Showing papers by "University of Adelaide published in 1995"

A missense mutation in the neuronal nicotinic acetylcholine receptor alpha 4 subunit is associated with autosomal dominant nocturnal frontal lobe epilepsy.

Abstract: Epilepsy affects at least 2% of the population at some time in their lives. The epilepsies are a heterogeneous group of disorders, many with an inherited component. Although specific genes have been identified in a few rare diseases causing seizures as part of a more diffuse brain disorder, the molecular pathology of the common idiopathic epilepsies is still unknown. Linkage has been reported for some generalised epilepsy syndromes, but only very recently for familial partial epilepsy syndromes. Autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) is a partial epilepsy causing frequent, violent, brief seizures at night, usually beginning in childhood. The gene for ADNFLE maps to chromosome 20q13.2-q13.3 in one large Australian kindred. The neuronal nicotinic acetylcholine receptor alpha 4 subunit (CHRNA4) maps to the same region of 20q (ref. 12) and the gene is expressed in all layers of the frontal cortex. We screened affected family members for mutations within CHRNA4 and found a missense mutation that replaces serine with phenylalanine at codon 248, a strongly conserved amino acid residue in the second transmembrane domain. The mutation is present in all 21 available affected family members and in four obligate carriers, but not in 333 healthy control subjects.

Growth Stages of the Grapevine: Adoption of a system for identifying grapevine growth stages

Abstract: The foregoing paper by Lorenz et al. (1995), translated into English by P. May, describes a new system for the identification of grapevine growth stages called the BBCH system. This is an adaptation, for the grapevine, of a basic scale developed to cover all monocot and dicot crops. Appraisal of this and two other systems has led to a preference for that by Eichhorn and Lorenz (1977) but with some amendments. These amendments are discussed and a new system of measurement and description of stages of the grapevine is proposed which copes with the dual needs for a simple listing of major stages and, at the same time, provides intermediate detailed stages. It is called the Modified E-L system.

High-Density Lipoproteins Inhibit Cytokine-Induced Expression of Endothelial Cell Adhesion Molecules

Abstract: While an elevated plasma concentration of HDLs is protective against the development of atherosclerosis and ensuing coronary heart disease (CHD), the mechanism of this protection is unknow...

Weight loss results in significant improvement in pregnancy and ovulation rates in anovulatory obese women

Abstract: Obesity can affect ovulation and the chances of pregnancy. In this prospective study, a weight loss programme was assessed to determine whether it could help infertile overweight anovulatory women to establish ovulation and assist in achieving pregnancy, ideally without further medical intervention. The subjects acted as their own historical controls. They underwent a weekly programme of behavioural change in relation to exercise and diet over 6 months ; those who did not complete the 6 months were treated as the comparison group. Women in the study group lost an average of 6.3 kg, with 12 of the 13 subjects resuming ovulation and 11 becoming pregnant, five of these spontaneously. Fitness, diet and psychometric measurements all improved. Fasting insulin and testosterone concentrations dropped significantly, while sex hormone binding globulin concentrations rose. None of these changes occurred in the comparison group. Thus, weight loss with a resultant improvement in ovulation, pregnancy outcome, self-esteem and endocrine parameters is the first therapeutic option for women who are infertile and overweight.

A perspective on dryland river ecosystems

Abstract: The ecosystem concept should be reappraised as a basic model for rivers, with regard for flow as an organizing variable. This would facilitate comparisons between the large rivers of humid climates, where flow regimes are comparatively regular, and those of arid and semi-arid areas, where river regimes are highly variable. Ecosystem processes might be modelled by combining the river continuum and flood pulse concepts, with refinements to accommodate a complex flood pulse (e.g. variations in stage amplitude, timing, duration, rates of rise and fall). Patch boundaries (ecotones) such as the riverine littoral zone warrant close study because they strongly influence the structure and dynamics of the ecosystem. The general model needs a quantitative basis, perhaps focused on the balance of processes involved in the physical transport and biological transformation of carbon. The ultimate test of such a model will be in its capacity to predict the effects of flow regulation. Further development, however, is limited by data. In both research and management monitoring programmes need to be established to provide information and to develop a sustained, comprehensive approach to dryland rivers as ecosystems.

