Showing papers by "Royal Holloway, University of London published in 1989"

Synaptophysin expression during synaptogenesis in the rat cerebellar cortex

Abstract: In order to study the mechanisms of synaptogenesis in the rat cerebellar cortex, a library of monoclonal antibodies has been generated against proteins of the isolated synapse. One recognizes a glycosylated 38 kDa protein that is concentrated in the synaptic vesicle fraction and resembles synaptophysin biochemically in its molecular weight, charge, and pattern of glycosylation. In the adult cerebellar cortex, the antisynaptophysin(mabQ155) immunoreactivity is codistributed with synapses. Immunoreactivity is strongest in the molecular layer where punctate deposits of reaction product outline the Purkinje cell dendrites. Discrete small profiles, consistent with the distribution of basket cell axon terminals, surround the Purkinje cells, and in the granular layer the synaptic glomeruli are intensely stained. There is no immunoreactivity in the white matter axon tracts. Electron microscope immunocytochemistry confirms the synaptic location of the antigen and suggests that the reaction product is associated with synaptic vesicles. Both round and flat vesicle populations are immunoreactive. Antisynaptophysin(mabQ155) has been used to follow synaptogenesis in the developing rat cerebellum. In the newborn rat (P0), despite the paucity of synapses, there is some specific immunoreactivity, especially in the subcortical white matter. Electron microscopy shows that the antigenicity is associated with vesicles within growth cones, filopodia, and immature axon profiles. During development, antisynaptophysin immunoreactivity increases progressively, along with the maturing cell populations, for both the granule cell-Purkinje cell and the mossy fiber-granule cell synapses. Quantitative biochemical analysis confirms the cytochemical results. These data suggest that neuronal growth cones express a synapse-specific antigen before complete morphological synapses are present.

Contamination of indian-ocean asthenosphere by the kerguelen-heard mantle plume

Abstract: THE mid-ocean-ridge basalts (MORBs) from the Indian Ocean are isotopically distinctive. They have higher 87Sr/86Sr, 208Pb/206Pb and 207Pb/206Pb ratios than Pacific andAtlantic counterparts1,2 (see Fig. 1), suggesting that the upper mantle beneath the Indian Ocean has remained a partially isolated system2. The Australian–Antarctic discordance, a bathymetrically depressed segment of the South-East Indian Ridge, may represent a fundamental boundary between the Indian and Pacific mantle domains3. What processes are responsible for such domains? We argue here that the Kerguelen–Heard plume, which is producing Dupal-type basalts on Kerguelen and Heard Islands in the southern Indian Ocean, has contaminated large volumes of the Indian Ocean asthenosphere. This has produced the distinctive composition of Indian Ocean MORBs.

Digit dyslexia: A category-specific disorder in development dyscalculia.

Abstract: A case study of developmental dyscalculia is presented in which there is impairment of number processing. When reading and writing arabic numbers the syntactic component of the number is processed accurately but lexical processing results in incorrect digit selection. When reading arabic numbers the allocation of lexical items into syntactic frames is particularly poor for digits in the units position. Lexical allocation is unaffected by stimulus length. Despite poor short term memory, word reading is not impaired except for the reading of numeral words for which there is a category specific deficit. Reading errors to numeral words are more frequent than to arabic numbers but the nature of the errors is comparable. This reading deficit coexists with good phonological reading skills. The results are discussed in relation to models derived from studies of the acquired dyscalculias.

Time course of cigarette withdrawal symptoms while using nicotine gum.

Abstract: Ratings of withdrawal symptoms were provided at weekly intervals by 147 smokers clinic clients who managed complete abstinence for 4 weeks. The ratings followed a similar temporal pattern regardless of amount of nicotine gum used. Irritability, depression, difficulty concentrating and restlessness peaked in the 1 st week or two and returned to baseline by week 4. Hunger was more persistent. Craving was reported to be the most troublesome withdrawal symptom at first, although by the 4th week hunger was cited almost as often. Across all subjects,e venings were cited most often as the worst time of day for craving but among heavier smokers and those who used more nicotine gum mornings were considered worst.

Ikaite, CaCO3̇6H2O, precursor of the thinolites in the Quaternary tufas and tufa mounds of the Lahontan and Mono Lake Basins, western United States

Abstract: The thinolites in the Quaternary tufas and tufa mounds of the Lahontan and Mono Lake basins of the western United States are identified as being pseudomorphous after crystals of the mineral ikaite, CaCO36H2O. Ikaite is a metastable mineral in the sedimentary realm. It crystallizes from solution at temperatures close to zero Celsius but rapidly decomposes at warmer temperatures and becomes pseudomorphed in calcite by in situ redistribution of the calcium and carbonate ions. The likely implication is that the thinolites record ice-cold episodes during deposition of the tufas.

