Showing papers by "University of Queensland published in 1972"

Social control of sex reversal in a coral-reef fish.

Abstract: Males of Labroides dimidiatus control the process of sex reversal within social groups. Each group consists of a male with a harem of females, among which larger individuals dominate smaller ones. The male in each harem suppresses the tendency of the females to change sex by actively dominating them. Death of the male releases this suppression and the dominant female of the harem changes sex immediately. Possible genetic advantages of the system are considered.

The Distribution of Stock Returns

Abstract: A detailed examination is made of the distribution of stock returns following reports that the distribution is best described by the symmetric stable class of distributions. The distributions are shown to be “fat-tailed” relative to the normal distribution but a number of properties inconsistent with the stable hypothesis are noted. In particular, the standard deviation appears to be a well behaved measure of scale.

Leukocyte adherence inhibition: a simple test for cell-mediated tumour immunity and serum blocking factors.

Abstract: A proportion of peritoneal leukocytes from CBA mice adhered to glass haemacytometer surfaces and withstood a gentle washing. This proportion was reduced with cells taken from mice sensitized to a methylcholanthrene‐induced tumour, when the specific tumour antigen was added in the form of a soluble extract. The reaction of leukocyte adherence inhibition (LAI) may have an immunological basis similar to that of macrophage migration inhibition, but LAI is a much simpler procedure. Leukocytes were active in LAI when taken from animals bearing tumours and after tumour removal. When serum from mice bearing a particular tumour was added to sensitized leukocytes in the presence of the specific tumour antigen, the inhibition of adherence was substantially relieved or blocked. LAI could thus be used to demonstrate both cellmediated immunity to tumours and blocking factors in serum by a brief, simple procedure. A potential application to human tumour immunology is indicated. Copyright

Theory of the piezomagnetic effect in titanomagnetite-bearing rocks

Abstract: The stress sensitivitiesSx andSR of susceptibility and remanence for titanomagnetite-bearing rocks are calculated in terms of magnetostriction constantsλ100 andλ111 and anisotropy constantsK1,K2 of the magnetic minerals.Sx andSR are represented by quite different algebraic expressions but happen to have comparable numerical values over the whole range of titanomagnetite compositions. Both increase strongly with titanium content. This leads to more optimistic calculations of tectonomagnetic effects than with the previously assumed stress sensitivity for pure magnetite.

Petrography and Geochemistry of the Igneous Rocks from Eua, Tongan Islands

Abstract: A slightly metamorphosed igneous sequence is exposed beneath upper Eocene limestone on Eua, the southernmost of the eastern line of limestone-covered islands of the Tonga group. This igneous sequence occurs as lava, agglomerate, conglomerate, and tuff; compositions include high-alumina tholeiite, basaltic andesite, quartz gabbro, olivine basalt, and dacite tuff. Well-defined dikes of acid andesite (also pre-limestone) cut this sequence. Phenocryst mineralogy is typically highly calcic plagioclase, augite, and titanomagnetite, plus alteration products (mainly uralite, chlorite, epidote, calcite, and pyrite). Characteristic chemical features of the Eua igneous suite include relatively high alumina, very low K 2 O, P 2 O 5 , Rb, Ba, and REE, and relatively low TiO 2 , Ni, and Cr. The Na/K, V/Ni, and K/Rb ratios are high, and Rb/Sr ratios are very low. Measured Sr 87 /Sr 86 ratios (= initial) of a tholeiitic basalt and an acid andesite give 0.7034 and 0.7038, respectively. The Eua igneous suite evidently represents a very early stage of island arc evolution. Geochemically, these Eua rocks are decidedly less fractionated (or more “primitive”) than the recent Tongan basaltic andesite-dacite association which constitutes the western line of active volcanic islands of Tonga. This latter suite can be classified as one of the circum-Pacific “low potash andesite suites” (or “island arc tholeiitic series”). In terms of the trace and minor element data, the Eua igneous suite is similar in many respects to ocean-floor basaltic lavas, although perhaps characterized by lower TiO 2 , Ni, and Cr than is typical of most ocean floor lavas. It is concluded that the over-all chemistry and mineralogy of the Eua igneous suite suggest close similarities with the volcanic and mafic plutonic components of described ophiolite complexes; this is partly supported by the reported occurrence of peridotite and dunite from the nearshore flank of the Tonga trench. Thus, it is postulated that on Eua we have the topmost part of an underlying ophiolite complex exposed, possibly developed at the location of and at the inception of the site of initial subduction of lithosphere that has subsequently been responsible for the development of the Tonga arc system.