Lung Cancer in Radon-Exposed Miners and Estimation of Risk From Indoor Exposure

Abstract: Background : Radioactive radon is an inert gas that can migrate from soils and rocks and accumulate in enclosed areas, such as homes and underground mines. Studies of miners show that exposure to radon decay products causes lung cancer. Consequently, it is of public health interest to estimate accurately the consequences of daily, low-level exposure in homes to this known carcinogen. Epidemiologic studies of residential radon exposure are burdened by an inability to estimate exposure accurately, low total exposure, and subsequent small excess risks. As a result, the studies have been inconclusive to date. Estimates of the hazard posed by residential radon have been based on analyses of data on miners, with recent estimates based on a pooling of four occupational cohort studies of miners, including 360 lung cancer deaths. Purpose : To more fully describe the lung cancer risk in radon-exposed miners, we pooled original data from 11 studies of radon-exposed underground miners, conducted a comprehensive analysis, and developed models for estimating radon-associated lung cancer risk. Methods : We pooled original data from 11 cohort studies of radon-exposed underground miners, including 65 000 men and more than 2700 lung cancer deaths, and fit various relative risk (RR) regression models. Results : The RR relationship for cumulative radon progeny exposure was consistently linear in the range of miner exposures, suggesting that exposures at lower levels, such as in homes, would carry some risk. The exposure-response trend for never-smokers was threefold the trend for smokers, indicating a greater RR for exposure in never-smokers. The RR from exposure diminished with time since the exposure occurred. For equal total exposure, exposures of long duration (and low rate) were more harmful than exposures of short duration (and high rate). Conclusions: In the miners, about 40% of all lung cancer deaths may be due to radon progeny exposure, 70% of lung cancer deaths in never-smokers, and 39% of lung cancer deaths in smokers. In the United States, 10% of all lung cancer deaths might be due to indoor radon exposure, 11% of lung cancer deaths in smokers, and 30% of lung cancer deaths in never-smokers. This risk model estimates that reducing radon in all homes exceeding the U. S. Environmental Protection Agency's recommended action level may reduce lung cancer deaths about 2%-4%. These estimates should be interpreted with caution, because concomitant exposures of miners to agents such as arsenic or diesel exhaust may modify the radon effect and, when considered together with other differences between homes and mines, might reduce the generalizability of findings in miners. [J Natl Cancer Inst 87 :817-827, 1995]

Localization of a gene for autosomal dominant nocturnal frontal lobe epilepsy to chromosome 20q13.2

Abstract: The epilepsies comprise a group of syndromes that are divided into generalized and partial (focal) types1. Familial occurrence has long been recognized but progress in mapping epilepsy genes has been slow except for rare cases where the inheritance is easily determined from classical genetic studies. Linkage is established for three generalized syndromes: the EBN1 and EBN2 genes for benign familial neonatal convulsions (BFNC) map to chromosomes 20q and 8q(refs2–5),theEPM1 gene for Unverricht-Lundborg disease maps to 21 q (ref. 6) and the gene for the northern epilepsy syndrome maps to 8p (ref. 7). A claim for linkage of the EJM1 gene for the common generalized syndrome of juvenile myoclonic epilepsy to 6p is currently in dispute8,9. Autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) was recently described infivefamilies10,11. We now report the chromosomal assignment, to 20q13.2, for the gene for ADNFLE in one large Australian kindred with 27 affected individuals spanning six generations.

A novel naturally occurring hybrid gene encoded by a plant RNA virus facilitates long distance virus movement

Abstract: We recently identified a new cucumovirus-specific gene (2b) which is encoded by RNA 2 of the cucumber mosaic cucumovirus (CMV) tripartite RNA genome and whose coding sequence overlaps the C-terminal 69 codons of ORF 2a encoding the RNA polymerase protein. We have now found that although a CMV mutant lacking ORF 2b accumulated in the inoculated cotyledons of cucumber plants, it was unable to spread systemically, demonstrating involvement of 2b in long distance movement. The same mutant infected tobacco systemically with a much reduced virulence and delayed appearance of symptoms, indicating that 2b may contribute to long distance movement in this host. Deletion of the overlapping C-terminal part of ORF 2a did not change infectivity of the mutant in either host species, ruling out 2a mutation as the reason for the change of phenotype. Further infectivity studies with mutants containing partial deletions in ORF 2b further supported the conclusion that 2b encodes a host-specific long distance movement function. Sequence analysis revealed that 2b may represent a novel naturally occurring hybrid gene important to the evolutionary formation of the cucumovirus group and that it could provide a genetic basis for the wide host range of these viruses.

