bluuebunny/crossref_metadata_2025_split huggingface dataset:
The growth of transplanted mouse vertebrae: effects of transplantation under the renal capsule, and the relationship between the rate of growth of the transplant and the age of the host
Authors: Noel Janet F. , Wright E. A. 
Published: April 2021

ABSTRACTThe tail vertebrae of 7-to 8-day C3H mice were transplanted under the renal capsules of syngeneic animals of various ages. Morphological effects of transplantation included degeneration of the intervertebral joints, increase in the diaphyseal haemopoietic marrow and decreased formation of bone trabeculae. The growth rate of the transplanted vertebrae depended upon the age of the host. Those transplanted into animals of the same age as the donor grew faster than controls left on the tail. Those transplanted into young adults (aged 4 months) and senile adults (aged 17 months) grew at 71% and 64% respectively of the rate of those transplanted into 7-to 8-day hosts. These differences are interpreted as due primarily to age dependent changes in blood hormone levels.
Development in culture of rat foetuses explanted at 12·5 and 13·5 days of gestation
Authors: Cockroft D. L. 
Published: April 2021

ABSTRACT
As a result of the relatively simple operation of opening the yolk sac and thus exposing the foetal capillary circulation to flowing medium, it has proved possible to grow 12·5- and 13·5-day rat foetuses for a period of 42 h in culture. 25% rat serum, 75% Tyrode has been found to be a satisfactory and economic culture medium, and has the added attraction that foetal survival is improved compared with that obtained in whole rat serum. For both 12·5- and 13·5-day foetuses grown with open yolk sacs, a gas mixture of 95% O2, 5 % CO2 in equilibrium at 1 atm with culture medium flowing at about 15 ml/min has been found to give the best results. Under these conditions, foetuses explanted at 12·5 days increased their protein content from 1·0–1·3 mg to 2·3–2·7 mg during culture. Their somite number was 40–44 at explantation and reached 50–55 during culture. Foetuses explanted at 13·5 days increased their protein content from 3·2–4·0 mg to 6·1–7·5 mg during culture. Their somite number was 51–55 at explantation and reached 60–63 during culture.
Anaerobiosis in the Rana pipiens Embryo
Authors: Cohen Adolph I. 
Published: April 2021

ABSTRACT
Evidence is presented demonstrating that although a short burst of oxygen uptake follows transfer of Rana pipiens embryos from a nitrogen to an oxygen atmosphere, a similar burst follows transfer from air to oxygen. Since the material being oxidized exists in the reduced state in gastrulae raised in air, it cannot constitute a major source of anaerobic oxidations in gastrulae. Data and considerations suggesting that the amphibian embryo is normally partially anaerobic in the usual temperature range employed in physiological experiments are presented. A detailed description of the respiratory and lactate level changes of embryos transferred to an oxygen atmosphere after anaerobiosis is given and the significance of the findings is discussed.
Morphogenetic Effects of a Heat Shock on the Eggs of Limnaea stagnalis
Authors: Raven Chr. P. , Roon A. C. De , Stadhouders A. M. 
Published: April 2021

ABSTRACT
Eggs of Limnae stagnalis were subjected to a heat shock (37° C.) for or 3 hours at the 2-to 4-cell stage. Both exogastrulae and head malformations were produced. The exogastrulae produced by a heat shock differ considerably from those caused by lithium treatment in showing a much more serious disturbance of development, leading to the appearance of greatly atypical differentiations. No typical cyclocephalic malformations were produced by this treatment. Apparently a heat shock does not primarily act by depressing the animal gradient field. Local eye reductions were produced preferentially on the right side. Presumably the left-right asymmetry at early cleavage stages in Limnaea is attended with differences in physiological conditions between both sides. Lateral eye reduplications, leading to the formation of two eyes in a single tentacle field, occurred on both sides. The most characteristic heat-shock effect consists in a reduplication of the posterior part of the apical plate, with the formation of a median tentacle field containing an eye, and sometimes a tentacle. The splitting of the apical plate is not attended with a decrease in the number of apical plate cells, but in at least some of the cases with an increase. It is concluded that these median reduplications are caused by a strengthening of the animal gradient field, leading to the splitting of the apex of the gradient. It is possible that the lateral eye reduplications are due to a splitting of a secondary field apex. Dislocations of head organs, especially of the nervous ganglia, encountered in the treated embryos, show that the differentiation of cerebral ganglion, pedal ganglion, and statocyst does riot depend on the presence of a normal cerebropedal connective on that side of the body.
Histogenetic and Organogenetic Processes in the Development of Specific Characters in some South African Tadpoles1
Authors: Balinsky B. I. 
Published: April 2021

