Showing papers by "University of Sydney published in 1978"

X-ray crystal structure analysis of plastocyanin at 2.7 Å resolution

Abstract: The three-dimensional structure of plastocyanin, a ‘blue’ or ‘Type 1’ copper-protein, has been determined at a resolution of 2.7 A. The copper atom has a highly distorted tetrahedral coordination geometry. It is coordinated by a cysteine thiol group, a methionine thioether group, and two histidine imidazole groups.

The conductivity of lattices of spheres I. The simple cubic lattice

Abstract: We have extended a method devised by Lord Rayleigh to calculate the conductivity of a simple cubic lattice of conducting spheres in a conducting matrix. The extended theory is capable of including the effects of multipoles of arbitrarily high order, and yields excellent agreement with measurements on arrays of perfectly conducting spheres, even when they are close to touching. Calculations and measurements on lossy spheres are also compared. An explicit formula for the conductivity is given which takes into account poles of order $2^{7}$, and two empirical formulae are discussed.

Coexistence of coral reef fishes — a lottery for living space

Abstract: Data are summarised from studies of two reef fish communities — pomacentrids territorial on rubble patches, and fishes resident in small isolated colonies of coral. In each case there is evidence that availability of living sites limits numbers of fishes, and that similar species of fish use the same kinds of spaces. Priority of arrival as recruits, rather than subtle differences in requirements or competitive abilities of adults, appears to determine which species holds each site. Faced with a limited and patchy supply of living space, most reef fishes are sedentary as adults, and produce frequent clutches of pelagic larvae over extended breeding seasons In this way they maximise their chances of getting offspring into suitable living sites as such sites appear. It is argued that by adopting this strategy, reef fishes are preadapted for forming inter-specific lotteries for living space if several species with similar requirements occur together. Such lotteries among similar species may be a feature common to many reef fish communities, and may explain the typically high within-site diversity found in them.

The metabolism and excretion of curcumin (1,7-bis-(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione) in the rat.

Abstract: Curcumin labelled with deuterium and tritium was prepared. Oral and intraperitoneal doses of [3H]curcumin led to the faecal excretion of most of the radioactivity. 2. Intravenous and intraperitoneal doses of [3H]curcumin were well excreted in the bile of cannulated rats. 3. The major biliary metabolites were glucuronides of tetrahydrocurcumin and hexahydrocurcumin. A minor biliary metabolite was dihydroferulic acid together with traces of ferulic acid. Metabolites were identified using chemical ionization mass spectrometry.

Synthesis, intracellular transport and discharge of exportable proteins in the pancreatic acinar cell and other cells

