Showing papers by "University of Melbourne published in 1983"

Nitrogen Redistribution during Grain Growth in Wheat (Triticum aestivum L.) : IV. Development of a Quantitative Model of the Translocation of Nitrogen to the Grain

Abstract: Translocation of nitrogen was measured in wheat (Triticum aestivium L. cv SUN 9E) plants grown without an exogenous supply of nitrogen from the time that the flagleaf began to emerge, and a model of nitrogen translocation was constructed to describe translocation on one day during the linear period of grain growth. Nitrogen for grain development was derived entirely by the redistribution of nitrogen from vegetative organs. Leaves contributed 40%, glumes 23%, stem 23%, and roots 16% of the nitrogen incorporated by the grains on the fifteenth day after anthesis. Less than 50% of the nitrogen exported from leaves was translocated directly to the grain via the phloem, the rest was translocated to the roots and was cycled in the roots and exported to the shoot in the transpiration stream. Nitrogen imported by leaves and glumes via the xylem was not accumulated in these organs but was transferred to the phloem for reexport from the organs. A large proportion (60%) of the nitrogen in the transpiration stream was cycled in the glumes. The glumes were also a major source of nitrogen for grain development. It was considered likely that this organ always plays an important role in nitrogen metabolism in wheat.

Morphological and Biochemical Characterization of Four Clonal Osteogenic Sarcoma Cell Lines of Rat Origin

Abstract: The ultrastructural and biochemical properties of four clonal osteogenic sarcoma lines, UMR 104, 105, 106, and 108, have been compared with uncloned osteogenic sarcoma cells and normal osteoblast-rich cells derived from newborn rat calvaria High alkaline phosphatase activity and activation of adenylate cyclase by parathyroid hormone were used as biochemical markers of osteoblastic cells Cloning enriched both of these parameters above those of the parent tumor and far higher than that seen in normal cells, suggesting enrichment of the osteoblast phenotype Both of these properties have been retained through many passages in culture Morphologically, the clonal lines have also retained the "blast"-like appearance of the uncloned osteogenic sarcoma cells and consist mainly of flat, relatively featureless cells Many cells with mitotic figures were observed, indicating continuous cell division taking place in the malignant cells Each clonal line gave rise to characteristic tumors when reinjected into rats It is concluded that the clonal osteogenic sarcoma lines are highly differentiated tumor lines which have conserved the differentiated properties of the mature osteoblast, making them a suitable model for the study of the effects of hormones on the growth of a differentiated tumor, as well as for the study of hormonal regulation of the osteoblast

Structure of a genomic clone encoding biologically active human relaxin

Abstract: Relaxin is a peptide hormone1–4 synthesized in the corpora lutea of ovaries during pregnancy and is released into the blood stream prior to parturition. Its major biological effect is to remodel the mammalian reproductive tract to facilitate the birth process5. Determination of the structure of human relaxin is thus a first step in opening up the possibility of clinical intervention in cases of difficult labour. However, the limited availability of human ovaries during pregnancy has prevented both direct amino acid sequence determination and isolation of cDNA clones obtained from relaxin producing tissue. Our approach has therefore been to screen directly for a human relaxin gene using an homologous porcine relaxin cDNA probe. We report here the successful identification of a genomic clone from which the structure of the entire coding region of a human preprorelaxin gene has been determined. Synthesis of biologically active relaxin has shown that the novel gene structure described herein codes for an authentic human relaxin. We believe this is the first successful synthesis of a biologically active hormone whose structure was predicted solely from the structure of a genomic clone.

Tactile discrimination of gratings

Abstract: Human subjects were required to differentiate grating surfaces of alternating grooves and ridges by moving a finger back and forth across the surface. Their discriminative capacities were measured, as well as the movement and force profiles that they selected. To measure discrimination, a forced choice paradigm was used in which three surfaces were presented on each trial. Two surfaces were the same (standards) and the subject was required to indicate which of the three surfaces (the comparison) differed from the other two. Two series of surfaces were used with standards whose spatial periods were 770 and 1002 μ, respectively. Subjects were able to discriminate, at the 75% correct level, two gratings which differed in spatial period by the order of 5%. When tangential movement between the surface and the finger was eliminated, and only radial contact permitted, discrimination was degraded and the 75% correct levels increased to the order of 10%. Subjects were free to choose their own patterns of finger movement and of contact force between finger and surface. Movement was measured cinematographically. For all subjects movement patterns were close to sinusoidal, with frequencies in the range of 4.0 Hz and with mean velocities of the order of 160 mm/s. Patterns of contact force were measured by a force transducer. For all subjects the force varied rhythmically in synchrony with movement, but the patterns and magnitudes varied with the subject. Gratings were scaled for perceived roughness by a magnitude estimation technique: the relationship between perceived roughness and grating period was monotonic.

