Showing papers by "University of Liverpool published in 1989"

Development and application of a metric on semantic nets

Abstract: Motivated by the properties of spreading activation and conceptual distance, the authors propose a metric, called distance, on the power set of nodes in a semantic net. Distance is the average minimum path length over all pairwise combinations of nodes between two subsets of nodes. Distance can be successfully used to assess the conceptual distance between sets of concepts when used on a semantic net of hierarchical relations. When other kinds of relationships, like 'cause', are used, distance must be amended but then can again be effective. The judgements of distance significantly correlate with the distance judgements that people make and help to determine whether one semantic net is better or worse than another. The authors focus on the mathematical characteristics of distance that presents novel cases and interpretations. Experiments in which distance is applied to pairs of concepts and to sets of concepts in a hierarchical knowledge base show the power of hierarchical relations in representing information about the conceptual distance between concepts. >

The multidimensional nature of schizotypal traits: A factor analytic study with normal subjects.

Abstract: Fourteen published scales of psychotic traits or symptoms (measuring various delusional states, magical ideation, perceptual aberration, disposition towards hallucination, hypomanic personality, schizotypal personality, borderline personality and anhedonia) were combined with the Eysenck Personality Questionnaire to form a Combined Schizotypal Traits Questionnaire (CSTQ) which was administered to 180 normal subjects. Two factor analyses were carried out on the scale scores. The first analysis excluded symptom scores derived from the Delusions Symptoms States Inventory of Foulds and Bedford and yielded a three-factor solution which appeared to measure traits relating to (i) positive psychotic symptomatology; (ii) negative psychotic symptomatology; and (iii) aspects of schizotypy involving social anxiety and cognitive disorganization. The Foulds scales were included in the second analysis which yielded a four-factor solution. The first three factors were similar to those obtained from the first analysis; the fourth factor seemed to measure an asocial component of schizotypy. This last factor was mainly accounted for by the P scale from the EPQ. These results support previous findings suggesting that different schizotypy scales relate to different underlying aspects of schizophrenia. The findings also indicate that psychotic traits are distributed along at least three dimensions.

The underground economies : tax evasion and information distortion

Abstract: List of contributors Preface Introduction Edgar L. Feige Part I. The Meaning, Measurement and Policy Implications of the Underground Economies: 1. The meaning and measurement of the underground economy Edgar L. Feige 2. Information distortions in social systems: the underground economy and other observer-subject-policymaker feedbacks Robert R. Alford and Edgar L. Feige 3. Policy illusion, macroeconomic instability and the unrecorded economy Robert T. McGee and Edgar L. Feige 4. How large (or small) should the underground economy be? Bruno Frey Part II. The Underground Economy in Western Developed Nations: Measurement in Different Laboratories: 5. Monetary perspective on underground economic activity in the United States Richard D. Porter and Amanda S. Bayer 6. The unrecorded economy and the national income accounts in the Netherlands: a sensitivity analysis G. A. A. M. Broesterhuizen 7. Assessing the underground economy in the United Kingdom Michael O'Higgins 8. The underground economy in the Federal Republic of Germany: a preliminary assessment Enno Langfeldt 9. The underground economy in Sweden Ingemar Hansson 10. The irregular economy of Italy: a survey of contributions Bruno Contini 11. The hidden economy in Norway with special emphasis on the hidden labor market Arne Jon Isachsen and Steiner Strom 12. Canada's underground economy Rolf Mirus and Roger S. Smith 13. The underground economy in France Philippe Barthelemy Part III. The Underground Economy Under Central Planning: 14. The Soviet second economy in a political and legal perspective F. J. M. Feldbrugge 15. Second economy and socialism: the Hungarian experience Istvan R. Gabor Bibliography.

Pulsatile intracellular calcium release does not depend on fluctuations in inositol trisphosphate concentration

