Showing papers by "La Trobe University published in 1992"

Changes in cytosolic pH and calcium of guard cells precede stomatal movements.

Abstract: Stomatal opening is induced by indoleacetic acid (IAA), cytokinins, and fusicoccin (FC), whereas stomatal closure is induced by abscisic acid (ABA). To test the effect of these growth regulators on guard cell cytosolic Ca2+ ([Ca2+]cyt) and pH (pHcyt), epidermal strips were taken from the lower side of leaves of the orchid Paphiopedilum tonsum and were loaded with acetomethoxy-esterified forms of the Ca2+ indicator fluo-3 or the pH indicator 2',7'-bis(2-carboxyethyl)-5(6)carboxyfluorescein. Basal [Ca2+]cyt ranged from 0.05 to 0.3 M and was 0.22 +/- 0.015 (n = 21). Increases in both [Ca2+]cyt and pHcyt were observed in guard cells after application of 10-100 M ABA to open stomata, and these preceded stomatal closure. The increase in [Ca2+]cyt ranged from 1.5- to 3-fold and was seen in 7 of 10 experiments. Guard cell alkalinization began within 2 min of ABA treatment and continued for the next 8 min. The increase ranged from 0.04 to 0.3 pH unit and was seen in 13 of 14 experiments. Guard cell [Ca2+]cyt increased, whereas pHcyt decreased after treatment of closed stomata with IAA, kinetin, or FC. In response to 50-100 M IAA, [Ca2+]cyt increased 1.5- to 2-fold in all cases, and pHcyt decreased 0.2-0.4 unit within 5 min in 7 experiments. Within 12 min, 10-100 M kinetin caused [Ca2+]cyt to increase in 28 of 34 experiments (1.3- to 2.5-fold) and pHcyt fell 0.1-0.4 unit in 15 of 17 treatments. The response to 10-50 M FC was similar in both time and magnitude. These results show that stomatal opening is accompanied by an increase in [Ca2+]cyt and cytosolic acidification in the guard cells, whereas stomatal closure is preceded by an increase in [Ca2+]cyt and cytosolic alkalinization in the guard cells. The order of these events is still uncertain, but changes in pHcyt are correlated with stomatal movement, and these changes may be an important factor in the regulation of guard cell movement.

Evolution of sex determination and the Y chromosome: SRY -related sequences in marsupials

Abstract: IN mammals, testis determination is under the control of the testis-determining factor borne by the Y chromosome1,2. SRY, a gene cloned from the sex-determining region of the human Y chromosome, has been equated with the testis-determining factor in man3–5 and mouse6,7. We have used a human SRY probe to identify and clone related genes from the Y chromosome of two marsupial species. Comparisons of eutherian and metatherian Y-located SRY sequences suggest rapid evolution of these genes, especially outside the region encoding the DNA-binding HMG box. The SRY homologues, together with the mouse Ubely homologues8, are the first genes to be identified on the marsupial Y chromosome.

Do people believe behaviours are consistent with attitudes? Towards a cultural psychology of attribution processes.

Abstract: In individualistic English-speaking cultures such as Australia, the United Kingdom, or the United States, attitudes and behaviours are often believed to be consistent. By contrast, in the Japanese culture, people may be primarily conceptualized as embedded within social contexts; the belief in consistency between attitudes and behaviour (the ABC belief) may be less strong and behaviours seen to be less consistent with attitudes. In this paper, we report two studies designed to examine the hypothesis that the strength of ABC beliefs underlies inferences in attributions of behaviour to attitudes. In Study 1, the relation of ABC beliefs to attitude attributions was examined in a sample of Australian undergraduate students. In Study 2, ABC beliefs and attitude attributions were compared in Australia and in Japan. As predicted, the ABC beliefs of Australians were related to the extremity of attributions for unconstrained behaviours and the Australians had stronger ABC beliefs than the Japanese. The results are discussed in relation to global cultural dimensions of individualism and collectivism.

Identification of a mammalian 10-kDa heat shock protein, a mitochondrial chaperonin 10 homologue essential for assisted folding of trimeric ornithine transcarbamoylase in vitro.

Abstract: We have identified a 10-kDa stress-inducible mitochondrial protein. The protein is synthesized at elevated rates in cultured rat hepatoma cells challenged with heat shock or amino acid analogues and, therefore, designated heat shock protein 10 (Hsp10). Hsp10 was purified to homogeneity from rat liver and found to exhibit a native molecular mass of 65 kDa, as opposed to a monomeric molecular mass of 10,813.4 +/- 0.41 Da. The amino acid sequence of rat Hsp10 disclosed extensive sequence similarity with bacterial chaperonin (Cpn) 10. Rat Hsp10 and Escherichia coli Cpn60 were used to reconstitute functional trimeric rat ornithine transcarbamoylase from a chemically denatured state with high efficiency. This process depended completely upon rat Hsp10 and was abolished in the presence of a nonhydrolyzable ATP analogue. We conclude that Hsp10 is a eukaryotic Cpn10 homologue and, therefore, together with Cpn60 essential for mitochondrial protein biogenesis. The Cpn-mediated protein-folding apparatus, thus, exhibits a high degree of conservation between prokaryotes and mitochondria of higher eukaryotes.