Lead isotopic compositions of Tonga-Kermadec volcanics and their petrogenetic significance

Abstract: Lead isotopic compositions, and lead and uranium concentrations have been determined for samples from the Tongan islands of Late, Fonualei, Hunga-Ha'apai and Eua and for the Kermadec islands of Raoul, Macauley, Esperance and Napier. The Kermadec samples form a linear array in a Pb206/Pb204 vs Pb207/Pb204 plot which if interpreted in terms of a two stage mantle model indicates a mantle fractionation of Pb from U at about 1.2×109 yr. The Tongan volcanics, except Eua, have a very narrow range of isotopic compositions, only slightly exceeding the experimental error limits. This is interpreted to be the result of efficient mixing of the mantle in response to rapid extension behind the Tongan arc. The rate of extension appears to determine whether convection mixing can occur, since the sub-Kermadec mantle which experienced slower extension is not well mixed isotopically. The isotopic compositions show no evidence for a component in the magma derived from sediments dragged down the Benioff zone. The pre-Eocene Eua volcanics have lead which is substantially more radiogenic than the younger Tongan volcanics and are interpreted as a sample of the mantle before convective mixing occurred.

The Aspidogastrea, Especially Multicotyle purvisi Dawes, 1941

Abstract: Publisher Summary The Aspidogastrea are trematodes with a ventral disc (Baer's disc) divided into one to four longitudinal rows of alveoli or represented by a single row of ventral suckers. The ultrastructure of the tegument is examined in Multicotyle purvisi only. It corresponds in all details to the tegument of Digenea. The basal cell membrane is located above a well-developed basal lamina and has extensive invaginations which, however, never reach the surface and are partly lamellar. The tegument contains mitochondria and numerous ovoid bodies, in some areas also vacuoles and lamellated bodies. The intestinal tract of aspidogastrids is a simple tube, consisting of mouth cavity, pharynx, and caecum. The feature distinguishing the genital system of Aspidogastrea most clearly from that of other trematodes is the structure of the oviduct. All larval Aspidogastrea examined have a mouth cavity, prepharynx, pharynx, simple caecum, and a postero-ventral disc without alveoli. The digestive tract is examined with the electron microscope only in the larva of Multicotyle purvisi. Multicotyle, just as the other examined species , has an ectolecithal egg. However, the yolk cells do not lie at one pole as in Cotylogaster and Macraspis but surround the egg cell located in the centre of the egg as in Cotylaspis.

Metabolism of fatty acids by bovine spermatozoa

Abstract: The incorporation of 14C-labelled myristic, palmitic, stearic, oleic and linoleic acids in vitro into the lipids of bovine spermatozoa was measured at intervals from 2min to 2h. All acids were rapidly incorporated into diglycerides, myristic acid being metabolized to the greatest extent. Whereas the low incorporation of acids into total phospholipids reflected the relative stability of the major phospholipid fractions in sperm, the minor phospholipids, particularly phosphatidylinositol, showed comparatively high metabolic activity. Although, in general, saturated acids were incorporated more actively than unsaturated substrates, stearic acid was poorly incorporated into all lipids except phosphatidylinositol. In regard to fatty acid composition of sperm lipids it was notable that diglycerides contained myristic acid as the major component, and this acid was also a prominent moiety of phosphatidylinositol. Docosahexaenoic acid was the principal fatty acid of the major phospholipid classes. These findings have been discussed in relation to the role of lipids in the metabolism of spermatozoa.

Physical properties of the Earth's core

Abstract: Calculations of the compression and temperature gradient of the core are facilitated by the use of the thermodynamic Gruneisen ratio, γ=3αKs/ρ{variant}CP. A pressure-dependent factor in γ is found to have the same numerical value for the core as for laboratory iron, justifying the use of a constant value for γ (1.6) in core calculations. The density of the outer core is satisfied by the assumption that it contains about 15% of light elements, particularly sulphur, whereas the inner core is probably ironnickel with very little lighter component. The presence of sulphur in the outer core reduces its liquidus at least 600° below pure iron, so that the adiabatic gradient does not intersect the liquidus, as Higgins and Kennedy have shown would occur in a pure iron core. The inner core is probably close to its melting point, 4700 K, and the adiabatic temperature gradient of the outer is calculated with this as a fixed point, giving 3380 K at the core-mantle boundary. The estimated electrical resistivity of the outer core, 3×10-6 Σm, corresponds to a thermal conductivity of 28 W·m-1·deg-1, which, with the adiabatic core gradient gives a minimum of 3.9×1012 W of heat conduction to the mantle. The only plausible source of this much heat is the radioactive decay of potassium in the core. As pointed out by Goles, Lewis, and Hall and Murthy, the presence of potassium becomes geochemically probable once sulphur is admitted as a core constituent. Thus it appears that the recognition of sulphur in the core resolves the two major difficulties which we have faced in attempting to understand the core.