Abstract: Many hormones, neurotransmitters and growth factors evoke in their target cells oscillations in the free internal Ca2+ concentration [( Ca2+]i). In electrically non-excitable cells these fluctuations are due to periodic release of Ca2+ from intracellular reservoirs, stimulated by the internal messenger inositol trisphosphate (InsP3). Most models at present invoke fluctuating levels of InsP3 as a key component in generating the oscillations in [Ca2+]i. InsP3 injected into intact cells evokes irregular and transient oscillatory Ca2+-dependent current responses, but the intracellular InsP3 concentration is not constant in such experiments. Here we monitor changes in [Ca2+]i by measuring Ca2+-activated Cl- current in single internally perfused mouse pancreatic acinar cells and show that acetylcholine (ACh), acting through muscarinic receptors, evokes regular and repetitive current pulses which are mimicked by InsP3 applied through a patch pipette. To exclude the possibility that InsP3 is periodically phosphorylated or degraded, we replaced it by the non-metabolizable InsP3 analogue inositol trisphosphorothioate (InsPS3), which also evokes regular pulses of Ca2+-activated Cl- current. These effects are independent of external Ca2+, but abolished by high intracellular concentrations of a Ca2+-chelator. We conclude that repetitive pulses of intracellular Ca2+ release occur even when the concentration of InsP3 is constant.

A role for calpactin in calcium-dependent exocytosis in adrenal chromaffin cells

Abstract: Stimulation of bovine adrenal chromaffin cells results in a rise in the concentration of cytosolic calcium which triggers the release of catecholamines by exocytosis. Several cytosolic proteins that bind to secretory granule membranes in a calcium-dependent manner have been implicated in exocytosis and some belong to a family of calcium-binding proteins, the annexins. One of these, calpactin, is a tetramer consisting of two heavy and two light chains (relative molecular masses 36,000 and 10,000 respectively) and can aggregate and fuse membranes in vitro in the presence of arachidonic acid. Calpactin is found at the cell periphery and is phosphorylated when chromaffin cells are stimulated. We show here that both calpactin and calpactin heavy chain (p36) reconstitute secretion in permeabilized chromaffin cells in which secretion has been reduced as a result of leakage of cellular components. This effect is inhibited by an affinity-purified antibody against p36. Secretion from permeabilized cells is inhibited by a synthetic annexin-consensus peptide, but not by a nonspecific hydrophobic peptide; this inhibition is reversed by p36. Our results indicate that either calpactin or p36 is essential for exocytosis.

Periparturient diseases and their effect on reproductive performance in five dairy herds.

Abstract: The incidence of periparturient diseases and their effects on the calving to first service interval, the calving to conception interval and the mean number of services per conception were recorded in five Friesian-Holstein herds in the United Kingdom. The incidence rates of milk fever, milk fever followed by endometritis, retained fetal membranes, endometritis after retained fetal membranes, endometritis, or ovarian cysts, were 7.5, 1.4, 1.3, 3.3, 10.1 and 6.7 per cent, respectively, and the affected cows had significantly (P less than 0.05) extended calving to conception intervals (13, 66, 25, 51, 31 and 64 days, respectively) compared with herd-mates. Calving to first service intervals and services per conception were also adversely affected. In spite of treatment, milk fever, endometritis and ovarian cysts had a considerable impact on fertility. Improved methods of treatment and, or, prevention are clearly required.

Synchroneity of climatic change and extinctions in the Late Triassic

Abstract: Although the Late Triassic was a time of widespread aridity, evidence exists for a significant increase in rainfall during the middle to late Carnian. Upper Triassic playa-lake sediments were interrupted by late Carnian fluviatile sandstones with erosive bases and high kao-linite/illite ratios. There was also an increase in the clastic component of marine sequences during this interval. Middle and upper Carnian marine carbonates show an extreme depletion in δ 13 C values, consistent with increased fresh-water influx. Large-scale karstic phenomena in limestone areas subaerially exposed during the Late Triassic are a further indication of increased rainfall. Important faunal and floral changes occurred during the Carnian-Norian interval; marine invertebrate turnover was greatest at the lower/middle Carnian boundary, and terrestrial extinctions were concentrated at the Carnian/Norian boundary. The cause of this Carnian pluvial episode may have been related to the rifting of Pangea, through disruption of atmospheric and oceanic circulation patterns, eustatic changes, or the effects of volcanism associated with rifting. A change in surface ocean temperature, salinity or pH, or habitat loss may have caused the decline of many shallow-marine invertebrates at the start of the middle Carnian; a return to arid conditions at the Carnian/Norian boundary would account for the turnover among terrestrial vertebrates and plants.

Persecutory delusions and attributional style

Abstract: Seventeen psychotic patients with persecutory delusions were matched against depressed and normal controls and assessed for magical ideation, locus of control and attributional style. The deluded and depressed patients were found to make global and stable attributions when compared to the normal subjects. However, the deluded patients, in contrast with both control groups, made excessively external attributions for negative events and internal attributions for positive events. Highly significant differences were observed between the deluded group and the two control groups on magical ideation and on the ‘powerful others’ subscale of the locus of control questionnaire. Both psychiatric groups differed from the normal control group on ‘chance’ locus of control and a significant difference was observed between the persecuted and normal subjects on the ‘internality’ subscale of the questionnaire. The implications of these findings for the understanding and treatment of paranoid delusions are discussed.

