Showing papers by "University of Adelaide published in 1969"

Trace fossils from the precambrian and basal cambrian

Abstract: Certain worm-like configurations on rocks are recognized as shrinkage-crack infillings. Some genuine Precambrian trace fossils are briefly described. The early Cambrian contains a richer assemblage, including some distinctive and widespread form genera. The study of early trace fossils leads to conclusions not only on facies, but also on the evolution of behaviour and functional morphology in soft-bodied organisms.

A comparison of interhemispheric transmission times in acallosals and normals

Abstract: Interhemispheric transmission times for unstructured visual information were measured in two patients born without the corpus callosum and compared with similar measures for groups of normals. The results support an earlier suggestion (Jeeves, 1965) that lengthened interhemispheric transmission times in acallosals may be one important factor responsible for their reduced efficiency on tasks requiring bimanual perceptuomotor coordination under a speed constraint.

Buckland Park Aerial Array

Abstract: An aerial array 1 km in diameter has been constructed near Adelaide, South Australia. It will be used for observations of ionospheric drifts and meteors, and for other experiments in ionospheric physics.

The dimensions and numbers of small vesicles in cells, endothelial and mesothelial and the significance of these for endothelial permeability.

Abstract: SUMMARY Measurements were made of the diameters, numbers and other parameters of small, smooth-surfaced vesicles in the endothelium of blood capillaries and lymphatics, and in the mesothelial cells of the diaphragms of mice. Some measurements were also made on the aortic endothelium. With a few exceptions, there were no morphological differences between the various sites. It was found that between 25% and 35% of the non-nuclear cell volume was composed of vesicles, whose membranes accounted for about 55% of their volumes. Their internal volumes were ∼ 70,000 nm3, totalling ∼ 0·04 μm3/μm2 of luminal surface area. For each 1 μm2 there were ∼ 135 vesicles attached to each surface membrane of the cell, and between ∼ 200 and ∼ 350 vesicles lying free in the cytoplasm. There was probably a slight amount of shrinkage during the preparation of the material, and the true linear dimensions were probably ∼ 105% of those actually observed. Thus the values for the internal volumes were probably ∼ 85,000 nm3 and ∼005 μm3 respectively; the vesicular numbers were probably ∼ 125 attached to each surface and between ∼ 175 and ∼ 300 free. The vesicles attached to the plasma membranes often had quite long stalks; these were estimated to be ∼ 30 nm at the moment of rupture. Thus the vesicles must be released an appreciable distance away from the membrane. This modifies the conclusions of Shea & Karnovsky (1966), since it can now be shown that Brownian movement alone is capable of accounting for the release of the vesicles, their movements within the cells and their transportation of material. By combining these results with others estimating the endothelial permeability coefficients, it can be calculated that the average free lifetime of a vesicle is ∼1½ sec, from union with one plasma membrane to the next. It can also be shown that the average time of such an attachment is ∼ 2½ sec. There are many possible sources of error relating to these measurements; they must only be regarded as tentative. It appears likely, however, that they are of about the correct order of magnitude as they accord well with other data.

Tritiated water in the measurement of milk intake and tissue growth of ruminants in the field.

Abstract: MEASUREMENT of the turnover and content of water in grazing animals is a useful approach to their physiological ecology. Young ruminants obtain this water from milk. Linnaeus, when he named the mammals, recognized that the provision of milk is a major adaptation of these vertebrates to dry land, but it is not easy to measure the amount of milk taken by mammalian young in the field1. The supply of milk, however, determines not only the early growth but often the survival of neonates3. Most milk is more than 80 per cent water and the burning of hydrogen in the milk solids yields a volume of water near to that of the solids themselves, so that measurement of water turnover in the young provides a close estimate of milk intake4. The use of tritiated water in the young allows estimation of the body solids content as well as an integrated measure of milk taken, while mother and offspring live undisturbed (apart from recapture at 7–10 day intervals) in their normal environment.

Endocytosis: The different energy requirements for the uptake of particles by small and large vesicles into peritoneal macrophages

Abstract: SUMMARY The uptake of various, different-sized particles by macrophages was studied using the electron microscope. In addition to observing normal cells, cells were examined which had been inhibited by exposing them to low temperature (4°C), and to a number of metabolic poisons. It was found that large particles (> 01 μm) enter the cells and are contained in large vesicles (0·1–5 μm). Small particles (< 50 nm) may also enter the cells by this process. They enter most frequently, however, by passing into small (∼ 70 nm) vesicles. These may later coalesce and their contents adhere to give a second kind of large vesicle. The various inhibitors prevented the ingestion of the large particles (and of the small particles en masse) into large vesicles, but did not prevent their initial adsorption onto the plasma membranes. They did not prevent nearly normal numbers of small particles from entering the pre-existing small vesicles, nor their subsequent fusion into the second class of large vesicles.