Effects of regulation on the flow regime of the river Murray, Australia

Abstract: The flow regime of the River Murray has changed markedly over the last century, and especially the last 50 years, through increased diversions, construction of dams, weirs and levees and changes in operational procedures. A model developed by the Murray–Darling Basin Commission is used to compare simulated natural (unregulated) flows at eight stations with those at seven consecutive stages in the development of regulation. Monthly and annual average flows and coefficients of variation and skewness were computed, and the flow-duration, peak-flow and low-flow characteristics curves plotted. The results confirm that average monthly and annual flows are now considerably lower than those which prevailed under natural conditions. The seasonal distribution of flows has changed in the upper Murray, owing to the influence of dams. Flow-duration characteristics now vary considerably along the river, whereas there was little change under natural conditions. The effect of regulation on flow-duration characteristics is minimal at Albury and becomes more pronounced downstream; it is most apparent in regard to flows exceeded 20–80% of the time. The magnitude of average annual floods (annual exceedance probability 50%) has been reduced by over 50% at all stations, but big floods (average recurrence interval 20 years or more) are little affected. Further, the low flows for a given annual non-exceedance probability are higher under regulated conditions than those under natural conditions. These changes have profound implications for communities of native plants and animals in both riverine and floodplain environments, and also for the long-term utility of the river as a resource.

Calculating the equilibrium distribution in level dependent quasi-birth-and-death processes

Abstract: Quasi-Birth-and-Death (QBD) processes have been analysed in detail by many authors. This paper considers the calculation of equilibrium distributions in level dependent QBD processes which are an extension of the classical QBD process. In addition to the general case, we consider a number of special cases of level dependent QBD processes, presenting algorithms for computing the equilibrium distribution

The Engine of Growth or Its Handmaiden? A Time-Series Assessment of Export-Led Growth

Abstract: This paper presents an analysis of time-series data for the countries in the Summers-Heston (1991) data set, in an attempt to ascertain the evidence for or against the export-led growth hypothesis We find that standard methods of detecting export-led growth using Granger causality tests may give misleading results if imports are not included in the system being analysed For this reason, our main statistical tool is the measure of conditional linear feedback developed by Geweke (1984), which allows us to examine the relationship between export growth and income growth while controlling for the growth of imports These measures have two additional features which make them attractive for our work First, they go beyond mere detection of evidence for export-led growth, to provide a measurement of its strength Second, they enable us to determine the temporal pattern of the response of income to exports In some cases export-led growth is a long run phenomenon, in the sense that export promotion strategies adopted today have their strongest effect after 8 to 16 years In other cases the opposite is true; exports have their greatest influence in the short run (less than 4 years) We find modest support for the export- led growth hypothesis, if “support” is taken to mean a unidirectional causal ordering Conditional on import growth, we find a causal ordering from export growth to income growth in 30 of the 126 countries analysed; 25 have the reverse ordering Using a weaker notion of “support”--stronger conditional feedback from exports to income than vice versa, 65 of the 126 countries support the export- led growth hypothesis, although the difference in strength is small Finally, we find that for the “Asian Tiger” countries of the Pacific Rim, the relationship between export growth and output growth becomes clearer when conditioned on human capital and investment growth as well as import growth(This abstract was borrowed from another version of this item(This abstract was borrowed from another version of this item)

A three-dimensional nonhydrostatic ray-tracing model for gravity waves : formulation and preliminary results for the middle atmosphere

