Showing papers by "Brunel University London published in 1988"

Hydroxyl radical production and autoxidative glycosylation. Glucose autoxidation as the cause of protein damage in the experimental glycation model of diabetes mellitus and ageing.

Abstract: Protein exposed to glucose is cleaved, undergoes conformational change and develops fluorescent adducts (‘glycofluorophores’). These changes are presumed to result from the covalent attachment of glucose to amino groups. We have demonstrated, however, that the fragmentation and conformational changes observed are dependent upon hydroxyl radicals produced by glucose autoxidation, or some closely related process, and that antioxidants dissociate structural damage caused by the exposure of glucose to protein from the incorporation of monosaccharide into protein. We have also provided further evidence that glycofluorophore formation is dependent upon metal-catalysed oxidative processes associated with ketoaldehyde formation. If experimental glycation is an adequate model of tissue damage occurring in diabetes mellitus, then these studies indicate a therapeutic role for antioxidants.

Vitamin E analogue Trolox C. E.s.r. and pulse-radiolysis studies of free-radical reactions.

Abstract: The reactions between Trolox C, a water-soluble vitamin E analogue, and several oxidizing free radicals including the hydroxyl radical and various peroxy radicals were examined by using the pulse-radiolysis technique. The results demonstrate that Trolox C may undergo rapid one-electron-transfer reactions as well as hydrogen-transfer processes; the resulting phenoxyl radical is shown to be relatively stable, in common with the phenoxyl radical derived from vitamin E. The reactions between the Trolox C phenoxyl radical and a variety of biologically relevant reducing compounds were examined by using both pulse radiolysis and e.s.r. The results demonstrate that the Trolox C phenoxyl radical is readily repaired by ascorbate (k = 8.3 x 10(6) dm3.mol-1.s-1) and certain thiols (k less than 10(5) dm3.mol-1.s-1) but not by urate, NADH or propyl gallate. Evidence from e.s.r. studies indicates that thiol-containing compounds may also enter into similar repair reactions with the alpha-tocopherol phenoxyl radical. Kinetic evidence is presented that suggests that Trolox C may 'repair' proteins that have been oxidized by free radicals.

Free-radical generation by copper ions and hydrogen peroxide. Stimulation by Hepes buffer

Abstract: Hydroxyl radicals (OH.), generated by a phosphate-buffered Cu2+/H2O2 system, were detected by lucigenin-amplified chemiluminescence, deoxyribose degradation and benzoate hydroxylation. In each system the buffer, Hepes, was found to stimulate radical generation significantly. There are two main reasons for this effect: Hepes increases Cu2+ solubility in phosphate-buffered systems, and forms a complex with Cu2+ that is effective in generating OH. from H2O2. Pipes, a structurally similar buffer, and histidine, a known Cu2+ chelator, were found to have a similar effect. These data suggest that the crucial factor in such free-radical-generating systems is the availability of Cu2+, and that these actions of Hepes should be considered in the design of studies utilizing such systems.

Hydroxyl-radical-induced iron-catalysed degradation of 2-deoxyribose. Quantitative determination of malondialdehyde.

Abstract: The degradation of 2-deoxyribose to thiobarbituric acid-reactive material was investigated with two hydroxyl-radical-generating systems: (i) a defined gamma-radiolysis method and (ii) incubation with FeSO4 in phosphate buffer. In each case the thiobarbituric acid-reactive material can be accounted for by malondialdehyde, as measured by an h.p.l.c. method for free malondialdehyde. In the radiolysis system there is a large post-irradiation increase in free malondialdehyde if iron ions are added to the samples. It is proposed that this is due to iron ions catalysing the formation of hydroxyl radicals from radiolytically generated H2O2 as well as stimulating the breakdown of an intermediate deoxyribose degradation product. A mechanism for the formation of malondialdehyde during deoxyribose degradation is proposed.

A study of the structural, electrical and optical properties of copper tellurium oxide glasses

Abstract: The results of an investigation of some properties of CuO-TeO2 glasses are reported. X-ray diffraction, differential scanning calorimetry and optical absorption measurements are discussed with respect to the compositions. D.c. conductivity is measured in the temperature range 293 to 453 K and discussed in terms of small polaron theory.

