Showing papers by "Brunel University London published in 1989"
TL;DR: The results suggest that prolonged elevation of plasma cortisol, to levels well within physiological range, can affect a wide range of reproductive parameters in both brown and rainbow trout.
241 citations
TL;DR: It is found that purified bacterial alginate scavenges free radicals released by triggered macrophages as detected by lucigenin amplified chemiluminescence (CL) and reduction of cytochrome c.
185 citations
TL;DR: Radical attack decreased the affinity of LDL for the fibroblast apo B/E receptor, but did not enhance its endocytosis by mouse macrophages.
Abstract: The effects of defined oxygen-centred free radicals on human low-density lipoprotein (LDL) structure and receptor affinity are discussed in relation to the mechanisms of cell-mediated oxidative modification of LDL. Both hydroxyl (OH.) and hydroperoxyl (HO2.) radicals caused depletion of endogenous alpha-tocopherol and formation of hydroperoxides. Superoxide (O2-.) radicals produced only very limited oxidation, but could potentiate oxidation stimulated by the addition of Cu2+. All these radicals enhanced the net negative charge of intact LDL and induced fragmentation of apolipoprotein B-100 (apo B). OH. also caused cross-linking of apo B. Radical attack decreased the affinity of LDL for the fibroblast apo B/E receptor, but did not enhance its endocytosis by mouse macrophages.
158 citations
TL;DR: In this paper, the cross section for e+e− → hadrons from a scan around the Z0 pole was determined, based on 4350 hadronic events collected over seven energy points between 89.26 and 93.26 GeV, and a total decay width of 2.60±0.13 GeV.
156 citations
TL;DR: In this article, the Bernoulli-Euler theory of beam flexure was extended to allow warping of the beam cross-section, which can make a large difference to results for thin-walled beams of open section.
140 citations
TL;DR: In this article, the authors examined the scope and limitations of physisorption as a means of characterising porous solids, and showed that the Brunauer-Emmett-Teller (BET) method remains the most useful means available for the determination of the surface area of mesoporous materials.
136 citations
TL;DR: The micropore filling appears to occur in two stages: 1) a primary process in pores of molecular dimensions and 2) a secondary, or cooperative, process in somewhat wider pores as mentioned in this paper.
134 citations
TL;DR: In this article, the authors used the linearized theory of water waves to determine the frequencies of free oscillations under gravity of an arbitrary amount of fluid in such tanks and formulated the problems in terms of integral equations.
Abstract: The two-dimensional sloshing of a fluid in a horizontal circular cylindrical container and the three-dimensional sloshing of a fluid in a spherical container are considered. The linearized theory of water waves is used to determine the frequencies of free oscillations under gravity of an arbitrary amount of fluid in such tanks. Special coordinate systems are used and the problems are formulated in terms of integral equations which are solved numerically for the eigenvalues. Detailed tables of the sloshing frequencies are presented for a range of fill-depths of the containers.
132 citations
TL;DR: Male rainbow trout of an autumn- and a spring-spawning strain were sampled every 28 days over a period of 2 years, starting when they were approximately 6 months old, and there were a large number of differences--in the timing of first appearance of various parameters, in the timing and magnitude of various peaks, inThe histological appearance of the regressing testes, and in the heterogeneity of the male population.
128 citations
TL;DR: In this article, X-ray photoelectron spectroscopy (XPS) core level spectra of MoO3 substoichiometric amorphous thin films in the thickness range 100 to 670 nm were studied as a function of thickness.
Abstract: X-ray photoelectron spectroscopy (XPS) core level spectra of MoO3 substoichiometric amorphous thin films in the thickness range 100 to 670 nm were studied as a function of thickness. Some samples 500 nm thick were studied for different substrate temperatures in the range 293 to 543 K. It was observed that with the increase of thickness of the samples no change in the electron spectrum was observed in the material. Under vacuum conditions, MoO3 turned blue when the substrate temperature was higher than 373 K. XPS spectra supported the formation of the Mo5+ oxidation state in the blue samples. Blue coloration was observed after heating in vacuum and this was attributed to an internal electron transfer from oxygen to metallic orbitals by thermal ionization creating an Mo5+ oxidation state.
121 citations
TL;DR: The study concludes that the evaluation of the prescription charge policy requires more detailed study of both the incidence of the charge effect and the possible costs and health consequences of reduced utilisation due to the charge.
TL;DR: In this paper, a methode permettant de mesurer l'aire superficielle du metal is described, and the methode supports a catalyseur, SiO 2, TiO 2, Al 2 O 3.
