bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some Histochemical Observations on the Endometrium and the Yolk-sac Placenta of Erinaceus europea
Authors: Morris B. 
Published: April 2021

ABSTRACT
An account is given of the distribution of RNA, fats, iron, glycogen, and alkaline phosphatase in the endometria of non-pregnant animals and in the foetal tissues and decidua of the yolk-sac placentae of pregnant forms. The RNA content of the cytoplasm of the uterine and glandular epithelia of the oestrous uterus of Erinaceus is low, and little lipoidal material is present. Iron and glycogen are entirely absent. The uterine secretions must play only a minor role in the nourishment of the early blastocyst. The histochemical reactions of the tissues which comprise the avascular yolk-sac and the vascular yolk-sac placentae are described. The yolk-sac placenta is concerned in the nourishment of the embryo in early stages of pregnancy —up to about the 7-mm. stage, for it is involved in the uptake of substances, particularly fats and sugars from the maternal blood. Subsequently, the yolk-sac placenta retrogresses. Whereas in early stages the trophoblast of the yolk-sac wall is rich in alkaline phosphatase in late stages very little of the enzyme is present in this tissue. In Erinaceus the yolk-sac fluid of late stages of pregnancy cannot be regarded as an important source of absorbable substances, and it is improbable that the yolk-sac splanchnopleur, the histochemical reactions of which are described, is as important as a placental structure in this species as it is in the rodents. The histochemical and tinctorial reactions of Reichert’s membrane are described, and these reactions are compared with those that have been described for the membrane of Reichert formed in the rat. Since the membrane is unstained by Weigert’s resorcin fuchsin elastic tissue is not one of its components. Most of its observed properties suggest that it is formed of collagenous fibres. In the hedgehog its formation is more or less coincident with the onset of the retrogression of the yolk-sac placenta.
Studies on the Development of the Foregut in the Chick Embryo
Authors: Bellairs Ruth 
Published: April 2021

ABSTRACT
It is generally believed that the foregut in the chick embryo is induced by the mesoderm (Waddington & Schmidt, 1933; Waddington, 1952). In particular the splanchnic mesoderm is thought to be important (Rudnick & Rawles, 1937; Rudnick, 1952). In normal development the splanchnic mesoderm becomes fused with the presumptive foregut floor whilst the gut is developing and both become considerably thickened. During this period of induction there is a rise in the mitotic rate in this region of the endoderm (Bellairs, 1955). Similarly, Balinsky (1955) reported that the mitotic rate is raised in tissues when they are stimulated to form a limb. He also found that there is a high rate of division in the regions capable of inducing limb development.
The Effect on Embryogenesis of a Sex-linked Female-Sterility Factor inDrosophila melanogaster
Authors: Counce S. J. , Ede D. A. 
Published: April 2021

ABSTRACTEggs from females homozygous for a sex-linked mutant factor, fsnasA, will not support the development of a viable embryo. Approximately half of the eggs produced by fsnasA females are abnormal, containing little or no yolk. Twenty per cent, of the embryos die during the first 2 hours of development. The remaining embryos develop into monster larvae which are not capable of hatching from the eggs. The major effect of the factor is on the synchrony of cleavage and blastoderm mitoses. Moreover, the regular pattern in which disturbances occur suggests stratification of the egg cytoplasm. Gastrulation and all subsequent developmental processes are abnormal. Germ-band formation and the development of mesodermal elements are strongly affected. The posterior mid-gut invaginates from the ventral surface of the embryo, and the proctodaeum and Malpighian tubules never form. The possible effects of the factor on the processes of chromosome duplication during cleavage are discussed in connexion with Painter’s theory. The developmental effects of fsnasA are compared with those of a sex-linked recessive lethal factor X2. The basic similarities of the two are probably the result of abnormal rates of mitotic division during blastoderm stages. Differences between the two suggest there may be a posterior to anterior gradient in regional differentiation of the embryo. Gonad formation in fsnasA embryos from pole cells which migrate through the blastoderm wall during the early stages of gastrulation supports Poulson’s theory of gonad formation. The broader implications of studies on female-sterility genes in Drosophila are briefly discussed.
A cellular mechanism for the palatal shelf reorientation from a vertical to a horizontal plane in hamster: light and electron microscopic study
Authors: Shah Ravindra M. 
Published: April 2021