Capitalism and Underdevelopment

Abstract: The analysis considered in Part II focused upon the functioning and transformation of advanced capitalism. Each theory sought to provide an explanation of the ‘long boom’, understand the contradictions which would ultimately undermine it, and thereby account for the passivity of the working classes in the West, as well as locating the basis for any future radicalisation. In all cases the economic structures of backward areas and their relationship to those of developed countries figured hardly at all. Only Baran and Sweezy thought them to be significant, and even in Monopoly Capital they were of secondary importance. The forces of stability and change in the heartlands of capitalism were seen to operate primarily through the reproduction and growth of the major capitalist economies.

Abnormalities in structure and function of limb skeletal muscle fibres of dystrophic mdx mice

Abstract: In this study we have shown that the skeletal muscle fibres from adult (older than 26 weeks) mdx mice have gross structural deformities. We have characterized the onset and age dependence of this feature in mdx mice. The three dimensional structure of these deformities has been visualized in isolated fibres and the orientation of these deformities was determined within the muscle by confocal laser scanning microscopy. We have also shown that the occurrence of morphologically abnormal fibres is greater in muscles with longer fibres (extensor digitorum longus (EDL) and soleus, 6-7.3 mm long), than in muscles with shorter fibres (flexor digitorum brevis (FDB), 0.3-0.4 mm long). A population of post-degenerative fibres, with both central and peripheral nuclei coexistent along the length of the fibre, has also been identified in the muscles studied. We showed that a mild protocol of lengthening (eccentric) contractions (the muscle was stretched by 12% during a tetanic contraction) caused a major reduction in the maximal tetanic force subsequently produced by mdx EDL muscle. In contrast, maximal tetanic force production in normal soleus, normal EDL and mdx soleus muscles was not altered by this protocol. We suggest that the deformed fast glycolytic fibres which are found in adult mdx EDL but not in adult mdx soleus muscles are the population of fibres damaged by the lengthening protocol.

Psychosocial predictors of weight loss behaviors and binge eating in adolescent girls and boys

Abstract: This study examined the predictors of dieting, extreme weight loss behaviors, and binge eating in adolescents (606 females and 315 males). High school classes were administered measures of weight loss behaviors, binge eating, perceived current and ideal body size, body dissatisfaction, advantages of being thinner and physically fitter, satisfaction with fitness, depression, self-esteem, parental overprotection, parental caring, and family adaptability and cohesion. Principal component analyses grouped predictor (body image, psychosocial) and criterion (weight loss behaviors, binge eating) variables. The primary predictor of weight loss behaviors in both sexes and binge eating in girls was the desire to be thinner which included a larger current body size. Psychological and family variables played lesser roles but were significantly predictive in a number of cases. Sex differences in factor structures and important predictors emerged. © 1992 John Wiley & Sons, Inc.

Production of Pullulan and other Exopolysaccharides by Filamentous Fungi

Abstract: A great deal of recent interest has been shown in the ability of some microbes to synthesize exopolysaccharides. Most attention has been directed toward the prokaryote producers, yet many filamentous fungi also produce exopolysaccharides that have chemical and physical properties of considerable commercial potential. Surprisingly little is known about how and why fungi overproduce these metabolites and how yields are affected by both the physical and chemical environments. This review attempts to critically appraise the current literature on fungal exopolysaccharides, considers their chemical diversity, and examines factors that seem to affect their production. Although much of the published work has been carried out with the α-glucan pullulan, there is considerable literature on the β-glucans and, hence, both of these are discussed.

Urinary cortisol circadian rhythm in a group of high-functioning children with autism.

