Showing papers by "University College London published in 1986"
Book•
06 Mar 1986TL;DR: In this paper, the authors present a list of symbols for verb-verb communication in the context of Verbal Communication, including the following: preface to second edition, preface and postface to first edition.
Abstract: Preface to Second Edition. List of symbols. 1. Communication. 2. Inference. 3. Relevance. 4. Aspects of Verbal Communication. Postface. Notes to First Edition. Notes to Second Edition. Notes to Postface. Bibliography. Index.
5,408 citations
TL;DR: This paper reviewed the extensive literature on response bias, and particularly dissimulating a socially desirable response to self-report data, and found that social desirability is a relatively stable, multidimensional trait rather than a situationally-specific response set.
968 citations
TL;DR: NIR spectrophotometry provides valuable quantitative data at the cotside for the management of sick infants and for exploring the pathophysiology of damage to the brain.
903 citations
TL;DR: In both cases, it is found that in order for gene flow to be significantly reduced over much of the genome, hybrids must be substantially less fit, and the number of genes involved in building the barrier must be so large that the majority of other genes become closely linked to some locus which is under selection.
Abstract: Suppose that selection acts at one or more loci to maintain genetic differences between hybridising populations. Then, the flow of alleles at a neutral marker locus which is linked to these selected loci will be impeded. We define and calculate measures of the barrier to gene flow between two distinct demes, and across a continuous habitat. In both cases, we find that in order for gene flow to be significantly reduced over much of the genome, hybrids must be substantially less fit, and the number of genes involved in building the barrier must be so large that the majority of other genes become closely linked to some locus which is under selection. This conclusion is not greatly affected by the pattern of epistasis, or the position of the marker locus along the chromosome.
641 citations
TL;DR: The conditional average frequency can be calculated from the distribution of allele frequencies, a measure of the spread of this distribution, and so is analogous to the standardised variance, FST.
Abstract: The conditional average frequency of rare alleles has been shown in simulations to provide a simple and robust estimator of the number of individuals exchanged between local populations in an island model (Nm). This statistic is defined as the average frequency of an allele in those samples in which the allele is present. Here, we show that the conditional average frequency can be calculated from the distribution of allele frequencies. It is a measure of the spread of this distribution, and so is analogous to the standardised variance, FST. Analytic predictions for the island model of migration agree well with the corresponding simulation results. These predictions are based on the assumption that the rare alleles found in samples have reached a "quasi-equilibrium" distribution. As well as relating the conditional average frequency to the underlying allele frequency distribution, our results provide a more accurate method of estimating Nm from the conditional average frequency of private alleles in samples of different sizes.
580 citations
TL;DR: A framework for examining the way in which bilinguals control the use of their two languages is proposed, compatible with current findings, makes predictions about the performance of normal as well as brain-damaged bilinguals, and explains some previously puzzling findings.
567 citations
TL;DR: Despite the general fall in mortality the relative disadvantage of manual compared with non-manual classes has increased for each of these 4 cause groups and the regional differences in CHD mortality persist.
528 citations
TL;DR: A survey of five diagnostic enzyme loci across the hybrid zone near Cracow in Southern Poland to estimate the dispersal rate, selection pressures, and numbers of loci which maintain this zone suggests that the zone is maintained largely by selection against hybrids.
Abstract: The fire-bellied toads Bombina bombina and B. variegata differ extensively in biochemistry, morphology, and behavior. We use a survey of five diagnostic enzyme loci across the hybrid zone near Cracow in Southern Poland to estimate the dispersal rate, selection pressures, and numbers of loci which maintain this zone. The enzyme clines coincide closely with each other and with morphological and mitochondrial DNA clines. Although the zone lies on a broad transition between environments suitable for bombina and variegata, the close concordance of diverse characters, together with increased aberrations and mortality in hybrids, suggest that the zone is maintained largely by selection against hybrids. There are strong "linkage disequilibria" between each pair of (unlinked) enzyme loci (R = 0.129 [2-unit support limits: 0.119-0.139]). These are probably caused by gene flow into the zone, and they give an estimate of dispersal (σ = 890 [790-940] m gen-½ ). The clines are sharply stepped, with most of the change occurring within 6.15 (5.45-6.45) km, but with long tails of introgression on either side. This implies that the effective selection pressure on each enzyme marker (due largely to disequilibrium with other loci) is s* = 0.17 (0.159-0.181) at the center but that the selection acting directly on the enzyme loci is weak or zero (se < 0.0038). The stepped pattern implies a barrier to gene flow of 220 (48-415) km. This would substantially delay neutral introgression but would have little effect on advantageous alleles; the two taxa need not evolve independently. Strong selection is needed to maintain such a barrier: hybrid populations must have their mean fitness reduced by a factor of 0.65 (0.60-0.77). This selection must be spread over a large number of loci to account for the concordant patterns and the observed cline widths (N = 300 [80-2,000]).
