Showing papers by "Australian National University published in 1985"

Rapid transfer of DNA from agarose gels to nylon membranes.

Abstract: The unique properties of nylon membranes allow for dramatic improvement in the capillary transfer of DNA restriction fragments from agarose gels (Southern blotting). By using 0.4 M NaOH as the transfer solvent following a short pre-treatment of the gel in acid, DNA is depurinated during transfer. Fragments of all sizes are eluted and retained quantitatively by the membrane; furthermore, the alkaline solvent induces covalent fixation of DNA to the membrane. The saving in time and materials afforded by this simple modification is accompanied by a marked improvement in resolution and a ten-fold increase in sensitivity of subsequent hybridization analyses. In addition, we have found that nylon membrane completely retains native (and denatured) DNA in transfer solvents of low ionic strength (including distilled water), although quantitative elution of DNA from the gel is limited to fragments smaller than 4 Kb. This property can be utilized in the direct electrophoretic transfer of native restriction fragments from polyacrylamide gels. Exposure of DNA to ultraviolet light, either in the gel or following transfer to nylon membrane, reduces its ability to hybridize.

Effect of temperature on the CO2/O 2 specificity of ribulose-1,5-bisphosphate carboxylase/oxygenase and the rate of respiration in the light : Estimates from gas-exchange measurements on spinach.

Abstract: Responses of the rate of net CO2 assimilation (A) to the intercellular partial pressure of CO2 (p i ) were measured on intact spinach (Spinacia oleracea L.) leaves at different irradiances. These responses were analysed to find the value of p i at which the rate of photosynthetic CO2 uptake equalled that of photorespiratory CO2 evolution. At this CO2 partial pressure (denoted Г), net rate of CO2 assimilation was negative, indicating that there was non-photorespiratory CO2 evolution in the light. Hence Г was lower than the CO2 compensation point, Γ. Estimates of Г were obtained at leaf temperatures from 15 to 30°C, and the CO2/O2 specificity of ribulose 1,5-bisphosphate (RuBP) carboxylase/oxygenase (E.C. 4.1.1.39) was calculated from these data, taking into account changes in CO2 and O2 solubilities with temperature. The CO2/O2 specificity decreased with increasing temperature. Therefore we concluded that temperature effects on the ratio of photorespiration to photosynthesis were not solely the consequence of differential effects of temperature on the solubilities of CO2 and O2. Our estimates of the CO2/O2 specificity of RuBP carboxylase/oxygenase are compared with in-vitro measurements by other authors. The rate of nonphotorespiratory CO2 evolution in the light (R d ) was obtained from the value of A at Г. At this low CO2 partial pressure, R d was always less than the rate of CO2 evolution in darkness and appeared to decrease with increasing irradiance. The decline was most marked up to about 100 μmol quanta m-2 s-1 and less marked at higher irradiances. At one particular irradiance, however, R d as a proportion of the rate of CO2 evolution in darkness was similar in different leaves and this proportion was unaffected by leaf temperature or by [O2] (ambient and greater). After conditions of high [CO2] and high irradiance for several hours, the rate of CO2 evolution in darkness increased and R d also increased.

Effects of salt stress on the growth, ion content, stomatal behaviour and photosynthetic capacity of a salt-sensitive species, Phaseolus vulgaris L.

Abstract: Phaseolus vulgaris (cv. Hawkesbury Wonder) was grown over a range of NaCl concentrations (0–150 mM), and the effects on growth, ion relations and photosynthetic performance were examined. Dry and fresh weight decreased with increasing external NaCl concentration while the root/shoot ratio increased. The Cl- concentration of leaf tissue increased linearly with increasing external NaCl concentration, as did K+ concentration, although to a lesser degree. Increases in leaf Na+ concentration occurred only at the higher external NaCl concentrations (≧100 mM). Increases in leaf Cl- were primarily balanced by increases in K+ and Na+. X-ray microanalysis of leaf cells from salinized plants showed that Cl- concentration was high in both the cell vacuole and chloroplast-cytoplasm (250–300 mM in both compartments for the most stressed plants), indicating a lack of effective intracellular ion compartmentation in this species. Salinity had little effect on the total nitrogen and ribulose-1,5-bisphosphate (RuBP) carboxylase (EC 4.1.1.39) content per unit leaf area. Chlorophyll per unit leaf area was reduced considerably by salt stress, however. Stomatal conductance declined substantially with salt stress such that the intercellular CO2 concentration (Ci) was reduced by up to 30%. Salinization of plants was found to alter the δ13C value of leaves of Phaseolus by up to 5‰ and this change agreed quantitatively with that predicted by the theory relating carbon-isotope fractionation to the corresponding measured intercellular CO2 concentration. Salt stress also brought about a reduction in photosynthetic CO2 fixation independent of altered diffusional limitations. The initial slope of the photosynthesis versus Ci response declined with salinity stress, indicating that the apparent in-vivo activity of RuBP carboxylase was decreased by up to 40% at high leaf Cl- concentrations. The quantum yield for net CO2 uptake was also reduced by salt stress.

