Showing papers by "University of Western Australia published in 1984"

Melanoma of the skin.

Abstract: Melanoma of the skin is the fifth leading type of cancer in Washington State. Incidence rates have nearly doubled from 23 per 100,000 in 1992, the year the Washington State Cancer Registry was created, to 42 per 100,000 in 2004. In 2004, 2,611 Washington residents (1,393 men and 1,217 women) were diagnosed with melanoma. Melanoma is the most deadly of the skin cancers. In 2005, 170 people in Washington (105 men and 65 women) died of melanoma.

Courtship feeding increases female reproductive success in bushcrickets

Abstract: Parental investment theory suggests that investment by males through courtship feeding of their mates may represent an important source of nutrition which increases female fitness and ultimately influences patterns of sexual selection1,2. In certain insects males provide nutritional products from reproductive accessory glands during mating; these are either eaten by the female or are absorbed in her genital tract2,3. Male bushcrickets (Orthoptera: Tettigoniidae) feed their mates with an elaborate spermatophore consisting of a spermatophylax, which is eaten by the female after mating, and a sperm ampulla, eaten after the ejaculate has emptied4,5. Studies of bushcricket mating systems have indicated that spermatophore nutrients are important to females—females prefer to mate with males able to supply larger spermatophores6—and field studies of species with very large spermatophores have revealed a role-reversal in reproductive behaviour, with females aggressively competing for males capable of producing spermatophores7,8. Although radiolabelling experiments (with several insect species) have demonstrated that male-derived nutrients are incorporated into eggs3,9–11, these studies do not demonstrate that this sort of courtship feeding enhances female fitness. Here I report the results of an experiment which shows that feeding on the spermatophore enhances the reproductive success of female bushcrickets (Requena verticalis Walker) by increasing the numbers and size of eggs produced.

Attitudes to Science: an update

Abstract: (1984). Attitudes to Science: an update. Studies in Science Education: Vol. 11, No. 1, pp. 26-59.

Pattern beneath the chaos: the effect of recruitment on genetic patchiness in an intertidal limpet.

Abstract: Gene exchange among widely separated areas characterizes many marine organisms with planktonic dispersal. From an evolutionary perspective, the essential feature of such dispersal is that recruits to local populations come from somewhere else. Thus, localized adaptation is not accumulated over time, and changes in the genetic composition of adults reflect single-generation effects of selection and recruitment. The most obvious effect of planktonic dispersal is the reduction of geographic variation in genetic composition (e.g., Scheltema, 1971, 1978), and low variances of allelic frequencies have been found to be associated with planktonic dispersal (e.g., Berger, 1973; Levinton and Suchanek, 1978; Winans,

The effect of phosphorus on the formation of hyphae in soil by thevesicular‐arbuscular mycorrhizal fungus, glomus fasciculatum

Abstract: Summary Hyphae formed in soil by the vesicular-arbuscular (VA) mycorrhizal fungus, Glomusfasciculatum (Thaxter sensu Gerd.) Gerd. and Trappe were extracted using the membrane filter techniqe and their length was estimated by the grid intersection method. The effect of phosphorus on the formation of this external mycelium was assessed after sampling procedures had been investigated. Phosphorus supply was varied from amounts severely deficient to those adequate for the growth of subterranean clover. After 6 weeks, the alleviation of severe phosphorus deficiency increased both the length of infected root and the length of external hyphae per centimetre of infected root. Further additions of phosphorus decreased both of these measurements. However, the level of added phosphorus at which the most external hyphae was formed per centimetre of infected root was higher than the level of phosphorus which gave the greatest length of infected root. The increase in phosphorus supply which gave the greatest increase in the length of external hyphae per centimetre of infected root also decreased the formation of vesicles within infected roots. At phosphate levels adequate for growth of mycorrhizal plants, there was little development of either external hyphae in soil or vesicles within the mycorrhizal roots.

Factors affecting the secretion of luteinizing hormone in the ewe.

