Showing papers by "La Trobe University published in 1993"

The mitochondrial genome of the honeybee Apis mellifera: complete sequence and genome organization.

Abstract: The complete sequence of honeybee (Apis mellifera) mitochondrial DNA is reported being 16,343 bp long in the strain sequenced. Relative to their positions in the Drosophila map, 11 of the tRNA genes are in altered positions, but the other genes and regions are in the same relative positions. Comparisons of the predicted protein sequences indicate that the honeybee mitochondrial genetic code is the same as that for Drosophila; but the anticodons of two tRNAs differ between these two insects. The base composition shows extreme bias, being 84.9% AT (cf. 78.6% in Drosophila yakuba). In protein-encoding genes, the AT bias is strongest at the third codon positions (which in some cases lack guanines altogether), and least in second codon positions. Multiple stepwise regression analysis of the predicted products of the protein-encoding genes shows a significant association between the numbers of occurrences of amino acids and %T in codon family, but not with the number of codons per codon family or other parameters associated with codon family base composition. Differences in amino acid abundances are apparent between the predicted Apis and Drosophila proteins, with a relative abundance in the Apis proteins of lysine and a relative deficiency of alanine. Drosophila alanine residues are as often replaced by serine as conserved in Apis. The differences in abundances between Drosophila and Apis are associated with %AT in the codon families, and the degree of divergence in amino acid composition between proteins correlates with the divergence in %AT at the second codon positions. Overall, transversions are about twice as abundant as transitions when comparing Drosophila and Apis protein-encoding genes, but this ratio varies between codon positions. Marked excesses of transitions over chance expectation are seen for the third positions of protein-coding genes and for the gene for the small subunit of ribosomal RNA. For the third codon positions the excess of transitions is adequately explained as due to the restriction of observable substitutions to transitions for conserved amino acids with two-codon families; the excess of transitions over expectation for the small ribosomal subunit suggests that the conservation of nucleotide size is favored by selection.

Sex determination in the Hymenoptera: a review of models and evidence

Abstract: The haploid males and diploid females of Hymenoptera have all chromosomes in the same proportions. This rules out most familiar sex-determining mechanisms, which rely on dosage differences at sex determination loci. Two types of model — genie balance and complementary sex determination (CSD) — have been invoked for Hymenoptera. Experimental studies provide no good evidence for genie balance models, which are contradicted by the detection of diploid males in 33 disparate species. Furthermore, recent advances have shown that sex determination in the best-studied diploid animals does not depend on genie balance, removing the original justification for hymenopteran genie balance models. Instead, several Hymenoptera have single-locus CSD. In this system, sex locus heterozyotes are female while homozygotes and hemizygotes are male. Single-locus CSD does not apply to several inbreeding species and this probably reflects selection against the regular production of diploid males, which are sterile. A multilocus CSD model, in which heterozygosity at any one of several sex loci leads to female development has also been proposed. To date, multilocus CSD has not been demonstrated but several biases against its detection must be considered. CSD can apply to thelytokous races as long as the cytogenetic mechanism permits retention of sex locus heterozygosity. However, some thelytokous races clearly do not have CSD. The distribution of species with and without CSD suggests that this form of sex determination may be ancestral in the Hymenoptera. However, phylogenetic analyses are hindered by the lack of data from several superfamilies and the fact that the internal phylogeny of the Hymenoptera remains controversial.

Selection for T-cell receptor Vβ-Dβ-Jβ gene rearrangements with specificity for a myelin basic protein peptide in brain lesions of multiple sclerosis

Abstract: MULTIPLE sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system in which a restricted cellular immune response has been observed. In order to establish whether such T cell responses are likely to be antigen-specific particularly with regard to myelin basic protein (MBP), we analysed T-cell receptor (TCR) gene rearrangements directly from MS brain plaques, using the polymerase chain reaction on reverse transcribed messenger RNA, and compared these with TCR of previously described MBP-specific T cell clones from MS and the rat model experimental allergic encephalomyelitis. Rearranged Vβ5.2 genes were detected in the brains of all patients who were HLA DRB1*1501, DQA1*0102, DQB1*0602, DPB1*0401. The Vβ5.2–Dβ–Jβ sequences in these MS brain plaques revealed five motifs. One of the common motifs was identical to that described for the VDJ region of a Vβ5.2 T-cell clone. This clone was from an MS patient who was HLA DRB1*1501, DQB1*0602, DPB1*0401, and it was cytotoxic towards targets containing the MBP peptide 89–106 (ref. 1). The deduced amino-acid sequence of this VDJ rearrangement, Leu-Arg-Gly, has also been described in rat T cells cloned from experimental allergic encephalomyelitis lesions, which are specific for MBP peptide 87–99 (ref. 2). VDJ sequences with specificity for this MBP epitope constitute a large fraction (40%) of the TCR Vβ5.2 N(D)N rearrangements in MS lesions. The capacity of rat T cells with these VDJ sequences to cause experimental allergic encephalomyelitis2 and the prevalence of such sequences in demyelinated human lesions indicate that T cells with this rearranged TCR may be critical in MS.

