Multispectral reflectance imaging of brain activation in rodents: methodological study of the differential path length estimations and first in vivo recordings in the rat olfactory bulb

International audienceDynamic maps of relative changes in blood volume and oxygenation following brain activation are obtained using multispectral reflectance imaging. The technique relies on optical absorption modifications linked to hemodynamic changes. The relative variation of hemodynamic parameters can be quantified using the modified Beer-Lambert Law if changes in reflected light intensities are recorded at two wavelengths or more and the differential path length (DP) is known. The DP is the mean path length in tissues of backscattered photons and varies with wavelength. It is usually estimated using Monte Carlo simulations in simplified semi-infinite homogeneous geometries. Here we consider the use of multilayered models of the somatosensory cortex (SsC) and olfactory bulb (OB), which are common physiological models of brain activation. Simulations demonstrate that specific DP estimation is required for SsC and OB, specifically for wavelengths above 600 nm. They validate the hypothesis of a constant path length during activation and show the need for specific DP if imaging is performed in a thinned-skull preparation. The first multispectral reflectance imaging data recorded in vivo during OB activation are presented, and the influence of DP on the hemodynamic parameters and the pattern of oxymetric changes in the activated OB are discusse

Odor-Induced Neuronal Rhythms in the Olfactory Bulb Are Profoundly Modified in ob/ob Obese Mice

Leptin, the product of the Ob(Lep) gene, is a peptide hormone that plays a major role in maintaining the balance between food intake and energy expenditure. In the brain, leptin receptors are expressed by hypothalamic cells but also in the olfactory bulb, the first central structure coding for odors, suggesting a precise function of this hormone in odor-evoked activities. Although olfaction plays a key role in feeding behavior, the ability of the olfactory bulb to integrate the energy-related signal leptin is still missing. Therefore, we studied the fate of odor-induced activity in the olfactory bulb in the genetic context of leptin deficiency using the obese ob/ob mice. By means of an odor discrimination task with concomitant local field potential recordings, we showed that ob/ob mice perform better than wild-type (WT) mice in the early stage of the task. This behavioral gain of function was associated in parallel with profound changes in neuronal oscillations in the olfactory bulb. The distribution of the peaks in the gamma frequency range was shifted toward higher frequencies in ob/ob mice compared to WT mice before learning. More notably, beta oscillatory activity, which has been shown previously to be correlated with olfactory discrimination learning, was longer and stronger in expert ob/ob mice after learning. Since oscillations in the olfactory bulb emerge from mitral to granule cell interactions, our results suggest that cellular dynamics in the olfactory bulb are deeply modified in ob/ob mice in the context of olfactory learning

Dysfunctional play and dopamine physiology in the Fischer 344 rat

Juvenile Fischer 344 rats are known to be less playful than other inbred strains, although the neurobiological substrate(s) responsible for this phenotype is uncertain. In the present study, Fischer 344 rats were compared to the commonly used outbred Sprague-Dawley strain on several behavioral and physiological parameters in order to ascertain whether the lack of play may be related to compromised activity of brain dopamine (DA) systems. As expected, Fischer 344 rats were far less playful than Sprague-Dawley rats, with Fischer 344 rats less likely to initiate playful contacts with a playful partner and less likely to respond playfully to these contacts. We also found that Fischer 344 rats showed less of a startle response and greater pre-pulse inhibition (PPI), especially at higher prepulse intensities. The increase in PPI seen in the Fischer 344 rat could be due to reduced DA modulation of sensorimotor gating and neurochemical measures were consistent with Fischer 344 rats releasing less DA than Sprague-Dawley rats. Fast scan cyclic voltammetry (FSCV) revealed Fischer 344 rats had less evoked DA release in dorsal and ventral striatal brain slices and high-performance liquid chromatography revealed Fischer 344 rats to have less DA turnover in the striatum and prefrontal cortex. We also found DA-dependent forms of cortical plasticity were deficient in the striatum and prefrontal cortex of the Fischer 344 rat. Taken together, these data indicate that deficits in play and enhanced PPI of Fischer 344 rats may be due to reduced DA modulation of corticostriatal and mesolimbic/mesocortical circuits critical to the execution of these behaviors