Abstract: Summary (1) Luteinizing hormone (LH) is secreted as discrete pulses throughout all stages of the reproductive cycle of the ewe, including pre-pubertal, seasonal and lactational anoestrus, and the luteal and follicular phases of the oestrous cycle. Secretion is probably also pulsatile during the preovulatory surge of LH. (2) The secretion of LH is affected by the ovarian steroids, oestradiol and progesterone, both of which act principally to reduce the frequency of the pulses. During the luteal phase the two steroids act synergistically to exert this effect, and during anoestrus oestradiol acts independently of progesterone. Androstenedione secreted by the ovary apparently has no role in the control of LH secretion. (3) The amplitude of the pulses may also be affected by the steroids but there are conflicting reports on these effects, some showing that amplitude is lowered by the presence of oestrogen and others showing increases in amplitude in the presence of oestrogen and progesterone. (4) The secretion of LH pulses is affected by photoperiod, social environment and nutrition. Under the influence of decreasing day-length, oestradiol alone cannot reduce the frequency of pulses and the ewe experiences oestrous cycles. When day-length is increasing, the hypothalamus becomes more responsive to oestradiol which reduces the frequency of the pulses. (5) A hypothetical pheromone secreted by rams can increase the frequency of the LH pulses in anoestrous ewes and thereby induce ovulation, possibly by inhibiting the negative feedback exerted by oestradiol. (6) The relationships between nutrition and reproduction are poorly understood, but it seems likely that the effects of nutrition are mediated partly through the hypothalamus and its control of the secretion of LH pulses. (7) The pulses of LH secreted by the anterior pituitary gland are evoked by pulses of GnRH secreted by the hypothalamus. The location of the centre controlling the GnRH pulses and the neurotransmitter involved are not known.

Recursive causal models

Abstract: The notion of a recursive causal graph is introduced, hopefully capturing the essential aspects of the path diagrams usually associated with recursive causal models. We describe the conditional independence constraints which such graphs are meant to embody and prove a theorem relating the fulfilment of these constraints by a probability distribution to a particular sort of factorisation. The relation of our results to the usual linear structural equations on the one hand, and to log-linear models, on the other, is also explained

Sexual selection and sexual differences in mormon crickets (orthoptera: tettigoniidae, anabrus simplex).

Abstract: Darwin (1871) suggested that differences in the intensity of sexual selection on the sexes was a cause of secondary sexual differences. He proposed that behavioral and morphological traits possessed by males had evolved in the context of sexual competition, because fertilizable females are typically in short supply. Emlen and Oring (1977) pointed to several factors that are expected to change the ratio of fertilizable females to sexually active males (the operational sex ratio) and thus, the intensity of sexual selection on the sexes; theoretically both the investment of the sexes in offspring (parental investment; Trivers, 1972) and certain features of the social and physical environment are important. Parental investment theory (Trivers, 1972) predicts that females in species where males invest most in individual offspring should exhibit typically masculine traits by competing for access to sexually active males and males should exhibit typically feminine traits by being selective of mates. In vertebrate species where males provide the majority of parental care there is good evidence for a role-reversal in courtship behavior (Wittenberger, 1979; Petrie, 1983). In insects, paternal care of eggs and offspring is rare (Smith, 1980) but males of several groups supply their mates with nutritious prey items or glandular products (Thornhill, 1976a). These male efforts represent mating effort, as they apparently function in acquiring copulations (Alexander and Borgia, 1979). They are, however, "nonpromiscuous" mating efforts, potentially able to limit female reproduction (Thormhill, 1976b; Gwynne, 1984a) and thus are expected to influence the evolution of sexual differences in a similar way to male parental investment (Gwynne, 1984b). Males of many katydids (Orthoptera: Tettigoniidae) feed their mates with a large spermatophore which enhances female reproduction (Gwynne, 1984a). Mormon cricket males (Anabrus simplex Haldeman) produce a large spermatophore (Gillette, 1904), investing some fifth of their body weight in a single mating. I reported a reversal in the typical courtship roles for this species; females competed for access to singing males and males discriminated among females by selecting heavier individuals as mates (Gwynne, 1981). Here I show that this courtship rolereversal is found at certain sites but not at others. I examine sexual selection and its consequences at different sites by (1) testing the prediction that sexual selection on females, as estimated by variance in mating success, should be greater at sites where sexual competition among females is observed, (2) detailing the differences in courtship behavior between sites that have apparently resulted from differences in sexual selection, (3) testing the prediction that female body size should be greater at role-reversed sites as a consequence of intersexual selection for larger females, and (4) describing possible environmental differences between sites that have caused interpopulation variation in sexual differences.

