Showing papers by "Cardiff University published in 1988"

Association between an oncogene and an anti-oncogene: the adenovirus E1A proteins bind to the retinoblastoma gene product.

Abstract: One of the cellular targets implicated in the process of transformation by the adenovirus E1A proteins is a 105K cellular protein. Previously, this protein had been shown to form stable protein/protein complexes with the E1A polypeptides but its identity was unknown. Here, we demonstrate that it is the product of the retinoblastoma gene. The interaction between E1A and the retinoblastoma gene product is the first demonstration of a physical link between an oncogene and an anti-oncogene.

Note---Consumer Store Choice and Choice Set Definition

Abstract: Consumer store choice results from a process whereby information on various alternatives is evaluated by the consumer prior to the selection of one of these alternatives. In the application of store choice models it is often assumed that the information-processing strategy underlying store choice is a simultaneous one in which all possible alternatives are evaluated by an individual. A competing assumption, increasingly recognized in aspatial choice, is that individuals initially evaluate clusters of alternatives and then only evaluate alternatives within a chosen cluster. The nested logit model is a well-known formulation for capturing this type of choice process. This paper adds to the above understanding of consumer spatial choice in the following ways: i It describes an alternative to the nested logit model, known as a competing destinations model, which can be used to model hierarchical spatial choice processes. While this model has been described previously in the geography and planning literature, this paper contains a novel derivation of it from within the random utility maximization framework. ii A general choice formulation is derived from which the logit, nested logit, and competing destinations models can be obtained. This allows the behavioral assumptions embedded in each model to be seen clearly and it allows a comparison of the nested logit and competing destinations formulations. The latter is shown to be preferable in most spatial choice situations. In particular, the latter can be used when restricted choice sets are fuzzy. iii The errors that arise when spatial choice results from a hierarchical process and when a simultaneous choice structure is assumed are demonstrated and are related to the presence of consumer competition/agglomeration effects between stores which are thought to be important in store choice.

Experimental allergic encephalomyelitis: the balance between encephalitogenic T lymphocytes and demyelinating antibodies determines size and structure of demyelinated lesions.

Abstract: The effect of a circulating monoclonal antibody recognizing an antigen located on the surface of myelin sheaths (myelin/oligodendroglia glycoprotein, MOG) on clinical and histopathological expression of experimental allergic encephalomyelitis (EAE) was tested in a model of EAE passively transferred by monospecific T lymphocytes. Intravenous injection of anti-MOG antibody at the onset of the disease massively augmented clinical impairment as well as primary demyelination. The structure of the CNS lesions depended on the balance between encephalitogenic T cells and anti-MOG antibody: when EAE was induced with high numbers of T cells, circulating anti-MOG antibody resulted in ubiquitous perivenous demyelination in the spinal cord and medulla oblongata. On the contrary, focal confluent demyelinated lesions were observed in animals injected with low numbers of T cells (even as few as 104) and anti-MOG antibody. Our studies, thus, indicate that the formation of inflammatory demyelinating lesions may be due to a synergistic action of cellular and humoral immune mechanisms.

The chemical composition gradient across M 33

Abstract: Le gradient d'abondance dans M33 est etudie sur la base d'observations spectroscopiques IPCS et CCD des raies d'emission dans les regions HII, en utilisant O I I, O I II, S I I et S I II dans l'etendue λλ3700-9600 A pour affiner les abondances en oxygene dans les regions internes et etudier le comportement de S/O

Enteric neuron numbers and sizes in Auerbach's plexus in the small and large intestine of adult and aged rats

Abstract: Neurons in the myenteric plexus of Auerbach of the jejunum, ileum, colon and rectum in 6- and 24-month-old rats have been visualised by an enzyme histochemical method in laminar preparations of the muscularis externa. Neuron somata numbers and sizes were recorded in the preparations. Significant reductions, of at least 40%, in the numbers of neurons in the ganglia of the myenteric plexus of the 24-month animals were recorded in all regions of the intestine, especially in the colon where the neuron number decreased by over 60%. These figures do not take into account changes that might have occurred in the overall length of the intestine during adult life. Measurements of neuron sizes suggest that the neuronal fall-out with age affects all categories of neuron equally and implies that all the intrinsic neuronal systems of the gut could be equally affected in old age.

