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Biomedical subjects

D A Ede

Publications and source records attributed to D A Ede.

34 records · Page 2Linked to original sources
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↗
PubMed1975

Cell movement and adhesion in the developing chick wing bud: studies on cultured mesenchyme cells from normal and talpid mutant embryos.

Mesenchyme fragments from early wing buds of normal and talpid3 mutant chick embryos were explanted for culture in plastic Petri dishes and the behaviour of individual cells as they moved out on to the plastic surface was studied by time-lapse ciné photography, followed by statistical analysis. Two parameters of cell movement were recorded: (1) the distances moved over measured 100-s intervals and (2) the length of time each cell spent at rest before moving on. The average speed of movement over the whole path tracked for each cell, inclusive of time at rest, was significantly greater in normal than talpid3 cells. There was no significant difference between normal and mutant cells in the average distance mover per 100-s step, equivalent to the speed over the whole path exclusive of time at rest, but the percentage of time spent at rest was significantly less in normal than in talpid3 cells. This difference appears to be related to a difference in cell morphology, since it was observed that the mutant cells were more flattened than normals, with very extensive ruffled membranes and short spiky microvilli all round the cell periphery. The relation of these differences in cell morphology and behaviour in vitro to the production of the characteristically fan-shaped limb bud outgrowth and altered pattern of cartilage elements in the developing mutant limb bud is discussed.

Animals↗
PubMed1975

Cell proliferation in the developing wing-bud of normal and talpid3 mutant chick embryos.

Previous measurements on mitotic division rate or cell cycle time have been made on samples from a few discrete limb regions or by continuous sampling, but only down a unidimensional limb axis, disregarding morphological discontinuities such as the presence or absence of cartilage. This study presents a new analysis on normal and talpid3 mutant chick embryos, measuring mitotic rate and also cell density through the central proximo-distal axis and at the limb periphery, taking into account the development of cartilage regions. Differentiation of cartilage is correlated with a marked drop in mitotic rate, accounting for a proximo-distal gradient of mitosis in central counts which was not observed at the limb periphery. Talpid3 limbs at an early stage show a central mitotic gradient, but the reverse of that observed in normal limbs.

Animals↗