Showing papers by "Australian National University published in 1974"

Restriction of in vitro T cell-mediated cytotoxicity in lymphocytic choriomeningitis within a syngeneic or semiallogeneic system.

Abstract: RECENT experiments1–3 indicate that cooperation between thymus derived lymphocytes (T cells) and antibody-forming cell precursors (B cells) is restricted by the H-2 gene complex Helper activity in vivo operates only when T cells and B cells share at least one set of H-2 antigenic specificities Evidence is presented here that the interaction of cytotoxic T cells with other somatic cells budding4–5 lymphocytic choriomeningitis (LCM) virus is similarly restricted

Amino acid transmitters in the mammalian central nervous system

Abstract: 2. Evidence for A m i n o Acids as T ransmi t t e r s . . . . . . . . . . . . . . . . . . . . 99 2.1. Synthesis and Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 2.2. Synapt ic Release . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 2.3. Postsynapt ic Act ion . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 2.4. Postsynapt ic An tagon i s t s . . . . . . . . . . . . . . . . . . . . . . . . . 103 2.5. Inac t iva t ion and R e m o v a l . . . . . . . . . . . . . . . . . . . . . . . . . 104

The Parallel Evaluation of General Arithmetic Expressions

Abstract: It is shown that arithmetic expressions with n ≥ 1 variables and constants; operations of addition, multiplication, and division; and any depth of parenthesis nesting can be evaluated in time 4 log2n + 10(n - 1)/p using p ≥ 1 processors which can independently perform arithmetic operations in unit time. This bound is within a constant factor of the best possible. A sharper result is given for expressions without the division operation, and the question of numerical stability is discussed.

Immunological surveillance against altered self components by sensitised T lymphocytes in lymphocytic choriomeningitis.

Abstract: THE cytotoxic activity1,2 of immune thymus-derived lymphocytes (T cells) for 51Cr-labelled fibroblasts, or macrophages infected with lymphocytic choriomeningitis (LCM) virus is restricted by the H-2 gene complex3,4. Specific lysis of LCM-infected monolayer cultures occurs only when targets and overlaying, sensitised T cells share at least one set of H-2 antigenic specificities.

Geology of Coral Terraces, Huon Peninsula, New Guinea: A Study of Quaternary Tectonic Movements and Sea-Level Changes

Abstract: A spectacular flight of terraces occurs on the northeast seaboard of Huon Peninsula, New Guinea. The terraces are clearly developed for more than 80 km and rise to over 600 m. They are built dominantly of coral reefs but include subordinate deltaic gravel formations. Interpretation of the reef succession depends on analysis of facies changes across a number of sections, and this is developed after prior analysis of reefs, lagoons, deltas, and submarine terraces on the modern coast. A record of sea-level changes relative to the rising land is determined for each section. Radiometric dating of the terrace reefs indicates Pleistocene sea-level maxima at the following times (yr B.P.): 30,000, 40,000 to 50,000, 60,000, 80,000, 105,000, 120,000, 140,000, 185,000, 220,000. Good agreement with dated reefs elsewhere reinforces these age estimates. Tectonic uplift has varied along the terraced area, because heights of terraces diminish from southeast to northwest, parallel to the coast; and yet records of relative sea-level changes are similar between sections. By assuming that upper Pleistocene interglacial sea levels were little different from the present level, tectonic and sea-level changes can in principle be separated. Using least-squares search, a “best estimate” sea-level curve and corresponding tectonic uplift pattern are derived on the basis of 11 sections. The sea-level curve compares well with Emiliani9s generalized paleotemperature curve for the upper Quaternary.

The inhibition of mitochondrial calcium transport by lanthanides and ruthenium red.

Abstract: An EGTA (ethanedioxybis(ethylamine)tetra-acetic acid)-quench technique was developed for measuring initial rates of (45)Ca(2+) transport by rat liver mitochondria. This method was used in conjunction with studies of Ca(2+)-stimulated respiration to examine the mechanisms of inhibition of Ca(2+) transport by the lanthanides and Ruthenium Red. Ruthenium Red inhibits Ca(2+) transport non-competitively with K(i) 3x10(-8)m; there are 0.08nmol of carrier-specific binding sites/mg of protein. The inhibition by La(3+) is competitive (K(i)=2x10(-8)m); the concentration of lanthanide-sensitive sites is less than 0.001nmol/mg of protein. A further difference between their modes of action is that lanthanide inhibition diminishes with time whereas that by Ruthenium Red does not. Binding studies showed that both classes of inhibitor bind to a relatively large number of external sites (probably identical with the ;low-affinity' Ca(2+)-binding sites). La(3+) competes with Ruthenium Red for most of these sites, but a small fraction of the bound Ruthenium Red (less than 2nmol/mg of protein) is not displaced by La(3+). The results are discussed briefly in relation to possible models for a Ca(2+) carrier.

