Showing papers by "Brunel University London published in 1979"

Direct observation of a free radical interaction between vitamin E and vitamin C

Abstract: VITAMIN E (α-tocopherol) and vitamin C (ascorbic acid) react rapidly with organic free radicals, and it is widely accepted that the antioxidant properties of these compounds are responsible in part for their biological activity1–5. Tissue vitamin C levels are often considerably greater than those of vitamin E, for example in liver the values are approximately 2 mM and 0.02 mM, respectively. Nevertheless, vitamin E is considerably more lipophilic than vitamin C, and in biomembranes has been found to be the more potent antioxidant, particularly with respect to lipid peroxidation; penetration to a precise site in the membrane may be an important feature of the protection against highly reactive radicals6. Tappel has suggested that the two vitamins act synergistically, vitamin E acting as the primary antioxidant and the resulting vitamin E radical then reacting with vitamin C to regenerate vitamin E7. We now report direct observation of this interaction, which we feel may be an important feature in the maintenance of vitamin E levels in tissues.

Structure-activity relationships in the development of hypoxic cell radiosensitizers. I. Sensitization efficiency

Abstract: SummaryThe efficiency of 35 nitroaromatic and nitroheterocyclic compounds in radiosensitizing hypoxic Chinese Hamster cells in vitro was determined. The concentration C of the compound required to achieve an enhancement ratio of 1·6 was measured, and the redox and partition properties were quantified as the one-electron reduction potential at pH 7, E, and the octanol: water partition coefficient, P, respectively. Most of the compounds studied were 2-nitroimidazoles, but some 4- and 5-nitroimidazoles, 5-nitrofurans and nitrobenzenes were investigated for comparison. Together with data for nine nitroimidazoles previously reported, the results were fitted to a structure-activity relationship of the form using multiple linear regression analysis. Statistical tests showed that the coefficients b2 and b3 were not significantly different from zero and the simpler equation, obtained by omitting the terms in log P, explained 85 per cent of the variance in log C. Earlier reports that the radiosensitization efficien...

Learning, Change, and Evolution: An Enquiry into the Teleonomy of Learning

Abstract: Publisher Summary This chapter discusses Waddington's comments about the need to establish the logic of the relationships between evolutionary processes and behavior. It solves the problem of paradox of unity versus diversity. This is done by actually teasing out learning's teleonomic universals. The teleonomic universals are: (1) the evolutionary origins of learning are the same in all animals that can learn; (2) learning shares the same logical relationship to phylogenesis in all learners; and thus (3) learning always serves the same fundamental function. In doing so, it always tends to act in support of phylogenesis. At the same time, the nested relationship that learning has to phylogenesis demands diversity of learning. The chapter explains learning as one out of several classes of change in the internal organization of an animal that are consequent upon changes in external environmental order. All learning is a function of innate mechanisms of adaptability, which are both provided and primed by phylogenesis with respect to some specific primary referent.

Guide to pattern recognition using random-access memories

Abstract: About 12 years of work with a specific type of learning pattern-recognition system are reviewed. The principles and characteristics of the scheme, which is based on random-access-memory implementation, are discussed in some detail. Methods of improving performance and cost-optimising pattern recognisers are presented, together with case studies in a variety of fields including the recognition of alphanumerics, chemical data and faults in digital circuit boards.

Structure-activity relationships in the development of hypoxic cell radiosensitizers. II. Cytotoxicity and therapeutic ratio.

Abstract: This paper describes measurements of the aerobic cytotoxicity of 42 nitroaromatic and nitroheterocyclic compounds towards Chinese Hamster cells in vitro. The results of acute and chronic exposure were quantified, and the concentration C required to achieve a standard response estimated. Fitting the data to an equation of the form - log C = b0 + b1E, where E is the one-electron reduction potential, explained 47 and 71 per cent of the variance in the acute and chronic aerobic cytotoxicity respectively. The addition of further terms to the equation, quantifying partition properties, was not statistically significant. The coefficient b1 was similar for both acute and chronic exposure; the dependence of both cytotoxicity and radiosensitization efficiency on reduction potential was also similar. A therapeutic ratio derived from these in vitro measurements showed no dependence on redox or partition properties. The insensitivity of cytotoxicity and radiosensitization properties to variations in molecular structure, other than those which influence redox behaviour, offers exceptional flexibility in developing compounds of improved therapeutic ratio.

