Showing papers by "Keele University published in 1984"

Soluble synthetic polymers as potential drug carriers

Abstract: Soluble synthetic polymers provide a potential targetable drug delivery system. In this article we discuss the consequences of the attachment of pharmaceuticals to macromolecular carriers with special reference to endocytosis and lysosomotropic drug delivery. The types of polymers which may be used as carriers are reviewed with particular regard to the methodology currently available in polymer chemistry for the synthesis of polymers bearing cell-specific targeting residues and incorporating effective polymer drug linkages. In order to be successful in drug delivery, the polymeric drug carrier must behave in a predictable and favourable manner in the biological environment. Studies concerned with the biological properties of synthetic polymers are also reviewed. The idea of using drug carriers to improve the therapeutic efficacy of pharmacological agents is receiving increasing attention, and the relationship between soluble synthetic polymers and other proposed carriers is discussed together with possible clinical applications.

Intraplate lithosphere deformation and the strength of the lithosphere

Abstract: Summary. The intraplate deformation of continental lithosphere in response to applied stress has been investigated using a mathematical model which incorporates the elastic, ductile and brittle response of lithosphere material. Ductile deformation is assumed to be controlled in the crust by dislocation creep in quartz, and in the mantle by dislocation creep and plasticity in olivine. Brittle failure is predicted using modified Griffith theory. A fundamental feature of the model is the redistribution of stress within the lithosphere following stress release by both ductile and brittle deformation. This redistribution produces high levels of stress in the middle or lower crust immediately above the elastic-ductile or brittle-ductile transition, Lithosphere deformation is shown to be critically dependent on the temperature structure of which surface heat flow is a convenient indicator. For higher geothermal gradients, the release of stress in the lower lithosphere by ductile deformation is more rapid and complete and results in large stress levels in the upper lithosphere. For sufficiently large applied stresses or steep geothermal gradients, the stress levels in the upper and middle crust will cause complete fracture of the upper lithosphere. Whole lithosphere failure (WLF) then results, by continued brittle and ductile deformation, causing geologically significant strains. The critical value of applied stress required to give WLF has been calculated for both tensional and compressional deformation as a function of surface heat flow. The predicted lithosphere bulk strength is then compared with expected levels of intraplate stress arising from plate boundary forces and isostatically compensated loads, which are thought to give net stress levels in the continental lithosphere in the range +0.25 to -0.25 kB. Using these expected maximum stress levels, the model predicts significant extensional deformation in regions of moderate heat flow with q > c. 60mWm-’ (e.g. Central Europe) as well as for areas of high heat flow like the Basinand-Range Province. Significant compressional deformation is predicted for areas of high heat flow with q > c. 75 mWm-2 but only for restricted conditions of stress combination. These results are in good agreement with

Differential Scanning Calorimetry

Abstract: The purpose of this paper is to review briefly the technique of differential scanning calorimetry (1), and to indicate how it may be used to determine enthalpies of phase change and of certain chemical reactions.

Stratigraphy and structure of the Schoonover sequence, northeastern Nevada: Implications for Paleozoic plate-margin tectonics

Abstract: Radiolarian biostratigraphy and detailed geologic mapping have been used to resolve the complex structure and stratigraphy of part of the Golconda allochthon in the Independence Mountains, Nevada. Here, the Schoonover sequence is latest Devonian to Early Permian in age, spanning the time interval from the emplacement of the Roberts Mountains allochthon onto the shelf in the earliest Mississippian Antler orogeny to the inception of the Sonoma orogeny. The history of the Schoonover basin is tied to that of the adjacent shelf in Nevada and provides important insights into the upper Paleozoic paleogeographic framework of the continental margin. In the Schoonover sequence, latest Devonian (Famennian) chert overlies basaltic and andesitic greenstone and is in turn overlain by Early Mississippian (Kinderhookian) chert interbedded with tuff and volcaniclastic rocks derived from an island arc. The Kinderhookian volcaniclastic rocks grade upward, with no obvious depositional break, into siliciclastic turbidites and pebbly mudstones that contain debris derived primarily from erosion of the Antler orogenic belt, although in some beds volcanic rock fragments and greenschist-grade metasedimentary clasts are also common. The age of underlying (Kinderhookian) and interbedded and overlying (Osagian to Meramecian) chert sequences indicates that the siliciclastic turbidites are synchronous with the early deposits of the autochthonous foredeep basin of the Antler orogenic belt. The dual or composite source terranes represented by the Schoonover siliciclastic rocks place the basin between an arc and the Antler orogen on the edge of the shelf. Meramecian-age basalt flows in the Schoonover are coeval with subsidence and basaltic volcanism in autochthonous shelf sequences in northern Nevada, suggesting that a rifting event may have occasioned the end of Antler-age compression in Nevada. The onset of limestone turbidite deposition in the Schoonover corresponds to the reestablishment of carbonate shelf conditions on the continental margin in latest Mississippian–earliest Pennsylvanian time. The Late Devonian–earliest Mississippian part of the Schoonover depositional history has not yet been documented elsewhere in the Golconda allochthon, but Late Mississippian to Permian rocks in the Schoonover sequence are analogous to those of the Havallah sequence, suggesting deposition in the same basin. Thrust faults in the Schoonover repeat the Late Devonian to Permian section, detaching the basinal sequence from its depositional basement. Thrust faults extend along strike for at least 10 km, but thrust plates are The stratigraphic relations documented in the Schoonover sequence are compatible with a back-arc thrusting model for the formation of both the Roberts Mountains and Golconda allochthons, but they are more difficult to reconcile with models that interpret the allochthons as accretionary prisms developed in front of farther-traveled arcs that collided with a passive margin. In a broader context, the stratigraphy of upper Paleozoic allochthonous rocks in Nevada records short-lived episodes of crustal shortening along the continental margin, separated by longer episodes of extensional and/or transcurrent tectonics. This data suggest that the western United States was a southwest Pacific–style active margin at least as far back as the Devonian.

