bluuebunny/crossref_metadata_2025_split huggingface dataset:
The orientation of the visuotectal map in Xenopus: developmental aspects
Authors: Gaze R. M. , Feldman Joan D. , Cooke J. , Chung S-H 
Published: April 2021

ABSTRACT
Rotations and translocations of the eye anlage were performed in Xenopus embryos of stages ranging from 21/22 to 30. Some of the operations involved grafting wild-type eye anlagen into albino host orbits. Operations were performed under a variety of operating media and conditions. In later larval life, or after metamorphosis, the visuotectal maps from the operated eyes were recorded electrophysiologically. Results fell into two classes. In the majority, the orientation of the visuotopic map corresponded to the orientation of the eye at the time of recording. In the minority the visuotopic maps were ′compound′, consisting of two parts each with its own independent orientation. The organization of the compound maps was such that one component was oriented in correspondence with the orientation of the eye, while the other component was normally oriented. Histological analysis and observations on genetically marked grafts indicated that the component parts of the compound eye were of dual cellular origin. The component giving the rotated (or translocated) map belonged to the originally operated eye tissue; whereas the component giving the normally oriented map was derived from newly grown eye tissue coming from the optic stalk. In no case was a normally oriented map obtained from a rotated or trans-located eye. The results are discussed in relation to mechanisms proposed to account for the determination of map-related retinal specificity.
In vitro studies on skeletogenic potential of membrane bone periosteal cells
Authors: Thorogood Peter 
Published: April 2021

ABSTRACT
In the avian embryo ectomesenchyme cells, derived from the mesencephalic level of the cranial neural crest, migrate into the presumptive maxillary region and subsequently differentiate into the membrane bones and associated secondary cartilage of the upper jaw skeleton. The cartilage arises secondarily within the periosteum at points of articulation between membrane bones and provides an embryonic articulating surface. The stimulus for the differentiation of secondary cartilage is believed to be intermittent pressure and shear created at the developing embryonic movement. The development of one such system - the quadratojugal, has been analysed using organ and explant culture techniques and studied with particular reference to the differentiation of periosteal cells into secondary cartilage. A number of conclusions were reached.
Normally only cells at discrete loci express a chondrogenic potential in vivo: the periosteal cells at these sites of future articulation become committed to chondrogenesis during stage 35, more than 24 h before cartilage is identifiable in vivo. However, cells with a ‘latent’ chondrogenic potential are widespread in membrane bone periosteum and occur over most, if not all, of the surface area of the bone. This potential is expressed in the ‘permissive’ environment created by submersion of the tissue in explant culture or in submerged organ culture. This chondrogenic potential exists long before the time at which commitment of cartilage-forming cells occurs and even presumptive maxillary ectomesenchyme at stage 29 has a limited ability to form cartilage in vitro.
It is suggested that spatial position is a principal factor controlling the differentiation of secondary cartilage. Ectomesenchyme cells with the potential to form secondary cartilage are widespread but it is only those cells whose migration from the neural crest positions them and their progeny at the site of a presumptive joint which subsequently express this potential. This epigenetic interpretation is discussed in the general context of development mechanisms underlying the spatial and temporal patterns in which neural crest-derived cells differentiate to produce bone and cartilage during the formation of the head skeleton.
Immunofluorescence studies on deoxyribonuclease from mouse teratocarcinoma cells during cell differentiation
Authors: Soriano L. , Paulin D. 
Published: April 2021

ABSTRACT
Specific anti-DNase-I IgG have been used to detect deoxyribonuclease in teratocarcinoma cells by an indirect immunofluorescence method. All the cells studied show fluorescence staining. However, the patterns are quite different in embryonal carcinoma cells (amorphous cytoplasmic fluorescence and absence of nuclear staining) as compared to differentiated cell lines (diffuse, bright granular nuclear and fibrillar cytoplasmic fluorescence). It is possible by this method to distinguish different cell types derived from the same origin. Deoxyribonuclease from teratocarcinoma cells can therefore be considered as a marker of cell differentiation in this system.
Localization of cytoskeletal proteins in preimplantation mouse embryos
Authors: Lehtonen E. , Badley R. A. 
Published: April 2021

