Showing papers by "University of London published in 1979"

The universal dielectric response

Abstract: A brief description is given of the various manifestations of the universal fractional power law relaxation processes, which are contrasted with the classical or Debye law. It is shown that the universal law is indeed found in a remarkable variety of physical and chemical situations, and this is deemed to merit a special attempt at finding a suitably general theoretical model. Several such models are briefly described, and a novel very general approach based on the so-called energy criterion is introduced. It is concluded that it is not yet possible to establish with certainty the validity of any of the models. >

The Structure and Measurement of Intelligence

Abstract: One of psychology's outstanding successes has been the measurement of intelligence, and the demonstration that differences in intelligence, so measured, were due in large part of genetic factors. In recent years much work has been done to clarify the problem of the biological basis of these inherited differences, and work on the evoked potential in the EEG has generated important new findings in this field. We now know far more about intelligence, its inheritance, and its biological basis than we did even a few years ago.

The conditioning model of neurosis.

Abstract: The long-term persistence of neurotic symptoms, such as anxiety, poses difficult problems for any psychological theory. An attempt is made to revive the Watson-Mowrer conditioning theory and to avoid the many criticisms directed against it in the past. It is suggested that recent research has produced changes in learning theory that can be used to render this possible. In the first place, the doctrine of equipotentiality has been shown to be wrong, and some such concept as Seligman's “preparedness” is required, that is the notion that certain CS are biologically prepared to be more readily connected with anxiety responses than others. In the second place, the law of extinction has to be amended, and the law of incubation or enhancement added, according to which the exposure of the CS-only may, under certain specified conditions, have the effect of increasing the strength of the CR, rather than reducing it. The major conditions favouring incubation are (1) Pavlovian B conditioning, that is a type of conditioning in which the CR is a drive; (2) a strong UCS, and (3) short exposure of the CS-only.

Quantum interference and the quantum potential

Abstract: We re-examine the notion of the quantum potential introduced by the Broglie and Bohm and calculate its explicit form in the case of the two-slit interference experiment. We also calculate the ensemble of particle trajectories through the two slits. The results show clearly how the quantum potential produces the bunching of trajectories that is required to obtain the usual fringe intensity pattern. Hence we are able to account for the interference fringes while retaining the notion of a well-defined particle trajectory. The wider implications of the quantum potential particularly in regard to the quantum interconnectedness are discussed.

On the origin of the universal dielectric response in condensed matter

Abstract: The observed dielectric response of most materials is seldom in accord with Debye behaviour, but has been found experimentally to exhibit a remarkable ‘universality.’ It is proposed that this universality is a consequence of some ubiquitous correlated states which exhibit an infrared (IR) divergent-like response to induced transitions of the polarising species.

Serum amyloid P-component is an acute-phase reactant in the mouse

Abstract: THE acute-phase reaction in mammals is characterised by an increase in the concentration of certain plasma proteins which starts within hours or days of most forms of acute tissue damage or inflammation, and persists with chronic inflammation and malignant neoplasia1–4. Among acute-phase reactants are protease inhibitors, coagulation factors, complement components and transport proteins as well as proteins without known in vivo roles, such as the classical reactant, C-reactive protein (CRP)1–4. The pathophysiological significance of the acute-phase reaction is not known, but it is a usual accompaniment of tissue damage, and it is of clinical value in the assessment of disease activity4. We now report that in the mouse, serum amyloid P-component (protein SAP)5, which is a stable plasma protein in man6, is a major acute-phase reactant. In addition, our observations facilitate investigation of the function of protein SAP and of the pathogenesis of amyloidosis, which is a serious disease in man.

Events, Instants and Temporal Reference

Abstract: The truth of my claim: ‘It is raining’ depends on the time at which I made it It was true if and only if it was indeed raining (in my vicinity) at that time Similarly my assertion ‘it has been raining’, made at time t, is true if there was a time t′ preceding t such that it rained at t′

Non-exponential decay in dielectrics and dynamics of correlated systems

Abstract: A new model for the relaxation of a potential perturbation in dielectric materials is developed based on the correlated properties of a two-level system containing two types of decay mechanism. The time and frequency behaviour of the general relaxation process is shown to be in accord with recent experimental analyses. The technique developed to analyse the model is of general applicability in the solid, and liquid, state.

