Nuclear magnetic resonance spectroscopy. A stereospecific ^3J_(CF) coupling in the low-temperature ^(13)C nmr spectrum of 1,1-difluorocyclohexane

The proton-decoupled ^(13)C nmr spectrum of 1,1-difluorocyclohexane has been examined at room temperature and at -90 degrees C. There are only minor changes in the one-bond and two-bond carbon-fluorine scalar coupling constants at the lower temperature; however, the triplet observed for C-3 (^3J_(CF) = 4.7 Hz) collapses to a doublet (3JCF = 9.5 Hz) at -90 °C. It is proposed that only the equatorial fluorine is coupled with the C-3 carbon as the result of operation of a back-lobe orbital interaction

An improved version of white matter method for correction of non-uniform intensity in MR images: application to the quantification of rates of brain atrophy in Alzheimer's disease and normal aging

A fully automated 3D version of the so-called white matter method for correcting intensity non-uniformity in MR T1-weighted neuro images is presented. The algorithm is an extension of the original work published previously. The major part of the extension was the development of a fully automated method for the generation of the reference points. In the design of this method, a number of measures were introduced to minimize the effects of possible inclusion of non-white matter voxels in the selection process. The correction process has been made iterative. PI drawback of this approach is an increased cost in computational time. The algorithm has been tested on T1-weighted MR images acquired from a longitudinal study involving elderly subjects and people with probable Alzheimer's disease. More quantitative measures were used for the evaluation of the algorithm's performance. Highly satisfactory correction results have been obtained for images with extensive intensity non-uniformity either present in raw data or added artificially. With intensity correction, improved accuracy in the measurement of the rate of brain atrophy in Alzheimer's patients as well as in elderly people due to normal aging has been achieved

Realising increased photosynthetic efficiency to increase strawberry yields

As the global population continues to rise, new solutions are required to increase productivity of food systems. One such approach is to increase the efficiency of crop photosynthesis by genetic manipulation of rate-limiting enzymes, a method proven to be successful in a range of model and cereal crop species. This thesis aims to apply this to cultivated strawberry (Fragaria x ananassa Duch.) by first exploring species-specific factors limiting photosynthetic efficiency and then generating transgenic lines with enhanced photosynthesis. Variation of photosynthesis across a polytunnel was recorded to better understand photosynthesis in strawberry. It was found that availability of photosynthetically active radiation and stomatal behaviour are key factors in determining photosynthetic carbon assimilation and that this determines patterns in fruit yield seen across the tunnel. Plasmids were constructed containing coding sequences for sedoheptulose-1,7- bisphosphatase (SBPase), a Calvin-Benson-Bassham Cycle enzyme, and adenosine diphosphate glucose pyrophosphorylase (AGPase), a starch synthesis enzyme. Both genes have formerly been implicated in limiting photosynthetic rate, making interesting targets for study. Transgenic plants expressing both genes in concert and AGPase alone were regenerated from transformed callus tissue on hygromycin selection, though this rate of regeneration was significantly delayed by the selectable marker. The photosynthetic efficiency of transgenic plants was then tested via chlorophyll fluorescence imaging. A small, non-significant increase in photosystem II operating efficiency was observed in the double expressing line only, suggesting AGPase does not limit photosynthetic rate in strawberry while SBPase might. However, both transgenic lines had an increase non-photochemical quenching, suggesting a role of starch synthesis in regulation of the photosystem. Overall, these results lay the groundwork for realising increased photosynthetic efficiency in strawberry and other fruiting crops and describe genetic and physiological targets limiting strawberry photosynthetic rate for future study

Analysis of myocardial motion using generalized spline models and tagged magnetic resonance images