Experimental determination of the temperature and pressure dependence of the Fe-Mg partition coefficient for coexisting garnet and clinopyroxene

Abstract: An experimental study initiated to calibrate the distribution coefficient $$K_D = \frac{{({\text{FeO}}/{\text{MgO}})_{{\text{ga}}} }}{{{\text{(FeO}}/{\text{MgO)}}_{{\text{cpx}}} }}$$ in eclogites as a geothermometer has been done on (a) a mineral mis, (b) a glass of the typical tholeiite composition and (c) a series of glasses of tholeiite compositions with $$6.2 < \frac{{100{\text{Mg}}}}{{{\text{Mg}} + {\text{Fe}}^{ + + } }} < 93.$$ The mineral mix was found to be unsuitable as reactant due to incomplete equilibration but the minimum K D of the mineral mix and the K D from glass of tholeiite composition are identical within experimental uncertainty. These data constitute a reversal of the garnet/clinopyroxene partition relationship and provide justification of the use of glass as a reactant for the project. To eliminate any uncertainty in interpretation of mineral analyses due to possible variation in Fe+++/Fe++ between runs, experiments were carried out in iron capsules on the nine tholeiite glasses, thus maintaining iron as Fe++. Microprobe analytical techniques yielded mineral analyses of comparable accuracy to analyses of natural phases for experiments within the temperature range from 600° C to 1500° C and a pressure range from 20 kb to 40 kb. It has been shown that for $$6.2 < \frac{{100{\text{Mg}}}}{{{\text{Mg}} + {\text{Fe}}^{ + + } }} < 85$$ , the bulk chemical composition does not perceptibly affect the K D value. At 30 kb the K D value ranges from 18.0 at 600° C to 1.45 at 1400° C, defining the linear relationship in a ln K D vs 1/T(°K) plot. The pressure dependence of the K D -value has been shown to be greater than previously predicted. There is a straight line relationship in ln K D vs Pressure (Kb) between 20 and 40 kb at constant temperature (1100°C). This enables us to determine K D =fn (T, P) and $$T(^\circ {\text{K}}) = \frac{{3686 + 28.35 \times P({\text{Kb}})}}{{\ln K_D + 2.33}}$$ . This expression uniquely determines the temperature of equilibration of natural eclogites of basaltic bulk composition when the K ga,cpx is known and a pressure estimate can be given.

Spinal interneurone excitation by conformationally restricted analogues of L-glutamic acid

Abstract: L-GLUTAMIC acid is probably an excitatory transmitter of major significance in the mammalian central nervous system1. The L-glutamic acid molecule is relatively flexible, and in an attempt to gain some insight into its possible shape(s) during activation of receptors associated with excitation of central neurones, a study was made of four conformationally restricted analogues: (±)-cis-1-aminocyclohexane-1,3-dicarboxylic acid (‘cyclo-glutamic’ acid), ibotenic acid, kainic acid and its dihydro derivative.

Quantum theory of chemical valence concepts

Abstract: Electron density operators and projection operators are fundamental quantities in the general physical interpretation of quantum theory In this series of papers the aim is to explore their relevance to the definition and use of chemical valence concepts Here, the problems involved in defining the charge on an atom in a molecule are discussed, and a new approach is formulated in terms of these operators The approach depends on the result that, if a projection operator P is formed representing some subspace of a molecular Hilbert space, then the probability of occupancy of that subspace is Tr DP, where D is an appropriate electron density operator In particular, the molecular one-electron Hilbert space is considered, and projection operators for atomic orbitals, atoms, pairs of atoms, atoms in threes, and so on, are found The above result allows for the definition of corresponding occupation numbers From these follow definitions of the charge on an atom in a molecule and of occupation numbers for elec

Protein Pellicle of Stigmatic Papillae as a Probable Recognition Site in Incompatibility Reactions

Abstract: ANGIOSPERM pollen grains carry extracellular proteins in two sites: in the inner wall layer, the cellulosic intine, and in cavities in the outer exine, the sculptured part of the wall composed of sporopollenin1–3. The intine proteins, which include several acid hydrolases, are synthesised by the spore and inserted during growth; they are therefore gametophytic in origin. The exine proteins, in contrast, are produced in the tapetum, the nurse tissue of the anther, and injected into the exine cavities during the maturation of the pollen grains; they are thus sporophytic. The enzymic wall proteins seem to be concerned with germination, penetration of the stigma surface and the early growth of the pollen tube. Other fractions are involved in the recognition responses which control breeding behaviour, playing a part in both interspecific4 and intraspecific5,6 incompatibility systems.