TL;DR: It is found that the low-temperature resistance to cytotoxic concentrations of H2O2 is abolished by preincubation of cells with reductants such as ascorbate or reduced lipoic acid, implying that theLow-tem temperature resistance to H2 O2 cytotoxicity may be due to inhibition of cellular reductive processes.
Abstract: The principal mechanism of H2O2 toxicity is thought to involve the generation of hydroxyl (HO.) radicals through its interactions with Fe2+ ions by the Fenton reaction. Of particular interest has been the demonstration by Ward, Blakely & Joner [(1985) Radiat. Res. 103, 383-392] that the cytotoxicity of H2O2 is diminished at low temperature. We have now examined this phenomenon further with a mammalian epithelial cell line (CNCMI-221). Resistance of these cells to 100 microM-H2O2 added extracellularly exhibits a transition in the temperature range between 27 degrees C and 22 degrees C. We have found that the low-temperature resistance to cytotoxic concentrations of H2O2 is abolished by preincubation of cells with reductants such as ascorbate or reduced lipoic acid. This implies that the low-temperature resistance to H2O2 cytotoxicity may be due to inhibition of cellular reductive processes. The restoration of the cytotoxic action of H2O2 at 4 degrees C by ascorbate is prevented by pre-exposure of cells to desferrioxamine. This is evidence that transition-metal ions (such as iron ions) are involved in the cytotoxicity and is consistent with a mechanism of cell damage that depends on the Fenton reaction and a metal ion in the reduced state. Restoration of H2O2 cytotoxicity at low temperature by ascorbate is consistent with the artificial production of an intracellular reducing environment that at normal temperatures is sustained by cellular metabolism.
TL;DR: In the two-stage recovery of natural cashew nut-shell liquid by solvent extraction, the overall yields from half-shells obtained by mechanical cutting and from chilled fragmented shells (to solidify the phenols) by manual processing are identical, indicating that no physical loss of phenolic material occurs in the mechanical process as mentioned in this paper.
Abstract: In the two-stage recovery of natural cashew nut-shell liquid (CNSL) by solvent extraction, the overall yields from half-shells obtained by mechanical cutting and from chilled fragmented shells (to solidify the phenols) by manual processing are identical, indicating that no physical loss of phenolic material occurs in the mechanical process. At the first stage, prior to comminution, the yield from intact half-shells of mechanical origin is considerably less than that from manually processed shells due to extensive internal fracturing of the shell structure and greater solvent penetration in the latter case. Static solvent extraction of macerated shells gave the same yield as Soxhlet extraction, but the filtration stage was difficult and large volumes of solvent were required. Soxhlet solvent extraction or ultrasound/solvent extraction of manually processed shells at ambient temperature gave similar yields and economy in solvent usage. Both were much superior to mechanical agitation. By catalyzed decarboxylation of the recovered natural CNSL an almost theoretical yield (25%) of phenolic lipid rich in cardanol was obtained, which is considerably higher than that (10%) in the traditional recovery of technical CNSL by the hot oil bath industrial method. Natural CNSL contains a predominant amount of anacardic acid and represents a novel phenolic lipid source. Chemical reduction with air/aqueous hydrazine gave saturated natural CNSL. Polymerization of natural CNSL was effected in alkaline solution with paraformaldehyde.
01 Jan 1989
TL;DR: It is concluded that histidine and proline are important sites of protein attack by radicals; protein cleavage may result from these reactions.
Abstract: Our hypothesis that proline and histidine are major sites of damage during radical attack upon proteins, becoming respectively glutamate and aspartate. was investigated using proteins biosynthetically labelled with radioactive proline or histidine as targets. Free radicals were generated by copper and H2O2, or by gamma radiolysis. Protein-bound histidine was substantially converted into aspartate. Much proline was modified during radical attack, but it was not converted into glutamate. We conclude that histidine and proline are important sites of protein attack by radicals; protein cleavage may result from these reactions.
TL;DR: The data suggest that cisplatin itself may be the nephrotoxic species, since it is the intracellular platinum compound present in highest concentration during the early critical period after its administration.
