bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transferrin in foetal and adult mouse tissues: synthesis, storage and secretion
Authors: Meek Jennifer , Adamson Eileen D. 
Published: April 2021

ABSTRACT
Transferrin is an important growth-promoting serum glycoprotein synthesized chiefly in the liver in adults. The transferrin found in the mouse foetus is thought to be wholly a product of the foetus itself and its synthesis starts at least as early as the 7th day of gestation. The major sites of synthesis in mouse foetuses are the visceral yolk sac (VYS) and liver (Adamson, 1982). We now report that other murine foetal tissues synthesize readily detectable amounts, namely lung, spleen, spinal cord and rib cage. Very low levels are also synthesized by the brain, muscle and pancreas. We can detect no synthesis of transferrin in late foetal thymus, heart or skin although mid-gestation foetal skin may make a very small amount. No synthesis of transferrin can be detected in adult brain, lung and spleen, but approximately equal rates of synthesis are detected in adult liver and adult ear pinna.
Transferrin is accumulated by foetal and adult tissues in widely varying amounts and these have been measured by enzyme-linked immunosorbent assays of extracts. In addition to VYS and liver, high levels of transferrin are found in foetal skin, lung and rib cage with lower amounts in spinal cord, spleen and muscle tissues. Tissues of the 15th day foetus accumulate the highest concentrations of transferrin. A role for the mediation of transferrin in the stimulation of growth and differentiation by interacting tissues is discussed.
Acetylcholinesterase (AChE) and pseudocholinesterase (BuChE) activity distribution pattern in early developing chick limbs
Authors: Falugi Carla , Raineri Margherita 
Published: April 2021

ABSTRACT
The distribution of acetylcholinesterase (AChE) and pseudocholinesterase (BuChE) activities was studied by histochemical, quantitative and electrophoretical methods during the early development of chick limbs, from stage 16 to stage 32 H.H. (Hamburger & Hamilton, 1951).
By quantitative methods, true AChE activity was found, and increased about threefold during the developmental period, together with a smaller amount of BuChE which increased more rapidly in comparison with the AChE activity from stage 25 to 32 H.H.
Cholinesterase activity was histochemically localized mainly in interacting tissues, such as the ectoderm (including the apical ectodermal ridge) and the underlying mesenchyme. True AChE was histochemically localized around the nuclei and on the plasma membrane of ectodermal (including AER) and mesenchymal cells, and at the plasma membrane of mesenchymal cell processes reaching the basal lamina between the ectoderm and the mesenchyme. AChE together with BuChE activity was found in the basal lamina between the ectoderm and the mesenchyme, in underlying mesenchymal cells and in deeper mesenchymal cells, especially during their transformation into unexpressed chondrocytes.
During limb morphogenesis, the cellular and regional localization of the enzyme activities showed variations depending on the stage of development and on the occurrence of interactions.
The possibility of morphogenetic functions of the enzyme is discussed.
Cytoskeletal discontinuities in the cell body cortex initiate basal body assembly and oral development in the ciliate Stentor
Authors: De Terra Noël 
Published: April 2021

ABSTRACT
My previous work has shown that disconnecting the oral apparatus of Stentor into two parts induces mass assembly of basal bodies on the ventral cell surface and thus initiates oral development. This operation severs the extensive microtubule tracts joining the oral membranelles at their bases. To determine whether basal body assembly and oral development are also induced by permanently disconnecting the longitudinal microtubule fibre tracts (mt fibre tracts) of the cell body cortex, I interposed a ring of inverted (heteropolar) cortex between the anterior and posterior halves of interphase stentors. When successful, this operation made it impossible for these fibre tracts to rejoin at the heteropolar boundaries and always induced basal body assembly and oral development in the graft complex. By contrast, tripartite homopolar graft complexes rarely initiated oral development; when they did, it was apparently in response to the presence of disproportionately small oral structures, which is the normal stimulus for oral development in Stentor. The mt fibre tracts of tripartite homopolar grafts also eventually became continuous.
These results support the hypothesis that permanent, extensive discontinuities anywhere within the cortical cytoskeleton can trigger basal body assembly and oral development. Since the onset of these processes is known to initiate cell division in Stentor, the results also suggest that development of discontinuities within the cortical cytoskeleton during interphase growth may be the endogenous stimulus initiating cell division in Stentor.
Gene expression at the pink-eyed dilution (p) locus in the mouse is confirmed to be pigment cell autonomous using recombinant embryonic skin grafts
Authors: Stephenson Dennis A. , Hornby Janet E. 
Published: April 2021