DC and AC conductivity in hopping electronic systems

Abstract: The various theories of dc and ac conductivity in materials with hopping electronic charge carriers are critically examined in the light of the available experimental evidence. The temperature dependence of the dc conductivity suggests that in most materials the transition from nearest-neighbour hopping to variable-range hopping has been observed. However the theory in this region is insufficiently developed to enable meaningful determinations of the relevant parameters to be made from experimental data. The situation with ac theory is even less satisfactory, none of the existing theories being capable of accounting adequately for the observed behaviour. Neglect of many-body interactions and of the effect of the dielectric lattice, in addition to that of the charge carriers, are seen as the principal shortcomings. It follows, then, that the question of any relationship between the dc and ac conductivities cannot be answered at present, because of the lack of reliable data and because of insufficient theoretical understanding of the carrier processes in question.

Nerve fibre topography in the retinal projection to the tectum

Abstract: The orderly layout of visual fibres in the optic nerves of cichlid fishes suggests that they are guided most of the way to the brain by contact with their neighbours. Before they reach the visual map in the tectum, however, their arrangement in the cross-section of the nerve is reorganised in a way which requires longer-range guidance.

Nitrogen fixation in coral reef sponges with symbiotic cyanobacteria

Abstract: NITROGEN FIXATION by endosymbiotic cyanobacteria (blue-green algae) results in an important input of nitrogen into terrestrial ecosystems1; however, there is as yet little information on its significance in the marine environment2,3. Symbiosis of cyanobacteria with marine animals, although rare, is known to occur in an echiuroid worm4 and in sponges from coral reefs5 and the Mediterranean6. In the present study of sponge–cyanobacterial symbioses, several sponges from a coral reef in the Red Sea were tested, using the acetylene reduction technique7, immediately after their collection on reef-based platforms for their ability to fix nitrogen. Nitrogenase activity was detected in two sponges with cyanobacteria but not in a third with no cyanobacteria. This is the first demonstration of nitrogenase activity in an animal with symbiotic cyanobacteria. In two previous reports of nitrogen fixation in marine animals, the activity was attributed to bacteria in the gut8,9. Although these preliminary experiments are not sufficient to assess the significance of cyanobacterial nitrogenase activity in sponges, it is possible that any additional fixed nitrogen would be beneficial to sponges in tropical waters which are low in available nitrogen10 and in particulate nutrients11,12.

Novel α 2 -adrenoreceptors primarily responsible for inducing human platelet aggregation

Abstract: BLOOD PLATELETS isolated from humans, in contrast to those from other mammalian species, aggregate on exposure to adrenaline or noradrenaline1. Studies using α antagonists have shown that this effect results from occupancy of an α adrenoreceptor2,3. However, Jakobs has reported that selective α agonists such as clonidine and phenylephrine bind with high affinity to the platelet α adrenoreceptor4,5, but fail either to induce an aggregation response6 or to inhibit platelet adenylate cyclase6, in contrast to the effects of natural agonists such as adrenaline1,7. Instead, such α agonists seem to act as antagonists at the platelet adrenoreceptor6. α Adrenoreceptors in other tissues have been classified as α1 (postsynaptic) or α2 (presynaptic) on the basis of their affinities for various selective α agonists and antagonists8. Jakobs6 has, however, interpreted his data on the human platelet adrenoreceptor as indicating the existence of a third category of α adrenoreceptor at which only the natural catecholamines are agonists. We report here that we have confirmed the observation that clonidine and phenylephrine are ineffective in inducing aggregation of human platelets and act as inhibitors of the response to adrenaline. However, further examination has revealed that the effects of these selective α agonists differ in certain important respects from those of selective α antagonists, thus requiring substantial modification of the thesis advanced by Jakobs6.

Aerobic performance of female marathon and male ultramarathon athletes.