ABSTRACT
The immunofluorescence technique was used to detect the presence and distribution of actin, alpha-actinin, tubulin and 10 nm filament protein in early mouse embryos. Actin and alpha-actinin stainings showed a distinct concentration to a peripheral layer in the cleavage-stage blastomeres and in trophectoderm cells. Dots of fluorescence appeared in this cortical staining pattern. The distribution of tubulin staining in the blastomere cytoplasm was relatively even with apparent concentration at the perinuclear region and frequently at wide intercellular contact areas. 10 nm filament protein was distributed evenly in the blastomere cytoplasm without cortical concentration of the label. At the blastocyst stage, the trophectoderm cells in blastocyst outgrowths in vitro developed well organized cytoskeletons including both microfilament, microtubule and 10 nm filament elements. Comparable structures were not observed in blastocysts in vivo, or in late hatched blastocysts cultured in suspension. The morphogenetic significance of the observations is discussed.
Studies on the female-sterile phenotype of 1(1)su(f)ts76a; a temperature-sensitive allele of the suppressor of forked mutation in Drosophila melanogaster
Authors: Wilson Thomas G. 
Published: April 2021

ABSTRACT
A new allele of the suppressor of forked [su(f)] mutation in Drosophila melanogaster has been found and designated 1(1)su(f)ts76a. It is temperature-sensitive for suppression of forked (f) and has additional temperature-sensitive phenotypes of lethality, female sterility, and abnormal bristle formation at 29 °C. It closely resembles two other conditional alleles of su(f), 1(1)su(j)s67g and 1(1)ts726. Female sterility at 29 °C is characterized by both disorganized egg chambers in the ovarioles and also chorion-deficient oocytes. Both of these abnormalities may be the result of premature follicle cell death. The observations on 1(1)su(f) ts76a are consistent with the proposal that the similar allele, 1(1)ts726, is a cell-lethal mutation specifically affecting mitotically active cells.
An experimental analysis of somite segmentation in the chick embryo
Authors: Bellairs Ruth , Veini Marianne 
Published: April 2021

ABSTRACTIn a previous paper it was suggested that collagen fibrils play an important role in the process of somite segmentation. This paper was designed mainly to test that concept. In one series of experiments, embryos were treated with either α, α′-dipyridyl or L-azetidine-2-carboxylic acid, which are analogues that interfere with the formation of normal collagen. The reagents led to a reduction in the numbers of somites that formed, as well as to the production of other anomalies such as overall diminution in size and retardation. The older the embryo at the time of treatment, the further posteriorly were the major anomalies located. It is concluded that these results lend some support to the concept.In a second series of experiments an incision was made along one side of the neural tube and notochord to separate it from the segmental plate on one side. The result was that many more somites formed on the unoperated (control) side of the embryo than on the operated side. It is concluded that these results also lend support to the concept; but that they are of interest also in relation to the mechanisms involved in the control of somite numbers. In a third group of experiments, attempts were made to obtain somites in the absence of endoderm. Although this was not possible using surgery, it was achieved by treating the young embryos with u.v. irradiation. It was concluded that the presence of endoderm is not essential for the segmentation of mesoderm.
Effects of culture conditions on the developmental programme of mouse blastocysts
Authors: Sellens Martin H. , Sherman Michael I. 
Published: April 2021

ABSTRACTWe have investigated the developmental potential of mouse blastocysts cultured under a variety of conditions. A number of parameters were used as criteria for development and differentiation, namely hatching of blastocysts from the zona pellucida and their adhesion to the substratum, outgrowth and polyploidization of trophoblast cells, increase in cell number, protein content, β-glucuronidase activity, appearance of lactate dehydrogenase A subunits, plasminogen activator production, and Δ5,3βhydroxysteroid dehydrogenase activity. Under optimal culture conditions, embryos grew relatively rapidly and expressed all the differentiative markers for which they were tested. Under less supportive conditions, the production of the markers was usually reduced quantitatively; the expression of some markers could also be considerably delayed or even totally prevented. In fact, embryos cultured in the least nutritive medium (one designed to support development only through pre-implantation stages) appeared to be in a state of metabolic quiescence closely resembling that of blastocysts in ovariectomy-induced delay. Overall, the results of our investigations lead us to propose that the expression of each of the aforementioned markers is probably under independent control and subject to intrinsic programming. Finally, the observation that some markers are produced by embryos in suboptimal media whereas others are not, suggests that the minimum metabolic level necessary for expression varies from one marker to another.
The metabolism of exogenous fatty acids by preimplantation mouse embryos developingin vitro
Authors: Flynn Thomas J. , Hillman Nina 
Published: April 2021

