Mapping fibre orientation in complex-shaped biological systems with micrometre resolution by scanning X-ray microdiffraction

A fully automated procedure to extract and to image local fibre orientation in biological tissues from scanning X-ray diffraction is presented. The preferred chitin fibre orientation in the flow sensing system of crickets is determined with high spatial resolution by applying synchrotron radiation based X-ray microbeam diffraction in conjunction with advanced sample sectioning using a UV micro-laser. The data analysis is based on an automated detection of azimuthal diffraction maxima after 2D convolution filtering (smoothing) of the 2D diffraction patterns. Under the assumption of crystallographic fibre symmetry around the morphological fibre axis, the evaluation method allows mapping the three-dimensional orientation of the fibre axes in space. The resulting two-dimensional maps of the local fibre orientations - together with the complex shape of the flow sensing system - may be useful for a better understanding of the mechanical optimization of such tissues.

Potential prebiotic activity of oligosaccharides obtained by enzymatic conversion of durum wheat insoluble dietary fibre into soluble dietary fibre

Background and aims: Epidemiological evidence indicates that cereal dietary fibre (DF) may have several cardiovascular health benefits. The underlying mechanisms have not yet been elucidated. Here, the potential nutritional effects of physico-chemical. properties modifications of durum wheat dietary fibre (DWF) induced by enzyme treatment have been investigated. Methods and results: The conversion of the highly polymerised insoluble dietary fibre into soluble feruloyl oligosaccharides of DWF was achieved by a tailored enzymatic treatment. The in vitro fermentation and release of ferulic acid by intestinal microbiota from DWF before and after the enzymatic treatment were assessed using a gut model validated to mimic the human colonic microbial environment. Results demonstrated that, compared to DWF, the enzyme-treated DWF (ETD-WF) stimulated the growth of bifidobacteria and lactobacilli. Concurrently, the release of free ferulic acid by ET-DWF was almost three times higher respect to the control. No effect on the formation of short chain fatty acids was observed. Conclusions: The conversion of insoluble dietary fibre from cereals into soluble dietary fibre generated a gut microbial fermentation that supported bifidobacteria and lactobacilli. The concurrent increase in free ferulic acid from the enzyme-treated DWF might result in a higher plasma ferulic acid concentration which could be one of the reasons for the health benefits reported for dietary fibre in cardiovascular diseases. (c) 2008 Elsevier B.V. All rights reserved.

Fibre and effects on probiotics (the prebiotic concept)

The burden (economic and medicinal) of acute and chronic gut disorders continues to increase. As efficient therapies are few, attention has turned towards the use of so-called functional foods to mediate against gut disorder. These target particular genera of gut bacteria seen as beneficial, e.g. bifidobacteria, lactobacilli. The use of products containing live microbial species (probiotics) has a long history of use in humans and many trials have been reported as 'positive'. Taking the view that positive components of the gut flora already exist in the intestinal tract, the prebiotic concept has been developed. Here, dietary carbohydrates have a selective metabolism within the gut flora thereby shifting the community towards a more advantageous structure. Conventional fibres like pectins, cellulose, etc. are not selectively metabolised by gut bacteria. However, certain oligosaccharides do have this capability. Most research has been conducted with fructooligosaccharides, like inulin, which have a powerful bifidogenic effect. Trials are ongoing to determine the clinical benefits of prebiotic use. Intestinal disorders like ulcerative colitis, gastroenteritis and irritable bowel syndrome are particular targets. (c) 2004 Elsevier Ltd. All rights reserved.

Principles and calibration of solid phase microextraction fibre (passive sampler) for measurements of airflow and air infiltration in dwellings

Tracer gas techniques have been the most appropriate experimental method of determining airflows and ventilation rates in houses. However, current trends to reduce greenhouse gas effects have prompted the need for alternative techniques, such as passive sampling. In this research passive sampling techniques have been used to demonstrate the potential to fulfil these requirements by using solutions of volatile organic compounds (VOCs) and solid phase microextraction (SPME) fibres. These passive sampling techniques have been calibrated against tracer gas decay techniques and measurements from a standard orifice plate. Two constant sources of volatile organic compounds were diffused into two sections of a humidity chamber and sampled using SPME fibres. From a total of four SPME fibres (two in each section), reproducible results were obtained. Emission rates and air movement from one section to the other were predicted using developed algorithms. Comparison of the SPME fibre technique with that of the tracer gas technique and measurements from an orifice plate showed similar results with good precision and accuracy. With these fibres, infiltration rates can be measured over grab samples in a time weighted averaged period lasting from 10 minutes up to several days. Key words: passive samplers, solid phase microextraction fibre, tracer gas techniques, airflow, air infiltration, houses.