What future for British red squirrels

Abstract: The geographic range of red squirrels contracted sharply in Britain during the 1940s arid 1950s, as increasingly large areas were colonized by the congeneric North American grey squirrel Red squirrels remain common only on offshore islands, and in the large conifer forests of northern England and Scotland The initial replacement of red squirrels was in arras dominated by oak woodland, probably because acorn crops are exploited less efficiently by red squirrels than by grey squirrels Dirt studies have shown that acorns are digested less efficiently by the red squirrel, which occurs in conifers through most of its Eurasian range, than by the introduced grey squirrel, which is primarily a native of deciduous woodland The red squirrel will probably be replaced in deciduous and mixed woodland throughout mainland Britain, and may eventually persist only in large areas of conifers which arc far from oak trees The conservation of red squirrels on islands is therefore particularly important for their survival, perhaps making it worthwhile to create new island populations where they do not at present exist

Developmental dyslexics do not fit in boxes: Evidence from the case studies

Abstract: An examination is undertaken of conclusions drawn from some case studies of developmental dyslexia which have categorised subjects as phonological or surface dyslexics. Various criticisms are advanced of the conclusions drawn from these studies, such as the absence of data from a proper sample of poor readers to illustrate the distribution of performance on specific aspects of reading, the lack of agreed criteria for the classifications made, and inadequate analysis of the error data. It is concluded that no good grounds exist for the claim that developmental dyslexics fall into clearly distinguishable categories, determined by different specific processing deficits. Seymour (1986) reached a similar conclusion and suggested that a large number of different patterns of deficit exist. However, it is suggested here that all the cases discussed showed a deficit in phonological processes and that differences in performance on such aspects of reading as the ability to read irregularly spelled words, th...

Ammonium in spilitized basalts of southwest England and its implications for the recycling of nitrogen

Abstract: Spilitic alteration increases the ammonium content of basaltic rocks. A series of spilitic rocks from southwest England was found to contain an average of 54 ppm of ammonium ion. Most of this ammonium is fixed as an isomorphous constituent in feldspars and micas, but a small proportion (averaging 5 ppm) is held in an exchangeable form. Subduction of oceanic crust containing ammonium-enriched igneous rocks may be a mechanism for recycling atmospheric nitrogen back into the mantle.

An ultrastructural study of planozygotes and encystment of a marine dinoflagellate, Scrippsiella sp

Abstract: The fine structure of the planozygotes and encystment of Scrippsiella sp. have been studied by scanning and transmission electron microscopy. The planozygote is armoured and has two longitudinal flagella and one transverse flagellum. Unlike the vegetative cell, the planozygote has two pairs of basal bodies, large numbers of starch granules and many vesicles containing electron-dense particles. The build-up of storage materials and the reduction in size and number of the organelles in the cytoplasm, which are necessary processes for encystment, take place in the planozygote. The main feature of encystment is the formation of the thick cyst wall. The theca is shed at a very early stage of encystment before wall formation. During encystment the cell is surrounded by three layers c membranes. The cyst wall is constructed between the middle and the inner membrane and thickens due to the deposition of wall material on the inward side of the middle membrane. Mucofibrous material is seen between the outer and the...

Stratigraphic correlation across an arc‐continent collision zone: timor and the Australian northwest shelf

Abstract: The Kolbano area of southern West Timor comprises the subaerially exposed upper part of an imbricate stack at the leading edge of the Timor arc‐continent collision zone. Rocks of Permian to Plio‐Quaternary age are exposed in the Kolbano Complex. Detailed stratigraphic correlation between the Kolbano area and the Northwest Shelf of Australia (as recorded from petroleum exploration wells) demonstrates that the Kolbano area has close stratigraphic links with the Northwest Shelf, in particular with the Ashmore Block and Sahul Platform. Reconstruction of Jurassic‐Neogene palaeoenvironments for the Kolbano area indicates that the Kolbano area represents the outermost edge of the precollisional Australian passive margin. The region has been considerably shortened by Pliocene tectonism, but retains a predeformational distribution of facies with respect to Australia. The northern half of Timor is composed largely of Australian continental margin material. As this now lies to the north of the Kolbano area, interpre...

The Outer Hebrides fault: a major Proterozoic structure in NW Britain

Abstract: Mylonites in the Outer Hebrides fault zone on Scalpay, Hams, are cut by metabasite sheets which are probably of Scourie dyke age (2400–2200 Ma) and by pegmatites of late Laxfordian age (c. 1750 Ma). The mylonites contain relicts of a gneissose banding which probably formed in the Archaean c . 2700 Ma ago. These age constraints suggest that the fault formed in the Inverian event c. 2500 Ma ago, not in the Caledonian (Silurian-Devonian) as widely reported. The fault is a long-lived structure which was reactivated as an extensional fualt in the Laxfordian, late Proterozoic (Torr-idonian) and the Carboniferous/Early Mesozoic, and as a thrust in the Caledonian. In a regional context this interpretation has important implications for the structural evolution of the Lewisian complex, for the nature of the Caledonian event in the Laurentian craton (Caledonian foreland) and for the age and geometry of the sedimentary basins in the hanging wall of the Outer Hebrides fault.