Abstract: The WKB ray-tracing formalism is extended to accommodate internal gravity waves of all frequencies in a rotating, stratified, and compressible three-dimensional atmosphere This includes the derivation of equations governing the dispersion and refraction of the ray paths, a realistic wave amplitude equation that takes into account both radiative and turbulent damping effects, and extensions of previous wave saturation schemes to accommodate dynamical and convective instabilities along generally slanted axes These equations have been numerically coded into a global ray-tracing model that the authors have applied to the three-dimensional CIRA 1986 reference atmosphere model in a series of preliminary experiments to investigate the impact of the newly incorporated features on synthesized wave fields in the middle atmosphere Three main points emerge from these experiments First, there is a striking reduction in the high-frequency cutoff with decreasing horizontal wavenumber due to a more complete

Dispersion and zeta potential of pure clays as related to net particle charge under varying pH, electrolyte concentration and cation type

Abstract: Summary The effect of changing pH and electrolyte concentration on the dispersion and zeta potential of Na-and Ca-forms of kaolinite, illite and smectite was investigated in relation to changes in their net negative charge The percentage of dispersible Na-clay and the percentage increase in net negative charge was positively correlated with pH, but the slopes varied from clay to clay In general, the net negative charge was the primary factor in clay dispersion, and the pH affected clay dispersion by changing the net charge on clay particles Na-smectite had larger net charge at all pHs than Na-illite and Na-kaolinite, and it always had larger flocculation values The role of electrolyte concentration could be due to its effect both on flocculation and variable charge component of the clay minerals The zeta potential at different pHs also reflected the same trend of clay dispersion with net particle charge In Ca-clays the trends were similar to Na-clays up to pH 70 In more alkaline solution CaCO3 formation led to charge reduction on clay particles, resulting in flocculation and reduction of zeta potential At similar pHs the electrophoretic mobilities of all the clays showed constant potential behaviour However, the zeta potentials of Ca-clays were always smaller than those of sodic clays because the clays were more aggregated Net particle charge was the most important factor in controlling clay dispersion for the whole range of pH and ionic strength and for all types of cations

Engineering Noise Control

Abstract: This classic and authoritative student textbook contains information that is not over simplified and can be used to solve the real world problems encountered by noise and vibration consultants as well as the more straightforward ones handled by engineers and occupational hygienists in industry. The book covers the fundamentals of acoustics, theoretical concepts and practical application of current noise control technology. It aims to be as comprehensive as possible while still covering important concepts in sufficient detail to engender a deep understanding of the foundations upon which noise control technology is built. Topics which are extensively developed or overhauled from the fourth edition include sound propagation outdoors, amplitude modulation, hearing protection, frequency analysis, muffling devices (including 4-pole analysis and self noise), sound transmission through partitions, finite element analysis, statistical energy analysis and transportation noise. For those who are already well versed in the art and science of noise control, the book will provide an extremely useful reference. A wide range of example problems that are linked to noise control practice are available on www.causalsystems.com for free download.

Ectopic cyclin E expression induces premature entry into S phase and disrupts pattern formation in the Drosophila eye imaginal disc.

Abstract: During animal development, cell proliferation is controlled in many cases by regulation of the G1 to S phase transition. Studies of mammalian tissue culture cells have shown that the G1-specific cyclin, cyclin E, can be rate limiting for progression from G1 to S phase. During Drosophila development, down-regulation of cyclin E is required for G1 arrest in terminally differentiating embryonic epidermal cells. Whether cyclin E expression limits progression into S phase in proliferating, as opposed to differentiating, cells during development has not been investigated. Here we show that Drosophila cyclin E (DmcycE) protein is absent in G1 phase cells but appears at the onset of S phase in proliferating cells of the larval optic lobe and eye imaginal disc. We have examined cells in the eye imaginal epithelium, where a clearly defined developmentally regulated G1 to S phase transition occurs. Ectopic expression of DmcycE induces premature entry of most of these G1 cells into S phase. Thus in these cells, control of DmcycE expression is required for regulated entry into S phase. Significantly, a band of eye imaginal disc cells in G1 phase was not induced to enter S phase by ectopic expression of DmcycE. This provides evidence for additional regulatory mechanisms that operate during G1 phase to limit cell proliferation during development. These results demonstrate that the role of cyclin E in regulating progression into S phase in mammalian tissue culture cells applies to some, but not all, cells during Drosophila development.(ABSTRACT TRUNCATED AT 250 WORDS)

Bovine latent transforming growth factor beta 1-binding protein 2: molecular cloning, identification of tissue isoforms, and immunolocalization to elastin-associated microfibrils.