Isokinetic dynamometry. Applications and limitations.

Abstract: Isokinetic contraction is the muscular contraction that accompanies constant velocity limb movements around a joint. The velocity of movement is maintained constant by a special dynamometer. The resistance of the dynamometer is equal to the muscular forces applied throughout the range of movement. This method allows the measurement of the muscular forces in dynamic conditions and provides optimal loading of the muscles. However, during movements in the vertical plane, the torque registered by the dynamometer is the resultant torque produced by the muscular and gravitational forces. The error depends on the angular position and the torque potential of the tested muscle group. Several methods have been developed for the correction of gravitational errors in isokinetic data. The torque output also contains artefacts that are associated with the inertial forces during acceleration and deceleration periods before the development of the constant preset angular velocity. For an accurate assessment of muscle function, only constant velocity data should be analysed. The most frequently used isokinetic parameters are the maximum torque and the angular position where it was recorded, the torque output at different angular velocities of movement, the torque ratio of reciprocal muscle groups and the torque output during repeated contractions. The unique features of isokinetic dynamometry are optimal loading of the muscles in dynamic conditions and constant preselected velocity of movement. These features provide safety in the rehabilitation of patients with muscular and ligamentous injuries. Isokinetic dynamometry has also been used for the training of various muscle groups in order to improve the muscular performance in dynamic conditions. The movement velocity of different activities can be simulated during training in order to improve the training effect. Data acquisition and analysis have been improved by using computer systems interfaced to isokinetic dynamometers. Recently developed computer systems provide correction for gravitational and inertial errors, accurate computation of isokinetic parameters and real-time display of the torque output.

Evolution and stress-genotypic and phenotypic components

Abstract: Since stress can be defined as anything which reduces growth or performance, it follows that, if appropriate genetic variability is present, classical evolutionary changes in populations are to be expected in any situation where a consistent stress is occurring. There is now considerable evidence for such evolution, producing constitutive adaptations in plants in response to stress, which are specific to the stress concerned. Stress may however operate in a temporary or fluctuating manner. In these situations, facultative adaptations, able to be produced within a single genotype through phenotypic plasticity, will be more appropriate. Very different specific phenotypic response systems, both morphological or physiological, can be found in plants in relation to different fluctuating stresses, operating over a wide range of time scales. These response systems are under normal genetic control and appear to be products of normal evolutionary processes. They can however have quite complex features, analogous to the behavioural response systems in animals.

Localization and heterogeneity of agonist-induced changes in cytosolic calcium concentration in single bovine adrenal chromaffin cells from video imaging of fura-2.

Abstract: Temporal and spatial changes in the concentration of cytosolic free calcium ([Ca2+]i) in response to a variety of secretagogues have been examined in adrenal chromaffin cells using digital video imaging of fura-2-loaded cells. Depolarization of the cells with high K+ or challenge with nicotine resulted in a rapid and transient elevation of [Ca2+]i beneath the plasma membrane consistent with Ca2+ entry through channels. This was followed by a late phase in which [Ca2+]i rose within the cell interior. Agonists that act through mobilization of inositol phosphates produced an elevation in [Ca2+]i that was most marked in an internal region of the cell presumed to be the site of IP3-sensitive stores. When the same cells were challenged with nicotine or high K+, to trigger Ca2+ entry through voltage-dependent channels, the rise in [Ca2+]i was most prominent in the same localized region of the cells. These results suggest that Ca2+ entry through voltage-dependent channels results in release of Ca2+ from internal stores and that the bulk of the measured rise in [Ca2+]i is not close to the exocytotic sites on the plasma membrane. Analysis of the time courses of changes in [Ca2+]i in response to bradykinin, angiotensin II and muscarinic agonists showed that these agonists produced highly heterogeneous responses in the cell population. This heterogeneity was most marked with muscarinic agonists which in some cells elicited oscillatory changes in [Ca2+]i. Such heterogeneous changes in [Ca2+]i were relatively ineffective in eliciting catecholamine secretion from chromaffin cells. A single large Ca2+ transient, with a component of the rise in [Ca2+]i occurring beneath the plasma membrane, may be the most potent signal for secretion.