Abstract: SUMMARY 1After an outline description of pancreatic structure and function, and a more detailed account of acinar cell morphology, this review traces the pathway of amino acids as they are taken up by the acinar cell, incorporated into digestive hydrolases, transported through the cell and finally discharged from the cell, and considers the mechanisms by which these steps are controlled. At all stages comparisons are made with other secretory cells. 2The use of radioautography and cell-fractionation techniques in determining this pathway in the pancreas are described. The route and kinetics of the process in pancreas are compared with those in other cells. 3Amino-acid entry is by an active mechanism. However the intracellular pool of accumulated amino acids may not be used directly in protein synthesis. Selection of amino acids for incorporation into proteins may occur whilst they are associated with carrier systems within the plasma membrane. There is no convincing evidence that amino-acid entry can be influenced by the pancreatic secretagogues, cholecystokin-pancreazymin (CCK-PZ) or acetylcholine. 4Secretory proteins are synthesized on ribosomes bound to the endoplasmic reticulum (ER) and the nascent proteins vectorially transferred across the ER membrane into the ER cisternae. All messenger RNA molecules which are templates for secretory proteins appear to possess an initial sequence of codons whose translation produces a ‘signal’ sequence of amino acids. This signal sequence somehow triggers attachment of the ribosomes to the ER, thereby automatically determining that the final translation product is destined for the ER cisternae. 5The effects of CCK-PZ and acetylcholine on pancreatic protein synthesis are controversial. Whereas stimulation can be observed in vivo, this has not been convincingly demonstrated in vitro. I conclude that while CCK-PZ and acetylcholine may accelerate protein synthesis, the physiological significance of this effect remains to be clarified. Long-term stimulation can modify pancreatic enzyme synthesis and this, together with other factors, may be the means of dietary adaptation by the gland. 6Newly synthesized proteins travel from the ER cisternae via the peripheral Golgi components to the Golgi cisternae. Transport from ER to Golgi cisternae may occur by a vesicle shuttle service or by direct tubular connexions. Although sustained stimulation with CCK-PZ analogues can accelerate this intracellular transport step, pancreatic secretagogues have not yet been shown to accelerate transport under physiological conditions. 7The Golgi complex has a number of functions including: glycosylation and, where appropriate, sulphation of glycoprotein and mucopolysaccharide components of the zymogen granules (ZG) and granule membranes; sequestration of divalent cations which bind to secretory proteins; the formation of condensing vacuoles (CV) from the inner Golgi cisternae. 8Aggregation of proteins occurs passively within CV so as to form osmotically inert complexes, thereby reducing internal osmotic activity and causing water to diffuse out. This condensation imparts a gel-like consistency to the mature ZG so formed. 9Discharge of ZG occurs by a process of exocytosis involving fusion of the ZG membrane with the apical plasma membrane, release of the ZG contents, and retrieval of the ZG membrane from the plasma membrane by endocytotic mechanisms. The mechanisms responsible for migration of ZG towards the cell apex and for exocytosis remain unknown but may involve the participation of microtubules and/or microfilaments. Although there is a small, basal discharge of ZG at all times, stimulation with CCK-PZ or acetylcholine greatly accelerates the process. 10The basic tenet of the secretory mechanism summarized above is that, following synthesis, secretory proteins are confined within an intracellular organelle at all times. This ‘segregation’ hypothesis has been challenged by the ‘equilibrium’ hypothesis in which secretory proteins are suggested to move across cellular membranes and are therefore at equilibrium within the various compartments of the cell. While many of the observations on which the equilibrium hypothesis are based are tenuous, some others cannot readily be explained by the segregation model. Proponents of the equilibrium hypothesis therefore suggest that preferential release of individual hydrolases from ZG occurs, followed by their separate transport across the apical cell membrane. The claims of this alternative model are discussed. 11In the final section are discussed the intracellular mechanisms by which CCK-PZ and acetylcholine act on the acinar cell to cause discharge. The overall membrane perturbations brought about by CCK-PZ and acetylcholine appear to be the same and include cell depolarization, and perhaps increased phospholipid turnover. Both events may be related to an altered membrane permeability to cations. CCK-PZ, but not acetylcholine, will activate adenylate cyclase, but cyclic AMP does not appear to be involved in regulating enzyme discharge. Instead, Ca2+ is the major intracellular second messenger. However, rather than increase Ca2+ uptake into the cell, CCK-PZ and acetylcholine appear to raise the intracellular Ca2+ concentration by causing release of Ca2+ from intracellular stores. The mechanism by which they do this, and the role of Ca2+ in the discharge process remain unknown.

The conductivity of lattices of spheres II. The body centred and face centred cubic lattices

Abstract: The conductivities of body-centred (b. c. c.) and face-centred (f. c. c.) cubic lattices of spheres of a conducting material in a conducting matrix are calculated by using a method originally devised by Lord Rayleigh. Measurements of the conductivity of the b. c. c. lattice of perfectly conducting spheres are presented. Good agreement between theory and experiment is obtained. Our results are shown to be in agreement with asymptotic equations derived by other authors. A formula is given for the case of a disordered array.

Local distortional and lateral buckling of i-beams

Abstract: The finite strip method is used to study the local, distortional, and flexural-torsional modes of buckling of I-beams bent about their major axis. The interaction between these modes is investigated. The buckling loads so determined are compared with those derived using the simpler but approximate theories normally used to design against specific buckling modes. The effect of lateral and torsional restraints on the buckling modes is investigated. A design chart for the local buckling stress of I-beams subjected to major axis moment is presented.