ABSTRACTCellular and subcellular events during reorientation of the palatal shelf in hamster fetuses are described. An alteration in the morphology of the epithelial and the mesenchymal cells is observed during shelf realignment from a vertical to a horizontal plane. The mesenchymal cells elongate and subsequently appear to protrude in the medially bulging palatal shelf. Microtubules, microfilaments and close contacts are associated with elongation of the mesenchymal cells. The cells of the thickened epithelium may play a mechanical role in providing direction to the mesenchymal cells during palatal shelf reorientation. The altered morphology of the mesenchymal cells may be associated with the intrinsic shelf force implicit in Walker and Fraser′s theory of palatal shelf reorientation.
Molecular differentiation of inside cells and inner cell masses isolated from the preimplantation mouse embryo
Authors: Johnson M. H. 
Published: April 2021

ABSTRACT
Clusters of inside cells (ICs) were isolated immunosurgically from morulae and early cavitating blastocysts, and cultured for varying periods in vitro. The ICs responded to their changed position by transformation to a blastocyst-like vesicle and also showed a correlated synthesis of trophectodermal-marker polypeptides. Both changes were inhibited by α-amanitin, indicating that transcriptional events are involved in this response to changed position. Inner cell masses (ICMs), isolated immunosurgically from expanded blastocysts, did not undergo a morphological transformation to a blastocyst-like structure and did not show a corresponding and complete change in synthesis of trophectodermal-marker polypeptides. Elements of the change in polypeptide activity were, however, present, suggesting an ineffective response to position by the ICMs.
The target tissue of limb-bud polarizing activity in the induction of supernumerary structures
Authors: MacCabe Jeffrey A. , Parker Brenda W. 
Published: April 2021

ABSTRACT
When polarizing mesoderm from the posterior border of the 4-day chick limb bud is placed adjacent to anterior limb mesoderm and ectodermal ridge, the anterior ridge thickens and mesodermal outgrowth ensues, resulting in supernumerary limb structures. This apposition of anterior and posterior limb tissues can be accomplished by cutting off the apical one third of the limb bud and reimplanting it on the stump with its anteroposterior axis reversed. The preaxial response to polarizing activity can be obtained after only 12-18 h in the reoriented position. Reversed apical mesoderm develops supernumerary digits when combined with untreated ectoderm. The reciprocal combination, reversed ectoderm and untreated mesoderm, fails to develop supernumerary structures. We have interpreted this as evidence that, in inducing supernumerary limb structures, polarizing activity acts only on the mesoderm.
Reversible inhibition of chondrogenic expression by certain hyaluronidase preparations
Authors: Pennypacker John P. , Goetinck Paul F. 
Published: April 2021

ABSTRACTEmbryonic chick chondrocytes were cultured in the presence or absence of different preparations of testicular hyaluronidase. This treatment inhibited the accumulation of cartilage matrix as indicated by phase-contrast microscopy, by Alcian green staining, and by accumulation of 35S-labeled material. In addition, most preparations of testicular hyaluronidase caused a conversion of the cells to a fibroblastic phenotype characterized by a faster growth rate and the synthesis of type-I collagen. This effect was found to be concentrationdependent and was not observed at the minimum concentration of hyaluronidase required to inhibit matrix accumulation. Since two more highly purified hyaluronidase preparations prevented matrix accumulation but did not cause the fibroblastic transformation, it is likely that the conversion to a fibroblastic phenotype is caused by a contaminant in the other hyaluronidase preparations.
Metabolic co-operation between embryonic and embryonal carcinoma cells of the mouse
Authors: Gaunt Stephen J. , Papaioannou Virginia E. 
Published: April 2021