Introduction: Sociological orientations to representational practice in science

Abstract: Contributors to this Special Issue were asked to investigate the topic of "representational practice in science." We did not require that the studies adopt a particular theory of representation, or follow a specific methodological approach. Nor did we specify a preference for the fields of scientific practice to be investigated. Contributors were asked to consider any of the varieties of representational devices used in science: graphs, diagrams, equations, models, photographs, instrumental inscriptions, written reports, computer programs, laboratory conversations, and hybrid forms of these. Studies on the organization, interconnectedness, and use of such devices were to be related to general issues in the sociology and philosophy of science. Given this open-ended agenda, it is not surprising that this Special Issue contains a diverse collection of papers. With the exception of Paul Tibbetts' essay - a critical discussion on the sociology of scientific representation which helps to specify the context of inquiry for the other studies - the papers examine particular texts and activities. They investigate a number of different kinds of representation: visual and graphic documents of laboratory data, textual figures, biographical accounts of scientific "problems," instructions for novices, and "artificially intelligent" programs. While there are some "family resemblan

Alginate inhibition of the uptake of Pseudomonas aeruginosa by macrophages.

Abstract: Pseudomonas aeruginosa alginate was purified and characterized in terms of uronic acid, carbohydrate and protein content, as well as by infra-red spectroscopy and gel electrophoresis. Added exogenous bacterial alginate inhibited the uptake and degradation of both viable and non-viable radiolabelled non-mucoid P. aeruginosa by resident mouse peritoneal macrophages. Alginic acid (from seaweed) inhibited the same parameters to almost the same degree. Bacterial alginate also inhibited the uptake of fluorescent-labelled zymosan and latex particles. Starch, at equivalent viscosity to the alginate, inhibited the uptake and degradation of radiolabelled nonviable P. aeruginosa to a greater extent, but Dextran T500 had no effect. This suggests that the viscous nature of alginate exerts a non-specific inhibitory effect on the uptake and subsequent degradation of phagocytosible particles.

Hydroperoxide-mediated fragmentation of proteins

Abstract: 1. Chemiluminescence and benzoic acid hydroxylation were used to detect oxygen-centred free-radical production by 2.5 mM-H2O2 and 100 microM-Cu2+. Free radicals could not be detected by these methods when H2O2 was replaced with 10 mM-t-butyl hydroperoxide (TBH) or 10 mM-cumene hydroperoxide (CH). The inclusion of the thiol compound dithioerythritol (DTET; 100 microM) increased radical production by H2O2 and Cu2+ as judged by both assays. Mannitol scavenged radicals in the chemiluminescence system in a dose-dependent manner. 2. H2O2, TBH and CH, each with Cu2+, gave rise to substantial fragmentation of the protein bovine serum albumin (BSA). This fragmentation could be increased by the inclusion of DTET. Omission of Cu2+ or the addition of the chelator DETAPAC (diethylenetriaminepenta-acetic acid; 1 mM) lead to virtual abolition of fragmentation. Autoxidized lipid in the presence of Cu2+ caused protein fragmentation by reactions of lipid hydroperoxides. 3. Polyacrylamide-gel electrophoresis in the presence of SDS confirmed that production of fragments had occurred. 4. Susceptibility of BSA to enzymic hydrolysis by two different proteinases acting at pH 5 and pH 7.2 was increased after a limited exposure to hydroperoxides in the presence of Cu2+. 5. These results may have biological significance, particularly for proteins in lipid environments (e.g. membrane proteins and lipoproteins).

ASP: a cost-effective parallel microcomputer

Abstract: The author presents ASP architecture, which offers cost-effective support of a wide range of numerical and nonnumerical computing applications, using state-of-the-art microelectronic technology to achieve processor packing densities that are more usually associated with memory components, ASP is designed to benefit from the inevitable VLSI-to-ULSI-to-WSI (very large, ultra large, and wafer-scale integration) technological trend, with a fully integrated, simply scalable, and defect/fault-tolerant processor interconnection strategy. The author discusses the architectural philosophy, structural organization, operational principles, and VLSI/ULSI/WSI implementation of ASP and indicates its cost-performance potential. ASP microcomputers have the potential to achieve cost-performance targets in the range of 100 to 1000 MOPS (million operations per second) per $1000. This gives ASPs an advantage of two to three orders of magnitude over current parallel computer architectures. >

In vivo ovarian uptake and processing of vitellogenin in the rainbow trout, Salmo gairdneri