The characterization of ag sols by electron microscopy, optical absorption, and electrophoresis

Abstract: Several differently prepared silver sols and a gold sol were examined using electron microscopy optical absorption and microelectrophoresis techniques. The effects of 4-dimethyl-amino-pyridine and pyridine addition to the sols were also studied. In all cases of amine adsorption onto the sol particles, an accompanying decrease in the magnitude of the electrophoretic mobility of the particles was observed, and a long wavelength (>500 nm) absorption band was formed. The solution species responsible for these changes is an aggregate composed of the primary sol.

Callose and determination of pistil viability and incompatibility.

Abstract: Callose provides a useful phenotypic bioassay in plant breeding to determine: incompatibility system; gametophytic competition; and stigma and ovule viability. Callose appearance in ovules may be associated with senescence, and used to determine the effective pollination period. In incompatible matings, callose formation is specific and related to rejection phenomena. The stigma callose response is induced by informational molecules carried by the germinal line, i.e. self or interspecific pollen, but not by the somatic line. Several methods of visualizing callose are reviewed. The role of callose in pollen-stigma interactions has many analogies with host-parasite interactions, and a model is proposed based on relationships between callose, boron and inhibitor (phytoalexin-like) synthesis. The callose response provides a useful tool for the biotechnology of seed production.

Chronic Electrical Stimulation of the Auditory Nerve in Cats: Physiological and Histopathological Results

Abstract: The ability of spiral ganglion cells to survive long-term electrical stimulation is a precondition for the success of cochlear prostheses. In this study 10 cats were implanted bilaterally with bipolar scala tympani electrodes, and stimulated for periods of up to 2029 hours using charge balanced biphasic current pulses. The status of the auditory nerve was monitored periodically by recording electrically evoked auditory brainstem responses. At the conclusion of the stimulation program, spiral ganglion cell survival was assessed for stimulated and control cochleas; comparison of the two groups showed no statistically significant difference. The results of this study indicate that long-term intracochlear electrical stimulation, using carefully controlled biphasic pulses, does not adversely affect the spiral ganglion cell population.

Simulation of Electrostatic Systems in Periodic Boundary Conditions. III. Further Theory and Applications

Abstract: This paper makes some developments and clarifications of the theory for the application of periodic boundary conditions to the numerical simulation of the statistical mechanics of a cubic sample of dipolar particles. The reaction-field effect is treated rigorously. The anisotropies inherent in the periodic boundary condition Hamiltonian are allowed for in the derivation of a new fluctuation formula. A perturbation theory to account for anisotropic long-ranged terms is described, giving two di­-electric constant estimates from one simulation. These new results are illustrated with Monte Carlo simulations of the Stockmayer system at reduced density 0.8, reduced square dipole moment 2.0 and scaled temperature 1.35, giving a dielectric constant estimate of 25 ± 2 from all the data, and showing that the perturbation theories are very accurate. It appears possible to claim that periodic boundary conditions should be used with infinite external dielectric constant in almost all circumstances, because they then give a chain of configurations that provide compar­atively very stable estimates of dielectric constant.

Tumor-derived growth factor increases bone resorption in a tumor associated with humoral hypercalcemia of malignancy

Abstract: Evidence is presented that a tumor-derived transforming growth factor is responsible for stimulating bone resorption and causing hypercalcemia in an animal tumor model of the hypercalcemia of malignancy. Both conditioned medium harvested from cultured tumor cells and tumor extracts of the transplantable rat Leydig cell tumor associated with hypercalcemia contained a macromolecular bone resorbing factor with the chemical characteristics of a tumor-derived transforming growth factor.

Low-Reynolds-number turbulent boundary layers in zero and favorable pressure gradients

Abstract: Etude experimentale des proprietes moyennes de l'ecoulement dans des couches limites turbulentes avec des nombres de Reynolds inferieurs a 3000. Determination des distributions de vitesse et du frottement superficiel

Regulation of Alcohol Dehydrogenase (ADH) and Aldehyde Dehydrogenase (ALDDH) in Aspergillus nidulans