ABSTRACT
Mouse embryonal carcinoma (EC) cells form permeable junctions at their homotypic cell-to-cell contacts which permit intercellular exchange of metabolites (metabolic co-operation). Hooper & Slack (1977) showed how this exchange could be detected by autoradiography as the transfer of [3H]nucleotides between PCI3 (a pluripotential EC line) and PCI 3-TG8 (a variant of PC13 which is deficient in hypoxanthine guanine phosphoribosyltransferase). We now show that cells taken from several different tissues of early mouse embryos, that is, from the morula, the inner cell mass of the blastocyst, and the endoderm, mesoderm and embryonic ectoderm of the 8th day egg cylinder, are able to serve as donors of [3H] nucleotides to PC13TG8. In contrast, trophectodermal cells of cultured blastocysts, and the trophectodermal derivatives in the 8th day egg cylinder, that is, extra-embryonic ectoderm and ectoplacental cone cells, showed little or no metabolic co-operation with PC13TG8. With reference to some common properties of EC and embryonic cells, we suggest how our findings may provide insight into cell-to-cell interactions in the early mouse embryo.
Immunofluorescence studies for myosin, α-actinin and tropomyosin in developing hearts of normal and cardiac lethal mutant Mexican axolotls, Ambystoma mexicanum
Authors: Lemanski Larry F. , Fuldner Rebecca A. , Paulson Daniel J. 
Published: April 2021

ABSTRACT
Recessive mutant gene c in axolotl embryos results in an absence of normal heart function. Immunofluorescence studies were done to determine the distributions of myosin, tropomyosin and a-actinin in the hearts of normal and mutant siblings. Anti-myosin specifically stains the A bands of myofibrils in normal hearts and reveals a progressive increase in myofibril organization with development. Mutant hearts display less staining for myosin than normal and localization is mainly in amorphous collections. Anti-α-actinin stains the Z lines of myofibrils in normal myocytes. Mutant cells also have significant staining for α-actinin but show no striations. Antitropomyosin intensely stains the I bands of myofibrils in normal cells; however, there is very little staining for tropomyosin in mutant hearts. Thus, mutant myocardial cells have reduced but significant amounts of actin (Lemanski, Mooseker, Peachey & Iyengar, 1976) and myosin, even though non-filamentous, and substantial amounts of a-actinin. The cells appear to contain little tropomyosin.
Stable programming for map orientation in fused eye fragments in Xenopus
Authors: Straznicky C. , Gaze R. M. 
Published: April 2021

ABSTRACT
Compound eyes were formed in Xenopus embryos at stages 32/33 by fusion in the right orbit of (1) two right naso-ventral halves, (2) two right ventral halves, (3) two right temporoventral halves, (4) one right and one left naso-ventral half and (5) one right and one left temporo-ventral half. The contralateral visuotectal projections from the operated eyes later showed abnormalities reflecting the anatomical arrangement of the fused fragments. The experiments thus revealed considerable stability of the developmental programme leading to the later development of map orientation, in the face of operative disturbance of the types used.
Stable programming for map orientation in disarranged embryonic eyes in Xenopus
Authors: Gaze R. M. , Straznicky C. 
Published: April 2021

ABSTRACT
In Xenopus embryos of stage 32/33 either the temporal or nasal half of the right eye anlage was replaced by a corresponding left half, giving a right eye in which the grafted half was inverted dorsoventrally. In other embryos either the dorsal or ventral half of the right eye anlage was replaced by a corresponding left half, giving an eye in which the grafted half was reversed nasotemporally. These four types of operation were intended to produce eyes that were disarranged internally but which each had a complete range of positional values. The visuotectal projections from such eyes, recorded later in life, in most cases showed axial reversal of half of the map, reflecting the nature of the operation. The results thus demonstrate that the developmental programme in each of the fused retinal fragments is stable in relation to the eventual orientation of the map from that fragment.
Operations to produce eyes with an inverted temporal half, if performed in operating solution of low ionic strength, may result in mirror reduplication and the formation of double nasal maps. It is suggested that this phenomenon may underlie previous reports of reprogramming of one eye fragment by another.
Sulfated proteoglycan accumulation during development of the embryonic chick limb bud studied by electron microscopic autoradiography
Authors: Cioffi Moira , Searls Robert L. , Hilfer S. Robert 
Published: April 2021

