Showing papers by "University of London published in 1978"

Impulsiveness and venturesomeness: their position in a dimensional system of personality description

Abstract: A 63-item questionnaire was constructed for the measurement of three primary personality traits; impulsiveness, venturesomeness, and empathy. This questionnaire, together with the Eysenck Personality Questionnaire which measures personality dimensions Psychoticism, Neuroticism, and Extraversion, was administered to 402 male and 787 female adult subjects. Factor analysis of the questionnaire resulted in three factors similar to those postulated, and made possible the construction of scales for their reliable measurement. These scales were then located in the three-dimensional space created by the three higher-order factors Psychoticism, Extraversion, and Neuroticism, and it was found that Venturesomeness and Impulsiveness correlated positively with Psychoticism and Extraversion, but while Venturesomeness correlated negatively with Neuroticism, Impulsiveness correlated positively with Neuroticism. Empathy only correlated with Neuroticism (positively). The three primaries were largely independent of each oth...

Can social interaction be used to measure anxiety

Abstract: 1 Pairs of male rats were placed in a test box for 10 min and the time they spent in active social interaction was scored. Maximum active interaction was found when the rats were tested under low light in a box with which they were familiar. When the light level was increased or when the box was unfamiliar active social interaction decreased. 2 Exploration (time spent sniffing objects) decreased in the same way in relation to test conditions as did social interaction. As these decreased, defecation, and freezing increased. 3 Anosmic controls showed that the decrease in social interaction across test conditions could not be attributed to olfactory changes in the partner. 4 Chlordiazepoxide (5 mg/kg) given chronically prevented or significantly reduced the decrease in social interaction that occurred in undrugged rats as the light level or the unfamiliarity of the test box was increased. Controls showed that this effect could not be entirely attributed to chlordiazepoxide acting selectively to increase low levels of responding. 5 The effect of chronic chlordiazepoxide contrasts with its action when given acutely; in the latter case it has only sedative effects. 6 Whether this test can be used as an animal model of anxiety is discussed and this test is compared with existing tests of anxiety.

A new family of mathematical models describing the human growth curve

Abstract: A new family of mathematical functions to fit longitudinal growth data is described. All members derive from the differential equation dh/dt = s(t). (h1-h) where h1 is adult size and s(t) is a function of time. The form of s(t) is given by one of many functions, all solutions of differential equations, thus generating a family of different models. Three versions were compared. All were superior to previously described models. Model 1, in which s(t) was defined by ds/dt = (s1 - s)(s - s0) was especially accurate and robust, containing only five parameters to describe growth in stature from age two to maturity. Derived "biological" parameters such as Peak Height Velocity were very consistent between these three members of the family but, in some cases, differed signficantly from previous estimates.

Properties and physiological function of a glutathione reductase purified from spinach leaves by affinity chromatography.

Abstract: Glutathione reductase (EC 1.6.4.2) was purified from spinach (Spinacia oleracea L.) leaves by affinity chromatography on ADP-Sepharose. The purified enzyme has a specific activity of 246 enzyme units/mg protein and is homogeneous by the criterion of polyacrylamide gel electrophoresis on native and SDS-gels. The enzyme has a molecular weight of 145,000 and consists of two subunits of similar size. The pH optimum of spinach glutathione reductase is 8.5–9.0, which is related to the function it performs in the chloroplast stroma. It is specific for oxidised glutathione (GSSG) but shows a low activity with NADH as electron donor. The pH optimum for NADH-dependent GSSG reduction is lower than that for NADPH-dependent reduction. The enzyme has a low affinity for reduced glutathione (GSH) and for NADP+, but GSH-dependent NADP+ reduction is stimulated by addition of dithiothreitol. Spinach glutathione reductase is inhibited on incubation with reagents that react with thiol groups, or with heavymetal ions such as Zn2+. GSSG protects the enzyme against inhibition but NADPH does not. Pre-incubation of the enzyme with NADPH decreases its activity, so kinetic studies were performed in which the reaction was initiated by adding NADPH or enzyme. The Km for GSSG was approximately 200 μM and that for NADPH was about 3 μM. NADP+ inhibited the enzyme, assayed in the direction of GSSG reduction, competitively with respect to NADPH and non-competitively with respect to GSSG. In contrast, GSH inhibited non-competitively with respect to both NADPH and GSSG. Illuminated chloroplasts, or chloroplasts kept in the dark, contain equal activities of glutathione reductase. The kinetic properties of the enzyme (listed above) suggest that GSH/GSSG ratios in chloroplasts will be very high under both light and dark conditions. This prediction was confirmed experimentally. GSH or GSSG play no part in the light-induced activation of chloroplast fructose diphosphatase or NADP+-glyceraldehyde-3-phosphate dehydrogenase. We suggest that GSH helps to stabilise chloroplast enzymes and may also play a role in removing H2O2. Glucose-6-phosphate dehydrogenase activity may be required in chloroplasts in the dark in order to provide NADPH for glutathione reductase.