Motor and sensory flight neurones in a locust demonstrated using cobalt chloride.

Abstract: The central projections of motor and sensory neurons involved in the control of the wing beat in locusts have been analysed using cobalt chloride introduced axonally. From sections fo cobalt material, components of particular neuropile regions can be identified. The cobalt method offers an important advance in the analysis of insect neuropile. The flight motor neurones in the mesothoracic ganglion are all basically similar in shape, with no clear distinction between elevator and depressor neurones. All have a highly branched dendritic tree which ramifies extensively through the dorsal neuropile. A neurone innervating a particular muscle can be recognised in different individuals by characteristic features but the pattern of dendritic branching is variable. Neurones involved in both flight and walking have some branches in a deeper layer of neuropile than those concerned only with flight, where the branches lie superficially. Sensory projections from the flight sense organs are complex but compact and their positions in the neuropile are very predictable. They have large interganglionic components. The stretch receptors and wing sense organ projections lie mainly in the dorsal neuropile, whereas the other thoracic sensory receptors project ventrally, with branches to the dorsal neuropile at a few specific points. Associations between certain branches of sensory and motor neurones are demonstrated and their implications for the organisation of the flight reflexes discussed. It is suggested that parts of the motor neurone dendritic tree may be functionally equivalent to interneurones.

Potassium‐argon ages on the Cainozoic volcanic rocks of New South Wales

Abstract: During the Cainozoic there was widespread volcanism, mainly basaltic, in eastern New South Wales. Numerous new K‐Ar ages, together with previously published results, provide information on the age of virtually all the main volcanic provinces, and indicate that the volcanism started about 70 m.y. ago in the Late Cretaceous, and was continuous from about 60 m.y. ago (Palaeocene) until about 10 m.y. ago (middle Miocene). There has been no volcanic activity since 10 m.y. ago. The ages of uplift of the Eastern Highlands are estimated from the relationship of the dated basaltic flows to the topography. A major uplift is deduced some time between the mid‐Cretaceous and late Oligocene, followed by a quiescent period. A further uplift started some time after the middle Miocene, and it continues to the present day. The highland was uplifted differentially both along and transverse to the axis.

A one‐step procedure for separating mouse T and B lymphocytes

Abstract: A procedure is described for both depleting and obtaining in pure form Ig-bearing cells from mouse lymphoid populations. The Ig-bearing cells are identified by rosetting and the rosettes separated from the nonrosetting lymphocytes by centrifugation on Isopaque/Ficoll. The rosettes sink with the red cells and the nonrosetting lymphocytes float. The procedure is > 99.5 % efficient at depleting mouse lymphoid populations of Ig-rosetting cells and is also > 97 % efficient at removing the Ig-bearing cells detected by radioautography. Furthermore, after lysis of the red cells by hypotonic shock the Ig-bearing cells are recovered in a highly pure form. The total recovery of white cells and rosettes applied is > 85 %. This procedure was shown to produce a functional separation of T and B lymphocytes. The cell population depleted of Ig-rosettes behaved as a pure T cell preparation. It lacked precursors of antibody-forming cells, but contained virtually all of the Θ-positive lymphocytes, the bulk of the helper cells detected in two in vitro hapten carrier antibody responses and all the cells which responded and produced cytotoxic cells in MLC. In contrast, the preparation of Ig rosettes expressed B cell properties. This population contained all of the antibody forming cell precursors, few helper cells and Θ-positive lymphocytes and no MLC-responding cells. However, there was some evidence that a small subpopulation of T cells exists which possesses surface Ig. The separation system was used to formally demonstrate that carrier primed T cells collaborate with hapten primed B cells to generate an anti-hapten antibody response to a hapten-carrier conjugate. It was also established that in MLC responder B cells in no way collaborate with responder T cells to generate cytotoxic cells.