Larval foraging behavior in isofemale lines of Drosophila melanogaster and D. pseudoobscura

Abstract: Isofemale lines of Drosophila, recently sampled from nature, were used to study the withinand between-line phenotyplc variability of a preadult behavior. The locomotory component of larval foraging behavior was quantified by measuring the length of the path traversed by a foraging 3rd Instar larva on a yeasted dish. Significant between-line variation for this behavior was found in Drosophila melanogaster and in D. pseudoobscura. Matings between lines with extreme phenotypes indicated a relatively simple genetic basis for differences in larval foraging behavior.

The construction of Oxford, Bodleian Library, Junius II

Abstract: In recent years a number of books and articles has appeared in which new and contradictory claims have been made about the compilation of Oxford, Bodleian Library, Junius II In view of these contradictions it is necessary to re-examine the manuscript and to set out what information can be gained from it and what can reasonably be inferred from that information

Element mobility associated with syn‐metamorphic shear zones near Scotchport, NW Mayo, Ireland

Abstract: Three major blastomylonitic synmetamorphic (epidote amphibolite to mid amphibolite facies) shear zones are seen on the NW coast of the Mullet Peninsula in NW Mayo These shear zones occur at the contacts of major structural units and in an imbricated slice where rocks of the Erris Complex are deformed and chemically modified Chemical changes associated with individual shear zones have been deduced by comparing the compositions of various gneisses both within and adjacent to the shear zones Compositional changes are different in the constituent rock-types within each unit and many elements normally considered immobile have been selectively mobilized within the shear zones Little evidence of wholesale metasomatic introduction of components into these shear zones was found to accompany the selective mobilization

Identification of trail pheromone of the ant Tetramorium caespitum L. (Hymenoptera: Myrmicinae)

Abstract: The trail pheromone of the antTetramorium caespitum L. is a 70∶30 mixture of 2,5-dimethylpyrazine and 3-ethyl-2, 5-dimethylpyrazine. The average total amount of the two pyrazines present in the poison vesicle was found to be 3.9 ng per ant, of which 2.7 ± 0.4 ng is 2,5-dimethylpyrazine and 1.15 ±0.25 ng is 3-ethyl-2,5-dimethylpyrazine. The pyrazines constitute only 0.03% of the volume of the poison vesicle but account for the whole of the trail-following activity. A 70∶30 mixture of the respective pyrazines evoked the highest activity in artificial trail-following tests.

Stone movement on hillslopes in the Mojave Desert, California: A 16‐year record

Abstract: Previous research has shown that either hydraulic action or creep may be the dominant process transporting coarse debris down hillslopes in the American Southwest. This study analyses the movement over 16 years of painted stones on two hillslopes in the central Mojave Desert to ascertain which of these two processes dominate in this region. The distance moved (M) is found to be directly related to length of overland flow (X) and hillslope gradient (S), and inversely related to particle size (D). The fact that M is more highly correlated with X than with S suggests that hydraulic action rather than creep is the dominant process. It is concluded that this is probably the case over most of the Mojave and Sonoran Deserts on slopes up to at least 24°, and that it is only at higher elevations where winters are more severe that creep may become dominant.

Gas chromatographic analysis of fatty material from a Thule midden

Abstract: Fatty material from a Thule Eskimo site on Herschel Island, Yukon Territory, Canada was analyzed by gas chromatography and thin layer chromatography. The fatty acid composition of the samples was then compared with published data for a number of marine species which could have been food sources for the Thule peoples. The samples appear to be derived from seal or whale, or a mixture of these, but what is more surprising is that the fats have changed so little over the 1000 year period of their burial. See also AATA 12-764.