Abstract: The appearance of low-molecular-weight metabolites of cisplatin in the cytosol of cells from the cortex and outer medulla, of the rat kidney has been examined using HPLC up to 24 h following cisplatin administration. Comparison was made between these metabolites and those present in plasma, urine and liver. The effect of sodium chloride (NaCl) pretreatment, which is known to reduce cisplatin-induced nephrotoxicity, on these metabolites was also investigated. Platinum levels in the kidney cortex and medulla and the cytosol reached maximal levels within 1 h of i.p. injection of 5 mg/kg cisplatin. At least six platinum species, including cisplatin, were present 1 h post-dosing, with the principal species being the parent drug; all of these species were either neutral or negatively charged. Although the concentration of most of the platinum species fell with time, that of one species eluting before cisplatin rose, and by 24 h it was the major metabolite. Cisplatin and two other major cytosolic platinum species were also present in urine and plasma, both of which also contained a number of charged species that were absent from the cytosol. The liver cytosol contained at least five metabolites 1 h post-dosing, but, in contrast to the kidney cytosol at the same time, the predominant species was that eluting before cisplatin and not cisplatin itself. One of the metabolites in the cytosol and urine had the same retention time as an adduct of cisplatin with glutathione and with cysteine. Urinary samples also contained a metabolite coeluting with aquated cisplatin. Pretreatment of animals with NaCl significantly reduced the platinum concentration in the kidney, with a corresponding decrease in the cytosolic metabolites; this may have contributed significantly to the reduction in cisplatin-induced nephrotoxicity after NaCl pretreatment. NaCl also significantly reduced a possible aquated species present in the urine, which may also have contributed to the reduction in nephrotoxicity. The data suggest that cisplatin itself may be the nephrotoxic species, since it is the intracellular platinum compound present in highest concentration during the early critical period after its administration.
TL;DR: The relationships between antioxidant status, lipid peroxidation and membrane protein integrity have been studied in an isolated mitochondrial membrane system and α-tocopherol was shown to be present in both the outer and inner membrane of normal rat liver mitochondria.
TL;DR: The results support the possibility that vitamin A might play a role in protecting lipid membranes against thiyl free radical mediated damage.
TL;DR: Conditions of geometric continuity at a vertex where a number of patches meet are investigated and applications to the modelling of closed surfaces and the fitting or triangular patches into a geometric continuous patch complex are sketched.
TL;DR: In this paper, temperature-programmed reduction and quantitative X-ray photoelectron spectroscopy (XPS) have been used to characterise dried precursors to V2O5/TiO2 catalysts prepared either by wet impregnation with NH4VO3-oxalic acid solution or by grafting with either VOCl3 or VO(OiBu)3.
TL;DR: A polygonal patch is defined to fill an n -sided hole within a C 2 parametric continuous rectangular patch complex to form a continuous patch complex.
TL;DR: In this article, the value of semi-empirical equations relating relative viscosity to the volume fraction of ceramic powder was explored for ceramic injection molding suspensions containing up to 64 vol% alumina.
Abstract: The value of semi-empirical equations relating relative viscosity to the volume fraction of ceramic powder was explored for ceramic injection moulding suspensions containing up to 64 vol% alumina. The errors associated with the determination of volume fraction and viscosity were evaluated. An extension of the Chong equation was used for relative viscosity so that the effect of an unknown powder on viscosity could be established from a minimum of two viscosity measurements in a characterised organic vehicle. This simplifies decisions on composition to achieve a specified viscosity.
TL;DR: In this paper, the first measurements of the d.c. electrical conductivity and the low-frequency (static) dielectric constant of samarium phosphate glasses (in the composition range 5 to 25 mol% Sm2O3) are reported.
Abstract: The first measurements of the d.c. electrical conductivity and the low-frequency (static) dielectric constant of samarium phosphate glasses (in the composition range 5 to 25 mol% Sm2O3) are reported. A break in the slope of the Arrhenius plot divides the conductivity data into two temperature regimes, the conductivity mechanism at low temperatures having a lower activation energy than that at higher temperatures. An increase of Sm2O3 glass modifier content results in a decrease in the absolute value of the conductivity. The data are consistent with small-polaron transport and hence small-polaron theory has been used to establish the characteristic energies of the carriers. The dielectric constants range from 5.4 for a glass containing 5mol% Sm2O3 to 8·1 for that with 2Smol% Sm2O3; the temperature dependences of the dielectric constants are linear and positive, as is usual for glasses.
TL;DR: The architecture, software, and implementation of ASP modules are discussed, and the paper indicates that the potential of a peak performance of 1 TOPS could be achieved with only 10 ASP modules, within less than a cubic-foot, dissipating 1 KW, and for less than $1M.