The dust distribution within the inner coma of comet P/Halley 1982i: encounter by Giotto's impact detectors.

Abstract: Analysis of the data from Giotto’s Dust Impact Detection System experiment (DIDSY) is presented These data represent measurement of the size of dust grains incident on the Giotto dust shield along its trajectory through the coma of comet P/Halley on 1986 March 13/14 First detection occurred at some 287000 km distance from the nucleus on the inbound leg; the majority of the DIDSY subsystems remained operational after closest approach (604 km) yielding the last detection at about 202000 km from the nucleus

Fungal colonization of attached beech branches

Abstract: summary Fungal colonization of healthy beech (Fogus sylvatica L.) branches was studied by sectioning branch lengths and drying the sections under controlled regimes. Maintaining water saturation prevented any fungal development in the wood, while active mycelium was isolated as soon as 14 days after the start of the drying period. Fungi developing in these sections were naturally established in healthy branches in the field and formed a floristically denned group, dominated by Hypoxylon fragiforme (Scop.) Kickx., H. nummularium Buill.: Fr., Nectria coccinea (Pers.: Fr.) Fr., and Coniophora putaena (Fr.) P. Karst., and also included coelomycete species. This group was obtained independently of position of the branch in the canopy, season of sampling over an 11 -month period, and site, sampling including four sites in south-west Britain and one in the French Pyrenees. Several species in this group are specific or show a preference for beech as a host. Direct observations and isolation from sections with time indicated that whereas most species developed inwards from the bark, H. fragiforme and H. nummularium grew out from pockets within the wood. Each pocket contained a genetically different individual, as revealed by colony morphology and vegetative incompatibility tests. It was established that water content of the wood is the major determinant for the initial development of fungi in the xylem of beech, and that these early colonizers derive from inoculum latent in the healthy, living branches.

Voltage-dependent currents prolong single-axon postsynaptic potentials in layer III pyramidal neurons in rat neocortical slices.

Abstract: 1. Using isolated slices of rat cingulate and sensorimotor cortex, intracellular recordings were obtained from pyramidal neurons in layer III. Simultaneous extracellular recordings were obtained from neurons in ventral layer III and layer IV. Spike-triggered averaging was employed to investigate synaptic connections from neurons in layers III/IV to pyramidal cells in layer III. 2. Of 701 simultaneously recorded pairs of neurons, comprising 699 extracellularly and 128 intracellularly recorded neurons, synaptic connections were demonstrated in 30 pairs. Of these, 29 were excitatory postsynaptic potentials (EPSPs) and 1, an inhibitory postsynaptic potential (IPSP). Single-axon EPSPs with a wide variety of amplitudes were recorded: the range recorded at membrane potentials between -68 and -72 mV was 0.079-2.3 mV. Comparing recordings obtained from different cells, EPSP amplitude was found to be independent of both the membrane resistance of the postsynaptic neuron and the EPSP time course; i.e., the largest EPSPs were not necessarily those recorded from neurons with the highest input resistance, nor those with the briefest time course. 3. Shape indices: width at half amplitude and rise-time, indicative of both proximal and distal synaptic locations were obtained. Normalized rise-times were between 0.1 and 2 times the membrane time constant and half-widths between 0.8 and 20 times. 4. The majority of postsynaptic neurons displayed nonlinear voltage relations typical of pyramidal neurons, and the contribution to EPSP shape of voltage-dependent currents was investigated. EPSP amplitude and duration were found to be dependent on membrane potential. The majority of single-axon EPSPs (26 of 29), increased in amplitude and duration with membrane depolarization over the range -95 - -50 mV, despite the significant decrease in driving force for the EPSP that would be expected to accompany such large depolarizations. This increase coincided with an increase in the amplitude of voltage responses to small injected current pulses. 5. It is concluded that the amplitude and time course of single-axon EPSPs recorded in cortical pyramidal somata are affected not only by the amplitude of the postsynaptic current and the location(s) of the synapse(s) relative to the soma, but also by voltage-dependent currents. The possibility that the increase in amplitude and duration of these EPSPs with membrane depolarization is due to N-methyl-D-aspartate receptor involvement is discussed.