Characterisation of CCT271850, a selective, oral and potent MPS1 inhibitor, used to directly measure in vivo MPS1 inhibition vs therapeutic efficacy

BACKGROUND: The main role of the cell cycle is to enable error-free DNA replication, chromosome segregation and cytokinesis. One of the best characterised checkpoint pathways is the spindle assembly checkpoint, which prevents anaphase onset until the appropriate attachment and tension across kinetochores is achieved. MPS1 kinase activity is essential for the activation of the spindle assembly checkpoint and has been shown to be deregulated in human tumours with chromosomal instability and aneuploidy. Therefore, MPS1 inhibition represents an attractive strategy to target cancers. METHODS: To evaluate CCT271850 cellular potency, two specific antibodies that recognise the activation sites of MPS1 were used and its antiproliferative activity was determined in 91 human cancer cell lines. DLD1 cells with induced GFP-MPS1 and HCT116 cells were used in in vivo studies to directly measure MPS1 inhibition and efficacy of CCT271850 treatment. RESULTS: CCT271850 selectively and potently inhibits MPS1 kinase activity in biochemical and cellular assays and in in vivo models. Mechanistically, tumour cells treated with CCT271850 acquire aberrant numbers of chromosomes and the majority of cells divide their chromosomes without proper alignment because of abrogation of the mitotic checkpoint, leading to cell death. We demonstrated a moderate level of efficacy of CCT271850 as a single agent in a human colorectal carcinoma xenograft model. CONCLUSIONS: CCT271850 is a potent, selective and orally bioavailable MPS1 kinase inhibitor. On the basis of in vivo pharmacodynamic vs efficacy relationships, we predict that more than 80% inhibition of MPS1 activity for at least 24 h is required to achieve tumour stasis or regression by CCT271850

Fluorescence spectroscopy and multi-way techniques. PARAFAC

PARAllel FACtor analysis (PARAFAC) is increasingly used to decompose fluorescence excitation emission matrices (EEMs) into their underlying chemical components. In the ideal case where fluorescence conforms to Beers Law, this process can lead to the mathematical identification and quantification of independently varying fluorophores. However, many practical and analytical hurdles stand between EEM datasets and their chemical interpretation. This article provides a tutorial in the practical application of PARAFAC to fluorescence datasets, demonstrated using a dissolved organic matter (DOM) fluorescence dataset. A new toolbox for MATLAB is presented to support improved visualisation and sensitivity analyses of PARAFAC models in fluorescence spectroscopy. © 2013 The Royal Society of Chemistry

Lady Llanover and the creation of a Welsh cultural utopia

Lady Llanover (1802-1896) was one of the most important female contributors to the nineteenth century Welsh cultural revival and although historians have paid her a certain amount of attention, her life and works have never before undergone a full study. The purpose of this thesis is to analyse her place in the history of nineteenth century Wales and to consider the view that her life's actions ultimately led her to attempt to create a Welsh cultural Utopia for the Welsh tenants on her estate at Llanover in Monmouthshire. This study is not a conventional biography and therefore not every detail of Lady Llanover's life can feature, rather this thesis thematically explores her fascination with Wales, Welsh traditions and culture in order to throw light on what became a full and life long project. This thesis will focus on Lady Llanover's tenacious personality and explore her identity. It will take into account the economic, social and political changes that occurred in nineteenth century Welsh society and consider how Lady Llanover reacted and responded to such changes. Moreover, it will ask what influenced Lady Llanover's cultural ideals and reveal how her home was transformed into a centre of Welsh cultural scholarship. It will be revealed how she used her position of power to influence others and how this became an important aspect of her campaigns to safeguard her version of Welsh culture. She famously showed a special interest in the Welsh costume, triple harp and the Welsh language and therefore no work written on her could omit a discussion of those topics but what this thesis seeks to demonstrate is that even though Lady Llanover eventually came to be regarded by some, as an obsessive eccentric, she pored her energy into creating a haven for her version of Welsh culture.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Bioinformatics approaches to studying mesenchymal stem cell behaviour on artificial extracellular matrices