An experimental evaluation of competition between three species of intertidal prosobranch gastropods

Abstract: Previous investigations have shown that competition for space among sessile organisms in rocky intertidal communities is often reduced by predation or harsh environmental factors. Grazing gastropods are unlikely to compete for space, but at high densities might compete for food, unless some factor, such as predation, reduced the densities. The coexisting species of herbivourous gastropods on rock-platforms in New South Wales are not, however, subject to high levels of predation on shores sheltered from waveaction. In this study, three of these species were caged at densities from the natural, to 4 times the natural density on the shore, in different combinations of species, to investigate their competitive interactions. All three species, Nerita atramentosa, Bembicium nanum and the limpet Cellana tramoserica, showed increased mortality and reduced weight at increased density, over 100- or 200-day periods. The effect of high density on Cellana was greater than on Nerita or on Bembicium. In addition, Nerita was competitively superior to the other two species. Cellana, at high densities, adversely affected Bembicium. Nerita was not affected by high densities of either of the other two species, and Cellana was not affected by Bembicium.Under entirely natural conditions, the effects of increased density of Cellana on the mortality and tissue-weight of Bembicium could not occur, because of the high rate of mortality of Cellana when at increased density of its own species. The other effects of increased density of snails would, however, occur. Thus, there can be regulation of numbers of snails because of high densities of their own or other species on the shore.The supply of benthic, microalgal food is proposed as the limiting resource for which the species compete. Hypotheses are proposed to account for the mechanisms by which the three species acquire different amounts of the resource. These are based on aspects of the feeding biology of the snails.The continued coexistence, in intertidal regions, of Cellana, which shows the highest rate of mortality due to members of its own species, with the competitively dominant Nerita, which increases the mortality of Cellana, is apparently due to three factors. These are: (i) the presence of subtidal refuges for breeding populations of Cellana, (ii) regular spatial dispersion of Cellana which would probably decrease intraspecific competition for food, and (iii) the high variability in space and time of recruitment of planktonic larvae of both Cellana and Nerita. This last factor makes it unlikely that high densities of Nerita could occur on all shores in every year. Cellana could always recolonize any area where its density had previously been reduced, and thus, cannot be excluded by competitive interactions. Competitive interactions at high densities of gastropods can therefore cause reductions in the number of each species present on a shore. They cannot, however, lead to exclusion of any species or alter the composition of the community of herbivores on the shore.The difference between competition for space by sessile intertidal organisms, and competition for food by gastropods which graze on microalgae is discussed with respect to the structure of intertidal communities. In the former case, competitively dominant species must be dislodged from the resource, space, by disturbance (e.g. predation or hazards) before recolonization by inferior competitors can occur. In the latter situation, the food resource is renewable without further perturbation of the community, and the competitively dominant species could never consume it completely over a wide enough area, and for a sufficient length of time, to eliminate totally another species.

Fluvially transported charcoal gives erroneous 14C ages for recent deposits

Abstract: IN carbon dating of material included in fluviatile deposits, it is usually assumed that either there is little age difference between the dateable material and the fluvial deposit, or that the 14C sample and the deposit in which it is contained are sufficiently old for the age difference to be of little consequence We report here on how a series of dates on charcoal from the bed of the Macdonald River, New South Wales, Australia, casts doubt on these assumptions and indicates that serious errors can occur in relating the radiocarbon ages of charcoal samples to the fluvial deposits in which they lie

Endocrine influences on survival from malignant melanoma

Abstract: A series of 1861 patients with malignant melanoma was reviewed to determine if there were endocrine influences on survival from the disease. No change in prognosis for melanoma patients was detected during times of hormonal upheaval such as puberty menopause or estrogen administration. Parous women however irrespective of whether their pregnancies occurred prior to or coincident with diagnosis of melanoma tended to present at an earlier clinical stage of the disease and have a higher 5-year survival rate than nonparous women. In addition there was a statistically significant sex difference in prognosis with more women than men surviving 5 years. 2 factors possibly contributing to this longer survival were that women first presented at an earlier clinical stage of the disease and had primary lesions confined to more prognostically favorable anatomical sites than men. The disease seemed to develop the capacity to metastasize more slowly in women than in men. However the sex of the patient played an important role in prognosis only in patients first presenting with localized Stage 1 melanoma. 5-year survival rates in women first presenting with metastases were less than in men first presenting with metastases and thus endocrine influences that may previously have delayed growth had no further effect on the behavior of the tumor. We concluded that there may be endocrine influences on the rate of formation of metastases and the distributions of anatomical sites of primary lesions. (authors)

Cytogenetical studies in wheat

Abstract: Two genes for resistance to Puccinia graminis f. sp. tritici were located in chromosome 2B of Kota wheat. Both were mapped in the long arm. The first designated Sr28 was situated distally to Sr9 and showed 34·6±2·8 per cent recombination with the centromere. The second gene, which was not definitely distinguished from Sr16 either on the basis of recombination or by its response to several pathogen cultures, was inherited independently of the 2B centromere and of Sr9, but showed 38·2±1·9 and 29·2±4·2 per cent recombination with Sr28. Comparisons of present results with those from earlier studies suggested that Kota possesses at least five genes for resistance.