Black-hole normal modes: A WKB approach. III. The Reissner-Nordström black hole

Abstract: Complex frequencies of the normal modes of the Reissner-Nordstr\"om black hole are computed by two independent methods. The first is a high-order WKB approach devised by Schutz and Will and extended by Iyer and Will for the Schwarzschild case. The second is direct numerical integration using a method developed by Chandrasekhar and Detweiler, thereby extending earlier results of Gunter. The WKB results agree with the numerical ones with an error less than 1% for the lowest-order modes. For somewhat higher orders, the numerical techniques fail but the WKB method continues to give eigenfrequencies that should be reasonably accurate.

Late Ordovician–early Silurian destruction of the Iapetus Ocean: Newfoundland, British Isles and Scandinavia—a discussion

Abstract: The available data from Newfoundland, the British Isles and Scandinavia suggest that by late Ordovician–early Silurian times the ocean separating Laurentia from Eastern Avalonia and Baltica had partly closed with the consumption of intervening oceanic crust. Marine seaways, however, persisted until the middle or late Silurian. Phases of crustal transtension and transpression, predominantly under a major sinistral shear couple, occurred throughout the Silurian and early Devonian until the remnant Iapetus Ocean was completely destroyed. The most appropriate Recent plate tectonic models for Silurian sedimentation between Eastern Avalonia and Laurentia are probably the deep-marine foreland basins between Timor and the northern Australian margin, or between Taiwan and mainland China.

Surface X-ray scattering during crystal growth: Ge on Ge(111)

Abstract: The growth of Ge on Ge(111) has been monitored by in situ x-ray reflectivity and diffraction. For suitably chosen geometries, the scattered x-ray intensity is extremely sensitive to atomic-scale surface morphology; dramatic intensity changes occur upon deposition of a fraction of a monolayer. For substrate temperatures up to 200°C oscillations are observed in the scattered intensity, indicating growth by two-dimensional nucleation. Reflectivity curves reveal the detailed surface atomic geometry. All observations can be quantitatively understood by use of kinematical diffraction theory.

The reactive chemisorption of carbon dioxide at magnesium and copper surfaces at low temperature

Abstract: X-ray photoelectron spectroscopic studies reveal that the following species are present when carbon dioxides reactively chemisorbed at magnesium and copper surfaces: CO2(phys) CO3(a), CO 2 − (a) CO(a) and C(a). At Mg(0001) surfaces, it has been shown that there is a step-wise process, with a whole range of metastable species formed above 80 K. By contrast, at copper surfaces the chemistry is less complex, the most significant species being CO 2 − (a); these form preferentially under conditions which favour high surface concentrations of CO2(a) and therefore co-operative effects within the adlayer. The need to develop experimental methods for studying surface processes at high pressures is well recognised, however the present work shows that for some systems low temperatures (and pressures) offer a possible alternative strategy for delineating the step-wise nature of the reaction.

Suitability of Human, Bovine, Equine, and Ovine Tooth Enamel for Studies of Artificial Bacterial Carious Lesions

Abstract: The progress of artificial caries-like lesions created in human, bovine, equine, and ovine enamel has been studied. Lesions were produced by exposure to an acid gel system or by 5-day exposure to a sequential batch culture technique using Streptococcus mutans NCTC 10832. Longitudinal ground sections were prepared. The lesions were of similar appearance in all species when examined in polarized light. The depth in human enamel was approximately half that in the animal species. Microradiography confirmed subsurface demineralization in all four species. Similar depth ratios were seen in the scanning electron microscope, but there were structural differences between lesions in human and animal teeth. Lesions in bovine teeth were more like those in human, but lesions in equine and ovine teeth were markedly different. Substitution of these animal enamels for human enamel in caries experiments demands that these differences be taken into account. Scanning electron microscopy is capable of resolving features in artificial caries lesions which cannot be differentiated by polarized light techniques. The latter will demonstrate generalized mineral loss, but scanning electron microscopy is required to characterize the sites of mineral loss.

Schooling Ordinary Kids: Inequality Unemployment and the New Vocationalism

Abstract: Brown's book is one of the first major studies of the impact of unemployment on the school and it challenges much of what sociologists have taught us about education and the working class.