Reactivity to myelin antigens in multiple sclerosis. Peripheral blood lymphocytes respond predominantly to myelin oligodendrocyte glycoprotein.

Abstract: Although T cell responses to the quantitatively major myelin proteins, myelin basic protein (MBP) and proteolipid protein (PLP), are likely to be of importance in the course of multiple sclerosis (MS), cell-mediated autoimmune responses to other myelin antigens, in particular quantitatively minor myelin antigens, such as myelin-associated glycoprotein (MAG) and the central nervous system-specific myelin oligodendrocyte glycoprotein (MOG), could also play a prevalent role in disease initiation or progression. Highly purified myelin antigens were used in this study to assess cell-mediated immune response to MOG in MS patients, in the context of the reactivity to other myelin antigens, MBP, PLP, and MAG. The greatest incidence of proliferative response by MS peripheral blood lymphocytes was to MOG, as 12 of 24 patients tested reacted and, of these, 8 reacted to MOG exclusively. In contrast, only 1 control individual of 16 tested reacted positively to MOG. The incidence of responses to MBP, PLP, and MAG did not differ greatly between MS patients and control individuals. A predominant T cell reactivity to MOG in MS suggests an important role for cell-mediated immune response to this antigen in the pathogenesis of MS.

Cloning and expression of cytochrome p450 genes controlling flower colour

Abstract: BLUE and violet flowers generally contain derivatives of delphinidin; red and pink flowers generally contain derivatives of cyanidin or pelargonidin1.Differences in hydroxylation patterns of these three major classes of anthocyanidins are controlled by the cytochrome P450 enzymes flavonoid 3'-hydroxylase and flavonoid 3',5'-hydroxylase. Here we report on the isolation of complementary DNA clones of two different flavonoid 3',5'-hydroxylase genes that are expressed in petunia flowers. Restriction-fragment length polymorphism mapping and complementation of mutant petunia lines showed that the flavonoid 3',5'-hydroxylase genes correspond to the genetic loci Hfl and Hf2.

An adaptive Gaussian filter for noise reduction and edge detection

Abstract: Gaussian filtering has been intensively studied in image processing and computer vision. Using a Gaussian filter for noise suppression, the noise is smoothed out, at the same time the signal is also distorted. The use of a Gaussian filter as pre-processing for edge detection will also give rise to edge position displacement, edges vanishing, and phantom edges. Here, the authors first review various techniques for these problems. They then propose an adaptive Gaussian filtering algorithm in which the filter variance is adapted to both the noise characteristics and the local variance of the signal. >

Sustaining safe sex: a longitudinal study of a sample of homosexual men.

Abstract: Objective To assess the maintenance of safe sexual practice. (We use the term ‘safe’ sex throughout the paper, since ‘safe’ is the term adopted by the Australian National Committee on AIDS.) Design Maintenance was assessed by comparing sexual behaviour with both regular and casual partners reported in a 1986/1987 survey (time 1) with behaviour reported in a second survey in 1991 (time 2). Method The 145 homosexually active participants were a non-clinical sample recruited in 1986/1987 by advertisement and followed-up in 1991. A structured questionnaire was administered at both times. Items included questions about the nature of the men's sexual relationships and their sexual practices. Results Our findings indicate that the majority of men had sustained safe sex practices. HIV prevention strategies adopted included condom use, avoidance of anal intercourse and negotiated safety (i.e., the negotiated practice of unprotected anal intercourse within regular partnerships of concordant serostatus). Conclusions Negotiated safety is not the same as relapse.