Classification and dynamic simulation of the vertical density structure of lakes1

Abstract: Field data from two lakes of widely differing geometry and size are analyzed in terms of four nondimensional numbers which allow the principal mixing processes in each lake to be identified. The numbers are based on basin geometry, density stratification, wind stress, and rates of inflow and outflow. The procedure highlights the differences in the dynamics of the two lakes and allows assessment of the validity of the assumption of one-dimensionality. The result is that both lakes were dominated by one-dimensional, but different processes. The dynamics of the epilimnion of the smaller lake were dominated by stirring from surface wind and cooling, whereas shear at the pycnocline was also significant in the larger lake. In neither case did the effects of the earth’s rotation, inflow, or outflow generate significant horizontal gradients. A one-dimensional numerical model (DYRESM) was used to simulate the vertical temperature and salinity structures of both lakes over lengthy periods, with good results. The model is based on the parameterization of the important physical processes in a framework of horizontal layers of variable thickness and was applied in both lakes without alteration. The interpretative power of the model is demonstrated by examination of the formation and erosion of a thermal inversion in the larger lake.

The Wahlund effect and the geographical scale of variation in the intertidal limpet Siphonaria sp.

Abstract: Samples of Siphonaria sp. were collected between 1978 and 1982 from sites covering its known geographic range, from Kalbarri, Western Australia to Port Robe, South Australia. Geographic variation of 7 polymorphic enzymes was examined in this intertidal pulmonate limpet, and was found to be consistently small, indicating a large-scale influence of gene flow due to planktonic dispersal. Despite this large-scale uniformity, there is fine-scale genetic patchiness, which is repeated, rather than accumulated, on the larger scale. Throughout its geographic range, Siphonaria sp. shows deficits of heterozygotes for all 7 loci. The consistency among loci indicates that the causes of the deficits are populational, rather than locus-specific. A Wahlund effect, the departure from Hardy-Weinberg equilibrium due to mixing of individuals from groups with different allelic frequencies, is the simplest explanation of such deficits. The limited geographic variation of allelic frequencies, however, is grossly inadequate to produce these deficits through a Wahlund effect. Similarly, temporal variation in allelic frequencies in recruits does not explain the deficits. The largest contributor to a Wahlund effect appears to be binomial sampling variance among small local breeding groups. Thus, mixing of larvae on a scale of metres, rather than among geographical areas, apparently produces the deficits of heterozygotes.

Corporate distress in Australia

Abstract: In Australia, the task of developing a failure classification model for any one industrial sector is made difficult because of the small number of business failures from any one sector. This study develops a five variable business failure classification model for Australia which is sufficiently general to be applied across several industrial sectors. Instead of relying on traditional ratios, it uses an industry-relative approach in the classification model.

C-Peptide Measurement: Methods and Clinical Utility

Abstract: Proinsulin is the single chain precursor of insulin. It consists of insulin, plus a peptide which connects the A and B chains of insulin. This peptide is termed C-peptide. C-peptide an insulin are secreted in equimolar amounts from pancreatic beta-cells, Hence, circulating C-peptide levels provide a measure of beta-cell secretory activity. C-peptide measurements are preferable to insulin measurements because of lack of hepatic extraction, slower metabolic clearance rate, and lack of cross reactivity with antibodies to insulin. This article reviews the methods for determination of C-peptide levels in body fluids, and discusses the applications of C-peptide measurement. These include the investigation of hypoglycemia and the assessment of insulin secretory function in insulin-treated and non-insulin-dependent diabetics. The contribution of C-peptide measurement to the understanding of the interrelationships between insulin secretory function and age, sex, obesity, blood lipids, and blood glucose concentrations will also be evaluated.