Abstract: There is a single major alcohol dehydrogenase (ADH) and a single major aldehyde dehydrogenase (AldDH) in Aspergillus nidulans. Both ADH and AldDH are induced by ethanol and by acetaldehyde and both are subject to carbon catabolite repression. ADH and AldDH are necessary for the utilization of ethanol and of threonine, indicating that both compounds are utilized via acetaldehyde. ADH and AldDH each give a single major activity band on gel electrophoresis. Sodium dodecyl sulphate polyacrylamide gel electrophoresis of cell extracts shows at least two similar ADH polypeptides of approximate relative molecular mass (r.m.m.) 41 000 and two similar AldDH polypeptides of approximate r.m.m. 57 000. The in vitro translation of mRNA from induced, carbon derepressed wild-type cells gives up to three ADH polypeptides in the r.m.m. range 39 000-43 000 and an AldDH polypeptide of approximate r.m.m. 57 000. The mRNA from uninduced, carbon repressed wild-type cells does not direct the synthesis of the ADH and AldDH polypeptides. This indicates that the regulation of ADH and AldDH is at the level of transcription and/or post-transcriptional modification. The probable explanation of the multiple ADH polypeptides is post-transcriptional modification of the mRNA. Allyl alcohol mutants were made by using diepoxyoctane and $\gamma $-rays as mutagens. There are two classes, alcA and alcR. Neither class can utilize ethanol or threonine as a carbon source. The alcA mutants lack normal ADH and are recessive. Of the 47 alcA mutants examined 39 do not make the ADH polypeptides while eight do so. Therefore alcA is the structural gene for ADH. The two alcA mutants tested do not make functional mRNA for ADH. The alcR mutants lack both ADH and AldDH and are recessive. No alcR mutants make the ADH or the AldDH polypeptides. The three alcR mutants tested do not make functional ADH or AldDH mRNA. The mutant alcR125 is a nonsense mutant, which establishes that alcR codes for a protein. The alcA and alcR genes are adjacent on chromosome VII and a preliminary fine-structure map of the alcA gene has been made. Three mutants that cannot utilize ethanol or threonine and have ADH, but lack AldDH, define a gene AldA on chromosome VIII. The aldA25 mutant makes the AldDH polypeptides, the other two aldA mutants do not. Therefore aldA is probably the structural gene for AldDH. Our current hypothesis is that alcA and aldA are the structural genes for ADH and AldDH respectively and alcR is a transacting regulatory gene coding for a protein whose function is necessary for the expression of the alcA and aldA genes.

Completeness of the negation as failure rule

Abstract: Let P be a Horn clause logic program and comp(p) be its completion in the sense of Clark. Clark gave a justification for the negation as failure rule by showing that if a ground atom A is in the finite failure set of P, then ∼A is a logical consequence of comp(P), that is, the negation as failure rule is sound. We prove here that the converse also holds, that is, the negation as failure rule is complete.

Calcium and cell death.

Abstract: Irrespective of age or species, injured cardiac myocyles accumulate Ca2+. In this paper four different aspects of the Ca2+-overloading phenomenon are discussed. These aspects include the conditions under which it occurs, the possible routes of Ca2+ entry, the metabolic consequences of the raised tissue Ca2+ and possible protective procedures. The particular protective procedures that will be described involve the combined use of hypothermia and nifedipine (50μg/l), with and without K+induced chemical cardioplegia. Isolated, electrically paced rabbit hearts were made ischaemic for 60 to 180 min at 37, 28, 25, 15, 12 and 5°C and then reperfused at 37°C. In some experiments nifedipine was added to the perfusion buffer, with and without K+-induced cardioplegia. Recovery was assessed in terms of recovery of mechanical function, maintenance of the tissue stores of adenosine 5′-triphosphate (ATP) and creatine phosphate, and maintenance of the ATP-generating activity of the mitochondria. These results show that the cardioprolective effects of nifedipine and hypothermia are additive.

The bottom‐ice microalgal community from annual ice in the inshore waters of east antarctica1

Abstract: The structure, productivity and heterotrophic potential of an extensive microalgal community growing on the underside of sea ice near the Australian Antarctic Station of Casey, are described Underwater observations made near the Australian Antarctic stations of Davis and Mawson are also reported This community develops during September, is largely suspended from the bottom surface of annual sea ice and often extends into the underlying water column as conspicuous strands up to 15 cm long The algal community structure in the strands is dominated by an unidentified tube diatom belonging to the Amphipleura/Berkeleya group and chains of a species of Entomoneis cf Amphiprora paludosa var hyperborea (Grunow) Cleve Unlike previously described bottom ice environments, a brash ice layer under the hard sea ice is absent Living cells, predominantly Nitzschia frigida Grunow, also occur in microbrine channels in the bottom 3 cm of the ice Maximal primary production rates of 81 μg C · L-1· h-1 occurred during November, then began declining near the end of December Minimal rates (28 μg C · L-1· h-1) were reached in mid-January and coincided with changes in the physical structure of the sea ice and in the stability of the water column An abundant epibacterial community associated with the microalgal strands assimilated 3H-labelled amino acids suggesting significant heterotrophic recycling of dissolved organic matter Turnover times of assimilated amino acids in the bottom ice community averaged 55 h during November while negligible turnover of these substrates occurred in the water column 15 m below the ice These bottom ice communities have higher primary productivity than typical brash ice communities; they are also accessible to marine herbivores and so may be more important to the Antarctic marine food chain than previously supposed

Mangroves and sewage: a re-evaluation

Abstract: The capacity of mangrove systems to remove and immobilise nutrients, heavy metals and other constituents of sewage effluent is strongly influenced by tidal and drainage characteristics, and by the redox state of the soil. Some mangrove systems may not remove sufficient phosphorus and nitrogen to reduce the quantity of these nutrients in sewage effluent to a level below that required for significant biological activity in offshore waters. In particular, the common practice of discharging treated sewage effluent directly into estuaries or tidal channels fringed by mangroves would appear to be a relatively ineffective scheme for improving the quality of sewage effluent.