Abstract: The aerobic performance of thirteen male ultramarathon and nine female marathon runners were studied in the laboratory and their results were related to their times in events ranging in distance from 5 km to 84.64 km. The mean maximal aerobic power output (VO2 max) of the men was 72.5 ml/kg·min compared with 58.2 ml/kg·min (p<0.001) in the women but the O2 cost (VO2) for a given speed or distance of running was the same in both sexes. The 5 km time of the male athletes was closely related to their VO2 max (r=−0.85) during uphill running but was independent of relative power output (%VO2 max). However, with increasing distance the association of VO2 max with male athletic performance diminished (but nevertheless remained significant even at 84.64 km), and the relationship between VO2 max and time increased. Thus, using multiple regression analysis of the form: $$\begin{gathered} 42.2 km (marathon) time (h) = 7.445 - 0.0338 \dot V{\text{O}}_{{\text{2 max}}} ({\text{ml/kg }} \cdot {\text{ min}}) \hfill \\ - 0.0303\% \dot V{\text{O}}_{{\text{2 max}}} (r = 0.993) \hfill \\ \end{gathered} $$ and $$\begin{gathered} 84.64 {\text{km (London}} - {\text{Brighton) time (h) = 16}}{\text{.998 }} - {\text{ 0}}{\text{.0735 }}\dot V{\text{O}}_{{\text{2 max}}} \hfill \\ ({\text{ml/kg }} \cdot \min ) - 0.0844\% \dot V{\text{O}}_{{\text{2 max}}} (r = 0.996) \hfill \\ \end{gathered} $$ approximately 98% of the total variance of performance times could be accounted for in the marathon and ultramarathon events. This suggests that other factors such as footwear, clothing, and running technique (Costill, 1972) play a relatively minor role in this group of male distance runners. In the female athletes the intermediate times were not available and they did not compete beyond 42.2 km (marathon) distance but for this event a similar association though less in magnitude was found with VO2 max (r=−0.43) and %VO2 max (= −0.49). The male athletes were able to sustain 82% VO2 max (range 80–87%) in 42.2 km and 67% VO2 max (range 53–76%) in 84.64 km event. The comparable figure for the girls in the marathon was 79% VO2 max (ranges 68–86%). Our data suggests that success at the marathon and ultramarathon distances is crucially and (possibly) solely dependent on the development and utilisation of a large VO2 max.

Trypanosoma brucei: miniature anion-exchange centrifugation technique for detection of low parasitaemias: adaptation for field use

Abstract: The miniature anion-exchange/centrifugation (AEC) method, originally developed for the detection of submicroscopic trypanosomaemias in laboratory rodents, has been adapted for the diagnosis of trypanosomiasis in man in the field using blood samples obtained by finger-prick. It has been tested in a survey in The Gambia. The method is shown to be highly sensitive and to fulfil the first essential criteria for exploitation in the field, namely, that it can be operated in the open air under tropical conditions, and that an adequate number of subjects can be examined in a normal working day at an acceptable cost. The method also offers two advantages over the other highly sensitive method applicable to small blood samples, the microhaematocrit buffy-coat microscopy (MBCM) method, namely, that it minimized the requirements for highly critical microscopy and provides, in the same operation, samples of diluted plasma which can be used for serological study.

A test of anxiety that distinguishes between the actions of benzodiazepines and those of other minor tranquilisers and of stimulants.

Abstract: The effects of minor tranquilisers and of stimulant drugs were studied in the Social Interaction test of anxiety in which the illuminance and unfamiliarity of the test arena are manipulated. Acute administration of sodium phenobarbitone (25 mg/kg) was without effect. Acute administration of sodium phenobarbitone (35 mg/kg) and of meprobamate (60 mg/kg) produced sedation: both locomotor activity and social interaction were reduced. On the other hand, amphetamine sulphate (2 mg/kg) and caffeine citrate (20 mg/kg) reduced social interaction, but increased locomotor activity. Chronic administration dissociated the pattern of results produced by sodium phenobarbitone (35 mg/kg) from that produced by flurazepam (0.5 mg/kg). With chronic treatment (5 days) neither drug reduced motor activity, but whereas phenobarbitone increased social interaction regardless of the test illuminance and unfamiliarity, the increase produced by flurazepam was limited to the more stressful test conditions, i.e., when the arena was unfamiliar or brightly lit.

Memory for pain

Abstract: Memory for head pain was assessed by means of the McGill Pain Questionnaire (MPQ). Sixteen neurosurgical patients were divided into two groups in order to examine the decay of memory over time; one group recalled pain after 5 days and the other recalled pain after one day and then again, after 5 days. Contrary to expectations, the recall of pain was surprisingly accurate. The memory for pain showed little decay over time. The small subgroup of patients who made specific errors when recalling their pain comprised women who had high levels of pain and affect at the initial assessment. Overall, the findings provide some welcome reassurance about the accuracy and reliability of pain reports from memory.

Conversion of a stable T-cell lesion to a progressive B-cell lesion in the pathogenesis of chronic inflammatory periodontal disease: an hypothesis.

