bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis ofvestigialw(vgw): a mutation causing homoeosis of haltere to wing and posterior wing duplications inDrosophila melanogaster
Authors: Bownes Mary , Roberts Sarah 
Published: April 2021

ABSTRACTvg w is a homozygous lethal mutation killing embryos prior to formation of the syncitial blastoderm. In heterozygous condition it causes duplications of the posterior wing, ranging from very small duplications of the axillary cord and alar lobe to large duplications including much of the wing blade and the posterior row of bristles. No anterior margin structures are ever observed. The thorax is sometimes slightly abnormal, but rarely shows large duplications. The size of the wing is related to the number of pattern elements deleted or duplicated.Heterozygous vgw flies also show homoeosis of the haltere to wing. This occurs in the capitellum, where wing blade is observed, but no wing margin structures are found. As with the bithorax (bx) mutation which transforms anterior haltere to anterior wing this aspect of the phenotype is repressed by the Contrabithorax (Cbx) mutation. The transformed haltere discs show more growth than wild-type haltere discs.Flies heterozygous for vgw also show a high frequency of pupal lethality, those forming pharate adults generally show the most extreme vgw phenotype.No cell death has been observed in the Imaginal discs of third instar larvae, suggesting that if the wing defects result from cell death this must occur early in development. The homoeosis in the haltere discs and duplications of the wing disc are reflected by the altered morphology and growth of these discs.There are some minor differences in the expressivity of the phenotype when flies are reared at different temperatures. Chromosome substitutions suggested that all aspects of the phenotype related to the vgw mutation and that other mutations had not occurred in the stock. Cytological analysis indicated that vgw is a deletion or inversion on the right arm of chromosome 2 from 47F/48A to 49C.Complementation studies with various mutants thought to be located within the deletion, or inversion and which affect wing morphology have been undertaken.Cbx causes transformations of wing to haltere; this occurs in the posterior compartment far more frequently than in the anterior compartment. Cbx; vgw flies have wings where one of the duplicates is no longer present, presumably transformed to haltere, though this is difficult to identify. One copy of the axillary cord, alar lobe etc, the structures commonly duplicated in vgw, are present, but they are the anterior duplicate rather than the original posterior copy of these structures. Thus Cbx acts upon genuine posterior structures but not those posterior structures in vgw which form in anterior wing locations, suggesting that although these structures differentiate into posterior wing, to the Cbx gene product the cells are still ‘anterior’.
Staging the metamorphosis of Drosophila melanogaster
Authors: Bainbridge S. Paul , Bownes Mary 
Published: April 2021

ABSTRACT
A sequence of 51 visible changes is described during the course of metamorphosis in Drosophila melanogaster, and a series of 24 convenient stages is defined for use in the experimental analysis and exploitation of this part of the insect life cycle. The duration of each stage is estimated and times are suggested for batch collections of symphasic animals.
The regeneration of supernumerary cockroach antennae
Authors: French Vernon , Domican John 
Published: April 2021

ABSTRACT
Grafting experiments performed on the basal scape segment of the antenna of Blabera craniifer give very similar results to those of corresponding grafts done on the legs of cockroaches and many other insects. If the antenna is amputated and replaced on the stump, it heals, while a 180°-rotated graft de-rotates and sometimes forms a symmetrical partial supernumerary. If the antenna is grafted on to the contralateral stump, one transverse axis of the graft is reversed relative to the host, and this results in the regeneration of a supernumerary antenna with host orientation from each of the two points of maximum incongruity between graft and host. Sometimes one double supernumerary forms midway between these points, and its orientation suggests that it results from a secondary fusion of the two supernumeraries.
The similarity of these results to those of leg grafts suggests that legs and antennae have a similar general organisation of positional information and similar rules for cellular behaviour. Further, the two appendages may have the same set of positional values but have evolved different ways of interpreting it. Preliminary attempts to test this idea directly (by grafting between leg and antenna) were rather unsuccessful since only a few control grafts healed (poorly) and all rotated and contralateral grafts were eliminated.
Effect of Li+ on preimplantation mouse embryos
Authors: Izquierdo L. , Becker M. I. 
Published: April 2021