520 citations
TL;DR: Lead-210 and radium-226 measurements by direct gamma assay can now provide a record of changing concentrations in lake sedimemts sufficiently reliable and precise to form a suitable basis for age/depth and drysedimentation-rate calculations as mentioned in this paper.
Abstract: Lead-210 and radium-226 measurements by direct gamma assay can now provide a record of changing concentrations in lake sedimemts sufficiently reliable and precise to form a suitable basis for age/depth and drysedimentation-rate calculations. There are additional benefits in terms of non destructive sample preparation and simultaneous assay for other environmentally significant gamma-emitting radioisotopes (e.g. 137Cs and 241 Am). Results from L. Fleet, S. W. Scotland illustrate the value of this approach especially in lakes with disturbed catchments where variable input of supported 210Pb has occurred.
516 citations
TL;DR: It is concluded that a large part of the improvement in the ability to lift weights was due to an increased ability to coordinate other muscle groups involved in the movement such as those used to stabilise the body.
Abstract: The central changes associated with a period of strength training have been investigated in a group of 32 young healthy volunteers. Subjects participated in one of three 12 week training programmes, which required different degrees of skill and coordination. Study 1 consisted of unilateral isometric training of the quadriceps with the contralateral leg acting as a control, the apparatus providing firm back support and a lap strap. In Study 2 training consisted of unilateral concentric leg-extension with back support and hand-grips. In Study 3 subjects performed bilateral leg-extension with no back support. Measurements of maximum voluntary isometric strength were made at 2–3 week intervals and a continual record was kept of the weights lifted in Studies 2 and 3. The largest increase in isometric force was seen for the trained leg in Study 1 (approximately 40%). There was no significant change in strength in the contralateral untrained leg. In Studies 2 and 3 there was a large increase in training weights (about 200%) associated with smaller increase in isometric force (15–20%). It is concluded that a large part of the improvement in the ability to lift weights was due to an increased ability to coordinate other muscle groups involved in the movement such as those used to stabilise the body. The importance of these findings for athletic training and rehabilitation is discussed.
495 citations
TL;DR: This study traced the afferent and efferent connections of the inferior region of area 6 by injecting small amounts of wheat germ agglutinin conjugated to horseradish peroxidase and fluorescent tracers into restricted parts of inferior area 6 and in physiologically determined fields of area 4.
Abstract: The rostral part of the agranular frontal cortex (area 6) can be subdivided on the basis of its cytoarchitecture, enzymatic properties, and connections into two large sectors: a superior region, lying medial to the spur of the arcuate sulcus, and an inferior region, lying lateral to it. In this study we traced the afferent and efferent connections of the inferior region of area 6 by injecting small amounts of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) and fluorescent tracers (fast blue and diamidino yellow) into restricted parts of inferior area 6 and in physiologically determined fields of area 4. There is an ordered topographic pattern of connections between inferior area 6 and area 4. The region near the spur of the arcuate sulcus (hand field) projects to the area 4 hand field while the lateral part of inferior area 6 (mouth field) is connected with the corresponding field in area 4. The organization of the connections between the two fields is, however, different. The hand fields in area 6 and 4 have direct reciprocal projections, whereas the mouth field in the postarcuate cortex relays information to area 4 via a zone intermediate between the arcuate and the central sulcus. This zone corresponds to the cytochrome oxidase area F4 (Matelli, Luppino, and Rizzolatti: Behav. Brain Res. 18: 125-137, '85). The inferior area 6 also has topographically organized connections with the supplementary motor area. The inferior area 6 receives and sends fibers to a series of discrete cortical areas located in the lower cortical moiety (Sanides: The Structure and Function of the Nervous Tissue, Vol. 5. New York: Academic Press, pp 329-453, '72). These areas that form a broad ring around the central sulcus are the ventral bank of the principal sulcus and the adjacent area 46, the precentral operculum (PrOC), area SII (Jones and Burton: J. Comp. Neurol. 168:197-248, '76), the parietal operculum, and the rostral part of the inferior parietal lobule including the lower bank of the intraparietal sulcus. Finally, the inferior area 6 has sparse but consistent connections with insular and cingulate cortices. The functional significance of this complex pattern of connections is discussed.