Abstract: The in vivo uptake and processing of vitellogenin (VTG) into developing oocytes of rainbow trout were studied Oestrogenized trout injected with 32P and 3H-leucine incorporated these labels into newly synthesized vitellogenin This dual-labelled VTG was purified from the serum and injected intraperitoneally into sexually maturing female trout The 32P 3H-VTG was readily taken up from the peritoneal cavity into the blood, without degradation, and thus became available for sequestration by developing oocytes Ovarian uptake of 32P 3H-VTG was very rapid Eight h after injection, approximately half of the labelled VTG was in the blood, but this figure had fallen to 12% after 48 h, and to 02% after 2 weeks This fall in blood 32P 32H-VTG level coincided with increases in the level of both radiolabels in the ovary Eight hours post-injection, a significant amount of 32P 32H-VTG was found in the ovary homogenate Most of this material was intact, primarily representing VTG bound to the follicle surface However, small amounts were contained within the follicles and probably represented newly sequestered VTG which had not yet been degraded into the yolk proteins, lipovitellin and phosvitin Twenty-four hours post-injection, approximately 25% of the injected 32P 3H-VTG had been sequestered by the ovary Although a small proportion of the labels were associated with intact VTG, the majority of the 3H and 32P eluted with lipovitellin and phosvitin, respectively, the yolk proteins derived from VTG After 2 weeks, nearly 70% of the 32P 3H-VTG initially injected had been incorporated into the ovaries, all of which was present as labelled yolk proteins The rate of uptake of VTG was highest in the fish with the largest follicles, where it approached 120 ngmm2 follicle surface h−1 The results demonstrate that both the uptake and processing of VTG by trout oocytes are rapid features that are reflected in the rate of ovary growth seen during exogenous vitellogenesis

Vibrational properties of samarium phosphate glasses

Abstract: Samarium phosphate glasses in the composition range 5 mol% to 25 mol% Sm2O3 have been prepared. Raman spectra have been characterized in terms of structural components and their resemblance to those of other phosphate glasses shows that the samarium-modified glasses have similar structural features to those of other vitreous phosphates. The compositional dependences of the elastic constants and their hydrostatic pressure derivatives have been measured at room temperature. An increase in samarium content in a decrease of both C11 and the bulk modulus, Bs, to minimum values at a composition of about 20 mol% Sm2O3. Both C11 and C44 decrease with application of hydrostatic pressure: these glasses become easier to compress as pressure is increased. Such acoustic mode softening behaviour is not typical of other phosphate glasses. Visual examination in a diamond cell up to about 100 kbar does not reveal a structural or valence change associated with this vibrational instability. The vibrational anharmonicity and the pressure induced acoustic mode softening are discussed in terms of the Gruneisen approach. It is concluded that the anomalous elastic behaviour under pressure may arise from valence instability of the samarium ions.

The Nottingham Health Profile as a measure of quality of life following combined heart and lung transplantation.

Abstract: This paper reports on the use of the Nottingham Health Profile as a measure of patient quality of life before and after combined heart and lung transplantation at Harefield Hospital. A total of 125 profiles from 48 patients were analysed. In both section 1 and section 2 of the profile, large and statistically significant (p less than 0.05) improvements in quality of life were associated with transplantation. The profile proved easy to use either as part of an interview during assessment for transplantation or as a postal follow-up postoperatively.

Optical properties of amorphous thin films of MoO3 deposited by vacuum evaporation

Abstract: The absorption spectra of MoO3 amorphous thin films in the thickness range from 50 to 350 nm are studied as a function of thickness in the temperature range from 20 to 275°C. The validity of the Urbach rule is investigated and the related parameters are estimated. It is confirmed that absorption in these layers is due to non-direct transitions. A decrease in optical energy gap with annealing is reported. The analysis of optical absorption edge as a function of temperature is discussed with particular reference to amorphous molybdenum trioxide films. The decrease in the optical energy gap with increasing substrate temperature is reported and discussed in terms of current theory. Les absorption spectrales des couches minces de MoO3 avec leurs epaisseurs entre 50 et 350 nm etaient etudiees comme fonction de l'epaisseur. Pour les temperatures entre 20 et 275 °C, la validite de la regle d'Urbach etait etudiee et les parametres etaient calcules. On confirme que l'absorption optique dans les couches minces est contrǒlee par les transitions electroniques nondirectes dans l'espace k. Une decroissance du bandgap optique avec le traitement thermique est observee. L'analyse de la limite d'absorption comme fonction de la temperature est discutee avec le MoO3 comme exemple. La decroissance du bandgap optique avec l'elevation de la temperature est consideree avec l'emploi de la theorie recente.

