1,430 results for 1990, ResearchSpace@Auckland

  • Naamidine A is an antagonist of the epidermal growth factor receptor and an in vivo active antitumor agent

    Copp, Brent; Fairchild, CR; Cornell, L; Casazza, AM; Robinson, S; Ireland, CM (1998)

    Journal article
    The University of Auckland Library

    The known 2-aminoimidazole alkaloid naamidine A (1) was isolated from a Fijian Leucetta sp. sponge as an inhibitor of the epidermal growth factor (EGF) receptor. The compound exhibited potent ability to inhibit the EGF signaling pathway and is more specific for the EGF-mediated mitogenic response than for the insulin-mediated mitogenic response. Evaluation in an A431 xenograft tumor model in athymic mice indicated that naamidine A exhibited at least 85% growth inhibition at the maximal tolerated dose of 25 mg/kg. Preliminary mechanism of action studies indicate that the alkaloid fails to inhibit the binding of EGF to the receptor and has no effect on the catalytic activity of purified c-src tyrosine kinase.

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  • Isolation of 2-(3 '-bromo-4 '-hydroxyphenyl)ethanamine from the New Zealand ascidian Cnemidocarpa bicornuta

    Lindsay, Brent; Battershill, Christopher; Copp, Brent (1998)

    Journal article
    The University of Auckland Library

    From the ascidian Cnemidocarpa bicornuta, 2-(3'-bromo-4'-hydroxyphenol)ethanamine (3'-bromotyramine) (1) has been isolated along with the previously reported sponge metabolite, 1,3-dimethylisoguanine. The structure of 1 was confirmed by synthesis.

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  • Styelsamines A - D: New tetracyclic pyridoacridine alkaloids from the Indonesian ascidian Eusynstyela latericius

    Copp, Brent; Jompa, J; Tahir, A; Ireland, CM (1998)

    Journal article
    The University of Auckland Library

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  • Bolinaquinone: A novel cytotoxic sesquiterpene hydroxyquinone from a Philippine Dysidea sponge

    De Guzman, FS; Copp, Brent; Mayne, CL; Concepcion, GP; Mangalindan, GC; Barrows, LR; Ireland, CM (1998)

    Journal article
    The University of Auckland Library

    Sesquiterpene hydroxyquinones and hydroquinones have been isolated from various sponges.3-16 The sesquiterpene moiety of these metabolites usually have the normal drimane skeleton, as exemplified by spongiaquinone (1),3 a rearranged drimane skeleton, as in ilimaquinone (2)4 and isospongiaquinone (3),3.5 or a monocyclic sesquiterpenoid skeleton, as in metachromin C (4)6 (Chart 1). Recently, Patil and co-workers isolated related sesquiterpene derivatives, frondosins A???E, which feature a 6,7-bicyclic skeleton, as exemplified by frondosin A (5).7 We report here the isolation and structure determination of a cytotoxic sesquiterpene hydroxyquinone, bolinaquinone (6), which showed a rearranged drimane skeleton but with a different position for the hydroxyquinone moiety.

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  • Natural and synthetic derivatives of discorhabdin C, a cytotoxic pigment from the New Zealand sponge Latrunculia cf. bocagei

    Copp, Brent; Fulton, KF; Perry, NB; Blunt, JW; Munro, MHG (1994-12)

    Journal article
    The University of Auckland Library

    Modification of the spiro-cyclohexadienone skeleton of discorhabdin C (3) led to a series of derivatives 6???11. The biological properties of this series were evaluated in a wide range of screens for selective cytotoxicity, antifungal, and antimicrobial properties. The structure and biological properties of a further discorhabdin, discorhabdin E (5), from a New Zealand sponge Latrunculia cf. bocagei are also presented.

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  • Crystal structure of the cytotoxic marine alkaloid 2-bromoleptoclinidinone

    Lindsay, Brent; Oliver, Allen; Rickard, Clifton; Copp, Brent (1998)

    Journal article
    The University of Auckland Library

    2-Bromoleptoclinidinone methanol solvate, C18H8BrN3O??CH4O, crystallizes in the orthorhombic space group Pbca with a = 15.7013(2), b = 7.3308(1), and c = 26.9326(1) ??. The molecule is essentially planar, with the largest deviations occurring at bromine (???0.21 ??), carbonyl oxygen O(l) (+0.19 ??) and in ring-A (C(9) ???0.15 ??, C(10) ???0.15 ??). Methanol occupies the 1,10-phenanthroline-like metal binding site of the title compound.