Tooth Wear as a Mortality Factor in the Weddell Seal, Leptonychotes Weddelli

Abstract: A simple method for etching and staining macrosections of Weddell seal (Leptonychotes weddelli) canine teeth for aging by counting dentinal annuli is described. Weddell seals abrade sea ice with their teeth to maintain breathing holes during winter. This results in the tooth wearing away to the pulp cavity and subsequent infection and abscessing. An arbitrary scale was devised to measure dental wear and necrosis on 171 Weddell seal skulls for which age had been determined. An index of tooth wear and necrosis showed little change up to the average age of 8 to 9 years, followed by a marked increase in subsequent years indicating a correlation between tooth condition and mortality of adults.

Cytogenetics of Marsupials

Abstract: The Marsupialia are one of the orders of the Mammalia. They are of interest for several reasons. They diverged from the general line of mammalian evolution at an early stage and may therefore give us some insight into the early progenitors of present day eutherian mammals. The entry of marsupials into Australia and South America was accompanied by an explosive radiation of adaptations to occupy a diversity of ecological niches. Living members of the group are found in their greatest diversity and abundance in Australia and New Guinea where there are some 160 species (Darlington, 1957). The remainder of the order, about 60 species (Cabrera, 1957), are found in Southern and Central America, and one species extends into North America.

The biochemistry of nitrifying microorganisms.

Abstract: SUMMARY 1Biological nitrification is mediated primarily by two genera of bacteria, Nitrosomonas and its marine form Nitrosocystis, oxidizing ammonia to nitrite, and Nitrobacter, converting nitrite into nitrate. These are chemoautotrophic organisms since they usually derive their energy for growth by oxidizing these inorganic nitrogen compounds and their carbon from carbon dioxide, carbonates or bicarbonates. 2The morphology and structure of these Gram-negative bacteria studied by electron microscopy show numerous intracellular membranes reminiscent of those in photosynthetic bacteria and blue-green algae. These structures may therefore be associated with the production of ATP. 3The bacteria are difficult to grow in pure cultures in sufficient amounts for biochemical work since their generation time is around 10 hr. and the yields are only about one hundredth of those obtained with heterotrophic bacteria. Thus in continuous cultures great care must be taken to avoid ‘wash-out’ of the cells. Since Nitrosomonas and Nitrosocystis produce copious amounts of nitrous acid, which would eventually retard growth, pH stat units are used to titrate the cultures continuously with a solution of sodium carbonate, to hold the pH around 7–8. 4The respiratory chain which is associated with cell membranes, contains flavin, quinones and many cytochromes linking to oxygen as a terminal acceptor. In Nitro-somonas-Nitrosocytis hydroxylamine is oxidized by the electron transfer chain and in Nitrobacter nitrous acid is utilized. The ammonia-oxidizing system, which in Nitrosomonas probably resides near the cell surface, does not appear to survive cell breakage. During the oxidation of hydroxylamine and nitrous acid by the respiratory chains, a phosphorylation occurs but the P/O ratios around 0–30 are low. There is little energy reserve material in the cells, possibly β-hydroxybutyrate and some metaphosphates and as soon as the oxidative processes are impaired the cells cease dividing. 5Chemoautotrophic bacteria have a novel way of producing reduced nicotinamide adenine dinucleotide (NADH). This involves a reversal of electron flow from reduced cytochrome c to nicotinamide adenine dinucleotide (NAD) that is energy-dependent, thus requiring adenosine triphosphate. 6Reductase enzymes, nitrate, nitrite and hydroxylamine reductases in Nitrobacter and nitrite and hydroxylamine reductases in Nitrosomonas, have been described. They appear to be readily extracted in soluble form and are probably assimilatory enzymes since 16N labelled nitrate, nitrite and hydroxylamine respectively in Nitrobacter and the last two in Nitrosomonas are readily incorporated into cell nitrogen. It has been suggested that a particulate nitrate reductase in Nitrobacter is coupled to the synthesis of adenosine triphosphate but adequate experimental evidence for this concept has not been produced. 7Some recent observations with Nitrobacter suggest that it grows on acetate, deriving all its energy and carbon skeletons from this source but the mean generation time for the bacterium is unchanged. Under these conditions the carbon dioxide fixing enzymes of the pentose pathway are suppressed. This then is a case of facultative chemoautotrophy but there is no increase in the biosynthesis of the TCA enzymes. Whether this is a widespread phenomenon in other chemoautotrophic bacteria remains to be established. If this does prove to be the case it would aid their survival in a variety of habitats and extend their distribution in soils and seas. 8The carbon dioxide fixing enzymes of the pentose pathway are found in the soluble parts of the cells. The major route is via the carboxydismutase system with only a small incorporation via the phosphoenolpyruvate carboxylase enzyme. Enzymes of the tricarboxylic acid cycle have low activities compared with those in heterotrophs and this overall slow metabolism, rather than the lack of a specific enzyme such as NADH oxidase, may well account for the slow growth of these bacteria. Although there is very active glutamic dehydrogenase in Nitrosomonas that utilizes ammonia, the enzyme has a very small activity in Nitrobacter. This poses a problem of the route of incorporation of nitrite nitrogen into cell nitrogen in the latter bacterium. 9A few heterotrophic fungi have been described which oxidize ammonia to nitrate but their activity is small compared with that of the nitrifying bacteria. 10It is concluded that the nitrifying bacteria which have many novel biochemical features not met with in other organisms merit further study.