ABSTRACT
Two-cell mouse embryos were cultured in vitro for different periods in a medium in which NaCl was partially replaced by LiCl at concentrations ranging from 1 to 30 mM. The relative cell number diminished according to increasing LiCl concentrations but the onset of blastulation was not affected, thus resulting in blastulae with fewer cells than normal and with a reduced or absent inner cell mass. Results are discussed in terms of the possible mechanisms involved and are related with the vegetalization induced by Li+ on early embryos of echinoderms and amphibia.
Morphology of programmed cell death in the ventral nerve cord ofCaenorhabditis eleganslarvae
Authors: Robertson Alison M. G. , Thomson J. N. 
Published: April 2021

ABSTRACTIn the nematode C. elegans, cells undergoing programmed death in the developing ventral nerve cord were identified by Nomarski optics and prepared for ultrastructural study at various times after their birth in mitosis.The sequence of changes observed suggests that the hypodermis recognizes the dying cell before completion of telophase. The dying cell is engulfed and digestion then occurs until all that remains within the hypodermal cytoplasm is a collection of membranous whorls interspersed with condensed chromatin-like remnants. The process shares several features with apoptosis, the mode of programmed cell death observed in vertebrates and insects. The selection of cells for programmed death appears not to involve competition for peripheral targets.
Pioneer growth cones in virgin mesenchyme: an electron-microscope study in the developing chick wing
Authors: AL-Ghaith L. K. , Lewis J. H. 
Published: April 2021

ABSTRACTAxons grow out along predictable routes to specific destinations. An EM study of the early development of one of the main chick wing nerves -the interosseous nerve -helps to show how they do it. The growing tip of the nerve appears frayed, consisting of nerve fibres occurring singly or in small bundles, taking slightly divergent paths. Most of these pioneer nerve fibres have the characteristic appearance of growth cones. They are not seen to advance along fibrils of the intercellular matrix (as one might expect from some tissue culture experiments), but instead are generally in close contact over their whole surface either with mesenchyme cells or with other nerve fibres. The same is true of the axons at more proximal levels of the developing nerve: they too are never naked, but always in contact either with other axons or with mesenchyme cells. Later nerve fibres follow the pioneers: their growth cones travel out in contact with the pre-existing axons, within the primitive perineurium formed by the enveloping mesenchyme cells, and most often close to the periphery of the fascicle.
Regulation of meiosis in the foetal mouse gonad
Authors: Evans Clive W. , Robb Diana I. , Tuckett Fiona , Challoner Susan 
Published: April 2021

Abstract
In vitro culture of male and female gonads was found to have significant effects on gonadal structure and development. Culture resulted in a reduction of testicular cord diameter and a reduction in the number of Sertoli cells lining each cord in cross section. In the female, culture increased the percentage of pyknotic oocytes and fewer germ cells per unit of ovary volume reached diplotene. Mixed sex co-culture using different culture methods showed that day 14 p.c. testes inhibited meiosis in day 14 p.c. ovaries when the cultures were continued until the equivalent of day 21 p.c. Day 15 p.c. and mixed age co-cultures of mixed sex provided more equivocal data since meiosis was inhibited in some preparations but not in others. The possibility is suggested that prophase I may proceed irrevocably to diplotene after about day 15 p.c. and thus the inhibitory effects of foetal testes may be a function of female gonadal age. No evidence was found to support the hypothesis that mixed sex co-culture may stimulate meiosis precociously in foetal testes.
Fine structural analysis of limb development in the wingless mutant chick embryo
Authors: Sawyer Linwood M. 
Published: April 2021