The geochemical evolution of the moon

Abstract: Evidence for and implications of homogeneous accretion of the moon are considered Interelement ratios are used to calculate the composition of the highland crust The rare-earth data for the highlands show a positive Eu anomaly, allowing the deduction that the interior has a negative anomaly The Cr/Ni ratios in the highlands are considered in regard to the overall lunar abundance of the siderophile elements These abundance data and the constraints from the heat flow measurements are next used to set limits on the bulk composition for the moon The geochemical constraints are integrated with the petrological and geophysical data in an attempt to provide a consistent model for the geochemical evolution of the moon

Late quaternary history of vegetation and climate of the Rajasthan desert, India

Abstract: The results from stratigraphy, radiocarbon dating and pollen analysis of three salt-lake deposits at Sambhar, Lunkaransar and Didwana in western Raj9asthan, and one freshwater lake deposit at Pushkar in the Aravalli Hills, are described in conjunction with pollen analysis of some archaeological soil samples from the Indus Valley site at Kalibangan in northern Rajasthan. The salt-lake deposits studied are stratigraphically divisible into (a) pre-lacustrine, (b) lacustrine and (c) post-lacustrine sections. The pre-lacustrine section is characterized by a thick bed of aeolian sand underlying lacustrine sediments, while the lacustrine and post-lacustrine sections are broadly circumscribed by laminated clay and nonlaminated silt respectively. The pollen record from the four lake profiles studied is divided into local pollen zones. Four regional pollen assemblage zones are delineated for the area west of the Aravalli Range in Rajasthan. The environmental history deduced from the pollen record is divisible into phases I-V, of which phases II-V follow the regional pollen assemblage zones. Phase I is stratigraphically determined, and is representative of severe arid environments under which the sand dunes, now stabilized, are suggested to have been active. The plant microfossils first appear in phase II with the deposition of lacustrine sediments dated to around 10000 b . p . The vegetation comprises an openland steppe which is rich in grasses, Artemisia and sedges and poor in halophytes. Artemisa, Typha angustata, Mimosa rubicaulis and Oldenlandia , which now grow under areas of comparatively higher average annual rainfall (above 50 cm), appear to have flourished in the semi-arid belt, while the first two plant taxa had encroached even as far as the arid belt, both suggesting that a general westward shift of the rainfall belts had taken place. Vegetation destruction through burning by man is suggested to have started together with the first occurrence of Cerealia-type pollen at about 7500 b . c . and continued thereafter throughout phases III and IV. The increase in swamp vegetation and the intensification of vegetation cover inland together with the maxima of all mesophytic elements in phase IV ( ca. 3000 b .c . to ca. 1000 b .c .) indicate an increase in the rainfall, apart from a short relatively drier time about 1800-1500 b . c . at Sambhar which correlates with the decline of the Indus culture in northwest India. Phase IV is immediately followed by aridity for which there is stratigraphic evidence that the salt lakes started drying. At Pushkar, there is evidence that the vegetation showed a marked change in the Aravallis. The onset of this aridity is suggested to have been widespread. The climate did not ameliorate until about phase V (? early centuries a .d . to present) at which time the Rangmahal culture perhaps flourished in Rajasthan, the remains of which imply good water supply. In conclusion it is suggested that the Rajasthan desert is primarily natural, its history punctuated by at least one more vegetated, humid period during the Holocene, the climatic control of which as indicated by the vegetation history is consistent with climatic events elsewhere in the world.

T cell response to viral and bacterial infection.

Abstract: TTie adaptive immune response to antigens of infectious agents is an. important component of vertebrate defence mechanisms. In many itistances, a humoral antibody response plays a key protective role. However, in certain infectious diseases, notably those caused by ititracellular parasites, recovery from primary infection, and resistance to subsequent infection with the same agent, it not mediated by free antibody, and there are now a number of clear examples of the need for a cell-mediated immune (CMI) response. Over the past few years it has become evident that activated thymusderived (T) cells are specific effector cells* in a wide variety of CMI reactions. In infectious disease models in mice, extensive evidence on this point has been obtained, particularly from studies of ectromelia virus infection (mousepox) and Listeria monocytogenes infection (a bacterial infection). This article will be devoted largely though not entirely, to recent findings in these two model systems: it is not intended to be a comprehensive review. Detailed mechanistic analysis of T cell effector functions will not be included. T cell mediated cytotoxicity in allograft rejection and tumour immunity has been comprehensively reviewed recently (Cerottini & Brunner 1973, Henney 1973). T cell-B cell interaction in humoral responses will be mentioned only in passing. Cooperation between T cells and macrophages, outlined briefly below, has been discussed in detail in other reviews in this volume and elsewhere (W.H.O. 1973).