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  • Structural requirements for biological activity of the marine alkaloid ascididemin

    Lindsay, BS; Barrows, LR; Copp, Brent (1995-04-06)

    Journal article
    The University of Auckland Library

    Comparison of the biological activities observed for ascididemin (2) and synthetic precursors/analogs has established the importance of N-8 in ring A, and a completed ring E, to topoisomerase II enzyme inhibition, human tumor cytotoxicity and antifungal/antibacterial properties. The results also suggest the presence of multiple mechanisms of toxicity by 2 towards mammalian cell systems.

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  • Efficient and convenient pyridine ring-E formation of the cytotoxic marine alkaloid ascididemin and related analogues

    Lindsay, Brent; Pearce, Allison; Copp, Brent (1997)

    Journal article
    The University of Auckland Library

    Conversion of tetracyclic quinone 1 to the cytotoxic pentacyclic alkaloid ascididemin (2) in 80% yield is achieved by reaction with paraformaldehyde and ammonium chloride in refluxing acetic acid. High yielding annelations are also observed for the related analogues N-8 deaza ascididemin (3) and kuanoniamine A (4).

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  • 1,3-dimethylguanine, a new purine from the New Zealand ascidian Botrylloides leachi

    Lindsay, Brent; Battershill, Christopher; Copp, Brent (1999)

    Journal article
    The University of Auckland Library

    The new purine 1,3-dimethylguanine (1) has been isolated from the ascidian Botrylloides leachi. The structure of 1 was elucidated by analysis of spectroscopic data, by comparison with the regioisomeric purine 1,3-dimethylisoguanine (2), and by hydrolysis to theophylline (3).

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  • Rates of deformation, uplift, and landscape development associated with active folding in the Waipara area of North Canterbury, New Zealand

    Nicol, A; Alloway, Brent; Tonkin, P (1994-12)

    Journal article
    The University of Auckland Library

    Analysis of the geometry and ages of faulted and tilted late Quaternary fluvial terraces and their associated cover beds provide evidence of active folding at three localities in the Waipara area of North Canterbury, New Zealand, Terrace survey data, the occurrence of the approximately 22.6-kyr-old Aokautere Ash, and examination of soil profiles indicate that folding has continued into the late Holocene but that the amounts and rates of deformation are locally variable. Rates of uplift in the Waipara area are compared with those derived from marine terraces preserved at the Pacific coast, east of the study area. Results indicate that rates of measurable deformation reach a maximum along the Waipara range front, where bedrock deformation is most intense and shortening rates of up to 5.57??0.69%/100 kyr occur. Across the coastal ranges the average rate of shortening is 0.8??0.4%/100 kyr, which corresponds with an absolute shortening rate of 1.4??0.6 m/kyr and represents only a small proportion of the predicted plate motion vector in this region. Uplift rates range from 0???1.83 m/kyr for a late last glacial fluvial terrace and from 1.36???2.16 m/kyr for three marine terraces. Fluvial and marine terrace uplift rates vary in accord with the geometries of the folds in bedrock, and the spatial pattern of uplift directly reflects fold growth. The structure contour pattern of folded surfaces provides a first approximation to the spatial pattern of uplift. Differential uplift due to folding accounts for up to approximately 55???75% of the total uplift and has produced folds with structural relief of about 1300 m (i.e., amplitudes of 600???700 m). These folds have formed over the last 0.8??0.4 m.y. since the onset of Quaternary deformation in the Waipara region.