The yield and nutrient content of colostrum and milk of women from giving birth to 1 month post-partum.

Abstract: The intake of mammary secretion from delivery to day 5 post-partum was determined by test-weighing nine infants using an integrating electronic balance. The mean yield of colostrum for the first 24 h after birth was 37.1 (range 7.0-122.5) g and was 408 (range 98.3-775) and 705.4 (range 452.5-876) g/24 h on days 3 and 5 post-partum respectively. The milk yield of mothers on either day 14 or 28 post-partum was determined by test-weighing the mother. The mean milk yield was 1.156 (SD 0.167) kg/24 h. A significant correlation (P less than 0.001; r 0.85, n 42) was found between milk yield measured by test-weighing the infant and milk yield measured by test-weighing the mother, confirming that it is possible to obtain a similar estimate of milk consumed using either of the two methods of test-weighing. There was a significant positive correlation (P less than 0.001) between lactose concentration and milk yield for the first 5 d post-partum (r 0.76, n 22); a significant correlation (P less than 0.001) between protein concentration and milk yield (r-0.74, n 22) and no significant correlation between fat concentration and milk yield for the period studied. The calculated energy intake of infants during the first 24 h after birth was only 0.12 (range 0.02-0.29) mJ. This increased to 1.44 (range 0.83-2.18) and 2.99 (range 2.49-4.06) mJ/24 h by days 3 and 14-28 post-partum respectively.

Genetical structure within populations of the coral Pocillopora damicornis

Abstract: Genetic variation of allozymes within populations of Pocillopora damicornis from southwestern Australia was consistent with a primary role of local asexual proliferation of clones in population maintenance. Populations were composed typically of two to four multilocus genotypes accounting for 40 to 80% of individuals, with the remainder assigned to genotypes occasionally in twos or threes but more commonly singly. In the three populations where recruitment was examined genetically, 84% of all first-year recruits was assigned to clones represented in the population's resident adults. The majority of these recruits came from the most highly-replicated of the adult clones. The observed genotypic diversity was, on average, about half that calculated to occur for the same allelic frequencies in a sexually-reproducing population with free recombination. Despite the prevalence of asexual reproduction, both through planulae and fragments, the existence of a sexual mode of reproduction was inferred from the high level of variation produced by pooling populations, the existence of novel genotypes and the concordance of clonal gene frequencies at many sites with the predictions of Hardy-Weinberg equilibria.

Relationship of solar keratosis and history of skin cancer to objective measures of actinic skin damage

Abstract: Two methods for the assessment of severity of actinic skin damage were evaluated in a population-based survey of 1216 subjects. After controlling for the effects of age, skin texture changes graded by cutaneous microtopography were found to be associated strongly with the presence of solar keratoses and a past history of non-melanotic skin cancer. Changes in skin condition graded by paraocular photography had a weaker relationship with the presence of keratoses and showed no association with non-melanotic skin cancer. These results, together with a higher level of agreement between observers in grading cutaneous microtopographs, support the use of cutaneous microtopography as an index of actinic skin damage in epidemiological research.

The limitations of in vitro fertilization from males with severe oligospermia and abnormal sperm morphology.