Abstract: Monoclonal antibodies to fibrillin 1 (MP340), a component of elastin-associated microfibrils, were used to screen cDNA libraries made from bovine nuchal ligament mRNA. One of the selected clones (cL9; 1.2 kb) hybridized on Northern (RNA) blotting with nuchal ligament mRNA to two abundant mRNAs of 9.0 and 7.5 kb, which were clearly distinct from fibrillin mRNA (10 kb). Further library screening and later reverse transcription PCR by the rapid amplification of cDNA ends (RACE) technique resulted in the isolation of additional overlapping cDNAs corresponding to about 6.7 kb of the mRNA. The encoded protein exhibited sequence similarity of around 80% with a recently identified human protein named latent transforming growth factor beta 1 (TGF-beta 1)-binding protein 2 (LTBP-2), indicating that the new protein was bovine LTBP-2. This was confirmed by the specific localization of bovine LTBP-2 cDNA probes to human chromosome 14q24.3, which is the locus of the human LTBP-2 gene. The domain structure of bovine LTBP-2 is very similar to that of the human LTBP-2, containing 20 examples of 6-cysteine epidermal growth factor-like repeats, 16 of which have the consensus sequence for calcium binding, together with 4 examples of 8-cysteine motifs characteristic of fibrillins and LTBP-1. A 4-cysteine sequence which is unique to bovine LTBP-2 and which has similarity to the 8-cysteine motifs was also present. Antibodies raised to two unique bovine LTBP-2 peptides specifically localized in tissue sections to the elastin-associated microfibrils, indicating that LTBP-2 is closely associated with these structures. Immunoblotting experiments identified putative LTBP-2 isoforms as a 260-kDa species released into the medium by cultured elastic tissue cells and as larger 290- and 310-kDa species in tissue extracts. A major proportion of tissue-derived LTBP-2 required treatment with 6 M guanidine for solubilization, indicating that the protein was strongly bound to the microfibrils. Most of the guanidine-solubilized LTBP-2 appeared to be monomeric, indicating that it was not involved in disulfide-bonded aggregation either with itself or with latent TGF-beta. Additional LTBP-2 was resistant to solubilization with 6 M guanidine but was readily extracted with a reductive saline solution. This treatment is relatively specific for solubilization of microfibrillar constituents including fibrillin 1 and microfibril-associated glycoprotein. Therefore, it can be inferred that some LTBP-2 is bound covalently to the microfibrils by reducible disulfide linkages. The evidence suggests that LTBP-2 has a direct role in elastic fiber structure and assembly which may be independent of its growth factor-binding properties. Thus, LTBP-2 appears to share functional characteristics with both LTBP-1 and fibrillins.

Molecular, genetic, and topological characterization of O-antigen chain length regulation in Shigella flexneri.