ABSTRACT
The tadpoles of four species of Anura used for the experiments (Pyxicephalus adspersus, Pyxicephalus delalandii, Phrynobatrachus natalensis, and Xenopus laevis) differ in the structure of their adhesive organs, external gills, and mouth parts, as well as in size and other properties. To investigate whether the distinctions in the above organs are due to different reactive abilities of the ectoderm or to differences in inducing systems, parts of the presumptive ectoderm were transplanted in the early gastrula stage from one species to another. Adhesive organs, gills, and mouth parts-were developed from grafted ectoderm in conformity with its position in the host embryo, as a result of inducing influences from the underlying parts of the host. The organs developed from the grafts partly retained the characters of the donor species and partly acquired the characters of the host species. In respect of all characters concerned with the differentiation of special types of cells and with their mutual arrangement the graft ectoderm strictly retained the peculiarities of the donor species. These characters were: presence or absence of horny jaws and horny labial teeth; rhythm of differentiation of the labial teeth; shape of the adhesive organ; subdivision of the rudiment of the adhesive organ into two lateral organs or retention of an organ that is continuous across the midline (i.e. is single and median); branching of the external gills. It is proposed to distinguish processes of this type as histogenetic processes. They are presumably based directly on the genotype of the cells. The size of all induced graft structures, such as the mouth, the gill rudiments, or the adhesive organ, showed various degrees of approximation to the size of corresponding organs of the host, and this not through retarded or accelerated growth but through an increased or decreased initial size of the rudiments. Ectoderm of a species having only one pair of gills developed gills of a second pair when transplanted to an embryo having normally two pairs of gills. The length of the gill filaments was predominantly determined by the host. Processes controlling characters of this second type, that is characters involving the number or mass of cells and the position of areas differentiating in a specific way, I call organogenetic processes. Differences in organogenetic processes between related species may thus be due to a modification of the inducing systems and not to changes in reactive abilities of cells.
Studies on the Development of the Foregut in the Chick
Authors: Bellairs Ruth 
Published: April 2021

ABSTRACT
Mitotic counts have been made in the area pellucida endoderm of 10 chick embryos. In the head process stage embryos there was no evidence that any region of the endoderm consistently possessed a mitotic rate which was statistically significantly different from that of any other. In all the early somite stage embryos a region possessing a high mitotic rate was found in either the foregut floor or the presumptive foregut floor. It is suggested that as the histological structure of the developing foregut floor of the embryo changes from cubical to columnar, and the individual cells become narrower, a proliferation is needed to maintain the width of the region. There is no evidence that this high mitotic rate is necessary for the morphogenetic movements leading to the ventral closure of the foregut. There is no evidence to suggest that a lowering of the mitotic rate plays any part in the thinning of the roof of the developing foregut.
Dissociation and Reaggregation of Embryonic cells of Triturus alpestris
Authors: Feldman M. 
Published: April 2021

ABSTRACT
The dissociation of cells of neurulae of Triturus by means of sodium citrate or potassium oxalate and glycine is described. Suspensions of isolated cells of neural, mesodermal, and endodermal tissues were made to reaggregate in a slightly acid solution, and the aggregates were cultured within explants of ectoderm. Reintegration of some histogenetic patterns was observed. Differentiation of structures resembling neural tube and archenteron are described in aggregates of neural and endodermal tissues. Some factors involved in the dissociation and reaggregation processes are briefly discussed.
Abnormal microtubular systems in mouse spermatids associated with a mutant gene at the T-locus
Authors: Dooher Gerald B. , Bennett Dorothea 
Published: April 2021

