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Biomedical subjects

D A Ede

Publications and source records attributed to D A Ede.

At least 19 recordsLinked to original sources
PubMed1992

The mis-expression of posterior Hox-4 genes in talpid (ta3) mutant wings correlates with the absence of anteroposterior polarity.

Developing chicken wings homozygous for the talpid (ta3/ta3) mutation are polydactylous and have defects in the establishment of their anteroposterior polarity. We analysed the expression domains of the posteriorly restricted homeobox Hox-4 genes in such mutant wings. The Hox-4 genes are now expressed right across the anteroposterior axis instead of being expressed just posteriorly. This correlates well with the absence of clear morphological differences between the talpid3 digits and reinforces the idea that vertebrate Hox-4 genes are involved in setting up the limb anteroposterior asymmetry.

Animals↗
PubMed1992

Localization of delta-crystallin RNA during lens morphogenesis and differentiation in the normal and talpid3 chick embryo.

Embryonic lens fiber cell differentiation in the chick is marked by the accumulation of delta-crystallin protein. The levels of delta-crystallin RNA are shown here to rise dramatically in the cells of the posterior lens pit prior to their elongation and differentiation as lens fibers. This increase correlates with regional proximity to the underlying optic cup (future retina). This accumulation of delta-crystallin RNA during lens induction operates selectively on the delta 1-crystallin transcripts whereas delta 2-crystallin/argininsosuccinate lyase RNA is detectable at lower levels in all developing ocular tissues throughout this period. The talpid3 mutant forms a flat "bridge" of thickened placode-like cells in the head epithelium between the two lens placodes, and this bridge also accumulates delta 1-crystallin RNA, suggesting that the selective increase in delta 1-crystallin RNA levels over those of delta 2-crystallin represents an early event in cellular commitment to lens fiber differentiation in the chick. The significance of the sequence of temporal changes in inductive sources for lens fiber formation is discussed, and we propose that the role of the optic cup is to provide, bound to its extra-cellular material (ECM), a high local concentration of the same growth factors which act as fiber inducers in the older eye.

Animals↗
PubMed1990

An autoradiography study of myogenic cell movement in avian limb buds following heterospecific and homospecific transplantation.

Species specificity and the use of quail cells as a marker in the study of myogenic cell movement in the developing avian limb was investigated. In order to establish whether or not observed myogenic cell movement in quail/chick limb transplantation experiments might be an artefact produced by cellular interaction between these cell types a series of homospecific and heterospecific transplantations was performed. Chick wing fragments (staged 20-25 H.H.) were labelled with tritiated thymidine and inserted into unlabelled chick wing bud (homospecific) in ovo. In addition, quail wing fragments were also labelled with tritiated thymidine and transplanted in the same manner into chick (heterospecific), so that the effectiveness of tritium as a marker could be assessed. After 4 days post-incubation, myogenic cell movement was detected in eight out of the ten homospecific transplantations performed. Myogenic cell movement in avian limbs is therefore not produced by interaction between chick and quail cells, as migration was also detected in the chick/chick transplants. Nonetheless, heterospecific transplantation results revealed that autoradiographic methods failed to reveal completely the true extent to which myogenic cell movement occurred, because tritiated thymidine was subject to dilution.

Animals↗
PubMed1989

The capacity of normal and talpid3 mutant fowl myogenic cells to migrate in quail limb buds.

Talpid3 is a recessive lethal mutant of the fowl. It has been shown previously that, in vitro, talpid3 limb mesenchyme cells are more adhesive and less mobile than normal cells. It is therefore of interest to investigate the effect of the gene on cell movement in vivo, in the limb bud itself, in cells in which it is known to occur in normal embryos. Myogenic cells, which normally migrate into the limb bud from the somites, continue to move distalwards when grafted into the limb bud at a later stage. Blocks of normal or talpid3 limb mesenchyme containing myogenic cells were transplanted into quail limb buds in ovo. Since quail cells are histologically distinguishable from chick cells the progress of myogenic cell movement 5 days after transplantation could be observed. In 10 out of 14 cases normal myogenic cells migrated extensively in a proximo-distal direction within the limb bud of the quail host. In contrast, only 2 out of 11 talpid3 transplants showed a moderate degree of distalwards movement.

Animals↗
PubMed1989

A study on skeletal myogenic cell movement in the developing avian limb bud.

Quail limb mesenchyme containing myogenic cells of somitic origin were transplanted into chick limb buds to determine whether cell movement might play a role in avian limb myogenesis. In general, cell displacement was not detected 1-day after implantation: all quail cells were found at the graft site. Migration was evident 2-days after implantation but not all cell types were capable of movement; myogenic cells were very invasive while chondrocytes were relatively immobile. The spreading of myogenic cells was discernible up to 4-days after implantation and specifically in a proximodistal direction towards the apex of the limb.

Animals↗
PubMed1987

Eye development in the normal and Pupoid foetus (pf/pf) mutant mouse.