Social origins of depression: a reply

Abstract: Many of the criticisms of our work made by Tennant & Bebbington in the current edition of this journal touch on issues which have already been discussed in our recent book Social Origins of Depression. We do not think that any of their points pose significant threats to our aetiological model of depression. We welcome this opportunity to clarify their questions about our data, and to use their re-analysis of our material as a basis for a wider discussion of certain general aspects of the statistical analysis and interpretation of data and the pitfalls which await the unwary.

The differentiation of invasive and non-invasive Entamoeba histolytica by isoenzyme electrophoresis

Abstract: Cultures of 85 stocks of Entamoeba histolytica were compared by electrophoretic patterns of three enzymes: glucosephosphate isomerase, phosphoglucomutase and L-malate:NADP+ oxidoreductase (oxaloacetate-decarboxylating). Four groups of E. histolytica stocks have been distinguished. 18 of these stocks were derived from individual patients with clinical amoebiasis and all of these were of one enzyme group, which did not occur among the other stocks.

Movement and turnover of soil organic matter as indicated by carbon isotope measurements

Abstract: The distribution in a New Zealand pasture soil of total organic carbon, of 13C/12C and 14C/12C ratios, up to a depth of l m and over a period of 15 yr, has been analysed to provide models for radiocarbon enrichment and organic matter turnover. For the enrichment model, the parameters of C input, rates of decomposition and diffusion down the soil profile, and turnover rates have been determined. Input rates are compatible with herbage productivity measurements; the turnover period is estimated as 63 yr, and the downward diffusivity of C is estimated at 13cm2 yr−1. The steady state model indicates that a small fraction of the soil organic C, about 16%, is relatively very old and uniformly distributed throughout the soil profile. Most of the remaining fraction of modern C, other than “bomb” C, is less than 100 yr old and decreases exponentially with increasing depth. The models provide a rational integration of empirical measurements of C input, rates of organic matter decomposition, diffusivity and turnover, enabling an unknown to be calculated from measured parameters. They also provide a rational and precise method for determining the age of soil organic matter from radiocarbon measurements and have been used to examine alternative hypotheses for the distribution of UC with depth.

Isozymic heterogeneity of Trypanosoma cruzi in the first autochthonous patients with Chagas' disease in Amazonian Brazil.

Abstract: CHAGAS' disease, in which the aetiological agent is Trypanosoma cruzi, is a principal cause of morbidity and mortality on the South American continent; at least 10 million people are said to be infected1. There is no vaccine or acceptable chemotherapy2, and insecticide control of domiciliated triatomine vectors (Hemiptera, Reduviidae) remains problematical. Human survivors of the acute phase of infection commonly develop electrocardiographic abnormalities, chronic cardiomyopathy and singular chagasic syndromes consisting of cardiomegaly, megacolon and megaoesophagus. T. cruzi from diverse mammals and vectors are morphologically indistinguishable3, and are prudently treated as a single entity pathogenic to man. However, heterogeneity has been suspected4 from behaviour in experimental hosts, discordant therapeutic trials, and, most notably, from both the enigmatic, disparate geographical distribution of chagasic syndromes among infected populations5 and the different descriptions of the pathogenesis of the heart disease6,7. By means of enzyme electrophoresis, we show here, for the first time, the heterogeneity of T. cruzi infecting man.

Low-frequency dispersion in carrier-dominated dielectri

Abstract: Some dielectric materials with large densities of low-mobility charge carriers show an anomalous low-frequency dispersion of the real and imaginary components of the complex dielectric permittivity, both varying as ω n−1 , with n close to or equal to zero. This behaviour is likely to be found in any dielectric material at sufficiently low frequencies, but is seen in particular in the presence of sufficiently high densities of charge carriers. With non-zero values of n, the behaviour is linear and the proposed interpretation involves strong dipolar interactions within the framework of a recently proposed ‘universal’ model of dielectric response. With n = 0, the process is non-linear and is interpreted in terms of the formation of Schottky barriers at electrodes which are blocking to the charge carriers in question. Neither response is readily understandable in terms of Maxwell-Wagner and similar circuit-simulation mechanisms.