Abstract: Thirty-one patients whose infertility was attributed to oligospermia were included for treatment by in vitro fertilization and embryo transfer. Three subgroups were defined: severe oligospermia (≤5 million motile sperm/ml), moderate oligospermia (6 to 60% atypical). The fertilization rates were compared to those of a normospermic group managed concurrently. A modified overlay technique of sperm preparation is described for oligospermic samples so that the number of motile spermatozoa inseminated into each tube or culture dish containing a mature preovulatory oocyte was similar in each category, within the range 0.5 to 2×105/ml. Significantly fewer oocytes were fertilized in the severe oligospermic group (P<0.001), suggesting a reduced capacity for fertilization by spermatozoa from severely oligospermic males. The fertilization rate of oocytes was normal in the moderate oligospermic group and those with abnormal morphology, although in the latter there was a significant delay noted in reaching the pronuclear stage (P<0.001), and the embryos were at a less advanced stage of cleavage at the time of transfer (0.001

The effect of nutrition on the reproductive performance of first-litter sows. 1. Feeding level during lactation, and between weaning and mating

Abstract: A factorial experiment was conducted with 80 first-litter sows and involved two levels of feeding during lactation (ad libitum or 2·0 kg/day), and two levels of feeding between weaning and mating (4·0 or 1·5 kg/day).Average lactation length was 32·2 days. Sows given 2·0 kg/day during lactation lost more backfat (6·3 v. 0·9 mm; P < 0·05) and more live weight (36·8 v. 9·1 kg; P < 0·05) during lactation than sows fed ad libitum and whose average daily food intake was 4·47 kg. Sows receiving 20 kg/day during lactation took longer to return to oestrus after weaning. Within 8 days of weaning more sows fed ad libitum during lactation ovulated (0·90 v. 0·40; x2 = 20·0; P < 0·001) and exhibited oestrus (0·78 v. 0·38; x2 = 12·8; P < 0·001) than sows whose food intake throughout lactation was restricted. Ovulation rate, subsequent litter size and embryonic mortality were not significantly affected by feeding level during lactation.Post-weaning feeding level did not affect the interval between weaning and oestrus. However, sows receiving 4·0 kg/day between weaning and mating had higher ovulation rates (14·8 v. 13·0; P < 0·05) and a greater litter size (10·0 v. 8·8; P < 0·1) at the subsequent farrowing.

Genetic control of murine cytomegalovirus infection: virus titres in resistant and susceptible strains of mice.

Abstract: The course of MCMV infection was studied in a number of inbred strains of mice which differ in their resistance to the development of fatal disease induced by MCMV. Both H-2 and non-H-2 associated genes control this form of resistance and were found to influence the extent of virus replication during sublethal and severe infection. However, for a given strain the summated virus titre of the 5 organs studied was not always proportional to resistance strains. Peak titres of virus were found in the liver and spleen of each strain on days 2 to 3 during high dose infection and in resistant mice during low dose infection. Thereafter titres declined rapidly. When the proportion of the summated virus titre which was present in the spleen and liver was compared for a number of strains, variations in the growth of MCMV in the spleen were noted with 13–84 per cent of virus being found in the spleen of BALB/c, BALB.B, BALB.K and A/WySn mice and usually <3 per cent in the spleen of C57BL/6, C57 BL/10, B10.BR, C3H and CBA mice.

The effects of sexual and asexual reproduction on geographic variation in the sea anemone Actinia tenebrosa.

Abstract: Allelic and genotypic frequencies were determined for samples from 35 widely distributed Australasian colonies of Actinia tenebrosa and 2 South African colonies of A. equina. These data provided no evidence of gene flow between Australisian and South African Actinia colonies and indicated that there may be some restriction of gene flow between widely separated Australasian colonies. Both species are viviparous, and brooded A. tenebrosa are known to be produced asexually. The present data indicate that, within both species, almost all genotypic diversity is generated by sexual reproduction with recombination. Sexually produced juveniles appear to be widely dispersed and panmixis may occur over thousands of kilometres. However, successful sexual recruitment must be episodic or rare. Colonies on stable shores displayed relatively low levels of genotypic diversity, as compared with expectations for sexually reproducing populations, indicating strong local effects of asexual recruitment. Clonal genotypes may be spread over hundreds of metres of shore, but are typically restricted to discrete colonies. Asexual recruitment is highly localised and asexual dispersal appears to be limited by lengths of shore (≤500 m) which are unsuitable for colonization. Colonies on unstable shores are significantly more diverse genotypically and show little evidence of clonal proliferation.

