bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lens differentiation in vitro in the absence of optic vesicle in the epiblast of chick blastoderm under the influence of skin dermis
Authors: Mizuno Takeo 
Published: April 2021

ABSTRACT
Dissociation and recombination experiments in vitro were found useful for analysing inductive tissue interactions involved in lens differentiation in the chick. When the presumptive cephalic region (epiblast plus hypoblast) of the embryo at pre-definitive streak to one-somite stage is cultivated in vitro combined with the dermis isolated either from the dorsal skin of 6·5-day embryo or from the 13·5-day tarsometatarsal skin, a lens with fibres or lentoid is produced in the epiblast. In no case is there an optic vesicle present in the explant. When the presumptive cephalic region (epiblast plus hypoblast) is cultivated without dermis, the lens is no longer formed. If the epiblast alone, dissociated from the hypoblast of the presumptive cephalic region, is recombined with the dermis of the 6·5-day dorsal skin, lenses or lentoids fail to develop. Cultivation of the epiblast alone cannot cause differentiation of the lens or lentoid. The dermis can be replaced by other mesenchymes or embryonic organs : gizzard mesen-chyme, mesonephros, sclerotome, liver and neural retina, though they are less effective than the dermis in producing lenses or lentoids in the epiblast. It may therefore be concluded that the lens is induced in vitro by the actions of at least two factors: the epiblast first becomes competent under the specific influence of the hypo-blast of the cephalic region. The lens will then differentiate from the competent epiblast by the non-specific action of various tissues such as the skin dermis, mesonephros, or sclerotome. The primary stage of lens induction (action of the hypoblast on the epiblast) seems not yet completed by streak stage.
Electron microscopic studies on developing cartilage II. Demonstration and distribution of glycogen in chick and mouse epiphyseal cartilage
Authors: Goel Suresh C. , Jurand A. 
Published: April 2021

ABSTRACT
A procedure for the study of glycogen in the same cell, under both light and electron microscopes is described. The synthesis and accumulation of glycogen is a feature of chondrogenesis in the mouse epiphyseal cartilage and the amount of glycogen increases with the progress of differentiation. In contrast, no glycogen was detected in differentiating epiphyseal cartilage of the chick at any stage; except for a small amount of glycogen in the chick cartilage cells of the diaphysis. Because of this difference it is suggested that presence of glycogen is not essential for cartilage differentiation.
Properties of the primary organization field in the embryo ofXenopus laevis:III. Retention of polarity in cell groups excised from the region of the early organizer
Authors: Cooke J. 
Published: April 2021

ABSTRACTAn experiment is described whose results strengthen the classical conclusion, due to Spemann and co-workers, that amphibian gastrulation movements are co-ordinated and controlled by properties intrinsic to the invaginating mesodermal zone, rather than by interaction between this and any field of cell-guiding information, symmetrically disposed about the presumptive head ectodermal region in the animal hemisphere of the blastula/ gastrula. The possibility remains, however, that the field of information coming to reside in the marginal mesodermal zone, is itself originally set up utilizing the animal pole as an origin, as well as the presumptive organizer site.Experiments are then described where whole organizer apices, and also subapical squares of dorsal mesoderm from stage-10 donors, are implanted with presumptive polarity reversed 180° relative to that of the host. It is found that reasonably extensive migration, on the part of the graft and the influenced host tissue, is required for the individuation of recognizable axial structure, and that such migration is often prevented in reversed implants due to a retention of autonomous polarity in host and graft.Reasons are suggested for the apparently greater autonomy, in this respect, of apical organizer plugs, but evidence is given that autonomy is nevertheless expressed even by squares of dorsal presumptive mesoderm of side ca. 0·1 mm. The significance of this observation, for theory concerning the nature of the cellular properties involved in the maintenance of embryonic fields, is discussed.
Inhibitors in amphibian morphogenesis: Enzymic degradation of an inhibitor for the vegetalizing factor
Authors: Born J. , Tiedemann H. , Tiedemann H. 
Published: April 2021