Color Adaptation of Spatial Frequency Detectors in the Human Visual System

Abstract: Observers exposed alternately to a vertical grating of one spatial frequency in red light and a vertical grating of different spatial frequency in green light subsequently report frequency-specific color aftereffects when shown gratings in white light. Aftereffects occur, however, only when inspection gratings differ in spatial frequency by one octave or more and the frequency of at least one grating is above 3 cycles per degree. This spatial selectivity of the aftereffect is considered in terms of a neural adaptation model incorporating evidence on the tuning of spatial frequency detectors in the human visual system.

Isoenzymes and ontogeny.

Abstract: Summary 1. In this review, representative data on the nature of enzyme multiplicity and the developmental progressions of multiple enzyme forms have been collected, and the significance of this material has been discussed in relation to gene involvement during tissue differentiation. 2. In addition, emphasis has been directed towards the relevance of this onto-genetic information to a wide variety of biological phenomena, such as the possibilities of metabolic advantage conferred by the distinctive properties and physiological locations of these multiple enzyme forms, the insight into the subunit structure and compositional interrelationships of proteins, the aetiology of disease states, the relationship to hormone action, the extra nuclear specification of enzymes, and the transformations between particulate and soluble enzymes. 3. Three isoenzyme systems in particular have been chosen for the special development of these themes and treated in some detail; lactate dehydrogenase (LDH), aldolase and the esterases. Briefer accounts of the ontogeny of other less-studied series of multiple enzyme forms have also been included. 4. In relation to LDH, the major findings and conclusions of the pioneering investigators have been outlined, together with the reassessments which have been necessitated by recent studies of LDH ontogeny. It is evident, for example, that the early embryonic form of this enzyme is not necessarily parental as previously thought, and the realization appears to possess wide-ranging implications in regard to the control of synthesis of the enzymes. An indirect role of oxygen in LDH biosynthesis is indicated together with the independent regulation of the separate genes. 5. Recent developments in the enzymology of preimplantation ova have been discussed. It is noteworthy that the extraordinary levels of LDH activity which have been reported to be associated with these early developmental stages, may arise by extracellular adsorption rather than by an intrinsic synthesis of enzyme. Hence contemporary interest in this area has shifted towards a comprehension of the biochemical significance of the extremely unusual, selective concentrations of extracellular lactate dehydrogenase in the oviduct, the relation of this enzyme to the specialized growth requirements of the ova, and the influences of reproductive hormones on these oviducal isoenzymes. 6. The role of aldolase ontogeny as well as the composition, gene control, and native state of these lysases is also reviewed. This enzyme provides a particular example of the manner in which tissue modification of the catalytic and structural properties of enzymes may influence interpretations of the native state of purified proteins, and in this case, also, the observable microheterogeneity satisfies previous disquietude in regard to the existence of different subunits in the muscle enzyme. 7. The basic developmental importance of aldolase-C is stressed by the occurrence of this form of the enzyme in the early embryos of many different species. Furthermore, a significant addition to our knowledge of the possible biological purposes of isoenzymes and the rationale of their ontogenetic development during the establishment of tissue identity would appear to follow from the recent studies on reversible adsorption of aldolase to cell membranes. Aldolase-C. for example, is differentially inhibited in this way by the end product of anaerobic glycolysis, and other such metabolite-isoenzyme-tissue interactions allow for a wide range of tissue-specific responses regulating energy derivation and other important functions of the cell. 8. The remarkable extent of heterogeneity among the esterases, the distinctive species-specific nature of their multiplicity, and the overlapping substrate specificities have long presented a formidable barrier to the unravelling of the isoenzyme status of these enzymes. The advantages of systematic approaches utilizing differential substrate and inhibitor specificities have been emphasized, and the most recently available information summarized. 9. The carboxylesterases may be divided into five distinct groups, and recognizable subdivisions also occur within the other classes of esterases. Most of the different possibilities of isoenzyme causation are exemplified within the esterases, and the ontogenetic specificity of their heteromorphs seems to be greater than for any other recorded isoenzymic system. 10. In addition to the generative features displayed by the ‘soluble’ enzyme forms, the potential utility of latent isoenzyme activities have been illustrated by reference to catalase. The properties of such systems provide a useful means of studying such problems as the subcellular specification of enzyme synthesis and the nature of the mechanism governing the distribution of specific proteins between organelles and cytosol. 11. Catalase also provides a situation of special interest in that the existence of isoenzymes and even of activity in the cytosol have been disputed until very recently. Evidence establishing the reality of these occurrences, and the epigenetic nature of catalase multiplicity in some species, has been cited. 12. Recently available ontogenetic information of a number of oxidoreductases, transferases and hydrolases has also been collected together and discussed.