ABSTRACTFine structural observations of spermiogenesis in sterile mice homozygous for the t-allele tw2 reveal that spermatids develop severe morphological abnormalities during spermiogenesis. In a small proportion of late spermatids the nuclear envelope develops broad areas of discontinuity except at the level of the acrosome. Manchette microtubules, which in normal spermatids form an orderly perinuclear array, appear to undergo premature depolymerization in cells of this type although flagellar structures differentiate normally.The majority of late spermatids, on the other hand, contain unusually large numbers of disorganized microtubules. Spermatid head shapes likewise become very abnormal. Both acrosomal and post-acrosomal portions of the nucleus exhibit malformations. The presence of disorganized microtubular arrays is believed to contribute to the observed nuclear deformations.Although condensation of the chromatin occurs in these cells, the spermatids seldom survive to maturity. Most of the cells are phagocytized by Sertoli cells.Late spermatids from tw2 homozygotes are abnormal in that they fail to maintain a precisely ordered array of microtubules during the concluding stages of spermiogenesis. This defect may reflect an underlying abnormality in the structural or biochemical characteristics of the plasma membrane with which the microtubules become associated.
Ontogeny and localization of the lens crystallins inXenopus laevislens regeneration
Authors: Brahma Samir K. , McDEVITT David S. 
Published: April 2021

ABSTRACTOntogeny and localization of the lens crystallins, especially the γ-crystallins were investigated in Xenopus laevis lens regenerating system by the ‘indirect’ immunofluorescence staining method. Antibodies directed against Rana pipiens γ-crystallin antigen were used for the detection of this crystallin; the validity of such an experiment has been shown in a previous report. To detect total lens proteins we used X. laevis anti-total lens protein antibody.The regenerates were staged according to Freeman (1963) and the first positive reaction with both the two antisera was observed in an early stage-4 regenerate. The site of the immunofluorescence reaction was nearly identical in both, suggesting that γ-crystallins are one of the first, if not the first of the lens crystallins to appear during lens regeneration.The secondary fibres, when developed, showed less immunofluorescence than the primary fibres with R. pipiens anti-γ crystallin antibody, though the reaction was intense in the secondary fibres with X. laevis anti-total lens protein antibody.The intensity and distribution of immunofluorescence increased with the growth of the lens. With the R. pipiens anti-γ crystallin antibody, the lens epithelium did not show any immunofluorescence reaction at any stage of lens regeneration. With X. laevis anti-total lens protein antibody, the epithelium showed an immunofluorescence reaction earlier than in the normal lens development. With the two antisera we used, we did not observe any immunofluorescence outside the lens tissue.
Morphogenesis in Micrasterias: II. Patterns of morphogenesis
Authors: Lacalli T. C. 
Published: April 2021

ABSTRACT
The final form of the polar lobe and lateral wings of developing semicells of M. rotata results from combined action of three growth processes: tip growth, branching and lobe broadening. Tip giowth unaccompanied by branching or broadening occurs during normal development in M. radiata, but is observed only under abnormal conditions (e.g. raised temperature) in M. rotata. When branching and broadening do occur, they occur together and for this reason may be causally related. Autoradiograms demonstrate that specific patterns of cell wall incorporation can be associated with each of the three processes in M. rotata. Autoradiographic patterns found in the polar lobe differ from those found in wings. The growing polar lobe also responds to laser irradiation differently from the wings; lasings occasionally cause duplication of the polar lobe.
The development of trophoblast in vitro from blastocysts containing varying amounts of inner cell mass
Authors: Ansell J. D. , Snow M. H. L. 
Published: April 2021

ABSTRACT
When intact mouse blastocysts are cultured in vitro in medium supplemented with foetal calf serum, trophoblast cells proliferate and undergo giant cell transformation such as occurs in vivo. If the amount of inner cell mass in the blastocyst is decreased by culture with [3H]-thymidine then giant cell transformation occurs normally but proliferation is reduced. In the absence of inner cell mass no proliferation occurs, and giant cell transformation is more rapid than in undamaged blastocysts.
Demonstration of cytoplasmic processes in Millipore filters permitting kidney tubule induction
Authors: Lehtonen E. , Wartiovaara J. , Nordling S. , Saxén L. 
Published: April 2021