ABSTRACTA naturally occurring inhibitor for the vegetalizing inducing factor has been incubated with different enzymes. Pancreatic ribonuclease, ribonuclease-T1, deoxyribunuclease, neur-aminidase as well trypsin and papain diminish the inhibitor only very slightly or not at all. Pronase, a proteolytic enzyme from Streptomyces griseus inactivates the inhibitor completely.
Experimental studies on the organization of the preimplantation mouse embryo:I.Fusion of asynchronously cleaving eggs
Authors: Stern M. Susan , Wilson I. B. 
Published: April 2021

ABSTRACTThe interaction between mouse eggs conjoined in pairs of different ages and stages of development has been examined:Forty-two per cent of chimaeras formed from 8-cell eggs paired with late morulae or early blastocysts produced morphologically normal, but large, blastocysts. Fusion of pairs of vitally labelled and unlabelled eggs has shown that presumptive trophoblast derived from as late as the early blastocyst stage can become incorporated into the inner cell mass of chimaeras.These observations suggest that the preimplantation chimaeric embryo can regulate for chronological differences in its constituent cells and that the trophoblast up to the early blastcyst stage may still be developmentally labile.
The role of water-regulating mechanisms in the development of the haploid syndrome in Xenopus laevis
Authors: Hamilton Louie , Tuft P. H. 
Published: April 2021

ABSTRACT
The uptake of water by haploid and diploid sibling embryos of Xenopus laevis has been investigated by measuring the density changes which occur during the development of intact embryos from the blastula to the late tail-bud stage, and of explants from which most of the presumptive endoderm has been removed.
The results show that up to the mid-gastrula stage there is no difference between the haploid and diploid embryos; but from then on, whereas the diploid volume increases steadily, the haploid gastrulae undergo a series of cyclical volume changes due to loss of fluid through the blastopore. It is concluded that this is the result of an excessive inflow of water through the haploid ectoderm, because it was found that the volume of haploid ectodermal explants increased much more rapidly than the volume of similar diploid explants. Excess flow through the haploid ectoderm also accounts for other characteristics of the haploid syndrome-microcephaly and lordosis.
It is suggested that it is the doubling of the cell number in haploid embryos with the consequent 25% increase in aggregate cell membrane area which accounts for the difference between the uptake of water by the two types of embryos. It is also suggested that changes in the rate of water flow through the ectoderm and endoderm which are thought to account for the accumulation of water in the blastocoel and archenteron in the normal diploid embryo arise in a similar way.
Effect of growth conditions on development of the cellular slime mould,Dictyostelium discoideum
Authors: Garrod D. R. , Ashworth J. M. 
Published: April 2021

ABSTRACTThe effect of growth in the presence and absence of 86 mM glucose on fruiting-body number and size, fruiting-body proportions and morphogenesis in the slime mould Dictyostelium discoideum, strain Ax-2, has been investigated. Cells grown in the absence of glucose (N.S. cells) formed 2·1 times more fruiting bodies than glucose-grown cells allowed to differentiate under the same conditions and at the same cell density. Glucose fruiting bodies were 2·6 times larger than N.S. fruiting bodies.During aggregation, N.S. aggregation streams generally broke up into numerous secondary aggregation centres. Glucose streams generally did not break up but moved into the initial aggregation centre. Each secondary centre formed one small grex, whereas initial centres fragmented into several grexes which were larger than those formed from secondary centres. The preponderance of secondary centres in N.S. aggregation and of initial centres in glucose aggregation accounts for the difference in size and number of fruiting bodies. We speculate about the mechanism giving rise to the morphogenetic difference.The spore: stalk ratio was 3·95:1 in glucose fruiting bodies and 2·70:1 in N.S. fruiting bodies. This difference is not related to the difference in fruiting-body size because proportions are size invariant for both fruiting-body types. Some difference in the physiological mechanism which determines proportions is suspected.
Observations on the ultrastructure of chick-embryo cardiac myoblasts re-aggregated in long-term cultures
Authors: Zacchei Anna Maria , Caravita Silvia 
Published: April 2021