A Kainate Receptor Linked to Nitric Oxide Synthesis from Arginine

Abstract: In slices of young rat cerebellum, the glutamate analogue kainate induced a large accumulation of cyclic GMP, which was inhibited by non-TV-methyl-D-aspartate antagonists. Quisqualate and a-amino-3-hydroxy-5-methyl-4-isoxazoIepropionate evoked only small cyclic GMP responses and inhibited the effect of kainate. When tested in cerebellar cell suspensions, glutamate was also a potent antagonist of the cyclic GMP response to kainate. Superoxide dismutase enhanced the response in the isolated cells, whereas haemoglobin and methylene blue were inhibitory. The response in slices was Ca2+ dependent, augmented by arginine, and inhibited by l-NG-mono-methylarginine in a manner that could be reversed by additional arginine. It is concluded that stimulation of kainate receptors leads to activation of the enzyme that synthesises nitric oxide from arginine and that activation of soluble guanylate cyclase by the released nitric oxide accounts for the cyclic GMP generation.

Associations between types of lameness and fertility

Abstract: Four hundred and twenty-seven cases of first-reported foot lameness were recorded in 17 dairy herds in Somerset during the winter housing period. Lameness was classified into three categories: sole ulceration, digital disease (white line abscess, foreign bodies in the sole and pricked or punctured sole), and interdigital disease (lesions of the skin between claws and heel including foul in the foot, interdigital fibroma and dermatitis). In addition, a 'clinical effect score' was calculated to take account of the severity of lameness, the structures involved and the time for which the cows were clinically affected. The fertility records of lame cows were compared with those of the healthy cows nearest in parity and stage of lactation. In the lame cows the interval from calving to first service was four days longer, and the interval from calving to conception was 14 days longer than in the control cows, the pregnancy rate to first service was 46 per cent (controls 56 per cent), 2.14 services were required per conception (controls 1.72) and 16 per cent of lame cows were culled (controls 5 per cent). Lameness, first reported in the period 36 to 70 days after calving, was associated with a significant (P less than 0.01) increase in the interval from calving to first service of eight days; and sole ulceration, in the period 71 to 120 days after calving, was associated with an increase of 11 days (P less than 0.05). Lameness in all periods up to 120 days after calving was associated with significantly increased intervals from calving to conception (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of two distinct Ca2+-ATPase-like proteins and their relationships to the agonist-sensitive calcium store in adrenal chromaffin cells.

Abstract: MANY cellular functions are regulated by activation of cell-surface receptors that mobilize calcium from internal stores sensitive to inositol 1,4,5-trisphosphate (Ins(l,4,5)P3) (ref. 1). The nature of these internal calcium stores and their localization in cells is not clear and has been a subject of debate. It was originally suggested2–5 that the Ins(l,4,5)P3-sensitive store is the endoplasmic reticulum, but a new organelle, the calciosome, identified by its possession of the calcium-binding protein, calsequestrin6, and a Ca2+-ATPase-like protein7 of relative molecular mass 100,000 (100K), has been described as a potential Ins(l,4,5)P3-sensitive calcium store. Direct evidence on whether the calciosome is the Ins(l,4,5)P3-sensitive store is lacking. Using monoclonal anti-bodies raised against the Ca2+-ATPase of skeletal muscle sarcoplasmic reticulum8, we show that bovine adrenal chromaffin cells contain two Ca2+-ATPase-like proteins with distinct subcellular distributions. A 100K Ca2+-ATPase-like protein is diffusely distributed, whereas a 140K Ca2+-ATPase-like protein is restricted to a region in close proximity to the nucleus. In addition, Ins(l,4,5)P3-generating agonists result in a highly localized rise in cytosolic calcium concentration ([Ca2+]i) initiated in a region close to the nucleus, whereas caffeine results in a rise in [Ca2+]i throughout the cytoplasm. Our results indicate that chromaffin cells possess two calcium stores with distinct Ca2+-ATPases and that the organelle with the 100K Ca2+-ATPase is not the Ins(l,4,5)P3-sensitive store.

Galanin activates nucleotide-dependent K+ channels in insulin-secreting cells via a pertussis toxin-sensitive G-protein.