Obligate parasitism by phytopathogenic fungi

Abstract: Summary 1. This review is concerned with the obligate parasitism of the downy mildew, powdery mildew and rust fungi. 2. Mechanisms which determine resistance and susceptibility are incompletely understood. The three possibilities so far advanced, namely, hypersensitivity, phyto-alexins and nutrition are all inadequate to explain specificity. It is postulated that compounds carrying specificity are released by the invading pathogens and the interaction of the compounds with specific sites in the host cell determines whether a successful relationship is established. This hypothesis is based on the observation that host and pathogen protoplasts do not come in direct contact with each other and cells removed from the invading pathogen are affected. It should be possible to investigate this question now that some rust fungi have been cultured axenically. 3. Invasion of host tissue by these pathogens leads to alteration in host metabolism. Respiration rates and the activity of the pentose phosphate pathway are enhanced. Possible mechanisms for the reoxidation of NADPH by molecular oxygen are discussed. In the later stages of infection, photosynthetic activity is decreased and this decrease is coupled to the enhanced activity of the pentose phosphate pathway through NADPH availability. It is still not clear whether photosynthetic activity is increased or decreased during the early stages of infection. Nutrients from other parts of the plant accumulate at sites of infection, resulting in retarded growth of the host. Possible roles of hormones in nutrient mobilization and ‘green island’ formation are discussed. Changes in intermediary metabolism can be correlated with changes in amounts of nucleic acids in infected host cells. Chloroplast polysomes and ribosomes decrease during the early stages of infection but cytoplasmic ribosomes increase during patho-genesis. This increase more than compensates for the decrease in chloroplast ribosomes resulting in an overall increase in cellular RNA. 4. Some members of the Pucciniaceae and one member of the family Melamp-soraceae have now been cultured axenically. Nutritional studies indicate that these fungi are relatively non-specific with respect to their carbohydrate and amino-acid nitrogen sources but do have a specific requirement for either cysteine, methionine or homocysteine. Essential metabolites such as cysteine and cysteine-containing peptides move from hyphae into the medium and these may be important in amino-acid transport. Two stages in the development of axenic rust cultures are still imperfectly understood - the transition from germ tube to saprophytic mycelium and the fate of the colonies once formed. Further knowledge of the factors which control these stages may well suggest approaches to the axenic culture of other groups of obligately parasitic fungi.

Emotions and the skin: the conditioning of scratch responses in cases of atopic dermatitis.

Abstract: Summary.— To test the hypothesis that patients with atopic dermatitis would react with a scratch response to a variety of environmental signals a group of 18 patients and a group of normal controls, matched for age and sex, took part in a conditioning experiment with an itch as the unconditioned stimulus (U.C.S.). The dermatological patients were found to differ from the controls in terms of several personality measures, notably anxiety and hostility, and in the number of galvanic skin responses and scratch responses they produced during the conditioning sessions. The implications of these findings are explored and a tentative hypothesis about the aetiology and nature of atopic dermatitis is proposed.

A phylogeny of life-cycle patterns of the Digenea.

Abstract: Publisher Summary A comparison of helminth life-cycles reveals a number of singular features in the digenean pattern. Thus, in addition to the most singular feature, alternation of generations, there is the ubiquity of the cercaria, a stage designed for escape from the molluscan first host and for swimming, two patterns of behavior that are not called for in many life-cycles. To explain the ubiquity of the cercaria, it is postulated that the present molluscan first intermediate host was the original host of the proto-digenean and that escape of the cercaria from this host is primitive. And to explain the occurrence in many life-cycles of a free-swimming miracidium that penetrates the integument of the molluscan host, it is postulated that in an earlier stage the proto-digenean was an ectoparasite of the mollusc. Assuming that the proto-digenean was a visceral parasite of a mollusc and that it escaped from its host as an adult, presumably tailed, to lay its eggs, then the known life-cycles of contemporary digeneans may be interpreted as suggesting the following order in the acquisition of hosts: (i) vertebrate definitive (two-host life-cycle) and (ii) invertebrate second intermediate (three-host life-cycle). With regard to the succession of generations, it is postulated that the present adult was the original adult, that the mother sporocyst generation was the first of the new generations, that the redia was the second, and that daughter sporocysts have been derived from rediae several times.