The theory of reasoned action and cooperative behaviour: It takes two to use a condom

Abstract: The applicability of the Theories of Reasoned Action and Planned Behaviour to the cooperative behaviour of condom use were examined. Seventy-one male and 78 female students, all sexually active unmarried heterosexuals aged 17 to 21 years, gave information about their intentions for the next sexual encounter, as well as their attitude, subjective norm, expectancy-value attitude and subjective norm (including normative beliefs for their sexual partner), and their past behaviour with respect to condom use. After their next sexual encounter, they completed a questionnaire on their actual condom use. Results indicated that when behavioural conditions including the availability of a condom and an agreement with the partner to use it were satisfied, intention interacted with past behaviour to predict actual behaviour. These results imply that intentions which are consistent with past behaviour are stable enough to be carried out in the face of the interpersonal dynamics of a sexual encounter. Further, normative belief for the sexual partner had a direct influence on attitudes, subjective norm and intention. Neither the Theory of Reasoned Action nor the Theory of Planned Behaviour can fully explain these results, which point to the need for further theoretical inquiry into the dynamics of cooperative behaviour.

Sex Differences in Psychological Adjustment from Infancy to 8 Years

Abstract: The objective of this study was to explore sex differences in development from infancy to 8 years of age in a community sample. Measures of biological, social, interactive, and parental functioning as well as teacher reports were obtained. There were minimal differences in infancy, but major psychosocial differences emerged with increasing age. In the biological sphere boys were disadvantaged only in ratings of language and motor skills at 3 to 4 years old. They showed greater temperamental "difficulty" and low persistence factor scores from 5 years onward. Boys were significantly more likely to have problems with adaptive behavior and social competence and to show behavior problems of the hyperactive and aggressive type, as rated by mothers. Parent and family functioning measures did not differentiate between the sexes. Teachers rated boys as having more problems in academic and behavioral domains the first 3 years of school. Path analyses combining data sets gathered when the children were 3 to 8 years old demonstrated the differential courses of development for boys and girls although temperamental flexibility was the best predictor of behavioral adjustment for both sexes. A social learning explanation of the increased incidence of problems among males is supported, although biological influences are not ruled out.

Crossed products of C *-algebras by *-endomorphisms

Abstract: Crossed products of C *-algebras by *-endomorphisms are defined in terms of a universal property for covariant representations implemented by families of isometries and some elementary properties of covariant representations and crossed products are obtained.

Structural and thermal constraints on the initiation angle of detachment faulting in the southern Basin and Range: The Chemehuevi Mountains case study

Abstract: The Cenozoic normal fault system exposed in the Chemehuevi Mountains of the southern Cordillera provides constraints on the initiation angle and geometry of an extensional fault system that has accommodated extreme crustal stretching. There, three stacked, brittle, low-angle normal faults that formed at depths as great as 10-12 km cut gently down section northeastward through deformed Proterozoic and Mesozoic crystalline basement. Hanging-wall blocks are displaced relatively northeastward. The upper crust above the Chemehuevi detachment fault was pulled apart along high-angle normal faults that rotated to more gentle dips through time. In contrast, rocks of originally mid-crustal affinity in the footwall were only gently rotated and accommodated minor extension ( Application of 40 Ar/ 39 Ar and fission-track thermochronology to rocks in the footwall of the Chemehuevi detachment fault system provides further constraints on the timing and initiation angle of regional detachment faulting. At the onset of extension between 22 and 24 Ma, granitic rocks exposed in the southwestern and northeastern portions of the footwall were at ∼200 °C and 350-400 °C, respectively, separated by a distance of some 23 km down the known slip direction. This gradual increase in temperature with original depth is attributed to the gentle southwest tilting of broadly planar pre-extension isothermal surfaces and constrains the exposed part of the Chemehuevi detachment fault to have had a regional dip initially of about 15° to 30°. The fault system apparently cut gently down through the upper crust, to a minimum depth of ∼10-12 km, the deepest exposed parts of the system today, and was domed from midcrustal depths and locally denuded during continued slip. Together the structural and thermochronologic data confirm the suggestion that faults accommodating large-magnitude slip can be initiated and move within the seismogenic regime at moderate to low angles (that is, ≤30°).