Abstract: ASP (Associative String Processor) architecture and support software provide the base technology for the development of versatile, replaceable, and highly compact building-blocks for the simple construction of modular real-time DSP systems, offering step-function improvements in cost-performance, application flexibility, reliability, and ease of maintenance. Based on a fully programmable and fault-tolerant homogeneous computational architecture, emerging from research at Brunel University and being developed by Aspex Microsystems, ASP modules offer cost-effective support of a particularly wide range of DSP applications, by mapping application data structures to a common string representation supporting content-addressing, parallel processing and a reconfigurable inter-processor communication network. Moreover, by exploiting state-of-the-art microelectronics and packaging technologies, the ASP modules achieve processor packing-densities which are more ussually associated with memory components. Indeed, the ASP has been designed to benefit from the inevitable VLSI-to-ULSI-to-WSI technological trend, with a fully integrated simply scalable, and defect/fault-tolerant processor interconnection strategy. The architecture, software, and implementation of ASP modules are discussed, and the paper indicates that the potential of a peak performance of 1 TOPS (i.e., 1E12 operations (e.g., 12-bit adds) per second) with an input-output bandwidth of 3,200 Mbytes/second could be achieved with only 10 ASP modules, within less than a cubic-foot, dissipating 1 KW, and for less than $1M.
Journal Article•
TL;DR: A survey of mathematical representations including nerve cell bodies, myelinated and unmyelinated fibers of passage, branched systems, fiber terminals and composite neurons is provided, to show the significant role that current nerve cell models may play in attempts to understand mechanisms of neural stimulation, and in the development of more advanced strategies for electronic intervention and control of neural function.
Abstract: In general, complete mathematical modeling of electrical neurostimulation encompasses two separate problems; clear delineation of this article becomes important. Solutions are required for the time-varying macroscopic fields generated by the stimulating electrodes, and only then can biophysical analysis be brought to bear on neural structures within those fields. This article is focused on the second of these aspects, and provides a survey of mathematical representations including nerve cell bodies, myelinated and unmyelinated fibers of passage, branched systems, fiber terminals and composite neurons. Effects on nerve cells of fields generated by remote electrodes are given primary attention, although methods for obtaining field solutions in biological media are discussed in detail only where the issue is inextricably linked to the use of a particular neural model, or relates crucially to experimental validation. Within these guidelines, it is intended to show the significant role that current nerve cell models may play in attempts to understand mechanisms of neural stimulation, and in the development of more advanced strategies for electronic intervention and control of neural function.
TL;DR: The isolation of T.b. gambiense is reported by feeding cryopreserved primary isolates to laboratory-reared Glossina mors Titans morsitans, followed by rapid cultivation in vitro of procyclic forms dissected from infected tsetse fly midguts, which allows the characterization of hitherto unsampled populations and avoids selection due to long-term subpassage.
Abstract: Low infectivity to laboratory mammals and low virulence make Trypanosoma brucei gambiense difficult to isolate and grow in amounts sufficient for biochemical characterization. We report the isolation of T.b. gambiense by feeding cryopreserved primary isolates to laboratory-reared Glossina morsitans morsitans, followed by rapid cultivation in vitro of procyclic forms dissected from infected tsetse fly midguts. This technique allows the characterization of hitherto unsampled populations and avoids selection due to long-term subpassage. Of 16 primary isolates from trypanosomiasis patients of the Fontem focus in Cameroon, 12 (75%) produced infections in tsetse whereas only 4 (25%) infected rats. Ten isolates were subsequently cultivated as procyclic forms in vitro; 2 failed to grow owing to bacterial contamination. In addition, 2 primary isolates from Cote d'Ivoire patients and a stock of low virulence from the Congo Republic were similarly grown. Only one primary isolate produced tsetse salivary gland infections, an observation consistent with the hypothesis that some populations of T.b. gambiense are intrinsically incompatible with G.m. morsitans.
TL;DR: It is suggested that although a GTH II-like gonadotrophin is present in the pituitary gland throughout the period of gonadal growth, it does not appear to be released in any substantial amounts into the blood until near spawning.
TL;DR: The degradation mechanisms of four polyolefins of differing molecular weight were studied by thermogravimetric analysis in order to identify the material properties which facilitate the extraction of ceramic injection molding vehicles as discussed by the authors.
Abstract: The degradation mechanisms of four polyolefins of differing molecular weight were studied by thermogravimetric analysis in order to identify the material properties which facilitate the extraction of ceramic injection molding vehicles. Three weight-loss processes were identified and the corresponding activation energies were calculated. Low-molecular-weight vehicles were lost entirely by evaporation while higher-molecular-weight polymers underwent thermal degradation followed by evaporation of degration products. In oxidizing atmosphere the influence of oxidative degradation was confined to the surface region of moldings. It is shown that the summation of individual thermograms gives guidance on the likely weight loss behavior of blends.
TL;DR: An iodometric method for the analysis of hydroperoxides has been automated to allow analysis of aqueous biological samples and lipid hydroperoxide extracts and it allows detection of less than 100 pmol of peroxide.