Total fusion 40Ar/39Ar ages using Hifar reactor

Abstract: Total fusion 40Ar/39Ar ages have been determined on 22 samples, including biotite, muscovite, sanidine, hornblende, plagioclase, pyroxene, and whole rock samples of volcanics. The samples have conventional K‐Ar ages ranging from 14 m.y. to 2000 m.y. The neutron irradiations for the 40Ar/39Ar dating were made in the HIFAR reactor, using the standard biotite GA1550 as the flux monitor. The 40Ar/39Ar total fusion ages of 14 samples agree to within 2 percent with the conventional isotope dilution K‐Ar ages. The remaining 8 give measured 40Ar/39Ar ages from 3 to 9.5 percent greater than the conventional K‐Ar ages. These systematic discrepancies are due to significant neutron flux gradients in the reactor which become apparent because larger amounts of sample, compared with the amount of flux monitor, were used in these cases. With samples laid out in the reactor can as in the present study the precision of the 40Ar/39Ar ages is about 2 percent (standard deviation) in the ideal case. Correction factors...

Large numbers of cells in normal mice produce antibody components of isologous erythrocytes.

Abstract: THERE are a number of arguments against the idea1 that self-tolerance depends on a purge of all self-reactive clones early in development. First, antigens which appear later in development, for example, Ig idiotypes, must induce tolerance to themselves. Second, autoimmune diseases are often reversible, implying that when anti-self-reactive cells arise late, they may still be controlled. Third, the recent finding (refs 2–4 and L. M. Pilarski and A.J.C., unpublished) that single clones of antibody-forming cells rapidly produce variants also implies a continuous monitoring and control of immunocompetent cells. Self-reactive variants must arise during many immune responses, and must normally be prevented from causing autoimmune disease. Fourth, the distinction between anti-self and anti-not-self specificities is obviously not clear-cut. Given the great diversity of self components in mammals, it is probable that almost any antibody will react to some self antigens with low affinity.

Excess 26 Mg in the Allende Meteorite

Abstract: VARIATIONS in the isotopic abundance of magnesium (78.6% 24Mg, 10.1% 25Mg, 11.3% 26Mg) have been sought1,2 in meteorites because of the possible addition of radiogenic 26Mg by the decay of 26Al. This short-lived nuclide (half-life 7.4×105 yr) is formed by proton bombardment of light elements3 and is of particular interest in theories of nucleosynthesis and heat generation during the early history of the Solar System. Analysed material must have a high Al/Mg ratio to avoid the dilution of any radiogenic 26Mg by common Mg. Consequently, previous workers have chosen mainly feldspars from basaltic achondrites and metamorphosed chondrites. The apparent absence of excess 26Mg in such meteorites is, however, not suprising, because the condensation of chondritic material from the solar nebula now seems4 to predate its later metamorphism by some 80 Myr, and the magmatic activity that produced the basaltic achondrites is younger still. Thus, the feldspars that formed as a result of these processes would incorporate aluminium that was separated from a nucleo-synthetic event by at least 80 Myr and because of its short halflife in-sufficient 26Al would remain to generate a detectable 28Mg anomaly.

Megacrysts from the Newer Basalts and Other Basaltic Rocks of Southeastern Australia

Abstract: Megacrysts of aluminous clinopyroxene, aluminous orthopyroxene, anorthoclase, kaersutite, ferrokaersutite, titanbiotite, titanphlogopite, and apatite are present at some of the explosive alkaline basalt eruptive centers within the Newer Basalts province of Victoria and South Australia, and also in other basaltic rocks of southeastern Australia. Clinopyroxenes from particular Newer Basalts centers display a systematic chemical variation involving increasing Al, Fe, Ca, Ti, Na, and Fe 3+ with decreasing Si, Cr, Mg, and Mg/Mg+Fe ratio, which may reflect magmatic fractionation processes. Field, chemical, and experimental evidence suggest that clinopyroxene and orthopyroxene megacrysts represent disaggregated parts of pegmatitic polycrystal-line aggregates, precipitated as near-liquidus phases from basaltic (particularly basanitic) magmas in association with ultramafic xenoliths of the Al-augite series, at pressures of 10 to 20 kb. Magnesian kaersutite and titanphlogopite from The Anakies, Victoria, are possibly near-liquidus phases of their associated nepheline mugearite, but physical conditions of formation of such megacrysts cannot be uniquely fixed. The assemblage ferrokaersutite + titanbiotite + anorthoclase + apatite from The Anakies is considered to represent a near-solidus precipitate at pressures less than 12 kb. On the basis of a recurring association at four New South Wales localities, it is suggested that aluminous clinopyroxene and titanphlogopite are near-liquidus phases of wet olivine nephelinite or olivine analcimite magmas at high pressures. In the Newer Basalts province, the observed inconsistencies between megacryst assemblage and host basalt composition, as well as the varied compositions of the megacrysts, imply a random sampling of phases precipitated from possibly the host magmas and (or) derivative and parental magmas, and thus megacryst suites are probably of limited utility in deducing detailed fractionation trends in basaltic magmas.