Abstract: The rfb region of Shigella flexneri encodes the proteins required to synthesize the O-antigen component of its cell surface lipopolysaccharides (LPS). We have previously reported that a region adjacent to rfb was involved in regulating the length distribution of the O-antigen polysaccharide chains (D. F. Macpherson et al., Mol. Microbiol. 5:1491-1499, 1991). The gene responsible has been identified in Escherichia coli O75 (called rol [R. A. Batchelor et al., J. Bacteriol. 173:5699-5704, 1991]) and in E. coli O111 and Salmonella enterica serovar typhimurium strain LT2 (called cld [D. A. Bastin et al., Mol. Microbiol. 5:2223-2231, 1991]). Through a combination of subcloning, deletion, and transposon insertion analysis, we have identified a gene adjacent to the S. flexneri rfb region which encodes a protein of 36 kDa responsible for the length distribution of O-antigen chains in LPS as seen on silver-stained sodium dodecyl sulfate-polyacrylamide gels. DNA sequence analysis identified an open reading frame (ORF) corresponding to the rol gene. The corresponding protein was almost identical in sequence to the Rol protein of E. coli O75 and was highly homologous to the functionally identical Cld proteins of E. coli O111 and S. enterica serovar typhimurium LT2. These proteins, together with ORF o349 adjacent to rfe, had almost identical hydropathy plots which predict membrane-spanning segments at the amino- and carboxy-terminal ends and a hydrophilic central region. We isolated a number of TnphoA insertions which inactivated the rol gene, and the fusion end points were determined. The PhoA+ Rol::PhoA fusion proteins had PhoA fused within the large hydrophilic central domain of Rol. These proteins were located in the whole-membrane fraction, and extraction with Triton X-100 indicated a cytoplasmic membrane location. This finding was supported by sucrose density gradient fractionation of the whole-cell membranes and of E. coli maxicells expressing L-[35S]methionine-labelled Rol protein. Hence, we interpret these data to indicate that the Rol protein is anchored into the cytoplasmic membrane via its amino- and carboxy-terminal ends but that the majority of the protein is located in the periplasmic space. To confirm that rol is responsible for the effects on O-antigen chain length observed with the cloned rfb genes in E. coli K-12, it was mutated in S. flexneri by insertion of a kanamycin resistance cartridge. The resulting strains produced LPS with O antigens of nonmodal chain length, thereby confirming the function of the rol gene product. We propose a model for the function of Rol protein in which it acts as a type of molecular chaperone to facilitate the interaction of the O-antigen ligase (RfaL) with the O-antigen polymerase (Rfc) and polymerized, acyl carrier lipid-linked, O-antigen chains. Analysis of the DNA sequence of the region identified a number of ORFs corresponding to the well-known gnd and hisIE genes. The rol gene was located immediately downstream of two ORFs with sequence similarity to the gene encoding UDPglucose dehydrogenase (HasB) of Streptococcus pyogenes. The ORFs arise because of a deletion or frameshift mutation within the gene we have termed udg (for UDPglucose dehydrogenase).

Effect of age on bone density and bone turnover in men.

Abstract: Summary OBJECTIVE Little Is known about the pattern of age-related bone loss in men, and although androgens are required for optimum bone mass it Is not clear whether the fall in bone mass with age in men is related to failing androgens. DESIGN Cross-sectional measurement of bone density, at five sites, and markers of bone resorption and formation in 147 normal volunteers aged 20-83 years. SUBJECTS Healthy laboratory workers, hospital staff, their relatives, and husbands of women attending our osteoporosis clinic. MEASUREMENTS Forearm density (fat corrected), spine L2-L4, femoral neck, Ward's triangle and trochanter density; serum procollagen I C-terminal extension peptide, osteocalcin, bone alkaline phosphatase and collagen I C-terminal telopeptlde; fasting urine hydroxy-proline/creatinine, pyridinoline/creatinine and deoxy-pyridinoline/creatinine; and free androgen Index (FAI), measured as serum testosterone/sex hormone binding globulin. RESULTS Bone loss accelerated at most sites after age 50. There was a significant fall In FAI from the third decade onwards. The levels of ail bone markers fell with age. CONCLUSIONS Bone loss In men appears to accelerate from age 50 and is associated with decreased bone formation which may be associated with falling levels of free androgen.

Improving adaptation to simulated night shift: timed exposure to bright light versus daytime melatonin administration.

Abstract: Chronic circadian disturbance is thought to cause many of the health and social problems reported by shift workers. In recent years, appropriately timed exposure to bright light and exogenous melatonin have been used to accelerate adaptation to phase shifts of the circadian system. In this study we compared adaptation to night shift in three groups of subjects. The first treatment group received timed exposure to bright light (4-7,000 lux between 2400 and 0400 hours on each of three night shifts). The second treatment group received exogenous melatonin by capsule (2 mg at 0800 hours then 1 mg at 1100 and 1400 hours). The placebo control groups received either dim red light at less than 50 lux or placebo (sucrose) in identical capsules at the same time. Results indicated that all groups shifted significantly from baseline. Using the dim-light melatonin onset as a circadian marker, the bright-light group shifted the furthest, whereas there was no significant difference between the melatonin and placebo groups. Sleep quality as determined by wrist actigraphy was most improved in the light-treatment group, although the melatonin group also showed significant improvements. Cognitive psychomotor performance was most improved in the light-treatment group and the melatonin group again showed little difference from the control group. Although melatonin was unable to increase the amount of the phase shift following transition to night shift, it is likely that the intermediate levels of improvement in sleep reflect the hypothermic effects of melatonin. By lowering core temperature across the sleep period, sleep may be enhanced. This improvement in sleep quality did not produce concomitant improvements in shift performance for the melatonin group. This suggests that the enhanced performance in the light-treatment group may reflect more direct "energizing" effects. On the basis of these results, bright light is clearly superior in its ability ot phase shift the circadian system and thereby improve sleep and performance. However, melatonin may permit shift workers to override the circadian system for short periods and avoid the potential toxicity due to overzealous manipulations of the circadian pacemaker. In rapidly rotating shift schedules, melatonin may be preferable because it would not require workers to reverse the large phase shift induced by light.