Abstract: Changes in the host's immunological response or, alternatively, changes in the oral microflora have been implicated as possible mechanisms by which a stable lesion of chronic inflammatory periodontal disease may become a progressive lesion leading to tissue destruction and tooth loss. It has recently been established that the progressive lesion in humans can be unequivocally considered as a B-cell response. Circumstantial evidence exists which suggests that the stable lesion is in fact a T-cell-mediated mechanism. An hypothesis is presented to explain the change from a stable to a progressive state in terms of a shift from a predominantly T-cell lesion to one involving large numbers of B-cells. Mechanisms of this shift in cell populations are considered together with a discussion of possible means of preventing such a shift.

Mast cell population density, blood vessel density and histamine content in normal human skin.

Abstract: Mast cell population density was determined in normal skin from two regions of the arm of several healthy men and compared with blood vessel density and histamine concentration in the same sites. Mast cell and blood vessel counts were made in 1--1.5 micrometer thick plastic sections, by light microscopy and tissue-histamine concentrations were determined by automated fluorimetric analysis. Statistically significant correlations were found between mast cell counts, blood vessel counts and histamine content in skin from the upper arm but no similar correlations were obtained in the forearm. Anatomical differences between the two sites may have been the cause of this discrepancy. Wide variations in mast cell counts and blood vessel density were found in different sections from the same biopsy samples which confirms the notion that dermal mast cells are unevenly distributed. Analysis of variance of the mast cell counts showed that the variance between sections from different blocks from the same biopsy samples was greater than the variance between adjacent biopsies. There was also a marked variation in the histamine content between biopsy samples from sites only 2 cm apart in the same subject.

A general approach to linguistic approximation

Abstract: This paper describes a technique by which a fuzzy subset can be linguistically labelled. The technique involves the separation of a given fuzzy set into a certain number of specific subsets. The labelling is based on assignment of labels to these specific subsets and their concatenation with connectives “AND” and “OR”. The technique allows the user to specify, up to a certain number, his own primary subsets and their respective names. The input subset is also freely specified and properties like normality of input subsets do not constitute any constraint.

Melatonin, the pineal gland and human puberty

Abstract: Animal experiments have suggested that the pineal gland produces an anti-gonadotropic hormone. The hamster, for example, undergoes reproductive collapse when kept in short-day periods, an effect which is abolished by pinealectomy. Although there is little direct evidence about the endocrine role of the pineal gland in man, it has been noted that tumours of the pineal gland in young boys are associated with precocious puberty and the human pineal gland has been suggested to produce a substance that holds sexual maturation in check. This observation has been extended by Kitay, who has shown that destructive tumours are associated with precocious puberty whereas hyperactive tumours are associated with delayed puberty. However, no studies have described any change of pineal function with normal puberty. Because two pineal indoles, melatonin and methoxytryptophol, have been shown to be antigonadotropic when administered to animals, we have now measured them in schoolchildren. Our findings show that in young boys there is an abrupt fall in the concentration of melatonin with advancing development suggesting that it may play an important physiological role in the control of human puberty.

Hyperpolarizing `α2'-adrenoceptors in rat sympathetic ganglia

Abstract: 1 Receptors mediating catecholamine-induced hyperpolarization of isolated superior cervical sympathetic ganglia of the rat have been characterized by means of an extracellular recording method.2 (-)-Noradrenaline (EC(50), 1.7 +/- 0.6 muM) produced an immediate low-amplitude (< 400 muV) hyperpolarization. The hyperpolarization was increased on removal of external Ca(2+) or on reduction of external K(+) from 6 to 2 mM. Hyperpolarization was unaffected by changing the temperature from 25 degrees to 37 degrees C.3 Hyperpolarization was also produced by the following agonists (potencies relative to (-)-noradrenaline): (-)-noradrenaline 1; (+/-)-isoprenaline 0.41; (-)-phenylephrine 0.40; (+)-noradrenaline 0.13; 2-amino-6,7-dihydroxy tetrahydronaphthalene (ADTN) 0.25; dopamine 0.1; methoxamine 0.012; amidephrine 0.0015.4 Responses were antagonized by phentolamine (1 muM) but not by (+/-)-propranolol (1 muM), haloperidol (10 muM) or alpha-flupenthixol (1 muM). This suggested that hyperpolarization was mediated solely through alpha-receptor stimulation not through stimulation of beta-receptors or dopamine-receptors.5 Dose-ratio shifts produced by phentolamine varied with different agonists. The shift increased in inverse proportion to the ability of the agonists to inhibit [(3)H]-(-)-noradrenaline uptake, suggesting that uptake of agonists limited the dose-ratio shift. Cocaine and nortriptyline reduced catecholamine-induced hyperpolarization in concentrations (10 muM and 1 muM respectively) necessary to inhibit [(3)H]-(-)-noradrenaline uptake.6 Clonidine (0.01 to 1 muM), oxymetazoline (0.01 to 1 muM) and ergometrine (0.1 to 10 muM) produced a persistent, low-amplitude hyperpolarization, as though they were partial agonists. Responses to the agonists were blocked by yohimbine (1 muM) but not be prazosin (1 muM).7 It is concluded that the adrenergic cell bodies in the ganglion were hyperpolarized through activation of the same type of alpha-receptor (;alpha(2)-receptors') as those present at adrenergic nerve terminals.