ABSTRACTThe utilization of fatty acids from the culture medium has been examined in preimplantation mouse embryos developing in vitro.Incorporation of exogenous fatty acid into embryo lipids was examined by culturing 8-cell mouse embryos for 2 h in a medium containing 0·1 mM [9, 10-3H]palmitic acid (900 mCi/ mmol). Lipids were extracted from the embryos, and the total lipid extract was fractionated into various neutral lipid and polar lipid classes by thin-layer chromatography. Most of the radioactivity, over 93%, was recovered in neutral glycerides (monodi-, and triacylglycerols). About 2% of the total radioactivity was recovered in other neutral lipid species including fatty acids, fatty alcohols, and sterol esters. The remainder of the radioactivity was recovered in polar lipids. Seventy-four per cent of the polar lipid radioactivity was present in the choline phosphatides. Other labelled phospholipid and glycolipid species included ethanolamine phosphatides, inositol and/or serine phosphatides, sphingomyelin, choline lysophos-phatides, sulfatides, cerebrosides, and monoglycosylglycerides. Chemical degradation studies of labelled embryo lipids indicated that the tritium label was entering into embryo lipids as the fatty acid and not via metabolic recycling.The oxidation of exogenous fatty acids by mouse embryos was assessed by incubating variously staged embryos for 4h in medium containing 0·1 mM [U-14C]palmitic acid (50 mCi/mmol) and quantitating the production of 14CO2. The rate of fatty acid oxidation was found to be relatively constant from the unfertilized egg up to the 8-cell stage and then increase significantly between the 8-cell and late blastocyst stages. The results suggest that preimplantation mouse embryos developing in vitro can utilize fatty acids from the medium both for incorporation into embryo lipids and for energy production via oxidation.
Localisation and characterization of acid mucopolysaccharides in the early chick blastoderm
Authors: Vanroelen Ch. , Vakaet L. , Andries L. 
Published: April 2021

ABSTRACT
Acid mucopolysaccharides in the extracellular compartment of early chick blastoderms (16 h of incubation) were labelled with tritiated glucosamine and/or [35S]sulphate. The incorporation pattern was studied autoradiographically. Treatment with testicular hyaluronidase revealed a testicular hyaluronidase-sensitive fraction, mainly at the periphery of Middle Layer and Deep Layer cells, and a testicular hyaluronidase-resistant fraction, mainly at the ventral side of the Upper Layer.
A biochemical analysis, utilizing chondroitinase ABC and nitrous acid, followed by cellulose acetate electrophoresis, demonstrated the synthesis of a non-sulphated fraction, i.e. hyaluronic acid and/or chondroitin, and a sulphated fraction, comprising two undersulphated components, i.e. chondroitin sulphate, and heparan sulphate or heparin. The appearance of different AMPS in specific areas of the early chick blastoderm is regarded as an early specialization of the extracellular compartment.
Correlative scanning electron, transmission electron, and light microscopic studies of the in vitro development of mouse embryos on a plastic substrate at the implantation stage
Authors: Gonda Matthew A. , Hsu Yu-Chih 
Published: April 2021

