Anatomical integration and rich-club connectivity in euthymic bipolar disorder.

BACKGROUND: Although repeatedly associated with white matter microstructural alterations, bipolar disorder (BD) has been relatively unexplored using complex network analysis. This method combines structural and diffusion magnetic resonance imaging (MRI) to model the brain as a network and evaluate its topological properties. A group of highly interconnected high-density structures, termed the 'rich-club', represents an important network for integration of brain functioning. This study aimed to assess structural and rich-club connectivity properties in BD through graph theory analyses. METHOD: We obtained structural and diffusion MRI scans from 42 euthymic patients with BD type I and 43 age- and gender-matched healthy volunteers. Weighted fractional anisotropy connections mapped between cortical and subcortical structures defined the neuroanatomical networks. Next, we examined between-group differences in features of graph properties and sub-networks. RESULTS: Patients exhibited significantly reduced clustering coefficient and global efficiency, compared with controls globally and regionally in frontal and occipital regions. Additionally, patients displayed weaker sub-network connectivity in distributed regions. Rich-club analysis revealed subtly reduced density in patients, which did not withstand multiple comparison correction. However, hub identification in most participants indicated differentially affected rich-club membership in the BD group, with two hubs absent when compared with controls, namely the superior frontal gyrus and thalamus. CONCLUSIONS: This graph theory analysis presents a thorough investigation of topological features of connectivity in euthymic BD. Abnormalities of global and local measures and network components provide further neuroanatomically specific evidence for distributed dysconnectivity as a trait feature of BD.

The effect of temperature elevation on cryopreserved mesenchymal stem cells.

BACKGROUND: Cryopreservation is of particular importance in stem cell research and regenerative medicine as it permits long term stabilisation of biological cells. Cells retain their regenerative capacity after years of storage at cryogenic temperatures. However, elevation of temperature may occur due to variety of reasons, for example in the event of equipment malfunction or during delays in transportation. To date, a limited amount research has been carried out to examine the effects of temperature elevation on stem cell survival during cryopreservation. METHODS: Mesenchymal Stem Cells (MSCs) obtained from 8-12 week Sprague Dawley male rats were cryopreserved according to the standard procedures. Under experimental conditions, cryopreserved specimens were exposed to elevated temperatures ranging from -20 C to 37 C and cellular membrane integrity assessed via trypan-blue exclusion at various time points. RESULTS: An approximating model of multiple regression was fitted to the experimental data and optimisation of model parameters was carried out. This model provides an approximation of cell viability in response to elevated temperature conditions. DISCUSSION: The results demonstrate that elevation of temperature has a dramatic effect, even over short periods of time, on the viability of cryopreserved specimens. The model presented here could be used to predict the damage suffered by a specimen due to exposure to elevated temperature over a defined period of time.