TL;DR: In this paper, a molecule immunologically related to calcitonin gene-related peptide (CGRP-I) has been found in motoneurones in a variety of mammals including man.
Abstract: Innervation of muscle by motoneurones induces the development of a characteristic, high density cluster of acetylcholine receptors (AChRs) at the neuromuscular junction. Studies in vitro show that the accumulation of AChRs at nerve-muscle contacts results from both increased insertion of new AChRs into the muscle plasma membrane beneath nerve terminals and redistribution of preexisting AChRs; these two modes of AChR accumulation may be separately controlled since factors have been identified that influence AChR redistribution but not synthesis. Although many aspects of muscle development are regulated by nerve-dependent muscle activity, junctional AChR clusters still develop when neuromuscular transmission is blocked by either curare or alpha-bungarotoxin, suggesting that their formation is mediated by nerve-derived trophic factors other than activity. A molecule immunologically related to calcitonin gene-related peptide (CGRP-I) has been found in motoneurones in a variety of mammals including man. Here we provide indirect evidence that CGRP-I may be a motoneurone-derived trophic factor that increases AChR synthesis at vertebrate neuromuscular junctions.
TL;DR: These findings are consistent with the cell-division-counting hypothesis previously proposed to explain the timing of oligodendrocytes differentiation and unambiguously establish the phenotype of O-2A progenitor cells in vitro and demonstrate that these cells respond directly to growth factors produced by type-1 astrocyte monolayers.
TL;DR: Immunohistochemical studies show that the distribution of the extracellular matrix glycoprotein laminin is not significantly different in the cephalic region of Sey/Sey versus Sey/+ or +/+ embryos.
Abstract: Small eyes (Sey) is a semidominant, homozygous lethal mutation in the mouse (Roberts, 1967). It is allelic with SeyH, a radiation-induced homozygous prenatal lethal which has been mapped on chromosome 2. The effect of the Sey mutation is apparently limited to the growth and differentiation of the presumptive lens and nasal placodes. Homozygous Sey /Sey embryos can be distinguished as early as 10·5 days post coitum (p.c); the optic vesicles grow out, but the ectoderm does not give rise to a lens and nasal pits never form. Immunohistochemical studies show that the distribution of the extracellular matrix glycoprotein laminin is not significantly different in the cephalic region of Sey/Sey versus Sey/+ or +/+ embryos. Sey/Sey embryos develop to term but without eyes or nose, and die soon after birth. Further analysis of Sey/Sey embryos may throw light on the mechanisms underlying morphogenesis of craniofacial structures in mammals.
TL;DR: It is reported that proliferating bipotential oligoden-drocyte-type-2 astrocyte (0-2A) progenitor cells are present in the adult rat optic nerve, raising the possibility that these cells are produced continually from self-renewing stem cells throughout life.
Abstract: We have shown previously that the rat optic nerve contains three types of macroglial cells--oligodendrocytes and two types of astrocytes--which develop as two distinct lineages. Type-1 astrocytes develop from one type of precursor cell beginning at embryonic day 16 (E16), while oligodendrocytes and then type-2 astrocytes develop from a common, bipotential progenitor cell beginning at birth (E21) and postnatal days 7-10 (P7-10), respectively. Here we report that proliferating bipotential oligodendrocyte-type-2 astrocyte (0-2A) progenitor cells are present in the adult rat optic nerve, raising the possibility that these cells are produced continually from self-renewing stem cells throughout life.
DOI•
01 Dec 1986TL;DR: In this article, the use of "illuminators of opportunity" for bistatic radar systems is discussed, including using TV pictures to make the transmission more closely resemble a pulsed radar signal, and it is shown that the separation of targets from the direct signal and clutter requires extensive signal processing under all but the most favourable conditions.
Abstract: The paper discusses the use of `illuminators of opportunity' for bistatic radar systems. Experiments in the London area using the Crystal Palace transmitters are reported, including the use of TV pictures designed to make the transmission more closely resemble a pulsed radar signal. It is shown that the separation of targets from the direct signal and clutter requires extensive signal processing under all but the most favourable conditions.