Distributed water ingress and water potential measurements using fibre optics

We report on a distributed moisture detection scheme which uses a cable design based on waterswellable hydrogel polymers. The cable modulates the loss characteristic of light guided within a multi-mode optical fibre in response to relative water potentials in the surrounding environment. Interrogation of the cable using conventional optical time-domain reflectometry (OTDR) instruments allows water ingress points to be identified and located with a spatial resolution of 50 cm. The system has been tested in a simulated tendon duct grouting experiment as a means of mapping the extent of fill along the duct during the grouting process. Voided regions were detected and identified to within 50 cm. A series of salt solutions has been used to determine the sensor behaviour over a range of water potentials. These experiments predict that measurements of soil moisture content can be made over the range 0 to – 1500 kPa. Preliminary data on soil measurements have shown that the sensor can detect water pressure changes with a resolution of 45 kPa. Applications for the sensor include quality assurance of grouting procedures, verification of waterproofing barriers and soil moisture content determination (for load-bearing calculations).

Automatic optical fibre feedback potometer for transpiration studies

A new automatic feedback potometer for physiological studies of water uptake by root systems is described. A dual-optical-fibre amplitude-modulating displacement transducer of improved sensitivity is employed to detect the changes in liquid level. The merits of optimal double-cut fibres, which make full use of the critical angle and improve coupling between the emitter and the receiver, have resulted in a sensor that is 64 times more responsive than the simple emitter - detector probe. Positioning the optical fibre transducer in a narrow capillary and using feedback to control the liquid level allows continuous measurement of volumes in the nanolitre range. The optical sensor used does not need re-calibration for the different salt solutions used in such studies.

Modelling the structure of a polymer glass poly(methylmethacrylate) through neutron scattering experiments

Determination of the local structure of a polymer glass by scattering methods is complex due to the number of spatial and orientational correlations, both from within the polymer chain (intrachain) and between neighbouring chains (interchain), from which the scattering arises. Recently considerable advances have been made in the structural analysis of relatively simple polymers such as poly(ethylene) through the use of broad Q neutron scattering data tightly coupled to atomistic modelling procedures. This paper presents the results of an investigation into the use of these procedures for the analysis of the local structure of a-PMMA which is chemically more complex with a much greater number of intrachain structural parameters. We have utilised high quality neutron scattering data obtained using SANDALS at ISIS coupled with computer models representing both the single chain and bulk polymer system. Several different modelling approaches have been explored which encompass such techniques as Reverse Monte Carlo refinement and energy minimisation and their relative merits and successes are discussed. These different approaches highlight structural parameters which any realistic model of glassy atactic PMMA must replicate.

In Vitro Fermentation of NUTRIOSE® FB06, a wheat dextrin soluble fibre, in a continuous culture human colonic model system

Wheat dextrin soluble fibre may have metabolic and health benefits, potentially acting via mechanisms governed by the selective modulation of the human gut microbiota. Our aim was to examine the impact of wheat dextrin on the composition and metabolic activity of the gut microbiota. We used a validated in vitro three-stage continuous culture human colonic model (gut model) system comprised of vessels simulating anatomical regions of the human colon. To mimic human ingestion, 7 g of wheat dextrin (NUTRIOSE® FB06) was administered to three gut models, twice daily at 10.00 and 15.00, for a total of 18 days. Samples were collected and analysed for microbial composition and organic acid concentrations by 16S rRNA-based fluorescence in situ hybridisation and gas chromatography approaches, respectively. Wheat dextrin mediated a significant increase in total bacteria in vessels simulating the transverse and distal colon, and a significant increase in key butyrate-producing bacteria Clostridium cluster XIVa and Roseburia genus in all vessels of the gut model. The production of principal short-chain fatty acids, acetate, propionate and butyrate, which have been purported to have protective, trophic and metabolic host benefits, were increased. Specifically, wheat dextrin fermentation had a significant butyrogenic effect in all vessels of the gut model and significantly increased production of acetate (vessels 2 and 3) and propionate (vessel 3), simulating the transverse and distal regions of the human colon, respectively. In conclusion, wheat dextrin NUTRIOSE® FB06 is selectively fermented in vitro by Clostridium cluster XIVa and Roseburia genus and beneficially alters the metabolic profile of the human gut microbiota.