ABSTRACTMyoblasts obtained by trypsin dissociation of 6-day chick-embryo hearts re-aggregated in rolling tubes and formed a pulsating mass within 1 h.Newly formed intercalated discs (adhesion plaques) were the most frequent type of inter-cellular contact in the earlier stages of culture.Desmosomes were also present.Focal tight junctions were rare and difficult to identify.In advanced aggregates more extended regions of very close plasma membranes apposition could be observed; lanthanum infiltration did not reveal obliteration of the intercellular gap.The most striking feature, even after 12 days of culture, is the disorder of the contractile units within the sarcoplasm and the irregularity of the cell outlines. The ineffectiveness of the factors responsible for the orientated disposition of myofibrils in culture conditions has been emphasized.The smooth endoplasmic reticulum never attains a regular arrangement in relationship with the myofibrillar banding. Subsarcolemmal cysterns containing a finely granular matrix (peripheral couplings) have been found after the first 24 h of culture; it has been observed that they reach their mature form only in the last stages of culture.The T-system is lacking. Numerous pits, often complicated by beading, are present in the peripheral sarcoplasm.All these features may affect the physiological response that can be recorded from these cells.
The effect of methotrexate on DNA synthesis and its reversal by folinic acid
Authors: Berry C. L. , Germain Jocelyn , Looker T. 
Published: April 2021

ABSTRACTIn suckling mouse liver methotrexate is a powerful inhibitor of DNA synthesis, as assessed by the incorporation of tritiated deoxyuridine. Folinic acid is an effective antagonist.
Insulin and glucagon release from the isolated pancreas of foetal and newborn mice
Authors: Lernmark Åke , Wenngren Britt Inger 
Published: April 2021

ABSTRACTThe simultaneous release of insulin and glucagon was studied with isolated pancreas preparations from foetal and newborn mice. Glucose, alone or in combination with arginine, did not affect immunoreactive insulin (IRI) of glucagon-like immunoreactivity (GLI) release from the pancreases of 18-day-old foetal mice. However, on the first postnatal day, glucose stimulated the release of IRI and, in the presence of arginine, depressed that of GLI. It is concluded that the systems for recognition of glucose in mouse pancreatic α2-cells as well as those in the β-cells do not mature until after birth.
In vitrostudies inTubularia:a morphological role for digestive cells
Authors: Glickman Marc H. , Lesh-Laurie Georgia E. 
Published: April 2021

ABSTRACTA chemically defined in vitro system for Tubularia has been developed. At 24 h after explantation of coenosarc, digestive cells attached to the substrate and migrated from the explant. The digestive cells migrated by a gliding motion with a fan-like membrane acting as a leading edge. Within 48 h a digestive cell monolayer was formed and invasion of this area by epithelio-muscular, gland and interstitial cells occurred. Autoradiographic study of 48-72 h cultures treated with [3H]thymidine showed nuclear incorporation of the label in digestive, epithelio-muscular, interstitial, cnidoblast and gland cells.When explants were grown on collagen-coated coverslips, accelerated attachment and migration of digestive cells was observed. Explants were also grown on Millipore filters. No digestive cell attachment occurred but epithelio-muscular, gland and interstitial cell attachments to the filter were observed. From these experiments, a morphological role for the digestive cells as a substrate for other cells of the coenosarc is postulated.Hydranth extract was supplemented to the culture medium. Studies with this material were performed with coenosarc from ‘late summer’ animals in which only 10-15% of the explants normally entered culture. However, with the addition of the extract, 100% of the explants went into culture. Interstitial cell populations increased 2-3 times in extract-treated explants.
Morphogenesis in the cellular slime mouldDictyostelium discoideum;the formation and regulation of aggregate tips and the specification of developmental axes
Authors: Farnsworth P. 
Published: April 2021