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  • Volcanic-debris-avalanche deposits in New Zealand - Lithofacies organization in unconfined, wet-avalanche flows

    Palmer, BA; Alloway, Brent; Neall, VE (1991)

    Journal article
    The University of Auckland Library

    The lithofacies represent division of the debris-avalanche deposits into megaclast-rich (axial-A) and interclast matrix-rich (axial-B) parts and transformation of the avalanches into lahars (marginal lithofacies). Megaclasts preserving original volcanic stratigraphy in axial-A represent collapse and transport of coherent pieces of the edifice by the debris avalanches. Transformation into lahars occurred as the coarse avalanche debris came to rest and the finer portion continued to flow, enhanced by a secondary component eroded from underlying deposits. In general, flow across relatively featureless ring plains allowed multidirectional-lithofacies development, so that lobes of axial-A are surrounded by axial-B and marginal lithofacies both laterally and, where visible, distally. Variations in avalanche size and ring-plain physiography produced different lithofacies architectures in the New Zealand deposits. Large debris avalanches were little affected by physiography and spread out in fan-shaped sheets comprising near-concentric zones of each lithofacies. Smaller avalanches were confined at some point during flow, so that central parts of the deposit are shoestring diamictons of axial-B and the marginal lithofacies. The tripartite axial-A through axial ?? and marginal lithofacies associations are present in proximal areas of these deposits. Distal areas are usually axial-B and marginal lithofacies.

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  • The role of Egmont-sourced tephra in evaluating the paleoclimatic correspondence between the bio- and soil-stratigraphic records of central Taranaki, New Zealand

    Alloway, Brent; McGlone, MS; Neall, VE; Vucetich, CG (1992)

    Journal article
    The University of Auckland Library

    On the lower eastern flanks of Egmont Volcano, western North Island, New Zealand, several Egmont-sourced tephras have been correlated to a radiocarbon dated peat site that provides a late last-glacial to early post-glacial record of vegetation and climate change in central Taranaki. The pollen spectra at this site indicates a mosaic of grassland-shrubland and Prumnopitys taxifolia-dominant forest at ca. 13,100 BP and suggests a climate cooler and drier than at present. The ominance of tall podocarp forest by ca. 12,900 BP suggests that climatic amelioration was rapid towards the end of the last glacial period. Initially this forest was dominated by Prumnopitys taxifolia but at ca. 11,000 BP was succeeded by Dacrydium cupressinum indicating a steady shift to warmer and moister climate. Tephra interbedded with peat allows precise chrono-correlation into the Andisol-forming environment. The rapidity of climatic amelioration identified from variations in Andisol morphology and mineralogy concurs with that indicated from pollen changes in the peat.

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  • Particle size analyses of Late Quaternary allophane-dominated andesitic deposits from New Zealand

    Alloway, Brent; Neall, VE; Vucetich, CG (1992)

    Journal article
    The University of Auckland Library

    On the western North Island, New Zealand, a Late Quaternary sequence of allophane-dominated cover-bed (Andisol) deposits have accumulated from intermittent accretion and rapid, subsequent weathering of aerially transported detritus of dominantly andesitic provenance. Particle size analyses of Andisol samples were attempted for textural classification and provenance studies. The hydrometer and sedigraph techniques were unsuccessful due to difficulties arising from the flocculation of short-range order clay and organic constituents (SROCO), which prevented complete particle dispersion. Neither acidic (HCl) nor alkaline (NH4OH or NaOH) solutions were effective in completely dispersing samples, so an alternative chemical procedure was devised. This alternative pretreatment involves the selective dissolution of Andisol SROCO constituents by 0.2 mol acid-oxalate reagent (pH 3.0???3.5), and has considerable potential in the determination of particle size, soil textural classification and provenance of allophane-dominated andesitic deposits.

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  • Climate of the last glaciation in New Zealand, based on aerosolic quartz influx in an andesitic terrain

    Alloway, Brent; Stewart, RB; Neall, VE; Vucetich, CG (1992-09)

    Journal article
    The University of Auckland Library

    On western North Island, New Zealand, a record of climatic change during the last glaciation is preserved in a terrestrial coverbed sequence of dominantly andesitic provenance. Here, a succession of five loess-like Andisol units postdates the global high sea-level stand of oxygen isotope substage 5e (<125,000 yr). Tephra erupted from western and central North Island allow precise chronological correlation of the loess-like units. Aerosolic quartz additions determined by quantitative X-ray diffraction (XRD) record two major peaks that correlate with oxygen isotope stages 2 and 4. The most likely source of quartz-rich dust at these times is the surrounding continental shelf, then exposed by low sea level; however, quartz of Australian provenance may also be represented. This study provides the first confirmation from the terrestrial New Zealand record that rates of atmospherically transported particles increase during glacial stages.