Parallel mosaicism of supernumerary chromosomes and sex chromosomes in Echymipera kalabu (Marsupialia).

Abstract: Echymipera kalabu (Peramelidae: Marsupialia) does not have the full chromosome complement in all its adult somatic tissues. The chromosomes missing are the Y-chromosome in the male and an X-chromosome in the female. The full complement is present in the corneal epithelium and the reproductive tissue. A parallel mosaicism to this exists with respect to small supernumerary chromosomes which are found in certain animals of this species. These supernumeraries must be subject to the same control system as that which is responsible for the elimination of the sex chromosomes.

The Extraction, Characterization, And Significance Of Soil Polysaccharides

Abstract: Publisher Summary Although much is known about the nature and function of many polysaccharides synthesized by individual organisms, there is little information relating to the polysaccharides produced in an environment such as the soil, which in a unique way to bring together a great variety of biological forms. Polysaccharides have been extracted from soils by many different chemical reagents, and recently methods have been devised that enable most of the carbohydrates to be isolated from other soil materials. The extracted polysaccharides show a continuum of molecular sizes and contain a wide range of neutral and charged monosaccharides, amino acids, and other unidentified nitrogenous and acid components. Carbohydrates from different soils are similar in chemical composition suggesting that the microbial population of different soils is qualitatively similar. This chapter describes the mechanisms related to the extraction, characterization, and significance of soil polysaccharides. Many methods have been used to fractionate extracted soil polysaccharides, the most successful of which are based on gel filtration and chromatography on charged supports such as cellulose. The composition of soil polysaccharides suggests that in soils they may carry charged sites and take part in exchange reactions and act as energy sources for heterotrophic organisms. However, the main stimulus for the study of soil polysaccharides has arisen from repeated indications of their favorable influence on soil physical conditions. Much work has been directed toward this aspect, and it has been shown that microbially produced soil polysaccharides are capable of stabilizing soil aggregates against dispersion in water. Methods for the isolation of polysaccharides from other soil materials in good yield are now available and carbohydrate chemists have developed methods for the analysis of extracted polysaccharides.

Kinetics of Adsorption of Colicin CA42-E2 and Reversal of its Bactericidal Activity

Abstract: The kinetics of killing of Escherichia coli K-12 by colicin CA42-E2 have been studied, and the data were used to estimate the adsorption constant of this colicin under various environmental conditions. Evidence was obtained suggesting that the adsorption of colicin occurred in two stages; the earlier stage was reversible and did not lead to the death of the cell, the latter stage was irreversible and bactericidal. Cells which had adsorbed a lethal quantity of colicin could be rescued for a short time by inactivating the adsorbed colicin with trypsin. However, when the metabolic activity of the cells was totally arrested the lethal effect of adsorbed colicin was subject to trypsin reversal over long periods of time.