Structure of the scalar mesons f0(980) and a0(980).

Abstract: We investigate the structure of the scalar mesons ${\mathit{f}}_{0}$(980) and ${\mathit{a}}_{0}$(980) within realistic meson-exchange models of the \ensuremath{\pi}\ensuremath{\pi} and \ensuremath{\pi}\ensuremath{\eta} interactions. Starting from a modified version of the J\"ulich model for \ensuremath{\pi}\ensuremath{\pi} scattering we perform an analysis of the pole structure of the resulting scattering amplitude and find, in contrast with existing models, a somewhat large mass for the ${\mathit{f}}_{0}$(980) (${\mathit{m}}_{\mathit{f}0}$=1015 MeV, ${\mathrm{\ensuremath{\Gamma}}}_{\mathit{f}0}$=30 MeV). It is shown that our model provides a description of J/\ensuremath{\psi}\ensuremath{\rightarrow}\ensuremath{\varphi}\ensuremath{\pi}\ensuremath{\pi}/\ensuremath{\varphi}KK data comparable in quality with those of alternative models. Furthermore, the formalism developed for the \ensuremath{\pi}\ensuremath{\pi} system is consistently extended to the \ensuremath{\pi}\ensuremath{\eta} interaction leading to a description of the ${\mathit{a}}_{0}$(980) as a dynamically generated threshold effect (which is therefore neither a conventional qq\ifmmode\bar\else\textasciimacron\fi{} state nor a KK\ifmmode\bar\else\textasciimacron\fi{} bound state). Exploring the corresponding pole position the ${\mathit{a}}_{0}$(980) is found to be rather broad (${\mathit{m}}_{\mathit{a}0}$=991 MeV, ${\mathrm{\ensuremath{\Gamma}}}_{\mathit{a}0}$=202 MeV). The experimentally observed smaller width results from the influence of the nearby KK\ifmmode\bar\else\textasciimacron\fi{} threshold on this pole.

Cytokine secretion by macrophages in the rat testis.

Abstract: The rat testis contains a large population of resident macrophages, the physiological roles of which are yet to be established. To investigate the functional capacity of these cells, we have analyzed the secretion of the cytokines interleukin (IL)-1, IL-6, tumor necrosis factor alpha (TNF alpha), and granulocyte macrophage-colony stimulating factor (GM-CSF) by isolated testicular macrophages (TMs) and, for comparison, by isolated rat peritoneal macrophages (PMs). Cells were cultured for 48 h in serum-free medium alone or with lipopolysaccharide (LPS, 10 micrograms/ml) and/or recombinant interferon-gamma (rIFN gamma, 200 U/ml). Specific bioassays were used to measure cytokines in the media collected from cultures. Basal production of IL-1, TNF alpha, and IL-6 by TMs and PMs were similar, but TMs produced 8-fold greater levels of GM-CSF than did PMs. LPS, alone or in combination with IFN gamma, significantly enhanced the secretion of all cytokines by PMs (340-840% increase). LPS alone had little effect on TM secretion except to reduce GM-CSF levels some 4-fold. The addition of LPS and IFN gamma increased IL-1, IL-6, and TNF alpha levels (200-750% increase) and reduced GM-CSF levels to 45% of basal levels. Treatment of cultures with indomethacin to minimize prostaglandin production enhanced the LPS-induced effects in both cell types. Expression of the mRNA for each cytokine in cultures of testicular and peritoneal macrophages, as well as in intact testis, was confirmed by reverse transcription polymerase chain reaction. These studies indicate that macrophages resident within the rat testis have a novel cytokine secretion profile and an altered responsiveness to inflammatory activators compared with macrophages from the peritoneal cavity. This may be important in physiological processes in the testis and may contribute to the dysfunctional afferent immune activity thought to underlie the immunologically privileged status of the testes.