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  • Late Quaternary (post 28,000 year B.P.) tephrostratigraphy of northeast and central Taranaki, New Zealand

    Alloway, Brent; Neall, VE; Vucetich, CG (1995)

    Journal article
    The University of Auckland Library

    Mt. Egmont/Taranaki in western North Island, New Zealand, has been inactive during historic time and thus its pattern of eruptive history must be reconstructed by inference from the stratigraphy and chronology of associated volcanic and pyroclastic deposits. The most complete record of eruptive activity from Egmont Volcano is found on the surrounding ring plain rather than on the volcanic cone, where surficial deposits are readily removed by erosion or deeply buried by the products of more recent eruptions. In this study, a comprehensive post???28 ka record of the volcano's eruptive history is presented, and the relationship of andesitic tephra beds to andic soil material, Egmont???sourced volcaniclastic detritus, and two silicic tephra beds from Taupo Volcano are discussed, along with implications for inter???regional correlation. The post???28 ka tephra succession is recorded in sixteen andesitic tephra formations. These formations and their approximate ages are as follows: Manganui tephra (4 beds; c. 3.1 ka), Inglewood Tephra (2 beds; c. 3.6 ka), Korito Tephra (2 beds; c. 4.1 ka), Mangatoki Tephra (2 beds; c. 4.4 ka), Tariki Tephra (6 beds; c. 4.6???4.7 ka), Waipuku Tephra (1 bed; c. 5.2 ka), Kaponga Tephra (10 beds; c. 8.0???10.0 ka), Konini Tephra (2 beds; c. 10.1 ka), Mahoe Tephra (4 beds; c. 11.0???11.4 ka), Kaihouri tephra (8 beds; c. 12.9???18.8 ka), Paetahi Tephra (6 beds; c. 19.4???20.2 ka), Poto Tephra (15 beds; c. 20.9???22.7 ka), Tuikonga Tephra (4 beds; c. 23.4???24.0 ka), Koru Tephra (2 beds; c. 24.8???25.2 ka), Pukeiti Tephra (1 bed; c. 26.2 ka) and Waitepuke Tephra (3 beds; c. 27.5???28.0 ka). Many of these tephra beds are sufficiently distinct and widespread enough to permit the dating and correlation of ring???plain forming volcaniclastic deposits with which they are interbedded. The post???28 ka tephra succession can also be subdivided into three broad sequences on the basis of major variations in the morphological and mineralogical characteristics of inter???bedded andic soil material. At least 76 tephra events from Egmont Volcano with volumes exceeding 107 m3 have been recorded since c. 28 ka with an average eruptive periodicity of one in every c. 330 years. This frequency is considered minimal since more tephras of lesser magnitude may have been erupted but are only represented on the ring plain as intermittent accretion of fine???grained ash that has rapidly weathered to andic soil material.

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  • Revision of the marine chronology in the Wanganui Basin, New Zealand, based on the isothermal plateau fission-track dating of tephra horizons

    Alloway, Brent; Pillans, BJ; Sandhu, AS; Westgate, JA (1993-01)

    Journal article
    The University of Auckland Library

    The occurrence of tephra horizons in basins adjacent to volcanic arcs provide an excellent opportunity for establishing a reliable chronostratigraphic framework for detailed sedimentological studies. In this study, three widespread and stratigraphically important rhyolitic tephra horizons interbedded in Plio/Pleistocene strata of the Wanganui Basin, New Zealand, are dated by application of the isothermal plateau fission-track (ITPFT) technique to hydrated glass shards. All glass samples were corrected for annealing and consequently yield reliable ages. Rangitawa Tephra yielded statistically indistinguishable ages from three localities that are in excellent agreement with recently determined zircon fission-track age estimates of ca. 0.35 Ma. ITPFT ages of 1.05 ?? 0.05 and 1.63 ?? 0.15 Ma for Potaka Pumice and Pakihikura Pumice, respectively, are considerably older than previous FT estimates but consistent with new magnetostratigraphic data that places the Potaka within the Jaramillo Subchron, and Pakihikura within the Matuyama Chron between the Cobb Mountain and Olduvai Subchrons. Combining our fission-track ages with the magnetostratigraphy, the true age of sediments within the Wanganui Basin is found to be significantly underestimated. Sedimentation rates of between ca. 680-630 m/Ma from 1.63 Ma to 0.35 Ma are calculated in the eastern part of the basin and are much lower than those calculated using the previous FT chronology. This new ITPFT-age data demonstrates that the existing Plio/Pleistocene marine chronology in New Zealand will require age revision and has important implications when considering the evolution of several other sedimentary basins in southern North Island that contain the same ITPFT-dated tephra horizons.