Bacteria from the gut of Australian termites.

Abstract: The major gut bacteria of the worker caste of nine species of Australian termites, belonging to four families, were isolated and identified to generic level. All species were either facultative anaerobes or strict aerobes. A correlation appears to exist between the major gut bacterium and the family to which the termite belongs. The major bacterium from the two lowest termites, Mastotermes darwiniensis (family Mastotermitidae) and Cryptotermes primus (family Kalotermitidae), was Streptococcus; from four species belonging to the Rhinotermitidae (Heterotermes ferox, Coptotermes acinaciformis, C. lacteus, Schedorhinotermes intermedius intermedius) it was Enterobacter; and from three species of the Termitidae (Nasutitermes exitiosus, N. graveolus, N. walkeri) it was Staphylococcus. Enterobacter was a minor symbiont of M. darwiniensis, C. primus, and N. graveolus; Streptococcus was a minor symbiont of H. ferox, C. lacteus, S. intermedius intermedius, and N. exitiosus; and Bacillus was a minor symbiont of C. acinaciformis and S. intermedius intermedius. M. darwiniensis possessed another minor symbiont tentatively identified as Flavobacterium. C. acinaciformis from three widely separated locations possessed a similar microbiota, indicating some form of control on the composition of the gut bacteria. Bacteria, capable of growth on N-free medium in the presence of nitrogen gas, were isolated from all termites, except N. exitiosus and N. walkeri, and were identified as Enterobacter. No cellulose-degrading bacteria were isolated.

Finite-field method calculations. IV. Higher-order moments, dipole moment gradients, polarisability gradients and field-induced shifts in molecular properties: Application to N2, CO, CN−, HCN and HNC

Abstract: In this paper, theoretical methods developed in III are applied in calculating polarisabilities, polarisability gradients and field-induced shifts, by the finite-field method. Values of dipole moment gradients and higher-order moments, calculated from the unperturbed wavefunctions, are also reported. Results for N 2 , CO, CN − , HCN and HNC have been obtained at the SCF level; some CI results for the N 2 polarisability components and moments and for the dipole moment gradients of HCN are also given. The calculated polarisability gradients and dipole moment gradients have been used to estimate the Raman scattering intensities and depolarisation ratios and the IR absorption intensities. Model calculations of field-induced shifts in bond length, vibrational levels, spectroscopic constants, force constants and dipole moment gradient are reported for N 2 and CO. The discrepancy between the SCF and experimental bond dipole moment gradients for HCN, previously noted in the literature, has been re-examined and resolved by our CI results.

Naturalism, materialism and first philosophy

Abstract: In the first section of this paper I define and defend a spatio-temporal account of the general nature of reality. I call this doctrine "Naturalism". In the second section I define and defend the somewhat more specific, although still very general, doctrine of Materialism or Physicalism. (I take it to be a sub-species of Naturalism.) However, if we define ontology or "first philosophy" as the most abstract or general theory of reality, then it seems that neither Materialism nor even Naturalism is an ontology. In the third section I sketch very briefly the ontology which I favour. Unlike that adopted by many Naturalists and Materialists, it admits both particulars and universals. It is Realistic, not Nominalistic. I maintain, in particular, that only by adopting a Realistic (but not Platonistic) account of universals can the Naturalist and the Materialist solve the pressing problems of the nature of causation and of law-like connection.

Analysis of palaeomagnetic data from the New Hebrides

Abstract: Palaeomagnetic samples have been collected on eight islands of the New Hebrides island arc. Data are presented for 31 stable sites out of 46 with ages ranging from Pleistocene to early Late Miocene. These data show 30° clockwise rotation of the arc commencing 6 m.y. BP. Synthetic polar wander paths corresponding to microplate rotation may be computed from known major plate polar wander paths. Thus a physiographically reasonable reconstruction of the New Hebrides plate is shown to have a polar wander path which compares well with the observed data. A reconstruction of a pre-Late Miocene double arc, consisting of the Solomons, New Hebrides-Vityaz, Fiji and Lau-Tonga island arcs, is possible which supports in terarc geological correlations and which suggests Plio?Pleistocene growth of the North Fiji Basin by r-r-r triple junction development concomitant with the development of the Lau Basin.