Attractive forces between uncharged hydrophobic surfaces: direct measurements in aqueous solution.

Abstract: Long, double-chained alkylammonium acetate surfactants are soluble in water and, under suitable conditions, adsorb onto sheets of muscovite mica, forming an electrically neutral, hydrophobic surface. Attractive forces measured between such surfaces are 10 to 100 times stronger than expected from van der Waals theory over distances D up to about 10 nanometers. The forces decay exponentially [with a force proportional to exp(-D/1.4)] instead of following the power-law behavior of continuum theory. The results of these and earlier experiments indicate that the strength of these attractive forces depends critically on the degree of hydrophobicity of the surface and is due to the long-range influence of the surface on the structure of water. In addition, for very hydrophobic surfaces, the cavitation effects on pulling the surfaces apart are described.

Isolation and properties of soybean [Glycine max (L.) Merr.] mutants that nodulate in the presence of high nitrate concentrations.

Abstract: Soybean seeds [Glycine max (L.) Merr. ev. Bragg] were mutagenized with ethyl methanesulfonate. The M2 progeny (i.e., the first generation after mutagenesis) of these seeds were screened for increased nodulation under high nitrate culture conditions. Fifteen independent nitrate-tolerant symbiotic (nts) mutants were obtained from 2500 M2 families. In culture on sand with KNO3, nodule mass and nodule number in mutant lines were several-fold those of the wild type cultured under the same conditions. Inheritance of the nts character through to subsequent generations was observed in the 10 mutants tested. Mutant nts382 also nodulated more than the wild type in the absence of nitrate. Furthermore, nitrate stimulated growth in both the wild type and nts382, and these lines had similar nitrate reductase activity. These results indicate that nts382 is affected in a nodule-development regulatory gene and not in a gene related to nitrate assimilation.

A Supernodulation and Nitrate-Tolerant Symbiotic (nts) Soybean Mutant

Abstract: The nodulation characteristics of soybean (Glycine max) mutant nts382 are described. The mutant nodulated significantly more than the parent cultivar Bragg in the presence and absence of several combined nitrogen sources (KNO3, urea, NH4Cl, and NH4NO3). The number of nodules on the tap root and on lateral roots was increased in the mutant line. In the presence of KNO3 and urea, nitrogenase activity was considerably higher in nts382 than in Bragg. Mutant plants were generally smaller than wild-type plants. Although nts382 is a supernodulator, inoculation with Rhizobium japonicum was necessary to induce nodule formation and both trial strains CB1809 (= USDA136) and USDA110 elicited the mutant phenotype. Segregation of M3 progeny derived from a M2 wild-type plant indicated that the mutant character is inherited as a Mendelian recessive. The mutant is discussed in the context of regulation of nodulation and of hypotheses that have been proposed to explain nitrate inhibition of nodulation.

Dementia and depression among the elderly living in the Hobart community: the effect of the diagnostic criteria on the prevalence rates

Abstract: A survey was made of 274 non-institutionalized persons aged 70 and over living in Hobart. The prevalence of dementia and of depression was measured by interviewing subjects using a modified version of the Geriatric Mental State Schedule (GMS) (Copeland et al. 1976) and the Mini Mental State Examination (MMSE) (Folstein et al. 1975). Rates of morbidity were derived from different diagnostic procedures. These were: diagnoses made by a psychiatrist (A.S.H.) directly from the interview schedules and audiotapes, and rated as mild, moderate or severe; the criteria laid down in DSM-III, converted into algorithms describing 3 degrees of severity; and the algorithms for pervasive dementia and depression proposed by Gurland et al. (1983), and from these authors' rational scales. In addition, the relation between scales for dementia and for depression and the diagnosed categories was examined. Some problems in applying these methods to aged persons in the community are discussed. It is concluded that more detailed specification of criteria is desirable if the comparative epidemiology of dementia and depression in old age is to advance.