ABSTRACT
The fine structure of the normal and wingless chick limb bud was examined with scanning and transmission electron microscopy. The apical ectodermal ridge (AER) of the normal limb bud was composed of pseudostratined columnar cells. These cells contained gap junctions, electron-dense vesicles, and numerous microtubules and microfilaments that were oriented perpendicularly to the basal lamina. Microfilaments were also found coursing transversely in the basal cell cytoplasm.
The ectoderm of the wingless mutant limb bud lacked a well-developed AER and resembled the dorsal and ventral ectoderm of the normal embryo. Gap junctions and electron-dense vesicles found in the AER of the normal limb bud were not apparent in the mutant ectoderm.
The normal-limb bud mesoderm is composed of stellate cells that are oriented at right angles to the overlying ectoderm. There is a prominent subectodermal space that is traversed by numerous mesenchymal cell filopodia. The mesodermal cells of the mutant limb bud are compact and round and have short stubby filopodia, while the cells of the adjacent flank mesoderm are stellate. The subectodermal space is absent and the mesodermal cells are in intimate association with the basal lamina of the overlying ectoderm.
Ruthenium red was employed as an extracellular marker for glycosaminoglycans. No differences were found in the distribution of these substances in normal and mutant limb buds. In several cases the basal lamina of the mutant limb bud ectoderm was discontinuous and the lamina lucida was not apparent. The results indicate that the mutation has an effect on the limb buds’ ability to maintain a well-developed AER and basal lamina. It also suggests that the wingless gene affects the shape and possibly the mobility of the limb-bud mesoderm cells.
The phenotypic expression of a t
6
/t
6
/t
6 genotype
Authors: McGrath James , Hillman Nina 
Published: April 2021

ABSTRACT
In vivo, embryos which are homozygous for the t6 mutation die during egg cylinder development (gestation days 5·5-6·5). In vitro, these mutant embryos can be distinguished from their wild-type littermates by their developmental arrest and by the failure of their tropho-blast cells to transform to giant cells. We have investigated the nature of this lethality by constructing triploid embryos with varying combinations of the t6 mutant chromosome* The phenotypes of outgrowths from these triploid embryos were examined and compared with the phenotypes of outgrowths from 4-/ +, + /t6, and tft6 embryos. The data show 1) that + / t6/ t6 embryos are phenotypically wild-type, while t6/ t6/t6 embryos are phenotypically mutant and 2) that t6/t6/t6 and t6/ t6 embryos are developmentally arrested at the same stage of outgrowth.
Surface changes in the embryonic interdigital epithelium during the formation of the free digits: a comparative study in the chick and duck foot
Authors: Hurle J. M. , Colvee E. 
Published: April 2021

ABSTRACT
The formation of the free digits of the chick is accompanied by conspicuous surface changes of the interdigital ectoderm. These changes were much less pronounced or absent in the duck.
As early as the interdigital grooves were detected in the chick, the morphological features of the ectodermal cells changed from a polygonal shape and flattened appearance to a rounded shape and bulging appearance. These changes were not present in the webbed foot of the duck. On the other hand the development of the interdigital commissures was accompanied by the formation of ectodermal ridges consisting of an accumulation of rounded cells which were in some cases in course of detachment to the amniotic cavity. These ridges were very prominent in all the interdigital commissures of the chick. In the duck they were less pronounced and were only present in the first and third commissure. From these results it is suggested that in addition to the well-known interdigital mesenchymal necrotic process (INZ) the ectodermal tissue of the interdigits might also be actively involved in the formation of free digits.
The Localization of the Presumptive Cerebral Regions in the Neural Plate of the Axolotl Larva
Authors: Jacobson Carl-olof 
Published: April 2021

ABSTRACTBy means of vital staining it has been possible to project the most important areas of the fully developed brain of the axolotl, Siredon mexicanum, upon the neural plate of the larva. The map of presumptive areas is shown in Textfigs. 15-17. The investigation has shown that the presumptive fore-brain occupies space not only upon the foremost part of the neural plate, but also upon the transverse ridge. All material of the presumptive diencephalon and of the more caudally situated brain regions is situated in the plate proper. The position of the eye-forming area has been shown to be more medial than has been proposed by earlier authors. This mapping of the presumptive brain areas makes it possible to judge with greater certainty the question of self-differentiation and regulation in the transplantation experiments of previous authors.
The Development of the Nervous System in Chick Embryos, studied by Electron Microscopy
Authors: Bellairs Ruth 
Published: April 2021