Miospores, correlation and age of some Scottish Lower Old Red Sandstone sediments from the Strathmore region (Fife and Angus)

Abstract: The age of some Lower Old Red Sandstone sediments (Arbuthnott Group) is reassessed and confirmed as Lower Devonian (lower Gedinnian) on the basis of a reinvestigation of spore assemblages. The data upon which this age assessment is based are provided by recent palynological researches in the Welsh Borderland, the type area of the Gedinnian (Belgium), and the graptolite-bearing parastratotype for the Silurian-Devonian boundary (Podolia). Samples from the Arbuthnott Group at Wormit (Fife), associated with rocks dated as 407± 6 Ma by Thirlwall (1983) and regarded by him as Silurian, have yielded miospore assemblages of early but not earliest Devonian when compared with the Podolian Silurian-Devonian sequence. Samples throughout the sequence of the Arbuthnott Group as exposed in Angus and Fife have yielded miospores. These assemblages, occurring at levels above and below the Wormit samples, are all of lower Gedinnian age. The whole of the spore-bearing succession of the Arbuthnott Group, which is about 1,800 m thick, belongs to the micrornatus-newportensis Zone (lower and middle subzones) and is equivalent to part of the lower Ditton Group of Brown Clee Hill (Shropshire) of 20 to 30 m in thickness. There is no critical palaeontological evidence for age in the strata associated with the Arbuthnott Group, neither in the underlying Dunnottar and Crawton Groups nor in the overlying Garvock Group so the exact position of the Silurian-Devonian and Gedinnian-Siegenian boundaries is uncertain. A new spore Anteturma, namely Cryptosporites , is proposed. Qualisaspora fragilis gen. et sp. nov. is described herein and appears to have potential as an index fossil for the lower Dittonian of the British Isles. Some regional differences also occur as ? Dibolisporites sp. A and ? Samarisporites sp. A occur in beds dated as lower Gedinnian in Sotland whereas spores of similar sculpture and structure are present higher in the Anglo-Welsh sequence in beds dated as lower Siegenian.

Genetic differentiation amongst populations of the coral Pocillopora damicornis off southwestern Australia

Abstract: An electrophoretic study of genetic differentiation amongst local populations of the reef-coral Pocillopora damicornis was used to group coral heads into units defined as the area of effective dispersal of a clone, and termed “colonies”. For reefs off southwestern Australia, colonies were usually under a few hundred metres in extent. Although most new recruits within a colony were derived asexually, sexually produced propagules acted to connect populations outside the boundaries of a colony. Such connections were weak, and allelic frequencies varied considerably over a few kilometres. The primary agent of genetic differentiation was suggested to be the small effective population size resulting from the asexual proliferation of a few genotypes at any site. The effective number of genotypes per colony was approximately six. Asexual reproduction appears also to limit gene flow and accentuate selection in this species.

Spatial and Temporal Variations of Archaean Metallogenic Associations in Terms of Evolution of Granitoid-Greenstone Terrains with Particular Emphasis on the Western Australian Shield

Abstract: There is marked spatial and temporal heterogeneity in diversity and intensity of metallogenic associations in Archaean greenstone belts. On the greenstone basin scale, parameters such as intensity of faulting, rapidity of burial, water depth and extent of irruption of komatiitic and felsic magma appear to have controlled the nature and intensity of mineralization. These inter-related parameters apparently depend on the degree of extension during basin development.

Decomposable graphs and hypergraphs

Abstract: We define and investigate the notion of a decomposable hypergraph, showing that such a hypergraph always is conformal, that is, can be viewed as the class of maximal cliques of a graph. We further show that the clique hypergraph of a graph is decomposable if and only if the graph is triangulated and characterise such graphs in terms of a combinatorial identity.