The preparation of cadmium phosphate and cadmium zinc phosphate glasses and their electrical and optical properties

Abstract: The preparation of a range of glasses based on CdO-P2O5 and CdO-ZnO-P2O5 is described and data are reported on density, electrical conductivity and optical absorption. The electrical conduction is electronic rather than ionic and is due to hopping between localized states. The optical absorption is due to forbidden indirect electronic transitions.

Immunodepression and the course of infection of a chronic Trypanosoma brucei infection in mice.

Abstract: Summary The relationships between course of infection, antigenic variation, and immunodepression of antibody responses to heterologous antigens have been investigated in mice chronically infected with Trypanosoma brucei. T. brucei Brunel University Trypanosomiasis (BUT) 64 produces a fluctuating parasitaemia lasting about 80 days and ending fatally. It is demonstrated that recurring peaks of parasitaemia are associated with the appearance of new variant antigenic types. At 21 and 31 days of infection, IgG responses to the heterologous antigen, sheep red blood cells (SRBC), are absent and IgM responses are less than 5% of normal. When a single dose of cyclophosphamide (300 mg/Kg) was injected into mice on day 31 of infection, the parasitaemia rose sharply in an uncontrolled fashion and the treated mice died in about 10 days. Cyclophosphamide, given in this way, is known to ablate antibody production completely but temporarily. It is therefore concluded that even though infected mice make extremely poor anti-body responses to heterologous antigens, they are still capable of producing sufficient antibody to control peaks of parasitaemia associated with the emergence of new variant antigenic types. The significance of these findings is discussed in relation to current hypotheses of trypanosome-associated immunodepression.

Factors affecting glyphosate activity in Imperata cylindrica (L.) Beauv. and Cyperus rotundus L. II: effect of shade