Interaction of plant phenols and salivary phenolases in the relationship between plants and hemiptera

Abstract: Most sucking bugs secrete a salivary phenolase, at least some together with a diphenolic substrate. No function for this system has yet been demonstrated, but phytopathological fungi also secrete phenolases, and there is evidence that attacks both by sedentary insects and by fungi stimulate a defence mechanism in plants based on the oxidation of phenols to quinones. Details of the interaction are uncertain, but it seems possible that some of the toxic reactions of plants to the feeding of sucking insects are similar biochemically to the toxic or hypersensitive reactions of plants to invading fungi. Insect galls are classically associated with “tannins”, and phenols have been implicated particularly in the resistance of plants to cecidogenic insects such as the grape phylloxera and the woolly aphis. It is suggested that the production of quinones by the oxidation of phenols was evolved by plants as a non-specific mechanism that resists invading organisms, and that the further oxidation of the quinones to non-toxic polymers is a means by which some invading organisms have overcome this resistance. Stimulation of the growth of some of the plant's cells as a by-product of the interaction is biochemically possible and is suggested as an explanation of how cecidogenesis by insects has evolved. ZUSAMMENFASSUNG WECHSELWIRKUNG VON PFLANZLICHEN PHENOLEN UND SPEICHELPHENOLASEN IN DEN BEZIEHUNGEN ZWISCHEN INSEKT UND PFLANZE Die meisten pflanzensaftsaugenden Wanzen scheiden im Speichel eine Phenolase ab, zumindest einige bei einem diphenolischen Substrat. Bisher konnte keine Funktion dieses Systems nachgewiesen werden; jedoch scheiden phytopathogene Pilze ebenfalls Phenolasen ab, und es besteht die Wahrscheinlichkeit, das Angriffe sowohl von sessilen Insekten wie von Pilzen in den Pflanzen einen Abwehrmechanismus auslosen, der auf der Oxydation von Phenolen zu Chinonen beruht. Einzelheiten der Wechselwirkung sind unsicher, aber es scheint moglich, das einige der toxischen Reaktionen der Pflanzen gegenuber beisenden oder saugenden Insekten biochemisch den toxischen oder Uberempfindhchkeits-Reaktionen der Pflanzen gegenuber eindringenden Pilzen ahneln. Insektengallen sind gekennzeichnet durch ihre Verbindung mit “Tanninen”, und Phenole sind besonders mit der Resistenz von Pflanzen gegenuber cecidogenen Insekten, wie der Reblaus und der Blutlaus, in Beziehung gebracht worden. Es wird vermutet, das die Produktion von Chinonen durch die Oxydation von Phenolen von den Pflanzen als ein unspezifischer Mechanismus entwickelt worden ist, der dem eindringenden Fremd-Organismus Widerstand leistet, und das die weitere Oxydation der Chinone zu nicht-toxischen Polymeren ein Mittel ist, durch das einige eindringende Organismen diese Resistenz uberwunden haben. Wachstumsanregung fur einige der Pflanzenzellen als Nebenprodukt dieser Wechselwirkung ist biochemisch moglich und wird als Erklarung dafur vermutet, wie sich Gallenbildung durch Insekten entwickelt hat.

Purine metabolism in germinating wheat embryos

Abstract: 1. Both the acid-soluble fraction and the nucleic acid fraction of wheat embryos were extensively labelled after incubation for 6hr. in the presence of [8-(14)C]adenine. Subsequent incubation in the absence of labelled adenine resulted in no loss of radioactivity to the medium during a 48hr. period. Radioautography indicated that during this period there was a continuous increase in the radioactivity present in the acid-insoluble fractions of the root and leaf tissues relative to that present in the coleorhiza and coleoptile. 2. During incubation at 25 degrees there was a 26-fold increase in the activity of 3'-nucleotidase between 4hr. and 24hr.; the activities of enzymes hydrolysing AMP and IMP increased to a smaller extent. The activities of adenine phosphoribosyltransferase and hypoxanthine phosphoribosyltransferase increased three- to five-fold during incubation at 25 degrees for 24hr. 3. Adenosine kinase, inosine phosphorylase and 5-phosphoribosyl pyrophosphate synthetase activities were high in extracts from dry embryos and did not increase during 48hr. at 25 degrees . 4. The increase in 3'-nucleotidase activity was prevented by cycloheximide, cryptopleurine or incubation at 4 degrees , but not by actinomycin D; these treatments did not depress the activity of the other enzymes measured. 5. The results are discussed in relation to RNA translocation within the wheat embryo during germination.