Showing papers by "University of Liverpool published in 1984"

Calcium-activated potassium channels and their role in secretion

Abstract: Single-channel recording by the patch-clamp technique has now characterized three kinds of membrane potassium channels activated by intracellular calcium ions in animal cells. These play a crucial part in the regulation of membrane potential and of secretion.

The early radiation and phylogeny of echinoderms

Abstract: Summary 1. Living echinoderms are characterized by an extensive water vascular system developed from the larval left hydrocoel, a complex, multi-plated endoskeleton with stereom structure, and pentamery. Fossil evidence shows that stereom evolved before pentamery, but both were acquired during the Lower Cambrian. 2. Cladistic analysis of Lower Cambrian genera reveals very few characters in common between carpoids and true echinoderms, and that the split between them was the first fundamental evolutionary dichotomy within the Dexiothetica. 3. Helicoplacoids are stem group echinoderms with spiral plating and three ambulacra arranged radially around a lateral mouth. They are the most primitive echinoderms and the first to show a radial arrangement of the water vascular and ambulacral systems. Unlike later echinoderms, their skeleton shows no dorsal/ventral (aboral/oral) differentiation. They were probably sedentary suspension feeders. 4. Camptostroma is the most primitive known pentaradiate echinoderm and, in our view, possibly a common ancestor of all living groups. It had a short conical dorsal (aboral) surface with imbricate plating, a ridged lateral wall and a slightly domed ventral (oral) surface with five curved ambulacra in a 2-1-2 arrangement inherited from the triradiate pattern of the helicoplacoids. Interambulacral areas bore epispires and the CD interambulacrum contained the anus, hydropore and/or gonopore. All parts of the theca had plates in at least two layers. 5. All other echinoderms belong to one of two monophyletic subphyla, the Pelmatozoa and the Eleutherozoa. 6. Stromatocystites is the earliest known eleutherozoan and differs from Camptostroma in having a test with only one layer of plates and having lost the dorsal elongation. In Stromatocystites the dorsal surface is flat and the plating tesselate. Stromatocystites was an unattached, low-level suspension feeder. 7. The lepidocystoids are the earliest known pelmatozoans. They differ from Camptostroma in having an attached dorsal stalk which retained the primitive imbricate plating, and by developing erect feeding structures along the ambulacra. In Kinzercystis, the ambulacra are confined to the thecal surface and erect, biserial brachioles arise alternately on either side. Lepidocystis has a similar arrangement except that, the distal part of each ambulacrum extends beyond the edge of the theca as a free arm. 8. Pelmatozoans diverged more or less immediately into crinoids, with multiple free arms composed of uniserial plates, and cystoids sensu lato, which retained brachioles. Gogia (Lower to Middle Cambrian) is the most primitive known cystoid and differs from Kinzercystis principally in having all plating tesselate, while Echmatocrinus (Middle Cambrian) is the most primitive known crinoid and differs from Lepidocystis in lacking brachioles and in having more than five free arms with uniserial plates. 9. Post Lower Cambrian differentiation of pelmatozoan groups proceeded rapidly, exploiting the primitive suspension-feeding mode of life. Maximum morphological diversity was reached in the Ordovician, but thereafter crinoids progressively displaced cystoid groups and reached their peak diversity during the Carboniferous. The eleutherozoans were slower to diversify, but by the Arenig the earliest ‘sea-stars’ (in reality, advanced members of the eleutherozoan stem group) had reversed their living orientation and had begun to exploit a deposit-feeding mode of life. These in turn led to the ophiuroids, echinoids and holothuroids. 10. The basic echinoderm ambulacrum was already present in the helicoplacoids. It had biserial, alternate flooring plates and complexly plated sheets of cover plates on either side. The radial water vessel lay in the floor of the ambulacrum, external to the body cavity, and gave rise ventrally to short, lateral branches (fore-runners of tube feet) that were used to open the cover plate sheets, and dorsally was connected to internal compensation sacs which acted as fluid reservoirs (and were preadapted for a role in gaseous exchange). Plating on the cover plate sheets was organized and reflected the positions of the lateral branches from the radial water vessel. In Camptostroma, the cover plate sheets had biserially aligned rows of cover plates associated with the lateral branches. 11. Brachioles arose by extension of the lateral branches of the radial water vessel and associated serially aligned cover plates found in Camptostroma. They bear a single alternate series of cover plates. In Lepidocystis the ambulacra extended beyond the edge of the oral surface as true arms. Brachial plates of arms are homologues of primary ambulacral flooring plates, and arms bear multiple series of cover plates. Uniserial ambulacral plating is a derived condition and evolved independently in crinoids, paracrinoids and isorophid edrioasteroids. Pinnules in crinoids arose independently in inadunates and camerates by a progressively more unequal branching of the arms. Thus all parts of the subvective system in crinoids are internally homologous, whereas in cystoids, brachioles and arms (or ambulacra) are not homologous structures. 12. The position of the hydropore is the best reference point in orientating echinoderms. Carpenter's system of identifying ambulacra by letters, arranged clock-wise in oral view with the A ambulacrum opposite the hydropore, is consistent in all echinoderm classes. In all Lower Cambrian pentaradiate echinoderms the anus, gonopore and hydropore lie in the CD interambulacrum and this is accepted as the primitive arrangement. In helicoplacoids we tentatively suggest that the A ambulacrum spiralled down from the mouth while the two ambulacra that spiralled up represent the B + C and D + E ambulacra combined. 13. The pelmatozoan stem arose from a polyplated stalk, via a meric stem to a true column with holomeric (single piece) columnals. This happened independently in the crinoids and the cystoids. 14. Our analysis of echinoderm phylogeny leads us to recommend the following changes to the higher level classification of echinoderms: The phylum Echinodermata includes only those groups with radial symmetry superimposed upon a fundamental larval asymmetry. It has a stem group that contains the triradiate helicoplacoids and a crown group to which all other (pentaradiate) echinoderms belong. The crown group contains two monophyletic subphyla, the Pelmatozoa and the Eleutherozoa, and the Pelmatozoa contains two superclasses, the Crinoidea which are extant and the Cystoidea, which are extinct.