ABSTRACT
The presence of cytoplasmic material inside thin Millipore filters between interacting mouse metanephric mesenchyme and spinal cord was investigated using different fixation methods. .
The transmission of induction was studied from sections of Zenker-fixed paraffin-embedded expiants. Formation of kidney tubules was taken as evidence for induction. Filters with 0·8 and 0·22 μm pores permitted induction, whereas only 6 out of 31 filters with 0·1 μm pores did so.
Glutaraldehyde-fixed Epon-embedded explants were used for study of cytoplasmic penetration into filters. In thick sections, filters with large pores were seen to contain cytoplasmic material at all levels. Filters with 0·1 μm pores usually showed only shallow ingrowth, but those which had permitted passage of induction contained material at least half way from the spinal cord and shallow ingrowth from the mesenchyme. With 0·8 μm filters the ingrowths from both sides met first after 18 h of transfilter cultivation. This has previously been shown to be the minimum time needed for induction to take place in this system.
In electron microscopy cytoplasmic processes were seen deep inside the 0·8 and 0·22 μm filters regularly permitting induction. In small pores such material was only preserved by certain glutaraldehyde fixatives.
Diffusion studies did not reveal major differences between induction-permitting 0·22 μm filters and induction-preventing 0·1 μm filters.
Thus in the kidney tubule induction system this and our previous work speak in favour of a mechanism based on close apposition of cells rather than on long-range diffusion of inductive substances or on matrix interaction.
Reconstitutive ability of axial tissue in early rat embryos after operations and culture in vitro
Authors: Deuchar E. M. 
Published: April 2021

ABSTRACT
Longitudinal incisions have been made in the axis of 10-day-old rat embryos (post-neurula stage with 5–10 pairs of somites) at mid-trunk levels, dividing the axis into right and left halves. The embryos have then been cultured in vitro by New’s method and their ability to reconstitute tissues in each half has been studied.
After 20 h culture at 37 °C, there was no longer any external sign of the division of the axis. Histological studies showed that in nearly all cases, however, the neural tube was duplicated in the operated region. The two neural tubes lay in close contact in the midline, and ventral to them the gut was single. Apart from four cases in which the gut roof was slightly broadened and forked, all other tissues were normal.
The reconstitutive ability of the neural and gut tissue has been compared with that of amphibian and avian embryos, as observed in ‘twinning’ experiments by other workers.
The apparent delay in axial rotation in the operated rat embryos, as compared with controls, is attributed to the inability of the two separated halves of the somite series to co-ordinate their contractions. Further details of the rotation process in operated embryos will be the subject of a future study.
The tip of the Dictyostelium discoideum pseudoplasmodium as an organizer
Authors: Rubin Jonathan , Robertson Anthony 
Published: April 2021

ABSTRACT
We have extended Raper’s original work on the organizing ability of the tip of the Dictyostelium discoideum slug.
Our new results are that tips from all multicellular (pseudoplasmodial) stages act as organizers; that the structure organized by a tip depends on the developmental stage of the cells responding to the tip’s signal; that tips from all stages release a qualitatively similar signal which is continuous, most probably a gradient of c-AMP; and that the signal from fruiting-body tips appears stronger than that from conus tips.
We discuss these results with reference to the control of morphogenetic movement and patterned differentiation and point out that the D. discoideum tip is analagous to a classical organizer, whose signal is interpreted according to the state of determination of cells in its field of influence.
Quantitative studies of germ plasm and germ cells during early embryogenesis of Xenopus laevis
Authors: Whitington P. McD. , Dixon K. E. 
Published: April 2021