What do secondary school boys understand about evolution and heredity before they are taught the topics

Abstract: Results are reported of an investigation into what schoolboys understand about evolution and heredity before they are taught these topics. This was explored by means of open-ended interviews. It was found that the boys' understanding had seven foci: evolution as a phenomenon, why evolution occurred, the process of change, adaptation, selection, chance, and inheritance. The concept of adaptation was found to be particularly well established, that of chance least so. Naturalistic and Lamarckian interpretations of evolution were predominant. Key concepts in the boys' existing knowledge were identified and incorporated into outline teaching schemes.

Drug concentration in saliva.

Abstract: It is possible to predict plasma concentrations of drugs by measurement in saliva, obviating the need for venipuncture. Using a selection of weakly acidic and basic drugs, we have found this prediction reliable for drugs largely nonionized at normal plasma pH (phenytoin, phenobarbital, antipyrine) but unreliable for ionized drugs (chlorpropramide, tolbutamide, propranolol, meperidine). Deliberate alteration of saliva flow rate and pH using different stimuli have produced twofold changes in saliva drug concentrations. Wide interindividual variability of saliva pH is the likely explanation for the inconstancy of saliva to plasma concentration ratios for ionized drugs.

Current contradictions in adolescent theory.

Abstract: This article points out two contradictions in current adolescent theory. The first is between the “classical” point of view, espousing the notion of “storm and stress,” and the “empirical” view, supporting a concept of adolescence as relatively peaceful and harmonious. The latter approach, however, creates a second contradiction because it does not explain how young people cope with the major adaptations demanded as a result of changes in their physical, social, and emotional spheres of life. The article examines the status of concepts such as the “generation gap” and “identity crisis” and concludes with the formulation of a “focal” theory of adolescence which attempts to resolve the contradictions discussed earlier.

Phytoalexin production by hypocotyls of Phaseolus vulgaris in response to constitutive metabolites released by damaged bean cells

Abstract: Phaseollin and phaseollidin were the predominant phytoalexins formed when live and dead bean hypocotyl tissues were incubated in contact with each other. The phytoalexins were produced by the live cells which were in close association with the dead tissue and were then taken up and accumulated in the dead cells. Small amounts of phytoalexins were produced when live tissues were incubated together, but none were formed when dead tissue was incubated alone. Aqueous extracts of bean tissue stimulated phytoalexin formation, suggesting that when bean cells were damaged, e.g. by freezing or maceration, a water-soluble component capable of eliciting phytoalexin formation was released. The active component was insoluble in organic solvents, was heat stable and passed through a dialysis membrane. Phaseollin and phaseollidin levels decreased in solutions which contained live tissue, dead tissue or isolated hypocotyl cell walls. Both phytoalexins were easily extracted from dead tissue or cell wall material but very little could be recovered from live tissue. The results indicate that bean cells contain a constitutive component capable of eliciting phytoalexin production. This possibility, along with the accumulation of phytoalexins by dead cells and their metabolism by living cells, is discussed in relation to the accumulation of these phytoalexins which occurs in response to infection by Colletotrichum lindemuthianum and in response to other external stimuli.

Selection for and against insecticide resistance and possible methods of inhibiting the evolution of resistance in mosquitoes

Abstract: . 1. From published data on the rate of build-up of insecticide resistance in wild populations of Anopheles culicifacies and An.stephensi, calculations have been made of the coefficients of selection which would be required to produce these rates of evolution. It is assumed in turn that the resistances might be effectively dominant, recessive or intermediate. 2. The results in the case of DDT resistance in An.culicifacies indicated that the fitness of resistant individuals was 1.28–1.51 × that of susceptibles. 3. Published data have also been examined with reference to the reversions towards susceptibility which occurred when spraying has been withdrawn. The coefficients of selection against resistance, which would be required to produce the observed rates of reversion, have been calculated. In the case of An.culicifacies and DDT these coefficients were found to be inversely related to the initial frequency of the susceptibility gene. 4. The coefficients of selection have been used to assess the feasibility of inhibiting the evolution of resistance by spraying different insecticides in the alternate sectors of a grid pattern and/or periodically releasing susceptible males. If the proportion of migrants from sector to sector were 15–30%, a “grid” system would considerably reduce the rate of evolution of resistance, but to prevent resistance from ultimately building up to high levels periodic releases would also be required. These releases need not be frequent (approximately during one month each year) if resistance is effectively recessive in the field.

