A plethora of important, chemically diverse natural products are derived from plants. In principle, plant cell culture offers an attractive option for producing many of these compounds. However, it is often not commercially viable because of difficulties associated with culturing dedifferentiated plant cells (DDCs) on an industrial scale. To bypass the dedifferentiation step, we isolated and cultured innately undifferentiated cambial meristematic cells (CMCs). Using a combination of deep sequencing technologies, we identified marker genes and transcriptional programs consistent with a stem cell identity. This notion was further supported by the morphology of CMCs, their hypersensitivity to γ-irradiation and radiomimetic drugs and their ability to differentiate at high frequency. Suspension culture of CMCs derived from Taxus cuspidata, the source of the key anticancer drug, paclitaxel (Taxol), circumvented obstacles routinely associated with the commercial growth of DDCs. These cells may provide a cost-effective and environmentally friendly platform for sustainable production of a variety of important plant natural products.

In this review we describe label-free optical spectroscopy techniques which are able to non-invasively measure the (bio)chemistry in biological systems. Raman spectroscopy uses visible or near-infrared light to measure a spectrum of vibrational bonds in seconds. Coherent anti-Stokes Raman (CARS) microscopy and stimulated Raman loss (SRL) microscopy are orders of magnitude more efficient than Raman spectroscopy, and are able to acquire high quality chemically-specific images in seconds. We discuss the benefits and limitations of all techniques, with particular emphasis on applications in biomedicine—both in vivo (using fiber endoscopes) and in vitro (in optical microscopes).

Finite element electromagnetic simulations of scanning probe microscopy tips and substrates are presented. The enhancement of the scattered light intensity is found to be as high as 10(12) for a 20 nm radius gold tip, and tip-substrate separation of 1 nm. Molecular resolution imaging (< 1 nm) is achievable, even with a relatively large radius tip (20 nm). We also make predictions for imaging in aqueous environments, noting a sizable red shift of the spectral peaks. Finally, we discuss signal levels, and predict that high-speed Raman mapping should be possible with gold substrates and a small tip-substrate separation (< 4 nm).

Finite element (FE) models were built to define the optimal experimental conditions for tip-enhanced Raman spectroscopy (TERS) of thin samples. TERS experimental conditions were mimicked by including in the FE models dielectric or metallic substrates with thin dielectric samples and by considering the wavelength dependence of the dielectric properties for the metallic materials. Electromagnetic coupling between the substrate/sample and the SPM tips led to dramatic changes of both the spatial distribution and magnitude of the scattered electric field which depended on the substrate dielectric permittivity and excitation wavelength. Raman scattering as high as 10(8) with a spatial resolution of approximately 8 nm was estimated for gold SPM tips and gold substrate when excitation is performed at 532 nm (near-resonance wavelength). For dielectric samples (approximately 4 nm thick), the enhancement of Raman scattering intensity is estimated at approximately 10(5); this does not depend significantly on the sample dielectric permittivity for dielectric samples. These results suggest that TERS experimental conditions should be estimated and optimized for every individual application considering the geometric factors and electric properties of the materials involved. Such optimizations could enlarge the range of applications for TERS to samples eliciting weaker intrinsic Raman scattering, such as biological samples.

Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Abstract: It is well documented that hard bearing combinations show a running-in phenomenon in vitro and there is also some evidence of this from retrieval studies. In order to investigate this phenomenon, five Birmingham hip resurfacing devices were tested in a hip wear simulator. One of these (joint 1) was also tested in a friction simulator before, during, and after the wear test and surface analysis was conducted throughout portions of the testing. The wear showed the classical running in with the wear rate falling from 1.84 mm3 per 106 cycles for the first 106 cycles of testing to 0.24 mm3 per 106 cycles over the final 2×106 cycles of testing. The friction tests suggested boundary lubrication initially, but at 1×106 cycles a mixed lubrication regime was evident. By 2×106 cycles the classical Stribeck curve had formed, indicating a considerable contribution from the fluid film at higher viscosities. This continued to be evident at both 3×106 and 5×106 cycles. The surface study complements these findings.Keywords: metal-on-metal resurfacing, wear, running in, lubrication, simulator study INTRODUCTIONlarge-diameter metal-on-metal joints were not initially fully fluid film lubricated and friction tests on other types of metal-on-metal joint have revealed Early, small-diameter (less than 32 mm) metal-onmetal hip joints were prone to premature failure [1], lower friction factors post-wear than initially [8], pointing towards more favourable lubrication after although some examples are known to have been in place successfully for up to 20 years [2, 3]. This wear testing. It has also been noted that the average linear wear rate (microns per year) for retrieved suggests there is a favourable tribological condition in some cases, although not in the majority of cases metal-on-metal joints is lower for joints with a longer survivorship, indicating that this wearing-in phase is for the early designs of metal-on-metal joints. New-generation larger-diameter metal-on-metal hip also likely to occur in vivo [12]. All this suggests that the articulating surfaces run in during early stages of joints have been more successful in the midterm [4, 5] although longer-term clinical results are not yet the wear test, and that this improves the lubrication conditions and hence lowers the wear even further available.Hard bearing joints often show a wearing-in period as the tests progress. during simulator wear tests [6][7][8][9][10], where the initial wear rates are higher than the steady state wear...

The characterisation of stem cells is of vital importance to regenerative medicine. Failure to separate out all stem cells from differentiated cells before therapies can result in teratomastumours of multiple cell types. Typically, characterisation is performed in a destructive manner with fluorescent assays. A truly non-invasive method of characterisation would be a major breakthrough in stem cell-based therapies. Raman spectroscopy has revealed that DNA and RNA levels drop when a stem cell differentiates into other cell types, which we link to a change in the relative sizes of the nucleus and cytoplasm. We also used Raman spectroscopy to investigate the biochemistry within an early embryo, or blastocyst, which differs greatly from colonies of embryonic stem cells. Certain cell types that differentiate from stem cells can be identified by directly imaging the biochemistry with CARS microscopy; examples presented are hydroxyapatite -a precursor to bone, and lipids in adipocytes.

Finite element simulations of laser-induced heating in scanning probe microscopy are presented. The electromagnetic field is first simulated for a variety of tip and substrate materials, and for air and aqueous environments. This electromagnetic field, in the end of the tip and substrate under the tip, produces Joule heating. Using this Joule heat source, steady state thermal simulations are performed. As a result of the large enhancement of optical power by the tip-substrate cavity, predicted temperature rises can be over 3 orders of magnitude higher than the values predicted without a tip present, but the optical signal can be enhanced by over 10 orders. Gold tips and substrates are predicted to give the highest optical signal for a given temperature increase.

The aim of treatment in congenital adrenal hyperplasia is to suppress excess adrenal androgens while achieving physiological glucocorticoid replacement. However, current glucocorticoid replacement regimes are inadequate, because doses sufficient to suppress excess androgens almost invariably induce adverse metabolic effects. Although both cortisol and corticosterone are glucocorticoids that circulate in human plasma, any physiological role for corticosterone has been neglected. In the brain, the ATP-binding cassette transporter ABCB1 exports cortisol but not corticosterone. Conversely, ABCC1 exports corticosterone but not cortisol. We show that ABCC1 but not ABCB1 is expressed in human adipose, and that ABCC1 inhibition increases intracellular corticosterone but not cortisol and induces glucocorticoid-responsive gene transcription, in human adipocytes. Both C57Bl/6 mice treated with the ABCC1 inhibitor probenecid and FVB mice with deletion of Abcc1 accumulated more corticosterone than cortisol in adipose after adrenalectomy and corticosteroid infusion. This accumulation was sufficient to increase glucocorticoid-responsive adipose transcript expression. In human adipose tissue, tissue corticosterone concentrations were consistently low, and ABCC1 mRNA was upregulated in obesity. To test the hypothesis that corticosterone effectively suppresses ACTH without the metabolic adverse effects of cortisol, we infused cortisol or corticosterone in patients with Addison's disease. ACTH suppression was similar, but subcutaneous adipose transcripts of glucocorticoid-responsive genes was higher after cortisol than corticosterone. These data indicate that corticosterone may be a metabolically favorable alternative to cortisol for glucocorticoid replacement therapy when ACTH suppression is desirable, as in congenital adrenal hyperplasia, and justify development of a pharmaceutical preparation. 48