Low surface brightness galaxies in the Fornax Cluster - Automated galaxy surface photometry. III

Abstract: A sample of low surface brightness galaxies in the Fornax Cluster region which has been measured by the automated plate measuring machine is presented. Photometric parameters, namely profile shape, scale length, central brightness and total magnitude, are derived for the sample galaxies, and correlations between the parameters of low surface brightness dwarf galaxies are discussed, with particular reference to the selection limits. Contrary to previous authors, no evidence is found for a luminosity-surface brightness correlation in the sense of lower surface brightness galaxies having lower luminosities and scale sizes. In fact, the present data suggest that it is the galaxies with the largest scale lengths which are more likely to be of very low surface brightness. In addition, the larger scale length galaxies occur preferentially towards the center of the Cluster.

Triassic evaporites and Plio-Quaternary diapirism in western Greece

Abstract: Wide Triassic evaporite outcrops run parallel to the strike of Hellenide thrust faults in western Greece. They crop out along the leading edges of thrust sheets emplaced as part of the foreland-migrating fold-and-thrust belt. The evaporites acted as the plane of decollement for thrust-sheet emplacement over much of the External Hellenides. Plio-Quaternary diapirs occur locally within the broad outcrops of Triassic evaporite. They are the result of local mobilization of evaporite after its emplacement. Their rise may have been initially triggered by Hellenide thrust-sheet loading and subsequently accentuated by Plio-Quaternary subsidence. Geophysical records and onland exposures show that diapiric rise controlled local sedimentation patterns above the sites of earlier Hellenide thrusts. The subsequent intrusion of diapirs into these cover sediments caused localized extensional structures to develop. This is best seen in SE Zakinthos, where strain-hardened, conjugate faults developed in friable Pliocene sandstones early in the intrusion history. Principal strains calculated from these sets demonstrate patterns of extension sub-orthogonal to intrusion margins. They are comparable with patterns known from other field and experimental examples, but contrast with some recent studies on diapir-related strains.

Proportions of mitotic and apoptotic cells in a range of untreated experimental tumours.

Abstract: . The quantitative aspect of apoptosis in experimental tumours is often neglected. In this study, the apoptotic and mitotic indices for a range of tumours have been determined at light microscope level. It has been found that the apoptotic levels fall into a consistent range for all tumour types and agree well with those described by previous workers. It is suggested that these might be basic parameters of tumour expansion, as relevant to growth kinetics as mitotic levels.

Physicochemical aspects of percutaneous penetration and its enhancement.

Abstract: The classic diffusion model-based interpretation of percutaneous absorption is compared to a simple kinetic analysis. The physicochemical significance and the major deductions of the two approaches are shown to be in general agreement. In particular, the effect of penetrant oil/water partition coefficient on transdermal flux is consistently predicted by the two models. Diffusional and kinetic assessments of skin penetration enhancement are then shown to reveal similar dependencies upon penetrant physical chemistry. It is demonstrated that the requirements for successful promotion of a lipophilic drug's transdermal flux are quite different from those necessary for a hydrophilic penetrant. Finally, in light of published transport data and our increased comprehension of the stratum corneum barrier function, the evidence for (and significance of) different absorption paths across the stratum corneum is considered. In addition, the impact of penetrant “size” on transport is addressed. It is argued that currently held beliefs concerning (i) a putative “polar” route through the stratum corneum and (ii) the dependence of flux on molecular weight warrant considerable further attention before their unequivocal acceptance is appropriate.

The evolution of dwarf galaxies.

Abstract: We propose an evolutionary model for dwarf galaxies in Which initially metal-poor gas-rich dwarf irregular (dI) galaxies evolve through bursting Blue Compact Dwarf(BCD) stages and eventually fade from the BCD phase to become dwarf ellipticals (dE). During the bursting phase the surface brightness of the galaxy increases rapidly due to enhanced OB star formation. The source of fuel for the intermittent bursts of star formation is assumed to be primordial gas which continues to collapse onto the already formed central structure. The dE galaxies form as a result of eventual gas depletion through star formation. With this proposed dI~-+BCD~dE evolutionary sequence we can explain the similar photometric structure of the different dwarf types and the differences in their star formation rates, surface brightnesses, H I contents and Metallicities. A final central BCD burst can account for the nucleation in brighter dEs and their residual star formation, while earlier more widespread star formation bursts would fade to give an irregular dI. Inflow &gas may allow dEs to be less flattened than dis. Using galaxy fading and metallicity models we can reproduce the observed number ratios N(dI):N(BCD)and N(dI):N(dE) and also the observed metallicity magnitude relation of local dwarf spheroidal galaxies.