ABSTRACT
Cartilage cells are characterized by a high concentration of extracellular sulfated proteoglycan. Electron microscopic autoradiography was used to compare the incorporation of sulfate into proteoglycan by limb-bud chondrogenic and myogenic cells. From stage 19 to stage 21 there was no significant difference between the cartilage- and muscle-forming regions in the number of silver grains over either the extracellular space or the intracellular space. From stage 22 to 25 the number of extracellular silver grains was significantly greater in the chondrogenic region than in the myogenic region, but the number of intracellular silver grains was the same. Since most of the silver grains were intracellular, no significant difference in the total number of grains was found between the two tissues. Stage-26 and -27 embryos showed a significantly greater number of silver grains over both the cells and the extracellular space in the cartilage region than in the muscle region. Thus, the first step of cartilage differentiation involves a decrease in the extracellular deposition of sulfated proteoglycan in the myogenic region rather than an increase in deposition in the chondrogenic region between stage 22 and 25. After stage 25 there is an increase in sulfated proteoglycan synthesis in the chondrogenic region relative to the myogenic region.
Genetic and experimental studies on a pigment mutation, Pale (P
a), in the frog, Bombina orientalis
Authors: Ellinger Mark S. 
Published: April 2021

ABSTRACT
A mutant gene, Pale, (Pa) has been discovered in the discoglossid frog, Bombina orientalis. Breeding experiments indicate that the gene is recessive to the wild-type allele (P). Embryos, tadpoles and adults homozygous for the Pale gene are lighter in coloration than wild-type animals. Eggs produced by Pale females appear normally pigmented. Neural-retina defects were apparent in Pale tadpoles. Parabiosis experiments revealed that the Pale and wild-type phenotypes were unaffected by circulating factors from the opposite phenotype. Neuralcrest-grafting experiments revealed that Pale melanophores retain the Pale phenotype when placed in a wild-type cellular environment. Likewise, wild-type chromatophores are unaffected by residence in Pale tissues. Melanophores of Pale tadpoles display reduced numbers of mature melanosomes. This is the primary morphological basis of the Pale phenotype. However, other chromatophore classes (xanthophores, iridophores) were also less intensely pigmented, demonstrating that a single gene may affect the pigmentation of all chromatophore classes in B. orientalis.
Presence of cap structures in the messenger RNA of mouse eggs
Authors: Schultz G. A. , Clough J. R. , Johnson M. H. 
Published: April 2021

ABSTRACT
The presence of 5′-terminal 7-methylguanosine cap structures in the messenger RNA molecules in mouse eggs was assessed by (1) translational inhibition in a message-dependent reticulocyte cell-free system with the cap analogue 7-methylguanosine-5′-triphosphate, and (2) enzymatic removal of cap structures with tobacco acid phosphatase followed by endlabelling with γ-32P-ATP and polynucleotide kinase. The results suggest that the majority of mRNA molecules contain cap structures. There was no detectable difference in degree of capping in unfertilized versus fertilized egg mRNA.
Compositional and structural heterogenicity of the cardiac jelly of the chick embryo tubular heart: a TEM, SEM and histochemical study
Authors: Hurle J. M. , Icardo J. M. , Ojeda J. L. 
Published: April 2021

ABSTRACT
The hearts of chick embryos of stages 9 –13 were subjected to SEM, TEM and histochemical studies to ascertain possible regional differences in the structure and composition of the cardiac jelly. Two distinct regions, the cardiac jelly filling the space located between the myocardium and the endocardium (MECJ) and the cardiac jelly filling the dorsal mesocardium (EECJ), were distinguished by their structural and histochemical properties. MECJ is formed by amorphous and fibrillar material arranged between the endocardial and myocardial layer. The amount of its components increases when cetylpyridinium chloride is introduced into the fixative, and it appears intensely stained by ruthenium red and alcian blue at low concentrations of MgCl2. The amount and arrangement of its components increase during the beginning of the looping process of the heart tube. The EECJ is very rich in ruthenium-red-positive basal-lamina-like material and the addition of cetylpyridinium chloride to the fixative does not modify its appearance. It also appears poorly stained by alcian blue at low concentrations of MgCl2 and its arrangement undergoes modifications closely associated with the events of endocardial fusion. The possible significance of these results in the early morphogenesis of the heart is discussed.
Analysis of glycosaminoglycans during chondrogenesis of normal and brachypod mouse limb mesenchyme
Authors: Shambaugh Janet , Elmer William A. 
Published: April 2021

