Showing papers by "La Trobe University published in 1984"

Length dependence of changes in sarcoplasmic calcium concentration and myofibrillar calcium sensitivity in striated muscle fibres

Abstract: It has long been known that the contractile performance of striated muscle is strongly dependent upon the length of the muscle (e.g. Ramsey & Street, 1940) and the sliding filament theory of muscle contraction offers a ready explanation for many features of the isometric length-force relation of fully activated skeletal muscle fibres (Gordon et al., 1966b). Over the past decade, however, it has become increasingly more apparent that differences in the mechanical behaviour of striated muscle at different lengths, particularly if submaximally activated, often cannot be satisfactorily explained on the basis of filament overlap alone. There is growing evidence that changing the length of a muscle fibre alters not only the physical overlap of the filaments (i.e. the striation spacing or sarcomere length) but also modifies other processes involved in the activation of contraction. In particular it appears that both the characteristics of the sarcoplasmic Ca 2+ concentration change, which occurs upon excitation of the fibre, and the apparent sensitivity of the contractile proteins to Ca 2+ can vary with muscle length. This article will concern itself principally with the length dependence of these two aspects of contractile activation.

Interspecific competition is not a major organizing force in many insect communities

Abstract: Part of the current dogma in ecology is that competition between species for limited resources is not only common but also a major organizing force in many communities1,2 largely because studies on vertebrates, particularly birds, have played a major role in creating the traditional framework of niche theory and resource partitioning3–9. Other workers, particularly those studying insect communities, have suggested that significant interspecific competition is too rare and sporadic to be of major significance and have placed more emphasis on autecological processes10–13. Efforts to resolve the controversy have concentrated on the question of whether or not competition is common in nature1. Here we show that even where competition can be demonstrated, it need not have a major role in community organization.

Cognitive Processes in Improvisation

Abstract: Publisher Summary This chapter discusses cognitive processes in improvisation. Improvisation is thus central to the formation of new ideas in all areas of human endeavor. Its importance experientially rests with its magical and self-liberating qualities. Its importance scientifically is that it presents one with the clearest, least edited version of how one think, encoded in behavior. It is among the time-based arts, namely music, dance, theatre and mime that one find the greatest literature. From a survey of this material, certain facts emerge quite consistently, and allow the formulation of plausible cognitive models for improvisation. Much of the variety of improvisation comes from the many different types of referent which may be used, and the many kinds of relationships the improviser may choose to set up between the referent and the sounds, movement, words, etc., that constitute the improvised behavior.

The application of Sirofluor, a chemically defined fluorochrome from aniline blue for the histochemical detection of callose

Abstract: Sirofluor, a chemically defined fluorochrome from aniline blue in aqueous unbuffered solutions, complexes with isolated (1 → 3)-β-glucans, but not (1 → 4)-β-glucans, after embedding in JB-4 resin and sectioning. Under these conditions, callose deposits in plant tissues give a brilliant yellow fluorescence with essentially no background fluorescence.

Bilingual biscriptal deep dyslexia

Abstract: Studies of deep dyslexia in Japanese patients, and of non-word reading by deep dyslexic readers of alphabetic scripts, suggest a general principle that reading that depends on the mapping of characters onto phonological segments (phonemes in the case of alphabetic scripts, syllables in the case of syllabaries) is impossible in deep dyslexia. We describe a case of deep dyslexia in a patient who premorbidly could read English and Nepalese. As the latter is written in the syllabic Devanagari script, this case may be used to explore the generality of this principle. It would be expected that reading Nepalese words written in the syllabic script would be more difficult than reading English words written in the Roman alphabet. In oral reading tasks this was the case, even though Nepalese was the patient's first language. However, further studies showed that he could understand Nepalese words written in the syllabic script at least as well as English words written in the Roman alphabet, and that he could read al...

Origin of manganese giants: Sea-level change and anoxic-oxic history

Abstract: Inversely graded pisolites of manganese oxide in the mid-Cretaceous manganese giant at Groote Eylandt, Australia, were deposited during a regional fall in sea level, as indicated by their relationships to wave-cut benches. Dissolved manganese was concentrated in relatively anoxic waters of the intracratonic basin during a marine transgression and precipitated as oxides and carbonates during a regression. Ore bodies ultimately formed by concentration of abundant particulate manganese by a tidal-lag mechanism.

The Gains from Research into Tradable Commodities

Abstract: This paper develops a model for assessing the aggregate level and distribution of the benefits of reseach into tradable commodities. It estimates gains to Australia and to the rest of the world from research into the wool and wheat industries.