ABSTRACT
Sash (Wsh), a viable and fully fertile allele of the dominant spotting (W) locus (Lyon & Glenister, 1982) has been used in a modified test system to investigate the site of gene expression at the pinkeyed dilution (p) locus. Reciprocal recombinant epidermal//dermal skin grafts were constructed from 13-day embryonic skin of p and Wsh homozygotes. Thus in the reciprocal experiments pinkeyed dilution melanocytes were exposed to any environmental influence from the wild-type allele of the p locus in either the epidermis (when WshWsh) or the dermis (when WshWsh). The hair pigmentation of the grafts recovered after three weeks beneath the testicular tunica of adult male mice was always typical of the p phenotype showing that p is melanocyte autonomous. This result was supported by experiments using a modification of Mayer’s (1965) neural crest grafting technique and the construction of 14-day recombinant skin grafts.
Sash (WshWsh) epidermis can support melanocyte differentiation and pigment production but lacks functional melanocytes. The advantages of Wsh in experimental systems for testing the site of pigment gene expression have been demonstrated.
Control experiments confirmed the dermal influence of agouti (A) over non-agouti (a) epidermis but non-agouti dermis did not overrule agouti pink-eyed dilution (AA pp) epidermis suggesting an epistatic effect of p in the melanocyte.
Use of a monoclonal antibody recognizing a cell surface determinant to distinguish prestalk and prespore cells of Dictyostelium discoideum slugs
Authors: Krefft Marianne , Voet Ludwig , Gregg james h. , Williams keith l. 
Published: April 2021

ABSTRACT
Double labelling experiments on Dictyostelium discoideum cells at different developmental stages were carried out using monoclonal antibodies MUD1 (prespore specific), MUD9 (strong label on prestalk and anterior-like cells) and a fluorescence-activated cell sorter. The monoclonal antibody MUD9, which recognizes the surface of prestalk and anterior-like cells strongly and prespore cells weakly, is also present on the surface of vegetative amoebae and on mature stalk cells but not on the spore surface. Sharing of an antigenic determinant between vegetative, prestalk and anterior-like cells is consistent with these cells being ‘less differentiated’ than prespore cells.
Development of the lateral line system in Xenopus laevis : IV. Pattern formation in the supraorbital system
Authors: Winklbauer Rudolf , Hausen Peter 
Published: April 2021

ABSTRACT
The periodic pattern of the supraorbital lateral line organs forms in the epidermis of Xenopus by the subdivision of a streak-like primordium into a linear series of small cell groups. In normal development, each such organ initially contains about 8 cells (Winklbauer & Hausen, 1983a,b). To see whether this initial organ size depends on the size of the streak-like primordium at the time of organ segregation, primordium size was reduced experimentally before the onset of pattern formation. In such small primordia, the size of the primary organs formed is not adjusted so as to allow the formation of a normal number of organs. Instead, the initial organ size is kept approximately normal, and the number of organs is correspondingly reduced, i.e. the pattern forming mechanism is not capable of ‘size regulation’.
Lethality of a tritiated amino acid in early mouse embryos
Authors: Wiebold Janet L. , Anderson Gary B. 
Published: April 2021

ABSTRACT
2- to 4-cell and morula- to blastocyst-stage mouse embryos were cultured for 1 h in tritiated leucine at two specific activities and their subsequent development followed in vitro and in vivo (after transfer to recipients), respectively. 2- to 4-cell embryos that incorporated an average of 42 d.p.m. per embryo were impaired in their ability to develop to the morula and blastocyst stage. Recipients receiving morulae and blastocysts that had incorporated an average of 384 d.p.m. per embryo failed to produce young. Reduction of the specific activity improved the viability of embryos both in vitro and in vivo but development was still less than that of unlabelled embryos. Protein degradation curves were different for both 2- to 4-cell and morula- to blastocyst-stage embryos labelled at the two different specific activities. Most studies using tritiated amino acids have employed higher specific activities than those used here and they may have to be reevaluated due to the possibility of radiation-induced artifacts.
Cell proliferation in condensing scleral ectomesenchyme associated with the conjunctival papillae in the chick embryo
Authors: Kamp Maarten Van De , Hilfer S. Robert 
Published: April 2021