Abstract: Previous research has suggested that there may be dysfunction in the control of the hypothalamic-pituitary-adrenal axis in autistic children Both an abnormal cortisol circadian rhythm and failure to suppress cortisol secretion in response to dexamethasome have been reported This study investigated the basal urinary cortisol circadian rhythm in a group of high-functioning children with autism and matched controls No evidence was found for abnormal temporal placement of the circadian rhythm in the autistic group There was a tendency towards cortisol hypersecretion during the day, predominantly in those autistic children who were integrated into the normal school system While the temporal parameters of the cortisol circadian rhythm in these children with autism were probably normal, the tendency towards cortisol hypersecretion may indicate an environmental stress response in this group

Forms, Reactions, and Availability of Nickel in Soils

Abstract: Publisher Summary The forms of Ni in soil are diverse and range from those of high activity (water-soluble and exchangeable forms) to ones that have no reactivity in the short term (the life of a plant). The reactions of Ni are dominated by sorption reactions on soil colloids whose nature, relative proportions, and concentrations are important. Soil pH plays a major role in these reactions and thus influences the availability of Ni to plants quite markedly; few other factors appear to be as significant as pH. Deficiency of Ni in plants is unlikely to be a practical problem, but toxicity is more likely. Interest in the occurrence of Ni toxicity is dominated by research on serpentine soils (ancient Ni) and soils to which large quantities of Ni have been added in wastes (modern Ni), particularly in the forms of sewage and sewage sludge. Much of the understanding of the forms and reactions of Ni in soils comes from experiments dealing with the chemistry and biology of these two extreme situations. Needless to say, caution is essential when attempting to determine what is normal. Future research on Ni in soil could fruitfully pursue, for example, the role of microbes in influencing the behavior of Ni, the fractionation of Ni in studies of weathering and reversion of active forms of Ni to less active ones, and the speciation of Ni in the soil solution and the extent and cause of temporal changes.

Problem-based learning in nurse education: an Australian view.

Abstract: This paper addresses the need to adopt teaching-learning approaches in nursing education that develop links between theory and clinical practice in a meaningful way. Problem-based learning (PBL) is such an approach and is gaining popularity in tertiary nursing programmes in Australia. PBL, as an example of the constructivist philosophy, focuses on students' existing knowledge as a starting point for conceptual change teaching. The implications for the nurse educator's role when using PBL are discussed in terms of assumptions about the nature of teaching and learning; conceptual change teaching; ability to focus; the role of negotiation; and the ability to analyse student learning. These factors are seen to be critical components of the pedagogy necessary for nurse educators to utilize PBL approaches effectively.

The world as one of a kind: Natural necessity and laws of nature

Abstract: This world is one of a kind. Some philosophers have maintained that there are many other worlds which are spatially, temporally and causally unrelated to ours. We are not asserting that there are any such disconnected worlds. Nor do we assert that there are none. There is at least one world; and it is a member of a natural kind whether or not there are any others of its kind. If there were any other world, in addition to this one, or instead of this one, then there would be a nontrivial question whether that world was of the same natural kind as ours. We can imagine worlds which would be of the same natural kind as ours; but we can also imagine worlds which would not. Recognition that this world is one of a kind offers a new approach to the question of what a law of nature is. We argue that in general laws of nature are concerned with natural kinds. In some cases laws simply describe the essential properties of natural kinds. Maxwell's equations, for example, describe the essential properties of the electromagnetic field. In the case of other laws, for instance where there are interactions between things of different kinds, the laws stating how they behave are derivable from their essential natures. We hold that this is true even of the most fundamental laws of nature, e.g. the conservation laws, the principles of relativity, and the symmetry principles: they too are concerned with the essential properties of a natural kind. Their concern is with the kind of world this is. This theory of the nature of scientific laws derives from the basic idea that things behave as they do because of what they are made of, how they are made, and what their circumstances are. In so far as the behaviour of a thing depends on what it is made of, it depends on the essential natures of its constituents. In so far as its behaviour depends on how it is made, or on its

Dissociation of two frontal lobe syndromes by a test of verbal fluency

Abstract: Numerous researchers have attempted to localise the behavioural manifestations of frontal pathology to the regions of the frontal lobe. Three prinicpal syndromes have been identified; the disinhibited syndrome associated with damage to the orbital area, the apathetic syndrome associated with damage to the frontal convexity, and the akinetic syndrome associated with damage to medial structures. This study attempted to determine if two of these syndromes could be dissociated from each other on the basis of a test of verbal fluency. This study used some commonly occurring clinical entities as the treatment groups. The orbitally lesioned individuals produced higher levels of disinhibited responding on the test than did non-orbitally lesioned subjects. However, all pathological groups produced lower overall levels of responding than did normals on the fluency component of the test. A number of suggestions are made as to why this may have been the case, and some guidelines for the clinical interpretation of response patterns on the fluency test are suggested.

Toward a reconceptualization of the law of initial value.

Abstract: The traditional model of the law of initial value (LIV), "the higher the initial value, the smaller the response to function-raising, the larger the response to function-depressing stimuli" (Wilder, 1967, p. viii), is critically reviewed. Statistically, the usage of rDX, bDX, and bYX as the indices of LIV contains a spurious X(Y-X) effect. Moreover, defining initial value as a synonym of baseline is too narrow to cover an organism's various states. The parameter of structural relationship beta e value and a null hypothesis test (beta e = 1) are recommended to examine initial-value dependency for different levels of initial value and trends of change. Data suggest that LIV should be revised as follows: The higher the initial value, the greater the organism's following reactivity, although a tendency to reversed responses may occur when the initial value reaches its upper extremity. Both phenomena are probably due to constitutional and homeostatic mechanisms, respectively.