Interspecific hybridization in the genus Drosophila

Abstract: The first review of the phenomenon of interspecific hybridization in animals appears to be that of Haldane (1922), who catalogued all cases known to that time in which crosses performed artificially had yielded ten or more offspring with a distortion of the F1 sex ratio or fertility. Haldane’s examples encompassed Insecta (Lepidoptera, plus single instances in Diptera and Anoplura), Crustacea (a single instance in Cladocera), Aves, and Mammalia. On the basis of his compilation Haldane enunciated the empirical “law” that the absent or sterile sex is always the heterogamic one (“heterozygous” in the original terminology), although exceptions have subsequently been found in some groups (White, 1973).

Structural Variation in the Zebra Finch Distance Call

Abstract: and Summary The distance calls (DC) of free-living and recently captured zebra finches (ZF) were investigated in order to establish the extent of variation in the structure within and between individuals, colonies, sexes, geographic localities and subspecies. Most work was carried out on the Australian subspecies P. g. castanotis in south-eastern Australia. The calls were analysed sonographically and analysis of two frequency and two temporal parameters were undertaken. The spectral structure of the calls was also assessed subjectively. The main findings are as follows: 1 Each individual has its own uniquely structured DC. The calls of males are more distinct than those of females. 2 The differences between individuals are sufficiently large to expect that they could probably be perceived by individuals. 3 The DCs differ between the sexes. The female call is significantly longer. In P. g. castanotis the male call has two elements — a tonal element followed by a noise element; it also has fewer harmonics. The differences could be detected by ear. The Timor subspecies is thought to have lost the noise element. 4 Adjacent colonies have DCs that are not significantly different. 5 DCs from different and distant geographic localities are not significantly different except for a few locations where distinct local forms of the DC exist. The changing composition of colonies is thought to erode the development of dialects. 6 The DCs of both subspecies have the same basic complex tone with the same harmonic configuration. The calls of males are of the same duration in both subspecies but those of females are longer in P. g. castanotis. The calls of P. g. guttata have a higher fundamental frequency, fewer harmonics and a higher emphasized frequency (FMA). 7 The DC in P. g. castanotis is probably used to keep pairs together in the large flocks. It may also be used to detect relatives.

A proposed pathway for sorbitol production by Zymomonas mobilis

Abstract: Description d'une voie metabolique possible pour la production de sorbitol basee sur l'identification et la mesure de certaines activites enzymatiques dans Zymomonas mobilis

Interspecific Hybridization in the Genus Drosophila

Abstract: The first review of the phenomenon of interspecific hybridization in animals appears to be that of Haldane (1922), who catalogued all cases known to that time in which crosses performed artificially had yielded ten or more offspring with a distortion of the F1 sex ratio or fertility. Haldane’s examples encompassed Insecta (Lepidoptera, plus single instances in Diptera and Anoplura), Crustacea (a single instance in Cladocera), Aves, and Mammalia. On the basis of his compilation Haldane enunciated the empirical “law” that the absent or sterile sex is always the heterogamic one (“heterozygous” in the original terminology), although exceptions have subsequently been found in some groups (White, 1973).

The role of parental attitudes in the development of temperament in twins at home, school and in test situations.

Abstract: In the La Trobe Twin Study, data are collected on temperament and social development in 3-15 year old twins and singletons from four different sources: questionnaires to parents covering development from birth to the present plus the Bristol Social Adjustment Guide completed by the teacher, Sattler's Behavior and Attitude Checklist completed by the tester, and the Qualitative Score on the Porteus Maze Test. Particular stresses are identified which the parents perceive as distinguishing a multiple from a singleton birth. Whereas they perceive no differences between the first and second-born in birth complications, the second-born is judged less favourably particularly in MZ pairs. The distinction continues in the later assessments by the teacher and tester, where in addition the male twins are seen as being different from other children both in cognition and in temperament. It is proposed that social and cognitive development of twins are interrelated and have two unique components, one related to the greater problems accompanying a multiple birth and the other to comparisons between cotwins.

Divided genomes and intrinsic noise.