Abstract: Summary: Imperata cylindrica and Cyperus rotundus were grown under three different light regimes; unshaded, 50% shade, and 75% shade and no shade plus 75% shade before and after spraying, (temporary shade) in a heated greenhouse. Six weeks after the start of the experimenis, glyphosate was applied to the plants at 0·2, 0·4 and 0·8 kg/ha (for Imperata) or 0·3, 0·6 and 1·2 kg/ha (for Cyperus). Glyphosate toxicity was enhanced as shade increased. In Imperata, all shade regimes at all rates of glyphosate eaused greater damage to the plants than the unshaded regime. The reduction in shoot dry weight, rhizome dry weight and total carbohydrate content of Imperate rhizotties at 75% continuous and temporary shaiie conditions, with the lowest rate of glyphosate, was almost twice as much as the reduction in the same features m the unshaded plants caused by the highest rate of glyphosate. In Cyperus. glyphosate at the intermediate and highest rates decreased the shoot dry weight at 75% continuous shade by 79% and 98% respectively. Plants in 50% shade were significantly affected only at the highest rate of glyphosate. Sprouting ability of the tubers al 75% continuous shade was inhibited when the tubers were replanted for recovery. Enhanced toxicity of glyphosate in reduced light intensity was attributed to the morphological changes in the nature of the leaves caused by shade. Resume: Facteurs modifiant l'activite du glyphosate sur Imperata cylindrica (L.) Beauv. et Cyperus rotundus L. 2. Effet de l'ombrage. Imperata cylindrica et Cyperus rotundus ont etecultives dans une serre chauffee sous trois regimes differents d'eclairage: sans ombrage, avec 50% d'ombrage, avec 75% d'ombrage. ainsi que sans ombrage plus 75% d'ombrage avant et apres le traitement (ombrage temporaire). Six semaines apres le debut des experiences, le glyphosate a ete applique sur les plantes a raison de 0,2, 0,4 et 0,8 kg/ha (pour Imperata), et 0,3, 0,6 et 1.2 kg/ha (pour Cyperus). La toxicite du glyphosate a ete renforcee par l'augmentation de l'ombrage. Chez Imperata, tous les regimes d'ombrages a toutes les doses de glyphosate, ont provoque des degats plus importants sur les plantes que le regime sans ombrage. Avec la plus faible dose de glyphosate, la reduction du poids sec des pousses et des rhizomes et de la teneur totale en hydrates de carbone des rhizomes d'Imperata cultives au regime de 75% d'ombrage continu et temporaire, a etee presque le double de la reduction des memes parametres chez les plantes cultivees sans ombrage et avec la plus forte dose de glyphosate. Chez Cyperus, a 75% d'ombrage continu, le glyphosate, a la dose intermediaire et la dose la plus forte, a diminue le poids sec des pousses respectivement de 79 et de 98%. Les plantes cultivees a 50% d'ombrage n'ont ete significativement affectees que par la plus forte dose de glyphosate. La capacite de germination des tubercules obtenus a 75% d'ombrage continu a ete inhibee lorsque les tubercules ont ete replantes pour les faire repousser. L ‘augmentation de la toxicite du glyphosate en lumiere d'intensite reduite a ete attribuee aux modifications morphologiques dans la nature des feuilies, provoquees par l'ombrage. Zusammenfassung Faktoren, die die Wirkung von Glyphosat auf Imperata cylindrica (L.) Beauv. und Cyperus rotundus L. beeinflussen. 2. Die Wirkung von Schatten Imperata cylindrica und Cyperus rotundus wurden in einem beheizten Gewuchshaus bei drei verschiedenen Lichiverhult-nissen gezogen: ohne Schatten, 50% Sehatten und 75% Schatten. sowie ohne Schatten plus 75% Schatten (temporurer Schatten) vor und nach der Spritzung. Sechs Wochen nach Beginn der Versuche wurden die Pflanzen mit Glyphosat behan-delt: die Aufwandmengen betrugen bei Imperata 0,2, 0,4 und 0,8 kg/ha, bei Cyperus 0,3, 0,6 und 1,2 kg/ha. Die Wirkung von Glyphosat nahm mit zunehmendem Schatten zu. Bei Imperata verursachte Glyphosat bei allen Dosierungen in allen Schatten-varianten eine bessere Wirkung als bei den unbeschatteten Pflanzen. Die Abnahme im Spross- und Rhizomtrockengewiehi. sowie im Gesamtkohlenhydratgehalt von Imperata-Rhizomen war bei 75% Schatlen und bei temporurem Schatten bei der niedrigsten Herbiziddosis nahezu doppelt so hoch wie bei Anwendung der hochsten Herbiziddosis bei den unbeschatteten Pflanzen. Bei Cyperus senkte das Herbizid bei mittlererem und sturtkstem Schatten das Sprosstrockengewicht um 75%, bzw. 7% und bei Dauerschatlen um 98%. Pflanzen, die bei 50% Schatlen wuchsen, wurden nur durch die hochsle Herbiziddosis deutlich geschudigt. Der Austrieb der Knollen wurde gehemmt, wenn die Pflanzen kontinuierlich bei 75% Schallen wuchsen. Die versturkte phytotoxische Wirkung von Glyphosal bei reduzierter Lichtintensitut wurde der schattenbedingten Blattmorphologie zugeschrieben.

Lysosomes and Protein Degradation

Abstract: Considerable evidence from studies with group-specific proteinase inhibitors, in particular pepstatin, the aspartic proteinase inhibitor, implicates lysosomes in turnover of endogenous cellular proteins. Recent experiments using a new group-specific inhibitor of thiol (cysteine) proteinases, Z-Phe-Ala-diazomethyl ketone, are described. Lysosomal participation is most clearly established for the degradation of long half-life proteins in situations in which turnover is accelerated because of nutritional or hormonal deficiencies. Some evidence indicating their involvement in 'basal' proteolysis is also discussed. Whether lysosomal proteolysis is selective remains to be established, and possible approaches to this question are outlined.

Integration and regulation in organizations: a contextual approach

Abstract: O ut research on integration and regulation in organizations is based upon concerns we share about the way organizations adapt or, rather, fail to adapt in our society. We have observed situations in many kinds of organizations where most people are aware that values are not being served, concerns are not being met and issues are not being resolved, but where either no action is taken or, if it is, it fails to achieve desired results. We call these situations social deadlocks and our long-term normative interest is to see whether they can be broken.̂ Although this paper is addressed to methodological aspects of our work, we hope to demonstrate how the design of our research project and the concepts and methods we use are guided by these concerns. Starting with a very brief outline of three of the cases, we then identify a number of common themes and concepts as the key research interests. Some of the problems of pursuing these interests are raised in terms of problems of definition, the collection of evidence and of inference. We argue that attempts to deal with these problems lead us to adopt a particular jocus, design and approach for research. The paper then moves to a description of our methods and to some of the problems of analysis and explanation associated with the contextualist style of research we have adopted. Finally, we go back to the cases to demonstrate how our concepts and theories are refined by the research process, which is essentially a dialectic between emergent and imposed frameworks.