ABSTRACT
The role of cell proliferation in the formation of scleral ectomesenchymal condensations underlying the conjunctival papillae was examined with in vivo tritiated thymidine labelling in chick embryos ranging in age from 8 days 0 h to 10 days 12 h. Percentages of labelled nuclei were determined in both ectomesenchyme and the deeper fibrous sclera for short-term and continuous tritiated thymidine incubations. During formation of the ectomesenchymal condensations the percentages of labelled nuclei were consistently higher within the condensations than in corresponding non-condensing ectomesenchyme between papillae. The consistent differences of labelling percentages observed within the condensing versus noncondensing ectomesenchyme were not found in the fibrous sclera at any stage. All areas of both the ectomesenchyme and fibrous sclera showed decreases in the percentages of labelled nuclei from 8 days Oh to 10 days 12h, although the decline in the ectomesenchymal condensations beneath papillae occurred more slowly than in areas between papillae. The data suggest that the conjunctival papillae directly influence the proliferation in the subjacent condensing ectomesenchyme but have no effect on the ectomesenchyme between papillae or any region of the deeper fibrous sclera. The observations of this investigation are discussed in relation to other studies of the development of the pre-ossicular mesenchyme.
Relationship between timing of posterior neuropore closure and development of spinal neural tube defects in mutant (curly tail) and normal mouse embryos in culture
Authors: Copp Andrew J. 
Published: April 2021

ABSTRACT
The relationship between timing of closure of the posterior neuropore (PNP) and development of spinal neural tube defects (NTD) has been studied in individual mutant curly tail mouse embryos maintained in culture. Moderate delay in PNP closure results in development of tail flexion defects whereas extreme delay of PNP closure is associated with development of open NTD. Experimental enlargement of the PNP at the stage of 25 to 29 somites leads to delayed PNP closure and development of tail flexion defects in 36 % and 38 % respectively of non-mutant A/Strong embryos. In curly tail embryos, the effect of experimental enlargement of the PNP summates with the genetic predisposition to produce an increased incidence of spinal NTD among which open defects are proportionately more common. These results indicate that a causal relationship exists between delay in PNP closure and development of spinal NTD in mouse embryos. The method described for distinguishing between prospective normal and abnormal curly tail embryos at a stage prior to the appearance of malformations provides an opportunity to study the morphogenetic processes that precede the development of genetically determined spinal NTD.
The fate of larval chondrocytes during the metamorphosis of the epibranchial in the salamander, Eurycea bislineata
Authors: Alberch P. , Lewbart G. A. , Gale Emily A. 
Published: April 2021

ABSTRACT
The metamorphosis of the epibranchial cartilage, a skeletal component of the hyobranchial apparatus, in the salamander Eurycea bislineata entails a combination of the reabsorption of a larval cartilaginous element with the simultaneous genesis of an adult cartilage in the same place. In this study we focus on the fate of the larval chondrocytes. Two hypotheses are considered: one, larval cells simply die off during metamorphosis, or, alternatively, they dedifferentiate and participate in the formation of the adult element.
Thyroxine treatment and experimental tissue manipulation coupled with measurements of thyroxine levels using radioimmunoassay show that, within 24 h after T4 treatment, larval chondrocytes in the epibranchials exhibit large autophagocytic vacuoles, disruption of the rough endoplasmic reticulum, abnormally shaped mitochondria, abundance of lysosomes and nuclear degeneration, all symptoms of the onset of cell death. In conclusion, evidence from light microscopy, TEM and SEM show that the larval chondrocytes in response to rising levels of thyroid hormones undergo a process of lysosomal autophagocytosis and do not participate in the formation of adult structures.
DNA replication and compaction in the cleaving embryo of the mouse
Authors: Smith Roger K. W. , Johnson Martin H. 
Published: April 2021