ABSTRACTA general discussion of ‘organizing regions’ and the specification of biological patterns is followed by introducing the idea that the tip of the slime mould cell mass is such an ‘organizer’. This view is supported by a discussion of the developmental ubiquity of the tip and its effects.A staging system is described which assigns numbers to sequential morphological changes during development.A set of experiments investigating the role of the tip are described, using techniques of cell labelling, grafting and bisection of cell masses with barriers, and the manufacture and use of cylindrical barriers of permeable cellulose.The results of such experiments show:That the tip of the cell mass is made of the same group of cells from stage 10 (late aggregate) to stage 20+ (culmination). That a stage 10 aggregate will regenerate a new tip in an average time of 32 min. That if a stage 10 aggregate is bisected by an impermeable barrier two tips, indicating two new developmental axes, develop in an average time of 34 min. That if a stage 10 aggregate is bisected for 40 min, the barrier removed and one of the tips removed, the remaining tip inhibits the re-formation of the second tip, and the polarity of the aggregate is again reorganized with respect to the remaining tip. That if experiments (3), (4) and (5) are repeated with a stage 9 aggregate, which is an hour younger, all the regulation times are increased by about 60 min. Similarly a stage 8 aggregate takes over 120 min longer to show the effect. That if part or all of a cell mass from any stage is placed inside a cellulose tube, all the enclosed cells differentiate into stalk cells.These results are then discussed in relation to pattern formation and the role of the tip in polarization and the specification of new developmental axes in cell masses.A model for culmination in the slime mould is proposed which takes account of the above results. The essence of this model is that at no time are stalk and spore cells ‘determined’ in the classical sense, and that, by a non-signalling positional information system, the size invariance of the ratio of stalk to spore cells seen in the fruiting body is a result of the mechanical process of culmination.
The pattern of growth ofClytia johnstoni
Authors: Hale L. J. 
Published: April 2021

ABSTRACTA quantitative study of the growth of Clytia johnstoni is described. The distance between hydranths is most commonly between 3 and 4 mm. The average internode lengths and their variability frequently differs not only between colonies but also between stolons of a single colony. The differences are therefore unlikely to be genetic ones. Occasionally much longer internodes occur (up to 8 mm). Hydranths and their stalks differ widely in size but not in morphology. The differences can be caused by the amount of food given. Very vigorous and very poorly growing colonies tend to have slightly longer internodes than the more common colonies of average vigour. Most colonies produce both additional (secondary) hydranths and stolon branches. Hydranth branches grow spaced from existing hydranths; in normal colonies the spacing appears to originate from the hydranth away from the growing tip in an internode. Ln vigorous growth the hydranth towards the growing stolon tip is the place of reference. Stolon branches occur mostly near to hydranths, either primary or secondary, more especially near to the hydranth farther from the growing tip of the main stolon. There appears to be a limit to the number of branches to an internode. In vigorous growth an optimum of two and a maximum of three is found, either secondary hydranths, or stolons, or both. Stolons vary in their rate of growth. A stolon slowly increases its rate of growth as it gets longer. In a colony of little vigour, the rate is low and variable and may cease and restart; the coenosarc sometimes breaks, dividing the colony. Hydranths take 1–2 days to grow, sometimes 3 days in colonies of little vigour. They remain open for a limited period: normally about 5–7 days; sometimes longer -up to 9 or 10 days; and significantly shorter, 1–3 days, in a colony of little vigour. At the end of their period of existence, hydranths regress. They normally start to regenerate a new hydranth within 1–2 days but some do not do so for longer or very long periods. The whole cycle of hydranth growth, maturity and regression falls into either a 6-to 7-day cycle or a 10-to 11-day cycle. Evidence is presented to support the suggestion that there is a situation of competitive interaction between growth of the various parts of the colony. A priority series for the various parts of the colony is constructed.
Evidence of morphogenetically significant diffusion gradients inHydra viridislengthened by grafting
Authors: Shostak Stanley 
Published: April 2021