Do Migrants Rob Jobs? Lessons of Australian History, 1861–1991

Abstract: Historically, lands of recent settlement have had a thirst for immigrants, but one that has been procyclical (negatively related to unemployment rates). For a period in the early 1980s, Australia's major political parties supported high immigration in spite of rising unemployment. This article explores the long-run relationship between immigration and local unemployment, posing the question, “Do migrants rob jobs?” It also seeks to apply long-run historical analysis to recent economic debate: would Australia's unemployment rate have been lower in very recent times without so many immigrants?

A prevention program for disturbed eating and body dissatisfaction in adolescent girls: a 1 year follow-up

Abstract: This study evaluated an intervention program to reduce moderate and extreme weight loss behaviors, disordered eating and low body image. The Body Image and Eating Behavior Intervention Program consisted of five specialized classes addressing media images of women, determinants of body size, healthy and unhealthy weight control methods, and emotional eating. The program was conducted in year 9 in Schools 1 (n = 80) and 2 (n = 27), while students from the same year in School 3 (n = 29) were control subjects. Participants completed self-report questionnaires assessing eating behavior and body image attitudes prior to the program, 1 months after the program and at 12 months follow-up, while control subjects completed the questionnaires at the same time but did not receive the program. Data were analyzed using groups (Schools 1, 2 and 3) by testing occasion (pre, post and follow-up) analyses of variance with repeated measures on testing occasion. Measures of disordered eating and frequency of use of extreme weight loss behaviors were constant over testing occasion and showed no effect of the intervention program. Body dissatisfaction was consistently lower in School 1 but increased across all subjects over the year. The implications of these data for school-based intervention programs in this area are examined.

Successful use of S20098 and melatonin in an animal model of delayed sleep-phase syndrome (DSPS).

Abstract: In human delayed sleep-phase syndrome (DSPS), sleep onset and wake times occur far later than normal. In the population, DSPS may be an important contributor to complaints of sleep onset insomnia. We previously reported an animal model of DSPS in laboratory rats in which the onset of nocturnal activity is delayed by several hours [negative phase angle difference (PAD)]. The effect of melatonin 1 mg/kg SC and S20098 (Servier) 1 and 3 mg/kg on the negative PAD was investigated over 22 days of injections. In comparison to control injections of dimethylsulfoxide (DMSO), both melatonin and S20098 over approximately 9 days phase advanced the onset of activity toward the onset of darkness. At cessation of injections, activity onset delayed over approximately 11 days back toward, but as a group did not reach the original PAD. This effect of melatonin on the phase angle of entrained rats is consistent with its effects on delayed sleep in humans. It is likely, therefore, that S20098 may be of use to ameliorate DSPS in humans.

The genetics of central and marginal populations of drosophila serrata. i. genetic variation for stress resistance and species borders.

Abstract: A selection experiment was used to determine if levels of genetic variance in an ecologically important trait, desiccation resistance, were different in central and marginal populations. Four populations of Drosophila serrata were sampled from central and marginal areas of its distribution, along a 3000-km stretch of Australia's east coast. Rainfall patterns along this stretch of coastline change from a tropical cycle in the north to a temperate cycle in the south. Replicate lines from the four populations underwent selection for desiccation resistance for 14 generations. Realized heritabilities calculated after 10 and 14 generations of selection indicated that the four populations differed significantly in the level of genetic variation for desiccation resistance available to selection. Populations from the more southern marginal areas had lower realized heritabilities than more northern central populations. However, a corresponding increase in mean desiccation resistance toward the margin was not found. A mechanism by which D. serrata seemed to have responded to selection was a reduction in the extent that metabolic rate was increased when flies were exposed to low humidity. This response indicates genetic variation for the control of metabolic rate. In contrast, increased desiccation resistance was not associated with lipid or glycogen levels. Increased resistance to desiccation was accompanied by increased starvation resistance, but radiation resistance was not affected. Selection did not affect the degree that replicate lines or populations had diverged.

Direct and correlated responses to selection for desiccation resistance: a comparison of Drosophila melanogaster and D. simulans

Abstract: Replicate lines of Drosophila melanogaster and D. simulans originating from the same location in Australia were selected at two selection intensities (50%, 85% mortality) for increased resistance to desiccation, and scored for correlated responses to see if similar physiological changes were associated with the selection responses. Realized heritabilities were much higher in D. melanogaster. Selected lines of both species were more resistant than control lines to starvation and a toxic ethanol concentration. Both species also showed similar correlated responses for traits underlying the selection response: selected lines lost water at a slower rate and had reduced activity levels in a dry environment, but they did not differ in wet or dry body weight or in water content. For D. melanogaster, realized heritabilities for lines selected at 85% mortality were higher than for lines selected at 50% mortality, but there was no effect of selection intensity for D. simulans. Comparative studies of this nature may be useful in predicting the extent to which species can adapt to stress in the wild.