ABSTRACT
The effects of aphidicolin, a reversible inhibitor of DNA polymerase alpha, both on replication and on development of the mouse embryo from the 2- and 4-cell stages to the compacted late 8-cell stage have been assessed. The continuous presence of aphidicolin from G1 of the 4-cell stage resulted in inhibition of DNA replication and prevention of division from 4 to 8 cells, but was without effect on the timing or incidence of cell flattening, surface polarization and cytoplasmic polarization. The continuous presence of aphidicolin from Gx of the 2-cell stage resulted in inhibition of DNA replication, division, and polarization. Some slight intercellular flattening in a few embryos did occur. If addition of aphidicolin was delayed by 10 h to early in G2 of the 2-cell stage, further rounds of replication were blocked and some embryos failed to cleave to 4-cells. Nevertheless, almost all embryos showed evidence of flattening and polarization regardless of cell number. In contrast, if aphidicolin was added in G] of the 2-cell stage and removed after 10 h, the cells showed delayed DNA replication, little evidence of division, and no cell flattening or polarization. We conclude that DNA replication at the 2-cell stage may be essential for the components of compaction studied, but that DNA replication at the 4- and 8-cell stages is not.
A clonal analysis of the requirement for the trithorax gene in the diversification of segments in Drosophila
Authors: Ingham P. W. 
Published: April 2021

ABSTRACT
The requirement for the trithorax gene during imaginal cell proliferation has been analysed by clonal analysis. Clones carrying the allelic Regulator of bithorax and trithorax mutations were induced by mitotic recombination at different developmental stages. The results indicate that the trithorax gene is required at least until the beginning of the third larval instar to ensure the correct differentiation of head, thoracic, and abdominal structures, and are consistent with a role for the gene in maintaining the appropriate levels of Antennapedia and bithorax complex expression.
Prostaglandin synthesis during the course of limb cartilage differentiation in vitro
Authors: Gay Steven W. , Kosher Robert A. 
Published: April 2021

ABSTRACT
In the present study we have used radiometric thin layer chromatography (TLC) and radioimmunoassay (RIA) to examine the synthesis of various prostaglandins (PGs) during the progressive chondrogenic differentiation limb mesenchymal cells undergo in micromass culture. Throughout the 3-day culture period, [3H]arachidonic acid (AA) is metabolized to compounds which comigrate with authentic PGE2, PGF2α, 6-keto-PGF1α, TxB2, and PGD2. In micromass cultures prepared from the cells of whole stage-23/24 wing buds, all 3H-AA metabolites are produced in relatively small amounts during the initial period of culture, i.e. prior to the formation of extensive prechondrogenic cellular aggregates. Concomitant with maximum aggregate formation and the initiation of cartilage differentiation, there is a striking and progressive increase in the production of all the major classes of PGs from 3H-AA. PG production from 3H-AA is also at a maximum during the onset of chondrogenesis in micromass cultures prepared from the distal subridge mesenchymal cells of stage-25 wing buds in which more rapid, extensive, and homogeneous cartilage differentiation occurs. To complement these TLC studies, RIA has been used to examine the amount of various PGs synthesized from endogenous substrates by micromass culture homogenates at various times during in vitro chondrogenesis. These RIA studies also indicate that PG production is highest during periods of culture which coincide with the onset of overt chondrogenesis in both stage-23/24 whole limb and stage-25 subridge mesoderm micromass cultures. RIA indicates that PGE2 is the predominant PG produced from endogenous substrates during 1 h incubations at the onset of chondrogenesis, while radiometric TLC indicates compounds which comigrate with PGF2α are the major class of 3H-AA metabolites which accumulate during that time. This qualitative difference very likely reflects metabolism of parent PG compounds during the long (12 h) labelling and postlabelling incubations utilized in the TLC analyses. The temporal correlation between PG production and the initiation of chondrogenesis in vitro is consistent with previous studies implicating PGs in the regulation of limb cartilage differentiation.
Monoclonal antibodies to the cells of a regenerating limb
Authors: Kintner Chris R. , Brockes Jeremy P. 
Published: April 2021