Possible climatic impacts of land cover transformations, with particular emphasis on tropical deforestation

Abstract: The climatic impact of albedo changes associated with land-surface alterations has been examined. The total surface global albedo change resulting from major land-cover transformations (i.e. deforestation, desertification, irrigation, dam-building, urbanization) has been recalculated, modifying the estimates of Sagan et al., (1979). Tropical deforestation (11.1 million ha yr-1, or 0.6% yr-1, Lanly, 1982) ranks as a major cause of albedo change, although uncertainties in the areal extent of desertification could conceivably render this latter process of similar significance. The maximum total global albedo change over the last 30 yr for the various processes lies between 0.000 33 and 0.000 64, corresponding to a global temperature decrease of between 0.06 K and 0.09 K (scaled from the 1-D radiative convective model of Hansen et al., 1981), which falls well below the interannual and longer period variability.

Polyol metabolism in fungi

Abstract: Publisher Summary Polyols (sugar alcohols) are widely distributed in fungi. They could serve several roles in living organisms: (1)act as carbohydrate reserves, (2) act as translocatory compounds, (3) function in osmoregulation, and (4) in coenzyme regulation and storage of reducing power. This chapter describes several enzymes that are concerned with polyol metabolism in fungi. These include Glycerol dehydrogenase (NAD + ), Glycerol-3-phosphate dehydrogenase (NAD + ), Xylitol dehydrogenase (NAD + ), Mannitol-1-phosphate dehydrogenase, Polyol dehydrogenase (NADP + ), Mannitol dehydrogenase (NAD + ), Glyceroldehydrogenase (NADP + ), Ribitol-5-phosphate dehydrogenase (NADP + ), Mannitold ehydrogenase(NADP + ), Glycerophosphate dehydrogenase, Glycerol kinase, Mannitol kinase, Mannitol-1-phosphatase, Sorbitol (glucitol) dehydrogenase, and Glycerol oxidase. A number of enzymes have relatively high K m , values for their substrates and a high pH optimum for the oxidation of polyols, which is likely to be a consequence of the buffer more effectively consuming protons at such pH values. It is conceivable that these particular enzymes are membrane-bound. The groups to which the various fungi belong are identified and designated as—namely, Mastigomycotina (M), Zygomycotina (Z), Ascomycotina (A), Deuteromycotina (D) and Basidiomycotina (B).