Purification and properties of three (1→3)-β-d-glucanase isoenzymes from young leaves of barley (Hordeum vulgare)

Abstract: Three (1-->3)-beta-D-glucan glucanohydrolase (EC 3.2.1.39) isoenzymes GI, GII and GIII were purified from young leaves of barley (Hordeum vulgare) using (NH4)2SO4 fractional precipitation, ion-exchange chromatography, chromatofocusing and gel-filtration chromatography. The three (1-->3)-beta-D-glucanases are monomeric proteins of apparent M(r)32,000 with pI values in the range 8.8-10.3. N-terminal amino-acid-sequence analyses confirmed that the three isoenzymes represent the products of separate genes. Isoenzymes GI and GII are less stable at elevated temperatures and are active over a narrower pH range than is isoenzyme GIII, which is a glycoprotein containing 20-30 mol of hexose equivalents/mol of enzyme. The preferred substrate for the enzymes is laminarin from the brown alga Laminaria digitata, an essentially linear (1-->3)-beta-D-glucan with a low degree of glucosyl substitution at 0-6 and a degree of polymerization of approx. 25. The three enzymes are classified as endohydrolases, because they yield (1-->3)-beta-D-oligoglucosides with degrees of polymerization of 3-8 in the initial stages of hydrolysis of laminarin. Kinetic analyses indicate apparent Km values in the range 172-208 microM, kcat. constants of 36-155 s-1 and pH optima of 4.8. Substrate specificity studies show that the three isoenzymes hydrolyse substituted (1-->3)-beta-D-glucans with degrees of polymerization of 25-31 and various high-M(r), substituted and side-branched fungal (1-->3;1-->6)-beta-D-glucans. However, the isoenzymes differ in their rates of hydrolysis of a (1-->3;1-->6)-beta-D-glucan from baker's yeast and their specific activities against laminarin vary significantly. The enzymes do not hydrolyse (1-->3;1-->4)-beta-D-glucans, (1-->6)-beta-D-glucan, CM-cellulose, insoluble (1-->3)-beta-D-glucans or aryl beta-D-glycosides.

The Concept of Function

Abstract: It appears that the focus of occupational therapy on function has moved away from the concept to centre on assessments. Conceptual debate concerning function has been muted and lost in the technica...

Membrane potential, resting calcium and calcium transients in isolated muscle fibres from normal and dystrophic mice.

Abstract: 1. Single skeletal muscle fibres were enzymatically isolated from the flexor digitorum brevis muscles (FDB) of dystrophic mdx and control C57BL/10 mice aged 3-9 weeks. In this age range the majority (> 95%) of the mdx fibres were morphologically normal. 2. There was no significant difference between the resting membrane potential (RMP) of mdx and control mice, -71.2 +/- 1.21 (n = 26) and -70.6 +/- 1.15 mV (n = 42), respectively. 3. At RMP more negative than -60 mV the resting calcium (recorded with fura-2, free acid ionophoresed into cell) in the dystrophic mdx cells was not significantly different from the normal animals, 45.7 +/- 4.1 (n = 10) and 46.2 +/- 3.9 nM (n = 9), respectively. 4. The resting cytosolic calcium concentration was measured simultaneously with the RMP. At RMP between -60 to -17 mV there was an increase in the resting calcium concentration in both mdx and control ranging from 79.3 to 252 nM. This increase was most probably due to the activation of the slow calcium current. 5. Fura-2 calcium transients were produced via single action potential stimulation using an intracellular microelectrode both to stimulate the cell and record potential changes. There was no significant difference between the rise time (Tp) or half-decay time (T1/2) at 22 degrees C of the calcium transient in response to a single action potential in mdx compared to normal animals, 5.9 +/- 0.34 (n = 8) and 5.4 +/- 0.36 ms (n = 7); 39.5 +/- 2.9 (n = 8) and 40.75 +/- 3.7 ms (n = 7), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)