained at the presomitic stage develop in vitro up to 70 h. During the first 24 h development remains comparable in vitro and in utero. Afterwards, the chronology of embryonic development is modified and in our successful prolonged experiments (70 h culture), foetal organogenesis reaches a stage corresponding only to days in utero. In some instances a chorioallantoic circulation has been observed in the umbilical cord.

The three trophoblast cell types present in egg-cylinders at 8 days post coitum, develop in the same way in utero or in vitro. After 48 h culture electron microscopy shows that numerous annulate lamellae appear in the nuclei and in the cytoplasm of some of the giant cells. The syncytium does not differentiate between the trophoblast and the allantoic mesoderm. The haemo-trichorial placental barrier does not differentiate in vitro, although foetal capillaries form.

In vitro, the endoderm cells (from the splanchnopleure or from the omphalopleure) actively proliferate and form an homogeneous substance located between the giant and the polyhedric trophoblast cells.
Exocrine glands and the Chievitz organ of some mouse mutants
Authors: Grüneberg Hans
Published: April 2021

Thirteen mutant genes of the mouse have been scanned for the occurrence of anomalies of glands of the head region and of the Chievitz organ. In eight of these (ic/ic, my/my, Ph/Ph; Xt/Xt, Cd/Cd; fi/fi; or/or and ch/ch) such anomalies have been discovered; most of them are absence or reduction in size of a gland, but increases in size or numbers have also been seen. The anomalies are mainly and possibly entirely local consequences of pre-existing abnormalities of other organs and thus different from the systemic effect of the tabby syndrome. But in at least one instance no local cause for an isolated glandular defect has been discovered.
Cell proliferation patterns during cytodifferentiation in embryonic chick tissues: liver, heart and erythrocytes
Authors: Jeter James R. , Cameron Ivan L.
Published: April 2021

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

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

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

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

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

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

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

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

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

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

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

The 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

The 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.