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  • The Madras corporation band: A story of social change and indigenization

    Booth, GD (1996)

    Journal article
    The University of Auckland Library

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  • Maximum local scour depth at bridge piers and abutments

    Kandasamy, JK; Melville, Bruce (1998)

    Journal article
    The University of Auckland Library

    Results of recent laboratory investigations of local scour at bridge piers and abutments are presented. Similarities between the principal vortex occurring in local scour holes at abutments and the horseshoe vortex and downflow at piers are highlighted. Pier and abutment laboratory data, collected near the threshold conditions for sediment movement, display similar trends in the variation of scour depth with length and flow depth. This variation is best described in a three dimensional plot. A simple equation, that can be used to predict the maximum local scour depth at either piers or abutments aligned perpendicular to the flow, is presented and compared with field data.

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  • Stratigraphy and chronology of the Stent tephra, a c. 4000 year old distal silicic tephra from Taupo Volcanic Centre, New Zealand

    Alloway, Brent; Lowe, DJ; Chan, Robert; Eden, D; Froggatt, P (1994-03)

    Journal article
    The University of Auckland Library

    Tephrostratigraphic and chronologic studies in two areas of the North Island have identified a previously unrecorded, thin, distal silicic tephra derived from the Taupo Volcanic Centre. In Taranaki, three radiocarbon ages of the uncorrelated tephra are consistent with the independent radiocarbon chronology obtained from enveloping Egmont???sourced tephras. In western Bay of Plenty, where the uncorrelated tephra is also directly dated, it is overlain by Whakaipo Tephra (c. 2.7 ka) and underlain by Hinemaiaia Tephra (c. 4.5 ka). From these sites in Taranaki and western Bay of Plenty, seven radiocarbon dates obtained on the uncorrelated silicic tephra yield an error???weighted mean age of 3970 ??31 conventional radiocarbon years B.P. The ages on the uncorrelated tephra (informally referred to as Stent tephra) from both areas are statistically identical but significantly different from those on both Waimihia and Hinemaiaia Tephras. The occurrence of Stent tephra in Taranaki, c. 160 km upwind from the postulated source area, and in western Bay of Plenty, suggests that it represents the product of a moderately large plinian eruption. Until recently, its validity as a discrete eruptive event had been problematical, because a near???source equivalent deposit between Waimihia and Hinemaiaia Tephras was not recognised in the Taupo area. However, a revised stratigraphy proposed by C. J. N. Wilson in 1993 for eastern sectors of the Taupo area shows that multiple tephra layers were erupted from Taupo volcano between c. 3.9 and 5.2 ka. Of these newly recognised layers, unit???g???the product of a moderately large eruption (???0.15 km3) at c. 4.0 ka???is tentatively correlated with Stent tephra. Other eruptive units recognised by Wilson are either too old or too small in volume to be considered as likely correlatives.

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  • Sediment control at water intakes

    Wang, YL; Odgaard, AJ; Melville, Bruce; Jain, SC (1996)

    Journal article
    The University of Auckland Library

    Submerged vanes are shown to be effective in preventing bed load transport from entering water intakes. By generating a secondary circulation in the flow, the vanes change the magnitude and direction of the bed-shear stresses and cause a redistribution of the flow and sediment transport in the area affected by the vanes. As a result, the riverbed aggrades in one portion of the channel and degrades in another. The performance of two vane installations, designed according to guidelines developed earlier, are evaluated by comparing the bed topography before and after vanes were installed. The design guidelines, which utilize a numerical model developed earlier, are shown to be appropriate. The guidelines apply only when the intake flow is small enough that the withdrawal causes little change in the river flow velocity in front of the intake.

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