Leaf Conductance in Relation to Rate of CO2 Assimilation: I. Influence of Nitrogen Nutrition, Phosphorus Nutrition, Photon Flux Density, and Ambient Partial Pressure of CO2 during Ontogeny

Abstract: Plants of Zea mays were grown with different concentrations of nitrate (0.6, 4, 12, and 24 millimolar) and phosphate (0.04, 0.13, 0.53, and 1.33 millimolar) supplied to the roots, photon flux densities (0.12, 0.5, and 2 millimoles per square meter per second), and ambient partial pressures of CO(2) (305 and 610 microbars). Differences in mineral nutrition and irradiance led to a large variation in rate of CO(2) assimilation per unit leaf area (A, 11 to 58 micromoles per square meter per second) when measured under standard conditions. The variation was shown, with the plants that had received different amounts of nitrate, to be related to variations in the nitrogen and chlorophyll contents, and phosphoenolpyruvate and ribulose-1,5-bisphosphate carboxylase activities per unit leaf area. Irrespective of growth treatment, A and leaf conductance to CO(2) transfer (g), measured under standard conditions were in almost constant proportion, implying that intercellular partial pressure of CO(2) (p(i)), was almost constant at 95 microbars. The same proportionality was maintained as A and g increased in an initially nitrogen-deficient plant that had been supplied with abundant nitrate. It was shown that p(i) measured at a given ambient partial pressure was not affected by the ambient partial pressure at which the plants had been grown, although it was different when measured at different ambient partial pressures. This suggests that the close coupling between A and g in these experiments is not associated with sensitivity of stomata to change in p(i).Similar, though less comprehensive, experiments were done with Gossypium hirsutum, and yielded similar conclusions, except that the proportionality between A and g at normal ambient partial pressure of CO(2) implied P(i) approximately 200 microbars.

Evolutionary Ecology of Marsupials

Abstract: Preface 1. Introduction 2. Marsupials and their resources 3. The marsupial life history 4. Life histories of the carnivorous marsupials 5. Life histories of the herbivorous marsupials 6. Antechinus as a paradigm in evolutionary ecology 7. Coevolution and community structure 8. Future directions Appendix 1 Appendix 2 References Marsupial genus and species index Subject index.

Constitutive synthesis of interleukin-3 by leukaemia cell line WEHI-3B is due to retroviral insertion near the gene.

Abstract: Interleukin-3 (multi-CSF) is a multilineage haematopoietic growth regulator that initiates the proliferation and differentiation of multipotential stem cells. Complementary DNA clones encoding interleukin-3 (IL-3) have recently been isolated and the structure of the IL-3 gene determined. IL-3 is produced by T lymphocytes or T lymphomas only after stimulation with antigens, mitogens or chemical activators such as phorbol esters. The myelomonocytic leukaemia line WEHI-3B also produces IL-3 but its production is constitutive and the WEHI-3B cells do not appear to produce significant levels of any of the other lymphokines normally secreted by T lymphocytes after stimulation. It has been proposed that the genetic change leading to the constitutive expression of IL-3 may have been a key event in the development of this leukaemia. We report here that the constitutive synthesis of IL-3 by the WEHI-3B cell line is due to the insertion of an endogenous retrovirus-like element close to the 5' end of the gene. The insertion, an intracisternal A particle (IAP) genome, is positioned with its 5' long terminal repeat (LTR) close to the promoter region of the IL-3 gene, resulting in constitutive synthesis of IL-3.

Transformation relations for the conventional Okq and normalised O'kq Stevens operator equivalents with k=1 to 6 and -k⩽q⩽k

Abstract: Extensions of the conventional Stevens operators Okq to negative values of q and their transformation properties are reviewed and reconsidered. Transformation matrices with k=1 to 6 and -k

Biochemical Characterization of Chlorophyll-Free Mitochondria From Pea Leaves

Abstract: Mitochondria from pea leaves were purified by centrifugation on a self-generated Percoll gradient which contained a linear gradient of polyvinylpyrrolidone-25 (0-10%, w/v). The chlorophyll content of the purified mitochondria was less than 1 µg per mg protein. All substrates were rapidly oxidized by these mitochondria, the rate of glycine oxidation being between 200 and 300 nmol O2 min-1 mg-1 protein, depending on the age of the leaves used. These rates did not vary significantly over a period of 20 h, provided NAD+ was supplied exogenously, when the mitochondria were stored on ice. Respiratory control, ADP/O ratios and outer membrane integrity (always more than 95%) were also maintained during storage. The phospholipid composition of the membranes from the leaf mitochondria was virtually identical to that of mitochondria from non-photosynthetic tissues although their lipid to protein ratio was slightly lower. The polypeptide pattern of the membranes from green leaf mitochondria and those from etiolated leaves and hypocotyls were also similar, but marked differences were observed between the matrix proteins from the different tissues. In particular, intensely stained bands at 94, 51,41 and 15.5 kDa which were present in the matrix of green leaf mitochondria were missing or present in much smaller quantities in the non-photosynthetic tissues. This difference was correlated with the ability of the mitochondria to oxidize glycine, suggesting that the four polypeptides may be associated with the glycine decarboxylase complex.