ABSTRACT
Monoclonal antibodies were raised against differentiated cells, and blastemal cells from regenerating limbs of adult newts (Notophthalmus viridescens) and screened for specific staining by immunocytochemistry. In addition to antibodies that identify muscle, Schwann cells and cartilage, two reagents were specific for subpopulations of blastemal cells. One of these latter antibodies, termed 22/18, has provided new evidence about the origin of blastemal cells from Schwann cells and myofibres, and also identifies blastemal cells whose division is persistently dependent on the nerve supply.
The function and mechanism of convergent extension during gastrulation of Xenopus laevis
Authors: Keller R. E. , Danilchik Michael , Gimlich Robert , Shih John 
Published: April 2021

ABSTRACT
The processes thought to function in Xenopus gastrulation include bottle cell formation, migration of cells on the roof of the blastocoel, and autonomous convergent extension of the circumblastoporal region. A review of recent and classical results shows that only the last accounts for the bulk of the tissue displacement of gastrulation, including spreading of the marginal zone toward the blastopore, involution of the marginal zone, and closure of the blastopore. Microsurgical manipulation and explantation studies, analysed by time-lapse video and cine microscopy, shows that the dorsal circumblastoporal region contains two regions which show either autonomous or semiautonomous convergent extension. The dorsal involuting marginal zone (IMZ) undergoes convergence (narrowing) and extension (lengthening) after its involution, beginning at the midgastrula stage and continuing through neurulation, such that it simultaneously extends posteriorly across the yolk plug and narrows the blastoporal circumference. Concurrently, the corresponding region of the overlying non-involuting marginal zone (NIMZ) begins a complementary convergent extension, but at a greater rate, which spreads vegetally to occupy surface area vacated by the IMZ. Tissue recombination experiments show that the deep cells of the dorsal IMZ bring about convergent extension. Labelling of small populations of these cells with a cell lineage tracer shows that convergent extension involves intercalation of deep cells to form a longer, narrower array. Direct time-lapse video and cine micrography of deep cells in cultured explants show that convergent extension involves radial and circumferential intercalation. Removal of the entire blastocoel roof of the early gastrula, including all or part of the NIMZ, shows that convergent extension of the IMZ alone can bring about its involution and blastopore closure. The role of convergent extension in gastrulation of other amphibians and other metazoans and its significance to related problems in early development are discussed.
Maturation promoting factor and cell cycle regulation
Authors: Ford C. C. 
Published: April 2021

ABSTRACT
Cell cycles in early amphibian embryos are characterized by the absence of Gi and G2 phases. The simple cycle of S phase and mitosis does show similarities with other systems, particularly in the presence of cytoplasmic components advancing nuclei into DNA synthesis and mitosis. Maturation-promoting factor induces nuclear envelope breakdown and subsequent chromosome condensation. Cytoplasmic factors appear during maturation which are capable of inducing DNA synthesis, and arrest of the nuclear division cycle in metaphase (cytostatic factor). The timing of appearance of these activities is considered and their relationship in integrating DNA synthesis during early cleavage is discussed.
The Differential Growth Response of Embryonic Chick Limb-bone Rudiments to Triiodothyroninein vitro
Authors: Lawson Kirstie 
Published: April 2021

ABSTRACTThe cartilaginous limb-bone rudiments of the 6-day-old embryonic chick show a differential growth response to treatment with triiodothyronine (T3) during 8 days’ culture in vitro. The growth in length and wet weight of the tibia is reduced by l · 6 × 10–4g. T3/l. of medium, but the growth of the radius is increased. Tibia and radius explanted at comparable histogenetic stages respond differently to T3, but the responses are slightly modified by the stage of development at which the rudiments are exposed to the hormone: tibiae from 5-to -day-old embryos show a transitory stimulation of growth in length, followed by retardation, while increase in the growth in length of radii from 7- and 8-day-old embryos is less than that of radii from 6-day-old embryos. Five small limb-bone rudiments of a similar size (third metatarsus, radius, ulna, third metacarpus, and fourth metacarpus) respond differentially to T3. It is therefore unlikely that the differential growth-response of the tibia and radius is a result of the limited nutritional conditions in vitro.