Embryonic development of the mammalian eye has not been studied in such great detail as that of the avian eye, and preliminary observations have suggested that the sequence of events may differ. It is therefore likely that the relative importance of the cell and tissue interactions involved also differs and it would be interesting to compare these two systems. The pupoid foetus mutation in the mouse shows disruption of eye development due to abnormal epidermal properties and so the relative importance of individual events in triggering subsequent development can be studied by seeing what happens when the situation is modified in the mutant. The behaviour of the pupoid foetus epidermal cells in the interactive system of the eye may also help to further characterise the phenotype of the mutation.

Animals↗
PubMed1985

Embryonic development of the mouse mutant pupoid foetus (pf/pf).

The pupoid foetus mutation in the mouse is a recessive lethal mutation causing death of homozygous (pf/pf) embryos immediately after birth. From 11.3 days gestation onwards, these embryos are characterised externally by the development of a tail twist, followed by apparent stunting of the limbs and tail (when compared with the development of these structures in normal embryos), lack of digits, distortion of facial features, and possession of a smooth, mottled skin. Embryos ranging in age from 11.3 days gestation to full term have been examined using light microscopy and scanning and transmission electron microscopy. The skeletal structure and internal organs of the embryo are normal, but abnormalities occur in the external epidermis, the dermis, and the peripheral sensory nerves. Development of the palate and the eyes are affected by the behaviour of these tissues. The epidermis undergoes hypertrophy and fails to differentiate, and, on the basis of morphological criteria and theoretical considerations, it is suggested that the pf gene is activated in the epidermis during the keratinization pathway, preventing differentiation and altering the cell surface characteristics of the cells. Other abnormalities are explained in terms of interactions with the epidermis. This mutant is compared with other similar mutants.

Animals↗
PubMed1985

The behaviour in vitro of epidermal cells from normal and pupoid foetus mutant mouse embryos.

Pupoid foetus (pf/pf) is a recessive lethal mutation of the mouse causing epidermal hypertrophy and disorganization of peripheral sensory nerves and mesoderm. The comparative behaviour of epidermal cells from normal and pupoid foetus mutant mouse embryos was studied in vitro. Epidermal explants from the snout region of 12.5- to 13-day embryos were grown in culture for periods of up to 2 weeks. Cultures from both phenotypes were filmed using time-lapse cinemicrography for up to 3 days following explantation. Paths of individual cells were traced as they migrated from the explant, and their rate of locomotion and directional persistence were calculated. Differences in these parameters between the two phenotypes were tested statistically. The overall morphology of the cultures, and the tendency of the cells to detach from the periphery of the cell mass were also compared. The results show that, between 25 and 60 h after explantation, epidermal cells from pupoid foetus embryos move consistently more slowly than normal cells, and follow a more erratic path. This situation is reversed, however, between 16 and 25 h. This suggests that the pf mutation causes an alteration in epidermal cells that affects their locomotion, and which is maintained for a minimum of 3 days in the absence of other influencing factors.

Animals↗
PubMed1984

Myogenic cell movement in the developing avian limb bud in presence and absence of the apical ectodermal ridge (AER).

Fragments of quail wing bud containing myogenic cells of somitic origin and fragments of quail sphlanchopleural tissue were introduced into the interior of the wing bud of fowl embryo hosts. No movement of graft into host tissue occurred in the control, but myogenic cells from the quail wing bud fragments underwent long migrations in an apical direction to become incorporated in the developing musculature of the host. When the apical ectodermal ridge (AER), together with some subridge mesenchyme, was removed at the time of grafting, no such cell migration occurred. The capacity of grafted myogenic cells to migrate in the presence of AER persists to H.H. stage 25, when myogenesis has begun, but premyogenic cells in the somites, which normally migrate out into the early limb bud, do not migrate when somite fragments are grafted into the wing bud. Coelomic grafts of apical and proximal wing fragments showed that apical sections of quail wing buds become invaded by myogenic cells of the host, but grafts from proximal wing bud regions do not.

Animals↗
PubMed1981

Immunohistochemical localization of cyclic AMP during normal and abnormal chick and mouse limb development.

This paper describes the immunohistochemical localization of cAMP during limb chondrogenesis in talpid3 chick, brachypod mouse, and normal embryos. Comparisons were made between chick wing buds at Stages 22, 25, and 30, and mouse hind limb buds at Days 11, 12.5 and 14. At Stage 22, the normal mesenchyme in the chick displayed areas of bright fluorescence compared to a lesser intense and more evenly distributed fluorescence in talpid3. Sections of the central region from normal Stage 25 limb buds exhibited an intense fluorescence that was uniformly distributed, whereas, in talpid3 staining was more mosaic with some areas fluorescing brightly and others showing little fluorescence. At Stage 30 the staining pattern was similar between normal and talpid3, with the fluorescence being brighter in the cartilage tissue than in the surrounding soft tissue. Difference in the staining patterns of normal and brachypod limb tissue were not detectable. At Days 11 and 12.5, tissue from both genotypes displayed a very bright, uniform fluorescence. In the 14-day hind limb buds, the staining patterns were comparable to those observed in Stage 30 chick wing buds. However, under in vitro conditions conducive for the expression of the chondrogenic phenotype, differences in the intensity and extensiveness of fluorescent staining were detectable in cultures derived from 12-day normal and brachypod hind limb mesenchyme. Compared to the control, the uneven distribution of immunofluorescence in the talpid3 limb buds and the differences in intensity and extensiveness of fluorescence in the brachypod cultures support the hypothesis that cAMP is involved in limb cartilage differentiation.