Tenebrio molitor (Coleoptera): effect of metacestodes of Hymenolepis diminuta (Cestoda) on haemolymph amino acids

Abstract: Haemolymph free amino acids (HFAAs) in adult Tenebrio molitor varied in concentration with beetle age. Between 9 and 30 days post-emergence the concentration range was 34–94 mM with a peak occurring in 15-day-old insects. Much of this age-related variation was due to changes in the concentration of a single amino acid, proline. An analysis of concentrations of individual HFAAs in 15-day-old beetles, following infection with metacestodes of Hymenolepis diminuta, revealed that changes in female insects are more marked than those occurring in males. In the former, changes occurred in the concentration of 9 amino acids (isoleucine, leucine, arginine, serine, threonine, tyrosine, phenylalanine, proline and alanine/citrulline) whereas in the latter only 4 amino acids were affected (threonine, glycine, histidine and arginine). It is suggested that H. diminuta may interact with the endocrine system of its beetle host.

Combined solar aureole and solar beam extinction measurements. 1: Calibration considerations

Abstract: A small field-of-view microprocessor-controlled radiometer has been developed for measuring the spectral radiance in the solar aureole region and on the solar disk itself. Calibration problems which include the influence of instrumental scatter on solar aureole measurements and the effects of optical instability on Langley plot data have been investigated. A simple technique for measuring the instrumental scatter component is presented and comparisons are made with actual aureole data. Simultaneous measurements of NO2 columnar abundance were performed in order to assess the effect of variable NO2 optical depth on Langley plot calibration constants in the blue region of the spectrum. The aureole radiance at a constant angular distance from the sun is used to infer optical stability as affected by aerosol content variation. The latter two studies were felt to be particularly relevant given that our measurements were made in the vicinity of a large urban center.

Source Density Analysis of Scalp Potentials During Evaluated Action I. Coronal Distribution

Abstract: The distribution of source densities (the “Laplacean”) of event related potentials (ERPs) over the scalp during a goal-directed task has been derived by a novel method which presents seven samples in a hexagonal array, using an economical computing technique that affords much freedom from artefactual contamination. The task had four phases: waiting for a ball to appear, observing its coordinates and estimating action needed to get it through a goal-mouth, acting and awaiting the outcome, and finally evaluating the outcome as success or failure. Different phases of the task were characterised by significantly different distributions of sources. Failures were distinguished from success by consistent features of the last phase of the ERP. All locations within the reference hexagon (spanning a circle of approximately 12 cm diameter on the scalp) showed the latter features. In control experiments, the effects of response mode and of different cognitive interpretations of the input/output situation were studied. A check showed that with monopolar recording involuntary tongue movements can totally vitiate conclusions in such investigations. The Laplacean derivations proved relatively free of such artefactual contamination.

Pathophysiology of Hymenolepis diminuta infections in Tenebrio molitor: effect of parasitism on haemolymph proteins

Abstract: The effects of metacestodes of Hymenolepis diminuta on haemolymph proteins of Tenebrio molitor are restricted to female hosts. In beetles aged 15 days post-emergence, and harbouring 12-day-old metacestodes, haemolymph concentration is 46·7% higher than in non-infected animals and similar effects are found in longer standing infections. Electrophoresis of haemolymph revealed the presence of 13 bands. Densitometric analysis showed that only band 2/3 was significantly elevated in infected hosts although band 7/8 also showed an increase. These bands were also present in egg homogenates and are thought to be vitellogenins. It is therefore proposed that the excess protein found in infected beetles is a female-specific protein resulting from an interaction between the parasite and the host endocrine system.

A simple and inexpensive liquid helium cooled ‘slam freezing’ device

Abstract: SUMMARY A liquid helium cooled copper block device has been designed for the rapid freezing of biological material. The apparatus differs from previous designs in being easily constructed from readily available components. It incorporates a novel and simplified specimen carrying system. Construction of this apparatus is possible for any laboratory and makes the advantages of freeze substitution reliably available for many cell types at minimal cost.

The role of colleagues and text-editing programs in improving text

Abstract: This paper describes the suggestions for improvement made by nine colleagues about an article written by the author. These suggestions are placed in categories and examples of each are provided. The suggestions are then compared with those provided by a set of computer-based text-editing programs. The results suggests that both the contributions of humans and computers are limited in certain respects. Text-editing programs can deal well with textual issues (perhaps better than humans) but humans have prior knowledge and expertise about content which programs currently lack. An optimal approach would be to combine computer-based and human aids to writing and to explore further how computer-based programs can be made to match human skills.