‘Breathtaking’: the consequences of chronic respiratory disorder

Abstract: Chronic obstructive airways disease (COAD) is a major, though neglected, medical and social problem in the United Kingdom today. Dyspnoea is one of the most distressing and disabling symptoms of COAD, which is itself the largest single cause of absence from work in the United Kingdom. This paper reports on 92 patients suffering from COAD, who were interviewed in order to assess impairment, disability and handicap, and a smaller subsample of 24 of these patients who were followed-up using open-ended, semi-structured, tape-recorded interviews in order to cover in more detail some of the issues raised in the first quantitative stage of the study. Low correlations were found between lung function and disability (-0.38 p less than 0.001), accounting for only 14% of the variance, and high correlations between measures of dyspnoea and disability (-0.90 p less than 0.001). Major areas of disability and handicap included: household management, ambulation, sleep and rest, recreation and pastimes, and work. Financial problems and difficulties, housing problems and problems of social isolation were also frequently reported. The paper then attempts to explore the relationship between impairment, disability and handicap, drawing on both the quantitative and qualitative data collected in order to illustrate the variable nature of this relationship. The paper concludes by suggesting both the need for a more integrated approach to the care and rehabilitation of COAD patients and their families, and for a complementary social perspective and approach to COAD and its treatment.

Short Paper: Movement on proposed terrane boundaries in northern Britain: constraints from Ordovician–Devonian igneous rocks

Abstract: Regional chemical and isotopic differences seen in Ordovician–Devonian igneous rocks of northern Britain are thought to be due to subduction-related and collision magmatism tapping a variety of mantle and crustal sources. Matching of spatial chemical variation across major fault zones restricts post-magmatic transcurrent movement north of the Southern Upland Fault (SUF) to a few tens of kilometres on each fault. A unique mantle isotopic signature present in the same area may restrict post-1.5 Ga movement to less than a few hundred kilometres. No such restrictions exist on displacement across the SUF, to the south of which all magmas show a Pb isotopic component derived from southern sources.

An investigation of supercooled Lennard-Jones argon by quantum mechanical and classical Monte Carlo simulation

Abstract: Liquid Lennard-Jones argon has been abruptly cooled and compressed in quantum mechanical path-integral and classical Monte-Carlo simulations. Equilibration of the supercooled liquid so obtained leads either to amorphous or partially crystalline systems which are, in the context of the computer experiment, stable. Energies and pressures of the quantum mechanical and classical systems are compared and structural properties discussed. The properties of the amorphous systems are reproducible. Energy, pressure and the maximum value of the structure factor are much more sensitive probes of incipient crystallization than the radial distribution function. Three different path-integral techniques have been used.

The early Kimmeridgian ammonite succession at Staffin, Isle of Skye

Abstract: Synopsis Detailed mapping of the Staffin Shales in the vicinity of the Oxfordian/Kimmeridgian boundary has revealed a succession of ammonite faunas, one of which was only known previously from Greenland. Recognition of distinctive marker bands has enabled correlation of scattered outcrops along 3 km of coastline and has revealed details of the manner of operation of the Quirang landslip.

Changes in Na, K, Ca, Mg and Al content of submersed leaf litter, related to ingestion by the amphipod Gammarus pulex (L.)

Abstract: SUMMARY. 1. Changes in the amounts of Na, K, Ca, Mg and Al in fallen leaves of oak, alder and mat grass were measured during 13 weeks of submersion in seven streams differing in pH and ionic content. 2. In the first 2 weeks, Na, K and Mg leached from the leaves, but in the following weeks there was a net increase of Al, K and Mg and, in some instances, Na and Ca. Increases of K and Mg were relatively larger in circumneutral streams whereas the greatest increases of Al occurred in acid streams. Net gains are attributed to absorption of cations from water by saprophytic micro-organisms degrading the leaves, direct adsorption of Al on to leaf tissues - especially in acid streams - and capture of small particles of magnesium and aluminium silicates (clays). 3. Daily ingestion of elements was calculated as a percentage of whole body contents in Gammarus pulex (L.) and compared with daily loss rates. Leaf litter may be an important source of some major elements for ionic balance in juvenile G. pulex and a major source for uptake of potentially toxic aluminium in acidic, soft waters.