Heart wall motion abnormalities are the very sensitive indicators of common heart diseases, such as myocardial infarction and ischemia. Regional strain analysis is especially important in diagnosing local abnormalities and mechanical changes in the myocardium. In this work, we present a complete method for the analysis of cardiac motion and the evaluation of regional strain in the left ventricular wall. The method is based on the generalized spline models and tagged magnetic resonance images (MRI) of the left ventricle. The whole method combines dynamical tracking of tag deformation, simulating cardiac movement and accurately computing the regional strain distribution. More specifically, the analysis of cardiac motion is performed in three stages. Firstly, material points within the myocardium are tracked over time using a semi-automated snake-based tag tracking algorithm developed for this purpose. This procedure is repeated in three orthogonal axes so as to generate a set of one-dimensional sample measurements of the displacement field. The 3D-displacement field is then reconstructed from this sample set by using a generalized vector spline model. The spline reconstruction of the displacement field is explicitly expressed as a linear combination of a spline kernel function associated with each sample point and a polynomial term. Finally, the strain tensor (linear or nonlinear) with three direct components and three shear components is calculated by applying a differential operator directly to the displacement function. The proposed method is computationally effective and easy to perform on tagged MR images. The preliminary study has shown potential advantages of using this method for the analysis of myocardial motion and the quantification of regional strain

Loss of SOX10 function contributes to the phenotype of human Merlin-null schwannoma cells.

Loss of the Merlin tumour suppressor causes abnormal de-differentiation and proliferation of Schwann cells and formation of schwannoma tumours in patients with neurofibromatosis type 2. Within the mature peripheral nerve the normal development, differentiation and maintenance of myelinating and non-myelinating Schwann cells is regulated by a network of transcription factors that include SOX10, OCT6 (now known as POU3F1), NFATC4 and KROX20 (also known as Egr2). We have examined for the first time how their regulation of Schwann cell development is disrupted in primary human schwannoma cells. We find that induction of both KROX20 and OCT6 is impaired, whereas enforced expression of KROX20 drives both myelin gene expression and cell cycle arrest in Merlin-null cells. Importantly, we show that human schwannoma cells have reduced expression of SOX10 protein and messenger RNA. Analysis of mouse SOX10-null Schwann cells shows they display many of the characteristics of human schwannoma cells, including increased expression of platelet derived growth factor receptor beta (PDGFRB) messenger RNA and protein, enhanced proliferation, increased focal adhesions and schwannoma-like morphology. Correspondingly, reintroduction of SOX10 into human Merlin-null cells restores the ability of these cells to induce KROX20 and myelin protein zero (MPZ), localizes NFATC4 to the nucleus, reduces cell proliferation and suppresses PDGFRB expression. Thus, we propose that loss of the SOX10 protein, which is vital for normal Schwann cell development, is also key to the pathology of Merlin-null schwannoma tumours

Phosphate Deprivation Can Impair Mechano-Stimulated Cytosolic Free Calcium Elevation in Arabidopsis Roots.

The root tip responds to mechanical stimulation with a transient increase in cytosolic free calcium as a possible second messenger. Although the root tip will grow through a heterogeneous soil nutrient supply, little is known of the consequence of nutrient deprivation for such signalling. Here, the effect of inorganic phosphate deprivation on the root's mechano-stimulated cytosolic free calcium increase is investigated. Arabidopsisthaliana (cytosolically expressing aequorin as a bioluminescent free calcium reporter) is grown in zero or full phosphate conditions, then roots or root tips are mechanically stimulated. Plants also are grown vertically on a solid medium so their root skewing angle (deviation from vertical) can be determined as an output of mechanical stimulation. Phosphate starvation results in significantly impaired cytosolic free calcium elevation in both root tips and whole excised roots. Phosphate-starved roots sustain a significantly lower root skewing angle than phosphate-replete roots. These results suggest that phosphate starvation causes a dampening of the root mechano-signalling system that could have consequences for growth in hardened, compacted soils

Feeding the world: impacts of elevated [CO2] on nutrient content of greenhouse grown fruit crops and options for future yield gains

Several long-term studies have provided strong support demonstrating that growing crops under elevated [CO2] can increase photosynthesis and result in an increase in yield, flavour and nutritional content (including but not limited to Vitamins C, E and pro-vitamin A). In the case of tomato, increases in yield by as much as 80 % are observed when plants are cultivated at 1000ppm [CO2], which is consistent with current commercial greenhouse production methods in the tomato fruit industry. These results provide a clear demonstration of the potential for elevating [CO2] for improving yield and quality in greenhouse crops. The major focus of this review is to bring together 50 years of observations evaluating the impact of elevated [CO2] on fruit yield and fruit nutritional quality. In the final section, we consider the need to engineer improvements to photosynthesis and nitrogen assimilation to allow plants to take greater advantage of elevated CO2 growth conditions