ABSTRACT
Studies have been carried out to characterize radioactive incorporation rates and steadystate levels of hyaluronic acid (HA) and chondroitin sulfate (CS) as well as hyaluronidase activity in the hind limbs of normal and brachypod mouse embryos between 11 –14 days of gestation. The results of the analysis show that changes in the synthetic and degradative rates of HA and CS occur at about the 12·5-day stage in normal hind limbs. These changes include an increased rate of CS synthesis, a decreased rate of HA synthesis, and a correspondingly sharp, transitory rise in hyaluronidase activity. Similar changes also occur in brachypod hind limbs but appear to be delayed in onset by approximately one-half day. In addition, the mutant hind limb exhibits a slower loss of HA at a time when turnover would be expected to be on the increase. These changes are concomitant with cell surface alterations and abnormal mesenchymal condensation formation which have been previously shown to occur in this mutant.
Regeneration of reversed aneurogenic arms of the axolotl
Authors: Wallace H. 
Published: April 2021

ABSTRACT
Aneurogenic arms of young axolotls were implanted into the flank as heterotopic autografts with reversed proximo-distal orientation. The formerly proximal ends of such arms regressed to a variable extent, and then either regenerated or could do so following a second amputation. The regenerate always contained a complete sequence of skeletal elements between the adjacent stump skeleton and terminal digits, being a mirror image of the implanted arms with identical transverse axes but an opposed proximo-distal axis. Many reversed arms also regenerated fingers from the implanted hand. Identical results were obtained from reversed arms of control larvae, confirming previous studies on reversed well-innervated arms. Nerves are not required for the establishment of a new proximo-distal axis, therefore, and probably have no influence on the determination of any limb axis. Morphogenesis of the regenerate is clearly related to the position along the proximo-distal axis where the blastema originates. Although this axis is reasonably envisaged in terms of a gradient, its polarity is ignored during regeneration.
Behavioural properties of chick somitic mesoderm and lateral plate when explanted in vitro
Authors: Bellairs Ruth , Sanders E. J. , Portch P. A. 
Published: April 2021

ABSTRACT
Tissue culture, time-lapse cinematographic and electron microscopic techniques have been used to study the properties of chick mesoderm at several stages of differentiation. Lateral plate, unsegmented mesoderm (segmental plate), and newly formed somites were dissected from stage-12 embryos, whilst dermo-myotomes and sclerotomes were dissected from stage-18 embryos. Each type of mesoderm was found to exhibit a characteristic pattern of behaviour.
The explants from the unsegmented mesoderm, from the newly formed somites and from the older embryos could be placed in a developmental sequence; with increasing differentiation they settled and spread on the substrate more readily, whether explanted as pieces of tissue or as individual cells, and it was concluded that this implied an increased adhesion to the substrate. Similarly, with increasing differentiation, the cells segmented at a faster rate. No significant differences could be discerned in the internal structure of the different types of cells, although differences in the general shape were apparent.
The lateral plate mesoderm cells, which bear some resemblances to the unsegmented mesoderm cells in the embryo, also show some morphological resemblances to them in vitro. However, the lateral plate cells had a much greater success in attaching to glass or plastic substrates. They were also found to have the highest speed of locomotion of all the tissues studied, whereas the unsegmented had the lowest. It is concluded therefore, that although cells may look similar to one another morphologically, their behaviour may differ greatly, probably because they are already partially determined.
Changing patterns of proteoglycan synthesis during chondrogenic differentiation
Authors: Ovadia Michael , Parker Charles H. , Lash James W. 
Published: April 2021

ABSTRACTThe pattern of proteoglycan synthesis was examined in the cartilages of the anterior and the posterior limbs, the vertebra and the sterna of the developing chick embryo, during chondrogenic differentiation. At stage 18, the limb primordia synthesize small monomeric proteoglycans. In all nine cartilages examined, there was a shift during differentiation from small to larger intermediate forms followed by a transition toward the aggregate forms. As development proceeds, the proportion of aggregates increases and the small proteoglycans almost disappear. Chondrogenic differentiation is thus marked by a increase in the size of the proteoglycan molecules, and an increase in the proportion of the large proteoglycan aggregates.