ABSTRACTMorphogenetic inhibitory gradients were produced in Hydra viridis having 2–5 gastric regions or 2–5 peduncles grafted in tandem. The frequency of head regeneration at graft borders changed as a function of distance from the terminal head, and the frequency of foot regeneration changed as a function of distance from the terminal foot. The object of the study was to characterize and compare these morphogenetic inhibitory gradients in light of Crick’s (1970) model of diffusion gradients.Heads regenerate more easily on gastric regions and feet on peduncles. This is shown in several ways: (1) on gastric regions more heads and fewer isolated tentacles and ‘spikes’ (isolated hypostomes) form, while the opposite is true on peduncles; (2) more heads are regenerated at graft borders between gastric regions than at those between peduncles at comparable distances from the terminal head, while more feet are regenerated at graft borders between peduncles than at those between gastric regions at comparable distances from the terminal foot; (3) the Y intercepts for gradients of the frequencies of head and of foot regeneration as functions of distance (which are the theoretical frequencies of regeneration at the ends of the animal) are higher for head regeneration on gastric regions than on peduncles, and for foot regeneration on peduncles than on gastric regions. This is explained in terms of relative differences in either competence to regenerate or sensitivity to inhibitors.The slopes of the frequencies of head and of foot regeneration as functions of distance from the respective ends change inversely with the numbers of gastric regions and peduncles grafted. This is explained in terms of changes in the distance between the sources of diffusible inhibitors and the sinks which use them up. The results are taken to support Crick’s model in which a linear gradient of a diffusible substance is produced between its source and sink.
The development of tubular heart in RNA-treated post-nodal pieces of chick blastoderm
Authors: Niu M. C. , Deshpande A. K. 
Published: April 2021

ABSTRACT
Post-nodal pieces of the stage-4 chick blastoderms were transected 0·6 mm posterior to Hensen’s node and cultured in vitro with and without chicken-heart RNA. After 24 h the expiants were fed daily with fresh egg-extract medium for 4 days. On the 4th day pulsating heart was found in the RNA-treated but not in the untreated series. Histological examination revealed that cell differentiation other than of erythrocytes and epithelial tissue seldom occurred in the control and, in contrast, pulsating heart and cardiac myoblasts were present in most of the RNA-treated expiants that had differentiated.
Interactions between Ovary and Lateral Oviduct in Drosophila melanogaster
Authors: Pantelouris E. M. 
Published: April 2021

ABSTRACT
Experimental evidence is produced to show that during metamorphosis in Drosophila melanogaster:
The growth-of the lateral oviducts depends on an influence of the ovaries. The growth of the ovaries does not depend on a reciprocal influence. The growth of the vasa deferentia is independent of any influence from the testis.
The Development of the Otoliths of the Mouse
Authors: Lyon Mary F. 
Published: April 2021

ABSTRACT
The development of the otoliths in mice from days’ gestation to 3 days after birth was studied in alcohol-, formalin-, and Bouin-fixed material. The first sign of the otoliths in alcohol-fixed day material was an apparent protein precipitate. Then a PAS-reacting substance appeared among the protein, together with biréfringent particles. Calcium salts were then deposited in their typical crystalline form and the otolith flattened so that at days it consisted of a gelatinous layer surmounted by a layer of biréfringent calcareous granules with an organic matrix, which contained polysaccharide and phosphatase. Glycogen was also present. After formalin fixation very little otolith material was seen until days, and with Bouin very little until 2 days after birth; formalin preserved the calcium salts and granular matrix, Bouin the granular matrix only. Comparison of the results of the various fixatives showed that the localization seen after alcohol fixation was unreliable, so that the position of the otolithic material when it first appeared, and hence the site of its secretion, were unknown. The cells of the maculae showed phosphatase activity and probably took part in secreting substances; the secretory regions of the utriculus may also have done so. The mechanism of concentration and precipitation of the calcium salts remains unknown, but it is suggested that the polysaccharide matrix may take part.