Micro-magnetic resonance imaging and embryological analysis of wild-type and pma mutant mice with clubfoot.

Gross similarities between the external appearance of the hind limbs of the peroneal muscle atrophy (pma) mouse mutant and congenital talipes equinovarus (CTEV), a human disorder historically referred to as 'clubfoot', suggested that this mutant could be a useful model. We used micro-magnetic resonance imaging to visualize the detailed anatomy of the hind limb defect in mutant pma mice and performed 3D comparisons between mutant and wild-type hind limbs. We found that the pma foot demonstrates supination (i.e. adduction and inversion of the mid foot and fore foot together with plantar flexion of the ankle and toes) and that the tibiale and distal tarsals display 3D abnormalities in positioning. The size and shape of the tibia, fibula, tarsal and metatarsal bones are similar to the wild-type. Hypoplasia of the muscles in the antero-lateral (peroneal) compartment was also demonstrated. The resemblance of these features to those seen in CTEV suggests that the pma mouse is a possibly useful model for the human condition. To understand how the observed deformities in the pma mouse hind foot arise during embryonic development, we followed the process of foot rotation in both wild-type and pma mutant mice. Rotation of the hind foot in mouse embryos of wild-type strains (CD-1 and C57/Black) occurs from embryonic day 14.5 onwards with rotation in C57/Black taking longer. In embryos from both strains, rotation of the right hind foot more commonly precedes rotation of the left. In pma mutants, the initiation of rotation is often delayed and rotation is slower and does not reach completion. If the usefulness of the pma mutant as a model is confirmed, then these findings on pma mouse embryos, when extrapolated to humans, would support a long-standing hypothesis that CTEV is due to the failure of completion of the normal process of rotation and angulation, historically known as the 'arrested development hypothesis'.

Rapid and efficient cell labeling with a MRI contrast agent by electroporation in the presence of protamine sulfate.

AIMS: To investigate various protocols for magnetic labeling of human cancer cells with ferumoxides with a view to developing an effective and fast technique for potential clinical use in MRI. MATERIALS & METHODS: Transfection methods utilizing poly-L-lysine and protamine sulfate (PS), electroporation, and combination of PS with electroporation were evaluated in this in vitro study. RESULTS: Although transfection was more effective in terms of uptake rates (95-100%) and intracellular iron concentrations (4.01-7.34 pg/cell), all transfection agents required prolonged incubation. By contrast, electroporation yielded fast labeling but with a lower efficacy (68-75%, 1.63-2.59 pg/cell). The addition of PS to electroporation increased the labeling efficacy (80-91%, 2.84-4.16 pg/cell) and protected cell viability. This combined method also resulted in the best T(2)*-shortening effect in the in vitro cellular MRI. CONCLUSION: The combined PS-electroporation method provides a fast and efficient protocol for ferumoxide-based cellular imaging and therapeutic procedure.

Micro-magnetic resonance imaging of avian embryos.

Chick embryos are useful models for probing developmental mechanisms including those involved in organogenesis. In addition to classic embryological manipulations, it is possible to test the function of molecules and genes while the embryo remains within the egg. Here we define conditions for imaging chick embryo anatomy and for visualising living quail embryos. We focus on the developing limb and describe how different tissues can be imaged using micro-magnetic resonance imaging and this information then synthesised, using a three-dimensional visualisation package, into detailed anatomy. We illustrate the potential for micro-magnetic resonance imaging to analyse phenotypic changes following chick limb manipulation. The work with the living quail embryos lays the foundations for using micro-magnetic resonance imaging as an experimental tool to follow the consequences of such manipulations over time.