Sequential segmental analysis of congenital heart disease.

Abstract: 1 Department of Paediatrics, Cardiothoracic Institute, Brompton Hospital, London, England; 2 Department of Pathology, Wilhelmina Gasthuis, University of Amsterdam, The Netherlands; 3 Department of Cardiology, Hospital for Sick Children, Toronto, Canada; 4 Thoracic Unit, Hospital for Sick Children, London, England; 5 Department of Pediatric Cardiology, Centro Ramon y Cajal, Madrid, Spain; 6 Institute of Child Health, University of Liverpool, Royal Liverpool Children's Hospital, Liverpool, England; and 7 Department of Paediatrics, Guy's Hospital, London, England

The effects of gel-forming polyacrylamides on moisture storage in sandy soils

Abstract: Gel-forming, cross-linked polyacrylamides are new formulations of soil conditioners for use where short-term or persistent drought inhibits plant growth. Most commercial products absorb water to many times their own weight thus improving the water storage properties of porous soils, and delaying the onset of the permanent wilting percentage where evaporation is intense. However, there is notable variation between products in the binding tension of absorbed moisture, so changes in field capacity are of little diagnostic value for the soil moisture available to plants. Nevertheless, polymers with high absorption capabilities and low binding tensions in the range pF 2 to 4.2 could be important aids to growth of agricultural, horticultural and forestry crops in drought-prone environments.

Ovulatory rhythms and over-ripening of eggs in cultivated turbot, Scophthalmus maximus L.

Abstract: The aim of this study was to investigate ageing of ovulated eggs retained in the ovarian lumen of captive turbot, Scophthalmus maximus L., prior to handstripping. The ovulation times of egg-batches were determined by catheterization, handstripping and plotting the percentage fertilizations and hatches of resulting eggs against time. The catheterization experiments showed that eggs age and change appearance rapidly after ovulation. The stripping method demonstrated that freshly-ovulated eggs showed greater than 90% fertilization and up to 97% hatch, but ovulated eggs retained in the ovary lumen for 1 day before stripping gave 0% hatch. The turbot showed precise ovulatory rhythms. The time between ovulations varied between individuals but was constant for any one female, making it possible to predict future ovulation times. Three of the females studied had ovulatory periods of alternating length.

Parametrization of the shortwave flux over high albedo surfaces as a function of cloud thickness and surface albedo

Abstract: A simple method for the calculation of the net shortwave flux at the surface for overcast situations is presented. Explicit account is taken of the effect of cloud optical thickness and multiple reflections between the surface and cloud base. Using simple two-stream theory, a theoretical form for the flux is proposed, and then results from a detailed radiative transfer scheme are used to determine the values of a number of empirical coefficients. Over a range of cosines of the solar zenith angle from 0.1 to 0.7, of cloud optical thickness from 1.8 to 20 and of surface albedo from 0.0 to 0.9, the empirical equation reproduces results from the radiative transfer scheme to within 2.7%, and is shown to perform well outside the range of fit. The method was derived with high latitudes in mind but is applicable generally. It is shown that the spectral properties of snow and ice surfaces play an important role in surface net flux prediction. For totally overcast skies the influence of cloud height and atmospheric water vapour content are shown to be minor. Finally, for clear skies, an empirical equation due to J. W. Zillman is investigated and by adjustments to his coefficients, is brought into good agreement with the detailed calculations described here.