Bill color, reproduction and condition effects in wild and domesticated Zebra Finches

Abstract: Bill-color variability has the identical range and similar distributions in free- living Australian Zebra Finches (Taeniopygia guttata) and their wild-type domesticated de- scendants. Individual differences in bill color exist among adults of both sexes, both in nature and captivity. In laboratory birds, bill color changed over the course of the five-week breeding cycle, with lowest bill-color scores expressed at the end of the cycle. Longer-term patterns included a gradual decline of bill color over the course of multiple clutch attempts, followed by a rapid increase when resources for breeding were withdrawn. Among laboratory males, survivorship was clearly independent of bill color. Among females, bill color changed more rapidly in birds that subsequently died than in those that survived a two-year breeding experiment. High rates of reproduction were significantly associated with decline of male bill score, but not female bill score. The bill-color scores of laboratory males maintained on supplemented and basic seed diets for eight weeks did not diverge. Crowding of laboratory birds was associated with decreased bill color. For birds in nature, bill color tended to decline over the breeding season. Bill color of captive wild birds became more red over a six-week period when birds were fed ad libitum on the laboratory diet. Data for both laboratory and wild birds indicate that reproduction is associated with a decline of bill color in both sexes. Results of diet experiments were inconclusive, but helped to establish that the range of bill colors displayed by domesticated birds is similar to that encountered in nature. Our results, when considered in light of previous findings, suggest the possibility that bill color has different costs and benefits for the sexes and that genetic and/or physiological constraints prevent optimal phenotypic expression of bill color in Zebra Finches. Received 4 June 1990, accepted 21 July 1991.

Sexual arousal across phases of the human menstrual cycle.

Abstract: Three experiments assessing sexual arousal to erotic stimulation at several phases within the menstrual cycle are reported. Cross-sectional as well as longitudinal comparisons indicated that the subjective sexual arousal elicited during fantasy depicting specific themes was stable across the menstrual cycle. Measures of physiological sexual arousal recorded during film episodes and during fantasy demonstrated only minor variation over the course of the cycle. In addition, processes that are known to mediate sexual arousal (such as mood state, recent sexual experience, vividness of imagery during fantasy, distaste experienced during erotic stimulation) remained constant across the cycle. Results from the three experiments provide no support for the claim that female sexual response varies systematically across the menstrual cycle.

A reappraisal of Hydrolithon and its relationship to Spongites (Corallinaceae, Rhodophyta)

Abstract: Studies of tetrasporangial conceptacle development and anatomy have led to the conclusion that Spongites and Hydrolithon (of which Porolithon is considered to be a heterotypic synonym) are distinct genera of the Corallinaceae (Rhodophyta). In Australian populations of Hydrolithon reinboldii (Weber van Bosse et Foslie) Foslie, the type species of Hydrolithon, and Porolithon onkodes (Heydrich) Foslie, the type species of Porolithon, the tetrasporangial conceptacle pore canal is lined by a ring of conspicuous, elongate cells that arise from filaments interspersed amongst sporangial initials, do not protrude into the canal, and are oriented more or less perpendicularly to the roof surface. In Spongites fruticulosus Kutzing, the type species of Spongites, the pore canal is lined by cells that arise from peripheral roof filaments, protrude into the canal and are oriented more or less parallel to the roof surface. Tetrasporangial conceptacle development in Hydrolithon reinboldii and Porolithon onkodes i...

Reactivated tectonic boundaries and implications for the reconstruction of southeastern Australia and northern Victoria Land, Antarctica

Abstract: Rifted continental margins are strongly influenced by the location of zones of preexisting crustal weakness. Apatite fission track thermochronological data indicate that the Paleozoic lithospheric boundary between the Kanmantoo and Lachlan fold belts in western Victoria, Australia, was reactivated during Mesozoic rifting as a transfer fault. To the east of this boundary, 1-2 km of material was denuded during extension, while essentially no denudation took place during rifting to the west. The correlated tectonic boundary within the Bowers terrane of northern Victoria Land, Antarctica, was also reactivated upon rifting. During fragmentation of Gondwana, movement on this zone perpendicular to the direction of rifting probably determined the location of the Tasman Fracture Zone. When Australia and Antarctica are reconstructed along the trace of the Tasman Fracture Zone, the tectonic boundary in Victoria falls into precise alignment with the Bowers terrane.