Elongated Cells Drive Morphogenesis in a Surface-Wrapped Finite-Element Model of Germband Retraction.

During Drosophila embryogenesis, the germband first extends to curl around the posterior end of the embryo and then retracts back; however, retraction is not simply the reversal of extension. At a tissue level, extension is coincident with ventral furrow formation, and at a cellular level, extension occurs via convergent cell neighbor exchanges in the germband, whereas retraction involves only changes in cell shape. To understand how cell shapes, tissue organization, and cellular forces drive germband retraction, we investigate this process using a whole-embryo, surface-wrapped cellular finite-element model.

Root branching plasticity: collective decision-making results from local and global signalling.

Cells within tissues can be regarded as autonomous entities that respond to their local environment and to signals from neighbours. Coordination between cells is particularly important in plants, as the architecture of the plant adapts to environmental cues. To explain the architectural plasticity of the root, we propose to view it as a swarm of coupled multi-cellular structures, rhizomers, rather than a large set of autonomous cells.

Pathway to a phenocopy: Heat stress effects in early embryogenesis.

Background: Heat shocks applied at the onset of gastrulation in early Drosophila embryos frequently lead to phenocopies of U-shaped mutants-having characteristic failures in the late morphogenetic processes of germband retraction and dorsal closure. The pathway from nonspecific heat stress to phenocopied abnormalities is unknown.

Results: Drosophila embryos subjected to 30-min, 38 °C heat shocks at gastrulation appear to recover and restart morphogenesis.

A microfluidic-enabled mechanical microcompressor for the immobilization of live single- and multi-cellular specimens.

A microcompressor is a precision mechanical device that flattens and immobilizes living cells and small organisms for optical microscopy, allowing enhanced visualization of sub-cellular structures and organelles. We have developed an easily fabricated device, which can be equipped with microfluidics, permitting the addition of media or chemicals during observation. This device can be used on both upright and inverted microscopes.

Cerebral blood flow changes in acute experimental haemorrhagic vasospasm.

Subarachnoid haemorrhage was produced in 26 dogs by injecting fresh homogenous blood into the cysterna chiasmatica. Two types of vasospasm were observed, firstly segmental arterial spasm closely related to the bleeding point and secondly generalized arterial vasospasm not directly related to the bleeding point and often occurring some way from the bleeding point. Reduction in CBF occurred in 61% of cases and was always accompanied by radiological vasospasm.