ABSTRACT
The germ plasm in the egg is partitioned between the first four blastomeres by the first two cleavage planes. Although the blastomeres divide 10–11 times through the rest of cleavage, as shown by reduction in their size, the number of presumptive primordial germ cells (p.p. germ cells) does not increase significantly. During and as a result of the formation of the first two cleavage planes, the germ plasm aggregates together and moves towards and along the cleavage furrows. At subsequent mitoses, the germ plasm is localized at one of the poles of the spindle and hence is segregated to only one of the daughter cells, thus explaining how mitosis occurs without increase in the number of cells with germ plasm. Early in gastrulation, the germ plasm moves to a perinuclear position, therefore ensuring that as mitosis continues, both daughter cells receive germ plasm and the number of p.p. germ cells increases. Direct counts of the number of p.p. germ cells and measurements of their volume suggest that they divide twice between early gastrula and the stage at which they leave the endoderm. The p.p. germ cells behave similarly to the adjacent endodermal cells until they begin to migrate to the gonad, an event which may represent the first overt signs of differentiation. Measurements of the volume of germ plasm suggest that there is no change through cleavage. The general conclusion is drawn that during cleavage, the morphogenetic determinant germ plasm is segregated to a few cells by the normal processes of cleavage and that subsequently these cells undergo a small number of cloning divisions which are contemporaneous with the first signs of differentiation.
In vitrochondrogenesis of limb mesoderm from normal and brachypod mouse embryos
Authors: Elmer William A. , Selleck David K. 
Published: April 2021

ABSTRACTThis paper describes the cytodifferentiation of hind limb mesodermal cells from 12-day-old normal and brachypod (bpH) mouse embryos grown in vitro at high densities. Over a 3-day culture period normal cells underwent aggregation, nodule formation, and coalescence of nodules into large masses of cartilage. This was associated at the biochemical level with a cessation of cell division, with a concomitant increase in metachromatic matrix, and synthesis of collagen. Under the described culture conditions the collagen synthesized by 48 h cultures was predominantly of cartilage type with an αl: α2 ratio of 9:1. A change in the collagen synthetic program was observed when the entire medium was replaced after 48 h incubation with fresh, serum-free medium. Under these conditions the αl: α2 ratio was 4:1.In contrast, brachypod cells plated at the same density appeared large, flattened, and stellate. Upon aggregation, normal nodule morphology was only rarely observed. More often large, irregular clusters formed from suspended cells loosely attaching to the surface aggregates. Concomitant with the marked changes in the morphology of the mutant cells was a linear increase in DNA synthesis and the appearance of many mitotic figures. A biochemical transformation in matrix synthesis was not observed, however. After a 24 h delay, mutant matrix accumulated and stained intensely with toluidine blue. Collagen was synthesized at approximately the normal rate and was of the cartilage type with an αl: α2ratio of 9:1. When incubated in fresh, serum-free medium, the response of collagen subunit synthesis was identical to the normal cultures. In view of these results the possible manner in which brachy-podism causes developmental anomalies of the limb skeleton is suggested.
Ultrastructural features of chondrogenesis in the human hand plate: a cytochemical and autoradiographic study
Authors: Kelley Robert O. 
Published: April 2021

ABSTRACTUltrastructural features of chondrogenesis are correlated with the appearance of collagen and proteoglycan components of the cartilage matrix in the developing human hand (stages 16-18).Prechondral mesenchymal cells comprising the digital plate (stage 16) exhibit euchromatic nuclei, sparse granular endoplasmic reticulum, few polysomes, broad cell to cell associations, little enhancement of electron density after postfixation with osmium tetroxide/potassium ferrocyanide and scanty incorporation of 3H-proline. Extracellular matrix is electron-lucent.During stage 17, early chrondroblasts acquire affinity for OsO4/K4Fe(CN)6, develop filopodia, lose broad intercellular attachments, assemble cytoplasmic polysomes, incorporate 3H-proline and the extracellular matrix acquires electron-dense particles (10-20 nm in diameter).By stage 18, chondrogenic cells of digital blastemata exhibit affinity for osmium-ferrocyanide, and particles (10-20 nm in diameter) and filaments (5 nm in diameter) are present in the extracellular matrix. Mature chondrocytes are present.
Developmental changes in the composition and amount of mouse fetal fluids
Authors: Renfree Marilyn B. , Hensleigh Hugh C. , McLaren Anne 
Published: April 2021

ABSTRACTFetal fluid was studied in mice of the Q, C57BL/McL, C3H/Bi/McL and JU/Fa strains. The amount increases to day 16 of gestation, and then decreases. Amniotic fluid and fetal plasma contain three transferrins, five α-fetoproteins and albumin. Protein concentration in both increases during gestation; glucose decreases in amniotic fluid although it rises in fetal plasma; urea levels remain constant. The regulation of volume and biochemical composition of amniotic fluid, and its relation to the yolk-sac membrane, are discussed.