THE Role of the maxillary and labial palps in the feeding behaviour of schistocerca gregaria

Abstract: The role of the maxillary and labial palps in the initiation and maintenance of feeding has been analysed in female fifth-instar nymphs of Schistocerca gregaria. The ability to perceive single chemicals prior to feeding and to feed to repletion on them is markedly reduced in the absence of the palps. Increasing the sensory input of suboptimal diets by providing an attractive odour results in an increased meal length in insects without palps but not in controls. Insects without their palps reared on a diet of lettuce and bran eat relatively less bran and more lettuce than do the controls, although the total volume of food ingested is the same. The smaller dry weight of food consumed as a result of this greater lettuce intake results in a significantly smaller dry weight gain over the fifth instar. ZUSAMMENFASSUNG DIE ROLLE DER MAXILLAR- UND LABIALPALPEN BEIM FRASSVERHALTEN VON SCHISTOCERCA GREGARIA. Bei Funftlarven von Schistocerca gregaria wurde analysiert, welche Rolle die Maxillar- und Labialpalpen beim Frassbeginn und wahrend des Fressens spielen. Palpenlose Insekten nahmen einzelne Chemikalien vor dem Fressen weniger wahr und frassen auch weniger als Kontrolltiere. Die sensorische Qualitat suboptimalen Futters konnte durch einen attraktiven Geruch verbessert werden, was zu verlangerter Fresszeit bei palpenlosen Insekten, nicht aber bei Kontrolltieren, fuhrte. Palpenlose Insekten, die auf einer Diat von Salat und Kleie gehalten wurden, frassen weniger Kleie und mehr Salat als Kontrolltiere, wobei das Volumen der aufgenommenen Nahrung gleich blieb. Durch den erhohten Salatkonsum wurde die Trockensubstanzmenge der aufgenommenen Nahrung vermindert. Als Folge davon nahmen die Tiere wahrend des funften Larvenstadiums gesichert weniger an Trockensubstanz zu als Kontrolltiere.

Multiple Probe Frequency Acoustic Reflex Measurements

Abstract: Acoustic reflex impedance measurements are made on forty-seven normal and two otosclerotic ears using fixed probe frequencies from 220 to 2000 Hz. In general, the reflex increases the middle ear impedance up to 700 Hz probe frequency and decreases it thereafter. It is postulated that this characteristic is related to removal of the cochlear fluid resistance due to stapes decoupling. At one probe frequenc, in the range 500–900 Hz, the reflex of 50% of the normal ears has either a diphasic pattern or shows no change in the impedance vector length. The accompanying phase change is always monophasic. In the otosclerotic ear the diphasic reflex is present for every probe frequency. These factors should be taken into account when probe frequencies greater than 220 Hz are used for reflex measurement.

An empirical analysis of COBOL programs

Abstract: This paper describes results obtained from a static analysis of 340 COBOL programs collected from commercial and industrial installations. The analysis was performed by a syntax analyser designed specifically to analyse source program statements, gather detailed information and produce a report on the definition and use of data and language in the programs analysed.

Pupils’ Attitudes to the Social Implications of Science

Abstract: Summaries English Attitude statements, mostly concerned with the social implications of science, were administered to 2100 pupils of age 14+. The sample was divided into the top 25oO ('GCE') and the next 30‐40oo ('REST') of the ability range and further divided by sex and by coeducation and single‐sex education. Factor analysis yielded measures of five independent attitudes to (1) science as a school subject (SUBATT) and to its implications (SOCATT) regarding (2) aesthetic/humanitarian issues; (3) practical benefits (4) value to the state for money invested (S) the activities of scientists. The attitude scores were correlated with the biology, chemistry and physics choices made at this age and with liking for these subjects’ teachers. There were 26/60 significant but low overall correlations with physics and chemistry choices, but only 5/30 for biology. A further 26 significant correlations arose either at high or low teacher liking, the former predominating with boys and the latter with girls. A Kruskal‐...