An electron microscope study of developing nervous tissue has been made in the chick embryo, correlating the results with those obtained by other techniques. I have been especially concerned with (1) the relationship between ectoderm and mesoderm cells at the time of neural induction, and (2) the formation of the Nissl substance.
Tissue from 73 chick embryos incubated for periods between 1 and 13 days has been studied. Before fixation each specimen was staged according to the normal table of Hamburger & Hamilton (1951). The tissue was fixed either in osmium tetroxide, or in potassium permanganate (Luft, 1956). In either case the pH was buffered to 7·4 with sodium veronal (Palade, 1952) and fixation was at 0° C. In the early stages the whole embryo was fixed.
Metachromasia Observed in the Living Eggs ofArbacia punctulataand its Cytochemical Analysis
Authors: Mulnard Jacques , Auclair Walter , Marsland Douglas 
Published: April 2021

ABSTRACTThe analysis of the egg of Arbacia punctulata by means of vital staining with toluidine blue confirms the results obtained on other species. It shows a primary metachromasia due to tiny a granules scattered throughout the cytoplasm, and the appearance, at the time of the paired pronuclei, of secondary metachromatic β granules in close relation to the nucleo-mitotic apparatus.High-speed pressure-centrifugation (Marsland’s procedure) shows that the a granules are sedimented in the upper half of the vitelline zone, the ft granules in the lower half of the hyaline zone. These two metachromatic layers remain separated by the mitochondrial band. A third granular, metachromatic material can be detected which may be a precursor of the βgranules.Cytochemical tests verify the presence of acid phosphatase in all the metachromatic structures and show that all contain mucopolysaccharides, which account for the metachromasia. The Alcian-blue technique reveals that the β granules contain strongly acidic mucopolysaccharides, whereas the a granules contain less acidic mucopolysaccharides.
Immunochemical Studies of Muscle Proteins in Mature and Regenerating Limbs of the Adult Newt,Triturus viridescens
Authors: Laufer Hans 
Published: April 2021

ABSTRACTImmunochemical procedures were employed to analyse changes in contractile proteins during limb regeneration in the adult newt, Triturus. Methods for the isolation of myosin and actomyosin were modified for use in the newt. After these proteins were characterized biochemically they were shown to be antigenic in the rabbit. The activity and specificity of anti-actomyosin and anti-myosin sera were determined by means of agar diffusion techniques. Purified actomyosin was found to be contaminated by myosin and a second component, a nucleoprotein. The diffusion coefficients increased in the order actomyosin, myosin, nucleoprotein. The injection of myosin into rabbits elicited the formation of antibodies which, when tested in agar diffusion, usually demonstrated a minimum of one band but occasionally, when contaminated by minor quantities of actomyosin, two bands were seen. Some modifications of existing procedures are described for the use of small reagent samples in Ouchterlony plates. The development of muscle during limb regeneration was tested by the agar diffusion method. Actomyosin and myosin can first be detected in the regenerate at the stage of hand formation (‘palette’ stage). Thereafter there is an upsurge of synthesis of these proteins during the ‘early’ and ‘medium’ digital stages. The appearance of these contractile proteins probably coincided with the time of myofibril formation. A rise in nucleoprotein preceded the appearance of muscle protein and later decreased to a concentration characteristic of adult tissues. All tissues which were tested immunologically contained the nucleoprotein component. Infusions of rabbit serum and anti-muscle serum into the regenerate yielded a cytotoxic response which varied according to the serum used, the reaction to the immune serum being more severe. There was a temporary cessation of regeneration for a few days, the duration of which was related to the severity of the reaction. Observations of the histopathology of infused regenerates revealed sarcolysis attributable to the specific effects of the anti-muscle serum. Autoradiograms of limbs infused with I131 gamma globulin demonstrated the course and disposition of labelled protein within the regenerate and stump. There was localization of material about muscle-cells, suggesting a possible specificity of the reaction. The epidermis appeared to be an active organ for the elimination of foreign material.
Interactions of blastomeres suggest changes in cell surface adhesiveness during the formation of inner cell mass and trophectoderm in the preimplantation mouse embryo
Authors: Kimber Susan J. , Surani M. Azim H. , Barton Sheila C. 
Published: April 2021