Selectivity of protein sequestration by vitellogenic oocytes of the rainbow trout, Salmo gairdneri

Abstract: The selectivity of protein sequestration by vitellogenic oocytes of the rainbow trout, Salmo gairdneri, was investigated by comparing the rates of uptake of radiolabelled vitellogenin (VTG) and bovine serum albumin (BSA). Fish were injected simultaneously with equal amounts of both 3H-VTG and 14C-BSA and sampled subsequently at varying time invervals to assess the rates of uptake of these proteins into the developing oocytes. Both labelled proteins were taken up rapidly into the blood after their injection into the peritoneal cavity. Once in the blood, they became available for sequestration by the vitellogenic oocytes. There was both rapid and selective uptake of 3H-VTG; within 72 hours half of the 3H-VTG injected was present within the ovary, whereas only 2.5% of the 14C-BSA was similarly located. Once within the oocyte, 3H-VTG was specifically and rapidly processed to yield its constituent yolk proteins, which included 3H-lipovitellin. In contrast, after 72 hours 14C-BSA was present in the oocyte as the native, intact protein. However, after 13 days, whereas the yolk proteins had undergone no further processing, remaining stable within the oocyte, much of the BSA within the ovary had been degraded to an array of smaller peptides. Furthermore, after 26 days, whereas all of the 3H-VTG endocytosed remained within the oocytes as yolk protein, at least half of the BSA taken up initially had been exocytosed. Calculation suggested that 3H-VTG was sequestered about 60 times more rapidly than 14C-BSA. Other tissue did not incorporate 3H-VTG to any significant degree. These results suggest that VTG was sequestered into vitellogenic oocytes by receptor-mediated endocytosis, whereas BSA, along with other extraneous proteins, was taken up adventitiously.

An Assessment of the Value of Blue, Red, and Black Cotton Fibers as Target Fibers in Forensic Science Investigations

Abstract: Color is the primary characteristic used for comparing cotton fibers. Problems arising because of considerable intrasample variation may cause difficulty in assessing the matching of cotton fibers in a casework situation. Because of the number of dye classes used on cotton fibers, dye extraction and examination by thin-layer chromatography are more problematical than with other fiber types. This necessitates greater reliance on microspectrophotometry and fluorescence microscopy for dye comparison. Fibers from blue denim cannot generally be discriminated and are regarded as having little evidential value. Little or no published data exist on the evidential value of cotton fibers of other colors. This study was designed to assess the value of nondenim blue, red, and black cotton fibers as evidence. Of each color 46 samples were chosen at random (giving a total of 1035 comparisons per color). The number of matching pairs was established after using comparison microscopy, microspectrophotometry, and fluorescence microscopy. Some blue denim cotton fibers were also examined. Complementary chromaticity coordinates were computed for all samples. The results show that, provided adequate techniques are used to compare nondenim blue, red, and black cotton fibers, the chance of finding pairs with matching dyes by coincidence is low despite considerable color overlap. Black cotton fibers represent poorer value as evidence than either nondenim blue or red cotton fibers.

The influence of out-of-plane stress on a plane strain problem in rock mechanics

Abstract: This paper considers the excavation of a cylindrical cavity in a uniformly prestressed mass of brittle Mohr-Coulomb rock. Previous plane strain displacement solutions have assumed that the out-of-plane stress remains the intermediate principal stress at all points. It is here shown that when this assumption breaks down, an inner plastic zone is created in which σr < σz = σθ. A displacement solution is given for this case, using a variable-dilation plastic flow rule, and results are compared with the previous solution for specific problems. A significant difference is observed only for problems involving a large drop in strength upon yield.

Singularities of the Laplacian at corners and edges of three-dimensional domains and their treatment with finite element methods

Abstract: Three-dimensional Poisson problems containing boundary singularities are treated. The forms of the solutions for certain problems of this type are derived, where the domains of the problems can be represented in terms either of spherical- or of cylindrical-polar co-ordinates. These singular forms are used to augment the basis of a standard piecewise polynomial Galerkin space, thus producing an augmented Galerkin technique which is suited to the context of a problem involving a singularity. Error estimates are derived.

A 9-kbit associative memory for high-speed parallel processing applications

Abstract: The authors discuss the design, development and implementation of the 9-kb (256-word*37-bit) associative memory used in the single-chip array processing element (SCAPE) chip, a CMOS VLSI associative parallel processor (APP) that integrates 256 associative processing elements (APEs) on a single 68-pad chip to achieve high-speed, cost-effective image and signal processing. It is shown that a static CMOS content-addressable memory (CAM) design is unsuited to the constraints of the SCAPE chip architecture and that a purely nMOS CAM cell provides the best compromise between the conflicting area, speed, power, and control requirements. Comprehensive details of this design are given together with an evaluation of its performance. Finally, a description of the design methodology used in the construction of the SCAPE chip is presented with a breakdown of circuit areas and operational data. >

Towards testing with respect to formal specification

Abstract: Testing in the context of the use of formal development methods is addressed. A short review of testing methods is given, focussing on methods for test case construction and evaluation. The methods are then applied to a formal specification written in Z, to demonstrate their applicability. The problems of automating the generation of test case is discussed and research directions set.< >