Development of widespread mangrove swamps in mid-Holocene times in northern Australia

Abstract: Mangrove forests in northern Australia typically occur as fringes along tidal estuaries and relatively sheltered coasts. Radiocarbon dating evidence from the South Alligator River, presented here, suggests that extensive mangrove swamps developed between 6,500 and 7,000 yr ago and flourished for about 1,000 yr. Pollen analysis of a stratigraphic core at a mid-plains site links the growth of these forests with the interaction of sea-level change and sedimentation. This was succeeded by the development of flood-plains with tidal river channels, a dramatic ecological change that has implications for all coastal and nearshore systems.

Intracortical facilitation among co-oriented, co-axially aligned simple cells in cat striate cortex.

Abstract: Most neurons in cat striate visual cortex show inhibitory effects when moving contours are presented beyond the limits of classic receptive field regions. Facilitatory effects are also present in about 40% of simple cells. Here, we report a highly specific form of this facilitation, mediated only by neurons possessing both an orientation tuning matched to the test unit, and a receptive field position aligned with its long axis. This finding illustrates one of the intracortical interconnection schemes hypothesized by Mitchison and Crick (1982). Periodic clustering in long, intrinsic axons may signify a neuron seeking specific functional interactions like these across columnar systems in both the spatial and orientation domains.

Petrology and origin of primitive lavas from the Troodos ophiolite, Cyprus

Abstract: Parental magmas to the Troodos ophiolite are characterised by low TiO2 and Al2O3 and high SiO2. Extremely fresh and chemically primitive (high MgO) rocks are found within the Upper Pillow Lavas and along the Arakapas Fault Belt of Cyprus and contain forsteritic olivine±enstatite and groundmass clinopyroxene set in glass or plagioclase, with accessory magnesiochromite and sometimes hornblende. They are quartz-normative and may have originally contained up to 3 wt% H2O. Geochemically, there are three distinct groups of primitive lavas, based on TiO2 and Zr contents but also reflected by CaO, Na2O and REE abundances. These groups cannot be related by crystal fractionation and are considered to have been generated by incremental melting of a variably depleted source region. The parental magma to the least depleted group (Group I) was that of the major portion of the Troodos plutonic complex and is similar to those postulated for other “low-Ti” ophiolites. Chemically it has close affinities with komatiitic basalts. The most depleted lavas (Group III) all have U-shaped REE profiles and variable 143Nd/ 144Nd ratios, interpreted in terms of metasomatism of the source region by an incompatible element-enriched component which was probably derived from a subducted slab. These lavas represent an intermediate step in the development of boninite series rocks.

Adaptation of the Motion-Sensitive Neuron H1 is Generated Locally and Governed by Contrast Frequency

Abstract: Recordings from the motion-sensitive giant neuron H1 of the lobula plate of the fly Lucilia cuprina, indicate that small field, possibly retinotopic, units presynaptic to H1, adapt in response to motion in much the same way as photoreceptors do to their signal, light intensity. As a result their response is related to what we have called velocity contrast. This adaptation is shown to take place during or after the computation of motion, and is strongly dependent on contrast frequency (temporal frequency of a moving grating). Photometric contrast contributes much less to the rate of adaptation. This is best seen by the fact that at low contrast frequencies, strong photometric contrasts can saturate H1, and yet do not adapt H1 quickly. We propose that the dependence of the adaptation upon contrast frequency is a strategy for linking the radical changes of sensitivity and temporal resolution with adaptation to that signal parameter available to H1 that is most indicative of velocity change. The effects of changes in signal parameters not related to motion, such as sudden changes in photometric contrast, which might otherwise be construed as velocity changes, are reduced. Impulse response measurements confirm the increase in temporal resolution of velocity changes, during adaptation, as already known in adaptation to frequent impulses. The variable rate of adaptation means that the best measure of responsiveness is the peak instantaneous spike discharge rate. Taking this into account, the preferred contrast frequency of the H1 neuron in the unadapted state is 8-10 Hz, in close agreement with the optimum contrast frequency for initiating a landing response in tethered flies.