ABSTRACT
Correlative scanning electron, transmission electron, and light microscopy were utilized to study the morphogenic events occurring during mouse blastocyst outgrowth and earlyegg-cylinder development in vitro. After hatching and attachment of blastocysts on the plastic surface, the blastocoelic cavity collapses as the mural trophoblasts spread and migrate outward. The inner cell mass is covered with a differentiated endoderm on the blastocoelic cavity side and by the polar trophoblasts on the medium side at this stage. As the endodermcovered inner cell mass proliferates, being physically restricted from further downward expansion by the plastic coverslip and by lack of space in the collapsed blastocoelic cavity, it migrates upward and protrudes into the culture medium in a break between the polar and mural trophoblast cells. Polar trophoblast cells apposed to the base of the egg cylinder continue to proliferate forming the ectoplacental cone. Thus, the early egg cylinder lacking a trophoblast barrier begins inverting its growth pattern from towards the culture dish surface to a more upright position. Egg-cylinder development in vitro from the inner cell mass and polar trophoblast cells closely paralleled in vivo. The functional nature of various embryonic cell types observed in these embryos was revealed by scanning electron microscopy. These studies as well as those of Wiley and Pedersen (1977) suggest that blastocysts can serve as a source of in vitro developing early mouse egg cylinders that appear to resemble their in vivo counterparts and can be used in experimental studies of mouse embryogenesis.
Effect of follicular steroids on the maturation and fertilization of mammalian oocytes
Authors: Moor R. M. , Polge C. , Willadsen S. M. 
Published: April 2021

ABSTRACTPronuclear development was used to measure the effects on ovine oocytes of altering follicular steroidogenesis during maturation in vitro. Follicular steroid secretion was altered using enzyme inhibitors and exogenous steroid supplementation. Abnormalities induced during maturation were measured 24 h after transfer of oocytes to the oviducts of inseminated hosts.The presence throughout maturation of aminoglutethimide, an inhibitor of the conversion of cholesterol to pregnenolone, reduced steroid secretion to 7% of that in controls and decreased from 77% to 33% the number of normal oocytes. Abnormalities were substantially reduced by the addition of aminoglutethimide during the final 8 h of maturation only.The inhibition of 17 α -hydroxylase enzymes with SU10603 reduced oestrogen and testosterone secretion to about 10% of control levels but had no effect on progestin secretion. Only 13% of oocytes matured in the continual presence of SU10603 underwent normal fertilization. The number of oocytes undergoing normal fertilization was increased to about 50% by (i) delaying the addition of SU10603 until the last 8 h of the maturation period or (ii) adding exogenous steroids to follicles cultured with inhibitor from explantation.It is concluded that oocytes require a specific intra-follicular steroid environment for the completion of the full maturation process. Alterations to the steroid profile during maturation induce changes in the oocyte which are expressed as gross abnormalities at fertilization.
Intercellular bridges in the embryo of the Atlantic squid, Loligo pealei
Authors: Cartwright Joiner , Arnold John M. 
Published: April 2021

ABSTRACT
In the post-gastrulation embryo of the Atlantic squid, Loligo pealei, the cells of the developing blastoderm are joined to each other by intercellular bridges which may provide a means of cytoplasmic communication between the cells. This paper describes an electron microscope survey of bridges in the developing blastoderm just prior to, and during, the onset of differentiation. The bridges are similar to those described in the gonadal tissue of many animal species and appear to result from incomplete cytokinesis followed by the disappearance of the spindle remnant. The bridges persist and chains of cells result which are generally branched and coiled. In the undifferentiated blastoderm the chains of cells show no apparent orientation to each other. However, in the apical blastoderm undergoing differentiation, chains of bridged cells appear to coincide closely with the developing mantle and shell gland primordia.
The configuration a chain of cells assumes depends upon the degree of branching (i.e. the number of cells having three bridges) and the degree of coiling of the chain. Whereas coiling is probably affected by the crowding of neighboring cells, both branching and coiling appear to be functions of spindle orientation relative to previous bridges. During mitosis the bridges appear to become occluded by systems of transverse membranous cisternae, and mitotic nuclei are thus isolated. However, the bridges apparently re-open during G1, and during periods of protein synthesis the cells within a group share a common cytoplasm. It is suggested that gene products are shared and protein synthesis of the entire bridged group may be synchronized. As the sharing of control molecules may also be facilitated, these essentially syncytial groups may respond uniformly to inducers from the yolk syncytium, or other tissues and differentiation may be synchronized within the group.
Regional variation of cell proliferation within the facial processes of the chick embryo: a study of the role of ‘merging’ during development
Authors: Minkoff Robert 
Published: April 2021