Polyphenols, glucosinolates, dietary fibre and colon cancer: Understanding the potential of specific types of fruit and vegetables to reduce bowel cancer progression

Colorectal cancer is the third most prevalent cancer worldwide and the most common diet-related cancer, influenced by diets rich in red meat, low in plant foods and high in saturated fats. Observational studies have shown that fruit and vegetable intake may reduce colorectal cancer risks, although the precise bioactive components remain unclear. This review will outline the evidence for the role of polyphenols, glucosinolates and fibres against cancer progression in the gastrointestinal tract. Those bioactive compounds are considered protective agents against colon cancer, with evidence taken from epidemiological, human clinical, animal and in vitro studies. Various mechanisms of action have been postulated, such as the potential of polyphenols and glucosinolates to inhibit cancer cell growth and the actions of insoluble fibres as prebiotics and the evidence for these actions are detailed within. In addition, recent evidence suggests that polyphenols also have the potential to shift the gut ecology in a beneficial manner. Such actions of both fibre and polyphenols in the gastrointestinal tract and through interaction with gut epithelial cells may act in an additive manner to help explain why certain fruits and vegetables, but not all, act to differing extents to inhibit cancer incidence and progression. Indeed, a focus on the individual actions of such fruit and vegetable components, in particular polyphenols, glucosinolates and fibres is necessary to help explain which components are active in reducing gastrointestinal cancer risk.

Production and purification of xylooligosaccharides from oil palm empty fruit bunch fibre by a non-isothermal process

Oil palm empty fruit bunches (OPEFB) fibre, a by-product generated from non-woody, tropical perennial oil palm crop was evaluated for xylooligosaccharides (XOS) production. Samples of OPEFB fibre were subjected to non-isothermal autohydrolysis treatment using a temperature range from 150 to 220 °C. The highest XOS concentration, 17.6 g/L which relayed from solubilisation of 63 g/100 g xylan was achieved at 210 °C and there was a minimum amount of xylose and furfural being produced. The chromatographic purification which was undertaken to purify the oligosaccharide-rich liquor resulted in a product with 74–78% purity, of which 83–85% was XOS with degree of polymerisation (DP) between 5 and 40.

Mesomorphic behaviour in copoly(ester-imide)s of poly(butylene-2,6-naphthalate) (PBN)

Copolycondensation of N,N’-bis(4-hydroxybutyl)-biphenyl-3,4,3',4'-tetracarboxylic diimide at 20 and 25 mol% with bis(4-hydroxybutyl)-2,6-naphthalate produces PBN-based copoly(ester-imide)s that not only crystallise but also form a (smectic) mesophase upon cooling from the melt. Incorporation of 25 mol% imide in PBN causes the glass transition temperature (measured by DSC) to rise from 51 to 74 °C, a significant increase relative to PBN. Furthermore, increased storage- (G'), loss- (G'') and elastic (E) moduli are observed for both copoly(ester-imide)s when compared to PBN itself. Structural analysis of the 20 mol% copolymer by X-ray powder and fibre diffraction, interfaced to computational modelling, suggests a crystal structure related to that of α-PBN, in space group P-1, with cell dimensions a = 4.74, b = 6.38, c = 14.45 Å, α = 106.1, β = 122.1, γ = 97.3°, ρ = 1.37 g cm-3.

Investigating the influence of extracellular matrix and glycolytic metabolism on muscle stem cell migration on their native fibre environment

The composition of the extracellular matrix (ECM) of skeletal muscle fibres is a unique environment that supports the regenerative capacity of satellite cells; the resident stem cell population. The impact of environment has great bearing on key properties permitting satellite cells to carry out tissue repair. In this study, we have investigated the influence of the ECM and glycolytic metabolism on satellite cell emergence and migration- two early processes required for muscle repair. Our results show that both influence the rate at which satellite cells emerge from the sub-basal lamina position and their rate of migration. These studies highlight the necessity of performing analysis of satellite behaviour on their native substrate and will inform on the production of artificial scaffolds intended for medical uses.