Visual angle and apparent size of objects in peripheral vision

Abstract: Measurements of apparent size were obtained by distance adjustment of a peripherally viewed stimulus to produce a match to a foveally viewed standard. As eccentricity increased, the peripheral stimulus was adjusted at distances of progressively greater visual angle, indicating that a continuous diminution in apparent size occurs with increased eccentricity. This effect was found to be stable for several conditions of illumination and for changes in the light adaptive state of S. Apparent size diminution and apparent distance increase were also found for familiar objects viewed in an open field.

Effect of Oxygen on Several Enzymes Involved in the Aerobic and Anaerobic Utilization of Glucose in Escherichia coli

Abstract: By using the continuous culture technique, the transition from aerobiosis to anaerobiosis and its effect on a number of enzymes has been investigated in Escherichia coli K-12. A decrease in the oxygen partial pressure below 28.0 mm of Hg resulted firstly in an increase of the respiratory enzymes (reduced nicotinamide adenine dinucleotide [NADH] oxidase, 2.53-fold; succinic dehydrogenase, 1.4-fold; cytochrome b1 3.91-fold; and cytochrome a2, 2.45-fold) before the electron transport system gradually collapsed as cytochrome a2, followed by cytochrome b1 succinic dehydrogenase, and finally NADH oxidase decreased in activity. The change from respiration to fermentation was initiated well before the oxygen tension reached zero by the increase in levels of fructose diphosphate-aldolase, glucose 6-phosphate, and 6-phosphogluconate dehydro-genases and a decrease in 2-oxoglutarate dehydrogenase. When the dissolved oxygen tension reached zero, dry weight and CO2 formation together with isocitrate dehydrogenase decreased, whereas acid production and phosphofruc-tokinase synthesis started to increase. Enzymatic investigations revealed that the kinetics of the enzyme phosphofructokinase from strict aerobic cultures (6.9 ppm oxygen in solution) was adenosine triphosphate (ATP)-insensitive, whereas the same enzyme from anaerobic cultures was ATP-sensitive. A mech-anism is proposed for the change from aerobiosis to anaerobiosis together with the occurring change in glucose regulation.

Palm‐wine yeasts from parts of Nigeria

Abstract: Seventeen yeasts were isolated from samples of palm wine fermented from the sap of Elaeis sp. (9) and from the sap of Raphia sp. (8) in widely different localities in Nigeria. Twelve of the yeasts belonged to the genus Saccharomyces, four were Candida sp. and one was an Endomycopsis sp. The distribution of the yeasts did not appear to depend on the sap which was fermented or on locality. The implication of the findings with respect to palm‐wine fermentation studies is emphasised.

Effect of grinding on the decomposition of soil organic matter—I. The mineralization of organic nitrogen in relation to soil type

Abstract: The effect of grinding on aerobic nitrogen mineralization in ten soils of widely different properties was studied. The aerobic mineralization of nitrogen was increased in seven of ten soils when they were ground to

On the role of Brownian motion in the control of detrital remanent magnetization of sediments

Abstract: The field dependence of magnetic remanence in laboratory deposited sediments is re-examined in terms of the average orientation of small grains of magnetite subject to the combined effect of an aligning field and thermal agitation. The classical (Langevin) formula for paramagnetic susceptibility is generalized to describe an assembly of grains with magnetic moments having a uniform distribution of values between zero and an upper limit, yielding a simple analytical expression in excellent accord with the pioneering measurements of Johnson, Murphy and Torreson. Comparison of theory and observation shows that the grain moments are intermediate between the values expected for single domains and multidomains, confirming the existence of pseudo-single domain effects, as deduced from observations of thermoremanence.

Hypoxia and the energy charge of the cerebral adenylate pool.

Abstract: A brief period of anoxia in vivo causes a transitory decrease in the size of the adenylate pool in the rat brain. This is probably caused by feedback inhibition by AMP of adenine nucleotide synthesis. Exposing rats to various degrees of hypoxia suggests that the sensitivity of the brain to lack of O(2) results from the brain's limited ability to maintain an adequate energy charge in unfavourable circumstances.