ABSTRACT
Variation in rates of cell proliferation along the long axis of the maxillary process, within the lateral nasal process and in the zone of attachment between these structures was analyzed employing DNA labeling indices. Chick embryos were labeled with [3H]thymidine for 1 h and processed for histology and autoradiography. The percentage of labeled mesenchymal cells was determined in delineated areas.
Analysis of labeling indices indicated that rates of cell proliferation varied within each of the facial processes. Regions where rates of proliferation were maintained at elevated levels were the boundary areas of the facial processes (e.g. the anterior tip of the maxillary process) and the zones of attachment between the facial processes (e.g. between the maxillary process and the lateral nasal process). Despite the presence of elevated rates of proliferation in selected regions within the facial processes, however, the percentage of labeled cells in all areas declined with advancing developmental age.
These findings support the hypothesis, proposed by Streeter and Patten, that the ‘merging’ of adjacent facial primordia, suchas the maxillary and lateral nasal processes, is accomplished by elevated rates of cell proliferation within the zones of attachment compared to the rates of proliferation in adjacent regions.
Polar granules and pole cells in the embryo ofCalliphora erythrocephala:ultrastructure and [3H]leucine labelling
Authors: Lundquist Anders , Emanuelsson Hadar 
Published: April 2021

ABSTRACTThe polar granules in Calliphora undergo a gradual fragmentation during early cleavage, but reaggregate after pole-cell formation. Autoradiographic analysis showed that the pole cells in Calliphora acquire a higher [3H]leucine label than the rest of the embryo during the blastoderm stage. Such an increased label was not seen in the pole plasm before pole-cell formation or in the pole cells during gastrulation. Electron microscopic autoradiography revealed that the polar granules are substantially labelled during the blastoderm stage. At the same time, characteristic nuclear blebs appear in the pole cells. The observations are consistent with the hypothesis that polar granules contain maternal messenger RNA, which is released and translated into proteins.
Tunicamycin inhibits mouse tooth morphogenesis and odontoblast differentiationin vitro
Authors: Thesleff Irma , Pratt Robert M. 
Published: April 2021

ABSTRACTTunicamycin (TM), an antibiotic that selectively inhibits dolichol-mediated protein glycosylation, inhibited morphogenesis and differentiation of odontoblasts in the molar tooth germ in vitro. These effects of TM are reversible and dose-dependent, and in advanced teeth the effect of TM was not complete unless the basement membrane was removed prior to culture. TM did not prevent secretion of predentin or enamel when added to the cultures after initiation of predentin secretion. TM dramatically inhibited protein glycosylation and the accumulation of labeled proteoglycans and glycoproteins in the basement membrane. Our previous studies indicated that odontoblast differentiation is triggered by an interaction between the basement membrane and mesenchymal cells. We suggest that TM inhibits odontoblast differentiation by causing alterations in the basement membrane which prevent the necessary cell-matrix interaction required for odontoblast differentiation.
The role of divalent cations in the metabolic response of mouse blastocysts to serum
Authors: Fishel S. B. 
Published: April 2021

ABSTRACTUptake and incorporation of [3H]uridine by mouse blastocysts was measured in response to serum under various conditions of Ca2+ and Mg2+ availability. Previous studies (Fishel & Surani, 1978) showed that serum stimulated uptake and incorporation of uridine in blastocysts. Here it is shown that in Ca2+-deficient medium ( &lt; 20 μM-Ca2+) cell metabolism was also inhibited and increasing [Ca2+] resulted in increased uptake and incorporation. Maximum stimulation required an extracellular [Ca2+] of 0·25 mM. The effects of low Ca2+ were reversible and could also be alleviated by 15 and 20mM-Mg2+. Magnesium greater than 20 mM was deleterious. Inorganic phosphate (Pi) was used to complex free Mg2+ in order to maximize the effects of Mg2+ deficiency. Inhibition was reversed by increasing [Mg2+] or by 15–20 mM-Ca2+. Calcium concentrations greater than 20 mM inhibited maximum stimulation. Inhibitors of Ca2+ influx D600 and papaverine, inhibited stimulation at concentrations above 5 and 20 μM respectively. Magnesium concentration of 15 mM alleviated the inhibitory effects of 50 μM D600. The effect of Ca2+-deficient medium was also alleviated by Sr2+. The results suggest that both Ca2+ and Mg2+ are required for blastocysts to respond maximally to serum; their initial role appeared to involve the binding of stimulatory serum molecules to the cells of the blastocyst followed by an influx of these cations.