Division of Giardia isolates from humans into two genetically distinct assemblages by electrophoretic analysis of enzymes encoded at 27 loci and comparison with Giardia muris

Abstract: Giardia that infect humans are known to be heterogeneous but they are assigned currently to a single species, Giardia intestinalis (syn. G. lamblia). The genetic differences that exist within G. intestinalis have not yet been assessed quantitatively and neither have they been compared in magnitude with those that exist between G. intestinalis and species that are morphologically similar (G. duodenalis) or morphologically distinct (e.g. G. muris). In this study, 60 Australian isolates of G. intestinalis were analysed electrophoretically at 27 enzyme loci and compared with G. muris and a feline isolate of G. duodenalis. Isolates of G. intestinalis were distinct genetically from both G. muris (approximately 80% fixed allelic differences) and the feline G. duodenalis isolate (approximately 75% fixed allelic differences). The G. intestinalis isolates were extremely heterogeneous but they fell into 2 major genetic assemblages, separated by fixed allelic differences at approximately 60% of loci examined. The magnitude of the genetic differences between the G. intestinalis assemblages approached the level that distinguished the G. duodenalis isolate from the morphologically distinct G. muris. This raises important questions about the evolutionary relationships of the assemblages with Homo sapiens, the possibility of ancient or contemporary transmission from animal hosts to humans and the biogeographical origins of the two clusters.

The Experiences of International and Local Students at Three Australian Universities.

Abstract: In 1992 international fee‐paying and local students currently enrolled at the three tertiary institutions in South Australia were surveyed by a common questionnaire on students’ study‐related and personal experiences, and issues related to students’ choice and subsequent evaluation of their institution. The breadth of the student sample and the comparative data the questionnaire generated present an overarching view of the experiences and evaluations of a diverse range of university students. The results of the survey show that while international students experience more problems, and experience them to a more serious degree than their Australian counterparts, the nature of the issues which are of most concern are generally shared. These are concerns about financial issues such as access to Austudy for local students, and the level of fees for international students and the ability to find part‐time work for both groups. The other broad group of issues of concern was study related: workload, fea...

Active control of vibration using a neural network

Abstract: Feedforward control of sound and vibration using a neural network-based control system is considered, with the aim being to derive an architecture/algorithm combination which is capable of supplanting the commonly used finite impulse response filter/filtered-x least mean square (LMS) linear arrangement for certain nonlinear problems. An adaptive algorithm is derived which enables stable adaptation of the neural controller for this purpose, while providing the capacity to maintain causality within the control scheme. The algorithm is shown to be simply a generalization of the linear filtered-x LMS algorithm. Experiments are undertaken which demonstrate the utility of the proposed arrangement, showing that it performs as well as a linear control system for a linear control problem and better for a nonlinear control problem. The experiments also lead to the conclusion that more work is required to improve the predictability and consistency of the performance before the neural network controller becomes a practical alternative to the current linear feedforward systems. >

Wheat genotypes differ in Zn efficiency when grown in chelate-buffered nutrient solution

Abstract: Ten Triticum aestivum and two Triticum turgidum conv. durum genotypes were grown in chelate-buffered nutrient solution at Zn supplies ranging from deficient to sufficient (free Zn activities from 2 to 200 pM, pZn from 11.7 to 9.7). The critical level of Zn ion activity in solution for healthy growth of wheat plants was around 40 pM. Genotypes differed in the growth response: those classified as Zn-efficient suffered less reduction of shoot growth and did not change the rate of root growth at a Zn supply quite deficient for Zn-inefficient genotypes. Root growth of Zn-inefficient genotypes increased at deficient Zn supply. The shoot/root ratio was the most sensitive parameter of Zn efficiency; Zn-efficient genotypes showed less reduction in the ratio when grown at deficient compared to sufficient Zn supply. Classification of wheat genotypes into Zn-efficient and Zn-inefficient groups after screening in chelate-buffered nutrient solution corresponded well with classification obtained in field experiments on Zn-deficient soil.