TL;DR: It is suggested that GTP analogues can activate secretory processes by actions at two distinct locations: one may be at the level of the receptor7 involving the activation of polyphos-phoinositide (PPI) phosphodiesterase8 with consequent liberation of diacylglycerol (DG)9; the other involves direct activation of the exocytotic mechanism.
Abstract: The term ’stimulus-secretion coupling‘ has, since first enunciated1, been held to involve the mobilization of cytosol Ca2+, which in turn is sufficient to trigger exocytotic secretory processes in metabolically competent cells. However, recent studies on a wide range of secretory cell types indicate that a role for Ca2+ can be obviated: examples are stimulation with phorbol ester (phorbol myristate acetate, PMA)2,3 which causes the activation of protein kinase C4 or the stimulation of platelets with collagen5. Ca2+-independent exocytosis also occurs when analogues of GTP are injected through the lumen of patch pipettes directly into the cytosol of mast cells6. The results presented here suggest that GTP analogues can activate secretory processes by actions at two distinct locations: one may be at the level of the receptor7 involving the activation of polyphos-phoinositide (PPI) phosphodiesterase8 with consequent liberation of diacylglycerol (DG)9; the other involves direct activation of the exocytotic mechanism. These conclusions are based on measurements of exocytotic secretion from permeabilized neutrophils into which we have been able to introduce, individually and in combination, Ca2+ chelators (EGTA and BAPTA), Ca2+ (buffered at micromolar concentrations with EGTA), analogues of GTP and GDP and the direct activator of protein kinase C, PMA.
TL;DR: It is suggested that one role for C-afferent neuropeptides is a long-acting gain modulation of nociceptive inputs into the spinal cord.
TL;DR: Resonance Raman spectra are obtained when the wave number of the exciting radiation is close to, or coincident with, that of an electronic transition of the scattering species as mentioned in this paper.
Abstract: Resonance Raman spectra are obtained when the wave number of the exciting radiation is close to, or coincident with, that of an electronic transition of the scattering species. Such spectra are usually characterized by a very large enhancement of the intensities of particular Raman bands, sometimes with the appearance of intense overtone and combination tone progressions. The technique provides detailed information about excited electronic states because it is only the vibrational modes associated with the chromophore that are resonance-Raman active. Additionally, the high sensitivity is such that compounds at concentrations as low as 10−6 mol/L may be detected, enabling resonance Raman spectroscopy to be used as an analytical tool and for the study of chromophores in molecules of biological interest.
TL;DR: The effects of intrathecal morphine on the responses of 38 dorsal horn neurones in the intact rat under halothane anaesthesia to A and C fibre electrical stimulation and to natural stimuli applied to their receptive fields are studied.
Abstract: We have studied the effects of intrathecal morphine on the responses of 38 dorsal horn neurones in the intact rat under halothane anaesthesia to A and C fibre electrical stimulation and to natural stimuli applied to their receptive fields. Morphine selectively reduced the C fibre and pinch evoked activity in a dose-dependent naloxone-reversible manner with an ED50 of 7 nmoles. The ‘wind-up’ of neurones to repetitive stimulation was little altered except with the highest doses (50–150 nmoles) tested. By contrast, the A fibre evoked responses of the neurones were only slightly reduced by morphine and both the tactile responses and receptive field size to innocuous stimuli enhanced for certain cells. The results are discussed in relation to the spinal actions of opiates and their clinical applications.
TL;DR: In this article, the authors present the results of a computer simulation study of defect energies in BaTiO 3 and propose a defect model consistent with experimental studies, where intrinsic disorder is masked by oxygen vacancies which compensate accidental acceptor impurities.
TL;DR: It is suggested that dyslexics have difficulty with the nonlexical procedures (including phoneme segmentation) involved in verbal repetition; one consequence is that they take longer to consolidate "new" words; verbal memory and reading processes are also compromised.
TL;DR: Despite the early anatomical existence of a descending DLF pathway, there is no functional descending inhibition until days 10-12 of life and it is suggested that this is due to delayed maturation of crucial interneurones in the dorsal horn or to insufficient levels of 5-hydroxytryptamine or other neurochemicals in the descendingDLF axon terminals.