Electron spin resonance study in P2O5-MoO3 and P2O5-MoO3-CaO glasses

Abstract: ESR spectra of the glass systems P2O5-MoO3 and P2O5-MoO3-CaO are presented. The electron spin resonance results showed a strongly exchange-narrowed interaction with the [Mo5+]/[Mo6+] ratio and line shapes independent of temperature over the range 77 to 300 K. This result supports the concept of temperature-dependent mobility of the carriers and an unchanged paramagnetic site over this temperature range. The more important difference between the spectra of the binary and ternary glasses is that in the former with an increase in MoO3 content the concentration of Mo5+ ions decreases but in ternary glasses it is reversed, i.e. the ion concentration of Mo5+ increases with increase in MoO3 content.

The Influence of the Brain Hormone on Retention of Blood in the Mid-Gut of the Mosquito Aedes aegypti (L.) III. The Involvement of the Ovaries and Ecdysone

Abstract: Most female mosquitoes require a blood-meal in order to produce mature oocytes. An egg development neurosecretory hormone (EDNH), which is produced in the medial neurosecretory cells (m.n.c.) of the brain and stored in the corpus cardiacum, is released into the haemolymph following the ingestion of blood and is essential for the promotion of ovarian development to maturity. It has been shown that a factor from the m.n.c., presumably EDNH, is necessary if the blood-meal is to be retained in the mid-gut until the oocytes approach maturity. The present paper shows that retention is not a direct result of the action of EDNH, but is dependent on the ovaries and may well involve ecdysone. Removal of the ovaries before a blood-meal leads to early haem-defaecation, but delay can be restored by injection of ecdysterone. Sub-threshold feeders and mosquitoes decapitated immediately after the intake of blood, each of which would be expected to eliminate the blood-meal early, also show a delay in the onset of haem-defaecation when injected with ecdysterone. Further, both in ovariectomized insects and sub-threshold feeders the time of onset of haem-defaecation is associated with the dose of ecdysterone given.

Improved orders of approximation derived from interpolatory cubic splines

Abstract: Lets be a cubic spline, with equally spaced knots on [a, b] interpolating a given functiony at the knots. The parameters which determines are used to construct a piecewise defined polynomialP of degree four. It is shown thatP can be used to give better orders of approximation toy and its derivatives than those obtained froms. It is also shown that the known superconvergence properties of the derivatives ofs, at specific points of [a, b], are all special cases of the main result contained in the present paper.

Orthotropic elastic moduli for left ventricular mechanical behaviour

Abstract: The determination of numerical values for the elasticity of the myocardium is a prerequisite for any accurate analysis of the left ventricle. Such values as are normally quoted are for a modulus of elasticity for an isotropic homogeneous model. Here some current suggestions for the modulus of elasticity are collated and a further analysis for values on the assumption of an orthotropic left ventricle is presented.

The electroforming of thin films of polypropylene

Abstract: It is shown that on exceeding a threshold applied voltage, thin films of evaporated polypropylene in the form of a sandwich between metal electrodes (aluminium or copper) undergo an electroforming process. There is a resultant augmented current, the development at higher voltages of differential negative resistance. and the samples act as emitters of electrons into a vacuum. The results are consistent with a theory based on the generation of conducting filaments during the forming process.

Extracting an Education from a Course of Instruction

Abstract: Instruction is a valid and useful aspect of education, although for meaningful and valued learning to take place there must be some reorganization of the material by the learner. Psychological tools which have been offered to the learner in the past to bring into his awareness the structure of his models and his model-building facilities have been on the whole unhelpful. The repertory grid is one such tool which with the new methods of computer analysis developed by the authors has been transformed into a sensitive instrument that allows an individual to form a model of any topic he wishes in terms of his personal constructs. The computer programs FOCUS, PEGASUS, MINUS, CORE, SOCIOGRIDS and ARGUS are briefly described.

A Novel Technique for the Sampling and Gas Chromatographic Analysis of Vapours

Abstract: A conventional pyrolysis gas chromatography system has been adapted to the analysis of vapours. A Curie point pyrolysis wire is used as a holder for granular active carbon on which the sample can be adsorbed. Desorption is achieved in the pyrolysis unit, but no pyrolysis occurs. The present study reports on the completeness of adsorption by the sampler and on the degree of release of adsorbate from it.