The effects of polychlorinated biphenyls on plasma steroid levels and hepatic microsomal enzymes in fish

Abstract: Aroclor 1254 was administered intraperitoneally (25 mg kg body wt−1 in 1 ml of arachis oil) at weekly intervals for 4 weeks to trout and carp; arachis oil was used as the control. Activities of the following hepatic microsomal enzymes, aminopyrine demethylase, p-nitroreductase, UDP-glucuronyl-transferase and 1-leucyl-β-naphthylamide splitting enzyme were measured in both species; cytochrome P450 and microsomal protein contents were also determined. The changes in the levels of androgens, oestrogens and corticoid hormones were measured in the circulating blood of control and treated groups at weekly intervals. The blood was obtained by cardiac puncture. Results indicated (a) a significant increase in the activities of all the enzymes measured except 1-leucyl-β-naphthylamide splitting enzyme, (b) cytochrome P450 and microsomal protein contents were increased in trout, but not in carp, (c) a significant reduction in the plasma levels of androgens, oestrogens and corticoids in the treated groups, particularly at the end of the fourth week and (d) there was a correlation between increased enzyme activities and a decrease in plasma hormone levels.

Overcoming conduction failure in demyelinated nerve fibres by prolonging action potentials

Abstract: LOSS of myelin from central or peripheral myelinated nerve fibres results in conduction delays, increased refractoriness and, above all, conduction block1,2. Conduction failure could result either because a demyelinated axon is electrically inexcitable, or because the limited current available from a normal node is insufficient to excite it. Because continuous conduction along demyelinated internodes has been observed3, it seems likely that demyelinated axons in general are able to conduct impulses, but that the impedance mismatch at the junction of normal and demyelinated axon usually prevents the realisation of this ability. In support of this, two factors have been shown to improve transmission in experimental demyelination and also, transiently, in multiple sclerosis patients: lowered calcium ion concentration4,5, which reduces the threshold for nerve excitation, and lowered temperature6,7, which prolongs the action potential and thereby increases the time integral of current available to depolarise and excite the demyelinated axon. To test the suggestion that a drug that specifically prolongs the action potential might prove useful in the therapy of demyelinating diseases8, we have compared the effects of temperature and a scorpion venom on transmission in single fibres through a demyelinating lesion in rat spinal roots.

Recidivism of Sexual Offenders: A Re-Appraisal

Abstract: Few are likely to deny the relevance of the recidivism rates of sexual offenders in considering appropriate penal policy in relation to sexual offences. However, one should recognise from the outset that there are clear dangers in attaching too much importance to the recidivism rates of offenders consistently engaged in more trivial, though still criminal, behaviour; such a danger was demonstrated in the working of the sentence of preventive detention (introduced by the Prevention of Crime Act 1908) when petty but persistent offenders often received long prison sentences of preventive detention (Hammond and Chayen, 1963) which were quite disproportionate to any threat they represented to the community. On the other hand, if serious sexual offenders, such as rapists for example, were shown to repeat without exception the offence of rape, this finding could quite reasonably have important implications for penal policy. In fact we know comparatively little about the subsequent behaviour of sexual offenders and the present article stresses the limitations as well as questioning some of the assumptions of what is supposedly known on the recidivism of sexual offenders. It is important to stress that the condemnation of particular kinds of sexual behaviour is a relative matter. Certain sexual behaviour is legal in one society but not in another. Sexual behaviour which is regarded as serious in one decade may be considered as only inappropriate a decade later. For reasons of this kind we later take as our example the offence of adult males having or attempting sexual intercourse with girls under i3, for unlike some other possible examples there will probably not be much dispute about the seriousness of such behaviour. Furthermore, it is exactly the type of sexual activity where the issue of likely recidivism is rather pertinent. There is perhaps an apparent conflict in some of the views held about the recidivism of sexual offenders. On the one hand, psychiatrists on the basis of their clinical evidence probably tend to feel that sexual offenders possess a persistent tendency and are fairly likely to repeat the offence on a future occasion ; it is often overlooked that they base their views on detailed psychiatric studies of small and biased samples, for clinicians usually see offenders who are viewed as the more seriously disturbed with already a previous manifestation of the activity. On the other hand, criminologists, on the basis of more representative samples, indicate that sexual offenders, after a follow-up of three to five years, generally have a lower reconviction