We observe that there is a similar decrease of 30%% in amnioserosa loss tangent as dorsal closure progresses.
Our computations reveal markedly high values for the strain-to-myosin coherence, which further increase as dorsal closure progresses.
As we are interested in the relative, rather than absolute, changes in cell stress as dorsal closure progresses, we can keep these two parameters free.
Combining these estimates with the measurements for Δ reported in [ 22], we can therefore calculate the relative change in stress as dorsal closure progresses.
In addition, there is a reduction in strain-to-myosin lag, together suggesting a change in amnioserosa biomechanics as dorsal closure progresses.
We observe an increase in stiffness as dorsal closure progresses (Fig. 4 c), with values nearly doubling from t≃0 s onwards until reaching an apparent plateau at t≃4000 s.
We show that amnioserosa cells behave as a viscoelastic fluid at timescales relevant for tissue morphogenesis, with cells becoming stiffer and transitioning to a more solid-like behaviour as dorsal closure progresses.
Our preliminary results (data not shown) suggest that adherens junctions are also stabilised as dorsal closure progresses suggesting that the maturation of adherens junctions, and their ability to transmit tension, could also be underlying the observed changes in amnioserosa material properties over time.
Laser ablation experiments have established ratios of mechanical properties and a transition towards more solid-like behaviour in amnioserosa cells as dorsal closure progresses [ 22], but how insights from ablation relate to the active contractile forces in the system and how they reflect on the effective material properties of the tissue remain crucial unexplored issues.
But the Insolvency Service added: "Unfortunately, staff numbers will decline as the closure plan progresses".