ABSTRACTWhole 8-cell morulae can be aggregated with isolated inner cell masses from blastocysts. On examining semithin light microscope sections of such aggregates we found that cells of the morula changed shape and spread over the surface of the ICM, thus translocating it to the inside of the aggregate. Using single cells from 8-cell embryos in combination with single cells from other stage embryos or isolated ICMs we show that 1/8 blastomeres spread over other cells providing a suitably adhesive surface. The incidence of spreading is high with inner cells from 16-cell embryos (56 %) and 32-cell embryos (62 %) and isolated inner cell masses (64%). In contrast, the incidence of spreading of 1/8 blastomeres is low over outer cells from 16-cell embryos (26 %) and 32-cell embryos (13 %). Blastomeres from 8-cell embryos do not spread over unfertilized 1-cell eggs, 1/2 or 1/4 cells or trophectoderm cells contaminating isolated ICMs. When 1/8 cells are aggregated in pairs they flatten on one another (equal spreading) as occurs at compaction in whole 8-cell embryos. However, if 1/8 is allowed to divide to 2/16 in culture one of the cells engulfs the other (51 –62% pairs). Based on the ideas of Holtfreter (1943) and Steinberg (1964,1978) these results are interpreted to indicate an increase in adhesiveness at the 8-cell stage as well as cytoskeletal mobilization. Following the 8-cell stage there is an increase in adhesiveness of inside cells while the outside cells decrease in adhesiveness. The difference in adhesiveness between inside and outside cells in late morulae is probably central to the divergent differentiation of (inner) ICM and (outer) trophectoderm cell populations.
Evidence of male germ cellredifferentiation into female germ cells in planarian regeneration
Authors: Gremigni V. , Nigro M. , Puccinelli I. 
Published: April 2021

AbstractThe source and fate of blastema cells are important and still unresolved problems in planarian regeneration. In the present investigation we have attempted to obtain new evidence of cell dedifferentiation-redifferentiation by using a polyploid biotype of Dugesia lugubris s.l. This biotype is provided with a natural karyological marker which allows the discrimination of triploid embryonic and somatic cells from diploid male germ cells and from hexapioid female germ cells. Thanks to this cell mosaic we previously demonstrated that male germ cells take part in blastema formation and are then capable of redifferentiating into somatic cells. In the present investigation sexually mature specimens were transected behind the ovaries and the posterior stumps containing testes were allowed to regenerate the anterior portion of the body. Along with the usual hexaploid oocytes, a small percentage (3.2%) of tetraploid oocytes were produced from regenerated specimens provided with new ovaries. By contrast only hexaploid oocytes were produced from control untransected specimens. The tetraploid oocytes are interpreted as original diploid male germ cells which following the transection take part in blastema formation and then during regeneration redifferentiate into female germ cells thus doubling their chromosome number as usual for undifferentiated cells entering the female gonad in this biotype.
Analysis of the intermediate size proteoglycans from the developing chick limb buds1
Authors: Vasan Nagaswamisri 
Published: April 2021

ABSTRACTLimb-bud proteoglycans are heterogeneous molecules which vary in their chemical and physical properties with development. This report describes proteoglycan intermediates (PG-I) that predominate in stage-34 limbs, and compares them with proteoglycan aggregates (PG-A) in stage-38 limbs. We analysed proteoglycans and their components extracted with guanidinium chloride by subjecting them to density gradient centrifugation, molecular sieve chromatography, electrophoretic separation, and selective enzymatic degradation. PG-I and PG-A have similar chondroitin sulphate composition, amino sugars, chondroitin sulphate side-chain length, glycoprotein link factors, and hyaluronic acid binding capacity, and both cross react with antisera prepared against cartilage-specific chick sternal proteoglycans. However, PG-I has lower molecular weight, lower buoyant density, and fewer chondroitin sulphate side chains on the protein core. The PG-I in the developing limb can be considered a mixture of smaller aggregates and cartilage-specific large monomers in which the former predominate.