Stem cells have potential use in tissue engineering and regenerative medicine, and as they underlie the development and maintenance of tissues throughout life, how they function is also of interest. The extracellular matrix presents a variety of physical and chemical signals to stem cells to regulate their behaviour in vivo. Recapitulation of these signals in vitro could enable the control of explanted stem cells to facilitate their study. Biomaterials that display extracellular-matrix inspired cues are one way to do this. By combining surface chemistry and fibronectin, an extracellular matrix protein with cell binding and growth factor binding domains, the conformation of fibronectin was controlled to create artificial extracellular matrices. Adsorbed on a film of poly(ethyl acrylate), fibronectin adopted a network-like conformation which ostensibly increased the exposure of its functional domains, whereas on poly(methyl acrylate) it had an unconnected organisation with more concealed domains. The growth factors bone morphogenetic protein 2 and vascular endothelial growth factor, known to bind to fibronectin, were adsorbed to the network conformation. Prior studies have reported that these artificial extracellular matrices differentially affected cell behaviour. In this work, the growth and differentiation of human bone marrow stromal cell surface marker-1 positive mesenchymal stem cells was characterised on these substrates. It was shown that all combinations of fibronectin conformation and growth factors supported cell adhesion and growth. A high-content image processing and analysis pipeline was developed to take advantage of automated fluorescence microscopy to show that cytoskeletal, nuclei, and differentiation-associated protein features distinguished cells cultured on the artificial extracellular matrices. Those on the isolated conformation and the network conformation with vascular endothelial growth factor were particularly distinct. Further, metabolomics revealed several metabolic pathways that differed in activity between the fibronectin conformations. To analyse the metabolomics data a Quick Results web application was built, which extended the existing Polyomics integrated Metabolomics Pipeline. The application improves the visualisation and interpretation of untargeted liquid chromatography—mass spectrometry metabolomics data. This work gives insights into how these artificial extracellular matrices can control stem cell behaviour, and developed and demonstrated several tools to improve the understanding of these biomaterials and the use of metabolomics data

Lady Llanover and the creation of a Welsh cultural utopia

Lady Llanover (1802-1896) was one of the most important female contributors to the nineteenth century Welsh cultural revival and although historians have paid her a certain amount of attention, her life and works have never before undergone a full study. The purpose of this thesis is to analyse her place in the history of nineteenth century Wales and to consider the view that her life's actions ultimately led her to attempt to create a Welsh cultural Utopia for the Welsh tenants on her estate at Llanover in Monmouthshire. This study is not a conventional biography and therefore not every detail of Lady Llanover's life can feature, rather this thesis thematically explores her fascination with Wales, Welsh traditions and culture in order to throw light on what became a full and life long project. This thesis will focus on Lady Llanover's tenacious personality and explore her identity. It will take into account the economic, social and political changes that occurred in nineteenth century Welsh society and consider how Lady Llanover reacted and responded to such changes. Moreover, it will ask what influenced Lady Llanover's cultural ideals and reveal how her home was transformed into a centre of Welsh cultural scholarship. It will be revealed how she used her position of power to influence others and how this became an important aspect of her campaigns to safeguard her version of Welsh culture. She famously showed a special interest in the Welsh costume, triple harp and the Welsh language and therefore no work written on her could omit a discussion of those topics but what this thesis seeks to demonstrate is that even though Lady Llanover eventually came to be regarded by some, as an obsessive eccentric, she pored her energy into creating a haven for her version of Welsh culture