Density‐dependent pup mortality in the Antarctic fur seal Arctocephalus gazellu at South Georgia

Abstract: The extent and causes of pup mortality in the Antarctic fur seal, Arctocephalus gazella, were investigated at sites of high and low density at South Georgia. Mortality was greater at the high density site, (17—31% of annual pup production) than at the low density site (36%). The main causes of death, starvation and skull injury, occur more frequently at the high density site. Most starvation was caused by failure of the mother-pup bond to form, often caused by disturbance induced by the activities of breeding bulls. In some seasons starvation of older pups may be influenced by reduced food availability but this was usually of minor importance. Injury to the skull resulted from bites inflicted by females either accidently during birth or when pups tried to suck from females other than their mother. Trampling of young pups by bulls was probably responsible for the appreciable incidence of ruptured livers. Infectious disease and drowning played minor roles in pup mortality. Pups born late in the season suffered disproportionately greater mortality which may relate to female age and condition. Food availability (both during and prior to the breeding season) and weather are likely to account for year to year variation in pup mortality rates but the basic rate is primarily determined by breeding density. Further population increase and colonization of new beaches is expected until food resources during the summer, or more probably the winter, become limiting.

Effect of soluble salts on water absorption by gel‐forming soil conditioners

Abstract: The use of gel-forming synthetic polymers as aids to water retention in sandy soils is an important development to assist plant growth in arid regions. However, the water storage properties of these soil conditioners are significantly affected by the nature and concentrations of dissolved salts in irrigation waters. Moreover, the salt response of products in the three main chemical families—starch copolymers, polyvinylalcohols and polyacrylamides—is very different, emphasising the importance of detailed assays in selecting a product for a particular set of environmental conditions.

Aequorin measurements of free calcium in single heart cells.

Abstract: The performance of the heart depends on the concentrations of free calcium ions in the cytoplasm of the myocytes. However, direct evidence for changes in free Ca concentration in physiological events during response to drugs and in pathogenesis has been difficult to obtain because of technical problems in measuring free Ca at 10−7 M in cells with a volume of only a few picolitres1–3. Here we describe measurements made with the Ca-sensitive photo-protein aequorin3–5 in single ventricular myocytes isolated from rat heart6. We have detected signals from resting and contracting cells, and from cells exposed to media of altered ionic composition (raised K, lowered Na), ouabain and metabolic inhibitors. We report that free Ca in metabolically-poisoned myocytes is remarkably stable and that severe injury to the cell occurs before the free Ca concentration rises above 1–3 × 10−7 M, hence cell damage seems to be a cause, not a consequence, of a rise in free Ca. The technique used here should help to resolve many uncertainties regarding free Ca in heart function, and should be particularly valuable for investigating the role of free Ca in ischaemic pathogenesis.

Quality of life in treated head and neck cancer patients: a preliminary report.

Abstract: A psychological study of 48 elderly men after treatment for buccopharyngeal cancers was carried out to see whether treatment type (surgery alone, irradiation alone or salvage surgery after failed radiotherapy) was associated with differences in quality of life. Eight measures were used, covering functional disability, appearance, pain, depression, psychological well being and life satisfaction. Functional disability was lower and performance status high in those treated by irradiation alone. There was greater dissatisfaction with appearance in patients treated by surgery. Levels of depression were high in all groups. There were no significant differences between treatment groups however for depression, present pain, psychological well being or life satisfaction.

Nonlinear forces on a horizontal cylinder beneath waves

Abstract: Measurements of forces experienced by a submerged horizontal cylinder with its axis parallel to the crests in deep-water waves reveal nonlinear components with frequencies up to three times the fundamental wave frequency. The dominant nonlinear contribution to the loading is a t the third order in the wave amplitude, and, for Keulegan4arpenter numbers approaching 2, its magnitude was found to be as much as one-half that of the inertia force. It is suggested that the third-order force is associated with circulation generated by steady streaming in the oscillatory boundary layer on the cylinder. At higher Keulegan-Carpenter numbers, form drag becomes increasingly important, and velocity measurements close to the cylinder show the rapid development of the wake. Observations of nonlinear features of the transmitted waves are also discussed.