Cholesterol modulates activity of calcium-dependent ATPase of the sarcoplasmic reticulum.

Abstract: BIOMEMBRANES consist of an asymmetric lipid bilayer matrix into which and around which the various proteins are situated. The proteins may be attached to the outside of the lipid bilayer (extrinsic proteins), but in many cases the proteins (intrinsic proteins) are embedded within, and can span, the bilayer. Associated with this is the idea that in many cases the lipid matrix is in a fluid condition in which the lipids are essentially above their transition temperature (Tc) and able to diffuse along the bilayer length. The perturbation introduced into the lipid bilayer by the presence of an intrinsic protein has recently been discussed2,3. Some workers4,5 have suggested that intrinsic proteins, for example the Ca2+-ATPase of the sarcoplasmic reticulum, carry with them, even when excess bulk fluid lipid occurs, a shell of immobilised lipid, referred to as an annulus, which controls the enzyme activity. The shell is said to exclude cholesterol so that cholesterol molecules do not influence the enzyme activity. We report here the use of cholesterol-enriched liposomes to reversibly vary the content of cholesterol in the sarcoplasmic membranes. We show in contrast to the previous work that as the cholesterol content of the membrane varies so does the activity of the Ca2+-ATPase.

The molecular basis for the action of some DNA-binding drugs.

Abstract: Publisher Summary This chapter focuses on drugs that interact via various types of non-bonded forces. Many of these have been the subject of intensive and increasing study over the past few decades for two principal reasons; firstly, they have proved to be powerful probes of nucleic acid structure and function, and secondly, a number of them have clinically useful chemotherapeutic properties, of which anti-cancer activity is most prominent. The social and economic impetus for developing effective agents with this property in particular has without doubt been a dominant factor in both funding research in this area and influencing its course of direction. The drugs considered in this chapter exhibit a wide spectrum of biological activity, ranging from the bacteriostatic properties of the acridines such as proflavine and the trypanocidal properties of ethidium bromide to the anti-leukemic action of daunomycin.

Hepatitis B surface antigen produced by a human hepatoma cell line.

Abstract: Infection with hepatitis B virus is associated with the appearance in the serum of a specific antigen, hepatitis B surface antigen (HBsAg), a serologically complex structure present on the coat of the double-shelled 42-nm hepatitis B virus (HBV) particle. HBsAg is also present, often in large excess, in the form of small, spherical 20–25-nm particles in the sera of infected individuals1. The serologically distinct core (HBcAg) or nucleocapsid of the 42-nm virus is 27 nm in diameter and contains double-stranded circular DNA with a molecular weight (MW) of 1.6–2.0 × 106, and an associated DNA polymerase2. A third antigen, hepatitis B e antigen (HBeAg), appears to correlate with the number of virus particles3 and the relative degree of infectivity of surface antigen-positive sera4, is frequently detected free in the serum and has been shown to be closely associated with the viral core5. Failure to propagate hepatitis B virus serially in tissue culture is a major obstacle to precise biochemical characterisation of the antigens and the development of vaccines against this important infection. The use of purified HBsAg 20–25-nm particles prepared from the sera of persistently infected donors for the immunoprophylaxis of hepatitis B is being investigated6. Such preparations have been shown to protect susceptible chimpanzees on challenge with HBV7,8. There are, however, problems associated with the collection of HBsAg positive sera from persistently infected carriers. The recent establishment of a HBsAg-producing cell line from a human hepatoma9,10 has provided an alternative source of HBsAg particles with the added advantage that both the production and quality of the antigen may be more precisely controlled. The availability of this cell line also facilitates the study of HBV gene products by biochemical methods applicable to cultured cells, in the absence of contaminating serum proteins. In this study, the 20–25-nm HBsAg particles produced by these cells were characterised and compared with those derived from the sera of persistently infected human carriers.