Abstract: The effects of galanin (7-70 nM) on ATP-sensitive K+ channels (KATP channels), membrane potential and the release of insulin have been studied in the insulinoma cell line, RINm5F. Single-channel currents have been recorded from excised outside-out membrane patches as well as intact insulin-secreting cells and it is shown that galanin, added to the outside of the membrane, specifically activates KATP channels. Studies carried out using the fluorescent probe bisoxonol demonstrate that galanin hyperpolarizes RINm5F cells. Galanin was also found to abolish glyceraldehyde-stimulated immunoreactive insulin release from the insulinoma cells. Both the galanin-evoked hyperpolarization and inhibition of insulin release were abolished in cells pre-exposed to pertussis toxin. The possibility that the gating of KATP channels could be mediated by a G-protein was studied in patch-clamp experiments by adding F- to the solution bathing the inside of the cell membranes (open-cell), in order to generate the alumino-fluoride complex AlF4-. F- (1-10 mM) evoked dose-dependent activation of KATP channels and this effect was fully reversible. F- was also able to activate K+ channels inhibited by ATP. That the fluoride activation of KATP channels is mediated by the complex AlF4- was indicated by experiments in which AlCl3 (10 microM) was found to enhance further the activation of K+ channels evoked by 1 mM F- and by results showing that F(-)-stimulation of KATP channels was (i) abolished in the continued presence of F- by the Al3+ chelator deferoxamine (0.5 mM) and (ii) could be mimicked by VO4(3-) which has a structure similar to that of the AlF4- complex.

Pharmacokinetics of halofantrine in man: effects of food and dose size.

Abstract: 1. Plasma concentrations of halofantrine (Hf) and its putative principal plasma metabolite desbutyl halofantrine (Hfm) have been measured in two separate studies after oral administration of the hydrochloride salt. 2. Six healthy male volunteers each received single oral doses of 250, 500 and 1000 mg administered after an overnight fast. A washout period of at least 6 weeks was allowed between each dose. A further 250 mg single oral dose was administered to the same six subjects in a fasting state and after a standardised fatty meal in a randomised study, again with a washout period of at least 6 weeks. 3. AUC and maximum plasma concentration (Cmax) for Hf increased in proportion to the dose from 250-500 mg. This increase was non-proportional when the dose was increased from 500 to 1000 mg. For Hfm, in the dose range 250-500 mg, AUC but not Cmax increased in proportion in the increase in dose size. The increase in these parameters was non-proportional when the dose was increased from 500 to 1000 mg. Time to reach peak concentrations for Hf and Hfm and the elimination half-life of Hf remained unchanged across the dosage range. 4. Following a fatty meal, Cmax for Hf was increased from 184 +/- 115 micrograms l-1 (fasting) to 1218 +/- 464 micrograms l-1 (fed). AUC for Hf was increased from 3.9 +/- 2.6 mg l-1 h (fasting) to 11.3 +/- 3.5 mg l-1 h following a fatty meal.(ABSTRACT TRUNCATED AT 250 WORDS)

Defective recognition of familiar people

Abstract: Although they cannot recognise people from their faces, prosopagnosic patients are frequently able to identify people from their voices or clothing They can also retrieve information about these people in response to their name (eg De Haan, Young, & Newcombe, 1987) In contrast, we present details of a patient, BD, who, following herpes simplex encephalitis, has difficulty in identifying people from their face, their name, and their voice This seems to be a form of semantic memory impairment, and for BD it appears in the context of a more general impairment of knowledge of living things In learning tasks similar to those used by De Haan et al (1987) and Kapur, Heath, Meudell, and Kennedy (1986), however, BD shows evidence of preserved access to information concerning people that he does not recognise from their face or name The pattern of preserved access that is revealed is more extensive than that shown by De Haan et al's prosopagnosic patient PH BD shows covert knowledge of the politi

The adaptation of biological membranes to temperature and pressure: fish from the deep and cold.

Abstract: The homoeostatic regulation of bilayer order is a property of functional importance. Arguably, it is best studied in those organisms which experience and must overcome disturbances in bilayer order which may be imposed by variations in temperature of hydrostatic pressure. This article reviews our recent work on the adaptations of order in brain membranes of those fish which acclimate to seasonal changes in temperature or which have evolved in extreme thermal or abyssal habitats. The effects of temperature and pressure upon hydrocarbon order and phase state are reviewed to indicate the magnitude of the disturbances experienced by animals in their environments over the seasonal or evolutionary timescale. Acclimation of fish to altered temperature leads to a partial correction of order, while comparison of fish from extreme cold environments with those from temperate or tropical waters reveals a more complete adaptation. Fish from the deep sea also display adaptations of bilayer order which largely overcome the ordering effects of pressure.