Abstract: Segmental genomes (i.e., genomes in which the genetic information is dispersed between two or more discrete molecules) are abundant in RNA viruses, but virtually absent in DNA viruses. It has been suggested that the division of information in RNA viruses expands the pool of variation available to natural selection by providing for the reassortment of modular RNAs from different genetic sources. This explanation is based on the apparent inability of related RNA molecules to undergo the kinds of physical recombination that generate variation among related DNA molecules. In this paper we propose a radically different hypothesis. Self-replicating RNA genomes have an error rate of about 10−3–10−4 substitutions per base per generation, whereas for DNA genomes the corresponding figure is 10−9–10−11. Thus the level of noise in the RNA copier process is five to eight orders of magnitude higher than that in the DNA process. Since a small module of information has a higher chance of passing undamaged through a noisy channel than does a large one, the division of RNA viral information among separate small units increases its overall chances of survival. The selective advantage of genome segmentation is most easily modelled for modular RNAs wrapped up in separate viral coats. If modular RNAs are brought together in a common viral coat, segmentation is advantageous only when interactions among the modular RNAs are selective enought to provide some degree of discrimination against miscopied sequences. This requirement is most clearly met by the reoviruses.

2 Identification and Analysis of Plasmids at the Genetic Level

Abstract: Publisher Summary Many bacteria of diverse type and habitat are now known to harbour plasmid DNA. This observation lends credence to the view that these elements are ubiquitous among procaryotes and are likely to be detected in any species in which a thorough search for them is made. In recent years, the demonstration of plasmids in an increasing variety of bacteria has been striking and directly the result of the development of techniques that allow the physical demonstration, isolation and molecular characterization of plasmid DNA. Thus, plasmids in bacteria in which genetic analysis is presently limited or impossible, are as amenable to detailed molecular study as those from genetically well-characterized bacteria. Such investigations are satisfactory where the primary concern is the molecular characterization, comparison and in vitro manipulation of plasmids for specific purposes such as the construction of cloning vectors. This chapter describes the analyses of the latter type and deals with the primarily genetic procedures that can be used, first to identify a plasmid-encoded phenotype, and then to characterize further the element involved.

Further Mycosphaerella species causing leaf diseases of Eucalyptus

Abstract: Three previously described species of Mycosphaerella are discussed in relation to their original descriptions and type specimens. M. eucalypti does not appear to be a species of Mycosphaerella . However M. heimii is a distinct species but no Latin diagnosis was provided by the original author and the type specimen could not be located. M. molleriana is also distinct but it has not yet been collected from eucalypts in Australia. Three new species are described from diseased eucalypt leaves collected in southern Australia: M. delegatensis sp.nov., M. swartii sp.nov., and M. walkeri sp.nov. M. swartii and M. walkeri have identical teleomorphs, but distinct anamorphs, Hendersonia eucalyptorum and H. fraseri respectively, and have different host ranges.

Characteristics of pathogenic non‐fluorescent (smooth) and non‐pathogenic fluorescent (rough) forms of Pseudomonas tolaasii and Pseudomonas gingeri

Abstract: Pseudomonas tolaasii and Ps. gingeri cultures isolated from naturally diseased mushrooms and cultures obtained from other workers were all observed to contain both smooth and rough colony forms. The smooth forms produced mucoid, non-fluorescent, glistening opaque colonies with entire margins. The rough forms produced non-mucoid, fluorescent, dull, translucent greenish-yellow colonies with irregular margins. Smooth forms were observed to produce a toxin and were pathogenic to mushrooms, whereas rough forms did not produce toxin and were non-pathogenic. Isolates of Ps. tolaasii were distinguishable from Ps. gingeri by various biochemical tests. In general, however, biochemical differences between the rough and smooth forms of each species could not be detected. Rough forms of Ps. tolaasii and Ps. gingeri remained stable in culture but smooth forms were unstable, tending to convert to rough forms at a very high rate.

Olfactory response and resource utilization in Drosophila: interspecific comparisons

Abstract: Olfactory response and resource utilization in Drosophila were compared among three domestic (D. melanogaster, D. simulans, D. immigrans) and one Australian endemic (D. lativittata) species. Olfactory response was measured in a choice type olfactometer (Fuyama, 1976). The following chemicals common in Drosophila resources were used as odourants: acetaldehyde, acetic acid, propionic acid, methanol, ethanol, n-propanol, isopropanol, n-butanol. Resource status of these chemicals was determined either from the literature or by adult longevity tests. All species were attracted by acetaldehyde, while methanol, isopropanol and n-butanol were unattractive. Ethanol attracted all species except D. immigrans, while only D. lativittata and D. melanogaster were attracted to n-propanol, propionic acid and acetic acid Methanol and isopropanol were not utilized as resources by any of the species, while D. melanogaster and D. lativittata showed greater utilization/tolerance of the other chemicals. Some correlation between resource utilization and olfactory response was found at the interspecific level, although not all chemicals utilized as resources are attractants. The adaptive significance of the interspecific variation in olfactory response is discussed, especially in relation to habitats selected. The results provide suggestions for habitat selection studies at the intraspecific level.