Animals↗
PubMed1978

Cell interactions in the developing somite; in vivo comparisons between amputated (AM/AM) and normal mouse embryos.

Light and electron microscopy coupled to a quantitative analysis form a powerful technique for the analysis of cell behaviour in mutant and normal tissues. Using this approach the morphology of the cells and their contacts are examined in the somites of a recessive mouse mutant, amputated, and of its normal littermates. The results of the analysis show that cell density is the same in both mutant and normal sclertome but that mutant cells tend to form small clumps whereas normal cells disperse individually. There is a correspondingly greater area of cell contact per cell in the mutant. Filopodia are equally numerous in the mutant and normal but where in the normal they stretch across wide intercellular spaces to make contact at their tips with other cells, in the mutant they form a tangled web sticking back on to the surface of the cell of origin and adjacent cells. The appearance of mutant and normal sclerotome is compared with presomitic cells and with the cells of other mutants whose abnormal development has been shown to depend on cell contact morphology and behaviour.

Animals↗
PubMed1978

Control of somite number in normal and amputated mutant mouse embryos: an experimental and a theoretical analysis.

A regulation is shown for size and number of serially repeated axial structures, the somites, in a mammalian embryo. The mammalian embryo is normally inaccessible to operation at post-implantation stages. This problem is resolved by the quantitative analysis of somite size, number and development in a recessive mutant of the mouse, amputated, whose axial length is greatly reduced. The effect of the gene simulates an experiment ablating part of the embryonic tissue available for somitic segmentation. Regulation occurs at the time when the somite is first formed, by control of the quantity of cells included in each new somite. A model is devised for the control of somitic segmentation which explains most of the features observed and which can be simulated on a computer.

Amputation, Surgical↗
PubMed1978

Regional differences in the morphology and motility of mesodermal cells from the early wing-bud of normal and talpid3 mutant chick embryos.

A method of culturing has been employed to compare the properties of cells migrating from small mesodermal explants taken from different regions of normal and mutant limb-buds at different stages of development. An analysis by time-lapse cinematography of the morphology and mobility of cells migrating from explants defines a distal region within the limb-bud where these properties are distinct from those of cells from more proximal regions. In the normal wing-bud distal cells subjacent to the apical ectodermal ridge possess a characteristic multipolar morphology and translocate slowly in vitro. Cells from more proximal regions tend to be bipolar and translocate more rapidly. Distal and proximal cells also probably differ in their adhesive strengths. In the mutant, talpid3, distal and proximal cells do not differ in the above properties and cells from all regions of the limb-bud are multipolar, translocate slowly and are more adhesive than normal cells. A study of light micrographs and scanning electron micrographs suggests that these regional differences are found in the limb-bud in vivo and are not merely an effect produced by the in vitro culturing system.

Animals↗
PubMed1978

Facial development in the mouse; a comparison between normal and mutant (amputated) mouse embryos.

This work extends previous investigations into cell interactions involved in specific morphogenetic events during the development of normal and mutant (amputated) mouse embryos. In the mutant mesenchyme, cells tend to clump together and form far more extensive areas of cell contact than are found in normal mesenchyme. This is confirmed for mutant facial mesenchyme. Facial outgrowth in the mutant is retarded. The first stages of this abnormality can be seen in the naso-frontal region at 10.5 days after conception. Neither the quantity of cells contributing to naso-frontal outgrowth nor cell proliferation in the naso-frontal region differ from normal in the mutant, and these factors can be eliminated as causes of the anomaly. Instead, cell clumping and increased areas of contact in the mutant arrest the normal expansion of the naso-frontal mesenchyme which presumably occurs as a result of increased secretion of intercellular matrix material between 9.5 and 10.5 days of development. The importance of this early expansion phase for facial development has not previously been recognized.

Animals↗
PubMed1975

Intercellular adhesion and formation of aggregates in normal and Talpid-3 mutant chick limb mesenchyme.

It is demonstrated, using the Couette viscometer method, that talpid-3 mutant chick wing mesenchyme cells are more adhesive to one another than are normal cells. The relation of this to differences in the size and shape, and the internal architecture, of aggregates produced in rotation cultures of these cells was investigated. Sequences of sections through aggregates in all stages of formation, from 2-cell aggregates up to those with large cell numbers, were prepared. These confirm the theoretically predicted relationships among adhering cells which would produce the observed small, spherical talpid-3 aggregates and the larger, unevenly shaped normal aggregates. The cell contacts are further analysed with electron micrographs.

Animals↗