TL;DR: The substrate requirements for neurite outgrowth in vitro by chick embryo retinal ganglion cells, the only cells in the retina to send axons to the brain, are examined, showing the first evidence that central nervous system neurones may undergo a change in their substrate requirements in vitro as they mature.
Abstract: The decisive role played by adhesive interactions between neuronal processes and the culture substrate in determining the form and extent of neurite outgrowth in vitro1,2 has greatly influenced ideas about the mechanisms of axonal growth and guidance in the vertebrate nervous system. These studies have also helped to identify adhesive molecules that might be involved in guiding axonal growth in vivo. One candidate molecule is laminin, a major gly-coprotein of basal laminae3 which has been shown to induce a wide variety of embryonic neurones to extend neurites in culture4–8. Moreover, laminin is found in large amounts in injured nerves that can successfully regenerate but is absent from nerves where regeneration fails9–11. However, it is unclear to what extent the mechanisms that regulate axonal regeneration also operate in the embryo when axon outgrowth is initiated. Here we have examined the substrate requirements for neurite outgrowth in vitro by chick embryo retinal ganglion cells, the only cells in the retina to send axons to the brain. We show that while retinal ganglion cells from embryonic day 6 (E6) chicks extend profuse neurites on laminin, those from Ell do not, although they retain the ability to extend neurites on astrocytes via a laminin-independent mechanism. This represents the first evidence that central nervous system neurones may undergo a change in their substrate requirements for neurite outgrowth as they mature.
TL;DR: This paper reviews studies which have evaluated the use of acupuncture for the relief of pain and examines the criteria by which the adequacy of research reports in this field should be assessed.
Abstract: This paper reviews studies which have evaluated the use of acupuncture for the relief of pain. In the preceding paper the concepts and methods of acupuncture are outlined along with a discussion of the special problems of outcome research in this area. Since in our view the overall quality of published accounts of acupuncture research is poor, we have thought it important to examine the criteria by which the adequacy of research reports in this field should be assessed. The principal issues concerning outcome measures, follow-up assessment, trial design, etc., are therefore discussed in the preceding article. The review which follows describes both controlled and uncontrolled therapeutic trials where the major aim of treatment has been the relief of pain. It does not consider laboratory studies of experimentally induced pain. All studies known to the authors which include at least a no-treatment control group have been included unless they are pilot studies with excessively low patient numbers or are inadequately reported. The details of these controlled studies are summarised in Table I. Where uncontrolled trials are concerned, no attempt has been made to provide an exhaustive review. The studies which have been included generally involve either large patient numbers or other features of design or measurement which render them noteworthy.
TL;DR: In this article, a utility maximising model of the joint determination of male and female labour supplies using a sample of married couples from the U.K. Family Expenditure Survey is presented.
Abstract: This paper estimates a utility maximising model of the joint determination of male and female labour supplies using a sample of married couples from the U.K. Family Expenditure Survey. The emphasis is on the estimation of within period preferences that are consistent with intertemporal two-stage budgeting under uncertainty. However, the approach we adopt provides an alternative method of estimating certain aspects of life-cycle behaviour to the fixed effects λ-constant approach of Heckman and MaCurdy (1980), MaCurdy (1981) and Browning, Deaton and Irish (1985). Moreover, it relaxes some of the underlying restrictions that are implicit in these λ-constant models under uncertainty.
TL;DR: It is concluded that hyperlexia is not an autism-specific phenomenon, and there were no differences between autistic and nonautistic readers on any of the authors' tasks.
TL;DR: A dose-dependent differential action of morphine on the hamstring flexor withdrawal reflex recorded in flexor alpha-motoneurones has been found in the decerebrate-spinal rat and the relevance of these findings to the antinociceptive and analgesic actions of morphine is discussed.
TL;DR: The frequent occurrence of obsessive-compulsive disorder in patients with Gilles de la Tourette's syndrome suggests that the two disorders may share common neurobiologic mechanisms.
Abstract: The incidence of obsessive-compulsive disorder (OCD) in patients with Gilles de la Tourette's syndrome (GTS) was assessed with a specially designed questionnaire. The Inventory was administered to patients with OCD, patients with GTS, and normal controls. Fifty-one percent of the patients with GTS had significantly elevated Inventory scores. The frequent occurrence of OCD in GTS suggests that the two disorders may share common neurobiologic mechanisms.