Coagulation of Amphoteric Latex Colloids Reversibility and Specific Ion Effects

Abstract: Coagulation studies of amphoteric latex sols of various i.e.p. values in LiNO3, KNO3 and CsNO3 solutions are reported for a wide range of salt concentrations and pH. Three different techniques for the study of coagulation phenomena all indicate reversibility, in that sols coagulated by pH or salt are able to be redispersed. K+ and Li+ counter ions are able to stabilize these sols in the high salt concentration region. With NO3– and Cs+, the expected narrow zone of coagulation at low salt (i.e.p. coagulation) expands into the usual broad coagulation zone at high salt, where coagulation is observed at all pH values. The stabilizing effect of Li+ and K+ counter ions is attributed to a hydration barrier at the interface.

Shock waves at a fast-slow gas interface

Abstract: This paper presents the results of experiments on plane shock waves refracting at air/SF6 and He/CO2 interfaces. These are called fast-slow gas combinations because the speed of sound in the incident shock gas is greater than that in the transmitting shock gas. Our work was based on a generalization of the von Neumann (1943) classification of shocks into two classes called weak and strong. We introduced two subclasses of each of these, giving in all four groups of phenomena for study. This is possibly an exhaustive list, at least for conditions where the gases are approximately perfect. We present data on all four groups and study various transition conditions both within and across the groups. Our results appear to conflict with a previously reported irregular refraction; in fact we could apparently completely suppress this wave system by attention to our gas purity and boundary conditions. In its place we found a different system which appears to be a new phenomenon. We found another new system which has the appearance of a Mach-reflexion type of refraction but with its shock dispersed into a band of wavelets. It is interesting that the wavelets remain intense enough to induce identifiable vortex sheets in the flow. Finally we found yet another refraction of the Mach-reflexion type which had no detectable vortex sheet emanating from the triple point: such a system was foreshadowed by von Neumann.

Fallopian tube isthmic mucus and ovum transport

Abstract: The oviduct isthmus is capable of transporting spermatozoa and ova in opposite directions. A column of tenacious mucus that occupies the lumen of the rabbit oviduct isthmus during estrus may permit sperm transport. After ovulation the mucus disappears, with subsequent efforescence of cilia, which probably assist transport of ova to the uterus.

Mating behaviour of the queensland fruit fly, dacustryoni (diptera: tephritidae), in field cages

Abstract: The behaviour leading to mating in Dacus tryoni was studied in a field cage containing a peach tree. The behaviour in the field cage was similar to that which has been observed in nature. Under natural lighting conditions mating was entirely limited to a period of about half an hour as the light intensity fell at dusk, sexual activity beginning about 10 min before the official sunset time. All males in the cage aggregated into a loose flying swarm which soon settled on the windward side of the tree. Within the settled swarm each male defended a small area on a leaf where he stridulated and released pheromone. Females flew into the aggregation singly. Each female landed near a male and then walked up beside him. The male's behaviour did not change until the female entered his visual field. Then mounting occurred immediately and stable copulation was achieved within a few seconds. The relationship of the aggregation to the aerial swarming habit of many Diptera is discussed.

Control of Flowering in the Grapevine (Vitis vinifera L.): Formation of Inflorescences in Vitro by Isolated Tendrils

Abstract: Tendrils produced from shoot tips of grapevine (Vitis vinifera L.) cultured in vitro on Nitsch's medium developed into inflorescences when 5 to 10 mum benzyladenine (BA) or 6-(benzylamino)-9-(2-tetrahydropyranyl)-9H-purine (PBA) were applied directly to the tendril tips. Inflorescences did not form on tendrils if the cytokinins were supplied in the agar. Tendrils cultured in agitated liquid medium containing BA, PBA, or zeatin riboside showed profuse branching and tendrils were transformed into inflorescences. Calyx and corolla (calyptra) stamens and pistils developed normally in the presence of both zeatin riboside and PBA, but micro- and macrosporogenesis were absent.Inflorescences were formed by tendrils from five cultivars (Muscat of Alexandria, Shiraz, Carbernet Sauvignon, Wortley Hall, and Sultana syn. Thomson Seedless) and also on tendrils from 12- to 15-week-old-seedlings.