Abundance,species richness and feeding preferences of introduced molluscs in native grasslands of Victoria,Australia

Abstract Introduced molluscs have invaded endangered, remnant native grasslands of south‐eastern Australia, but few studies have investigated their distribution, abundance or potential impact. Molluscs were surveyed in grassland sites across an urban to rural transect west of Melbourne, Australia. It was confirmed that several introduced mollusc species have invaded these areas. Three snail and five slug species were identified, none of which was native to Australia. The most common species was the brown field slug (Deroceras panormitanum). Mollusc capture and species richness were positively related to the degree of urbanization in the surrounding landscape. There was also a negative relationship with fire frequency. Feeding trials revealed selective herbivory by the black‐keeled slug (Milax gagates) among native plants. Anecdotal evidence that variable glycine (Glycine tabacina) and button wrinklewort (Rutidosis leptorrhynchoides) are palatable to molluscs was supported. Mollusc herbivory may potentially lead to reduced fitness of palatable species, and changes in community composition and structure.     

Inferring changes in foliar mass and area from foliage cover: A mechanistic model

Measuring foliar area or mass directly is destructive, and precludes long‐term, repeated observations of individual trees as they suffer or recover from foliar damage. Instead, foliage cover indices are often used as a proxy for foliar mass. Patterns of fluctuations in foliage cover indices can be used to infer qualitative changes in canopy health. However, foliage cover is not necessarily linearly related to foliar area or mass, and this may confound the detection of significant foliar damage, and comparisons of herbivore browse impacts between individual trees, tree species or sites. I derived a mechanistic model to quantify the relationship between foliar area or mass and foliage cover measured as the proportion of sky occluded by leaves. This one parameter model is close to linear for single‐tiered trees, but increasingly non‐linear for multi‐tiered trees. I compared the non‐linear model to a linear model using foliage cover data from an artificial defoliation experiment on two single‐tiered, sub‐canopy species and from simulated photographic images of single‐ and multi‐tiered canopies. The non‐linear model had lower errors than the linear model, and errors did not increase with foliage density (leaf area per unit area), variation (of leaf sizes within and between canopies) or leaf geometry. The non‐linear model can be easily parameterized from relatively low‐cost observations of foliage cover, independently of empirical measurements of foliar area or mass, and is applicable to a wide range of tree species. It should therefore help managers quantify how changes in foliage cover due to natural fluctuations or foliar damage affect foliar area and mass, and can be used to quantify parameters for models of browse impacts in mixed forest.     

The relationship between possum density and browse damage on kamahi in New Zealand forests

To minimize the impacts of introduced pests and to justify and prioritize pest control, managers need to know the relationship between pest density and damage. This relationship can be difficult to quantify because pest impacts can be highly variable. In New Zealand, introduced brushtail possums (Trichosurus vulpecula) browse a wide range of native forest species. However, possum browse is extremely patchy making it difficult to quantify the relationship between density and damage, meaning the benefits of reducing possum densities are poorly understood. We quantified patterns of possum browse on kamahi (Weinmannia racemosa), a common canopy tree species, at 21 forest sites that were repeat‐measured over an 8‐year period in the North Island, New Zealand, during which time possum densities fluctuated widely. We fitted a multilevel statistical model in order to quantify the relationship between possum density and browse damage while simultaneously quantifying how browse varied among trees, sites and years. Higher possum densities were associated with greater browse damage, but browse was also patchily distributed among trees at the same site, and among sites and years for a given possum density. This heterogeneity meant there was no simple density damage relationship, with the relationship differing from tree to tree and among sites and years. Our results show that at most sites reductions in possum density would have little benefit in reducing the probability of heavy browse on kamahi trees, but at a few sites there would be substantial benefits. This approach provides insights into the pattern and potential causes of variability in possum impacts, and a quantitative basis for prioritizing sites for possum control.     

Relaxin family peptide receptors Rxfp1 and Rxfp2: mapping of the mRNA and protein distribution in the reproductive tract of the male rat

Background  

Relaxin is the endogenous ligand of the G-protein coupled receptor RXFP1, previously known as LGR7. In humans relaxin can also activate, but with lower affinity, the closely related receptor for the insulin-like peptide from Leydig cells, RXFP2, previously known as LGR8. The lack of relaxin impairs male fertility but the precise distribution and the function of relaxin receptors in the male reproductive tract is not known. We investigated the distribution of Rxfp1 and Rxfp2 in the reproductive tract of the male rat and the function of relaxin in the vas deferens, a tissue with high expression of both receptors.     

Lifestyle modifications to prevent and control hypertension. 1. Methods and an overview of the Canadian recommendations. Canadian Hypertension Society,Canadian Coalition for High Blood Pressure Prevention and Control,Laboratory Centre for Disease Control at Health Canada,Heart and Stroke Foundation of Canada

OBJECTIVE: To provide updated, evidence-based recommendations for health care professionals on lifestyle changes to prevent and control hypertension in otherwise healthy adults (except pregnant women). OPTIONS: For people at risk for hypertension, there are a number of lifestyle options that may avert the condition--maintaining a healthy body weight, moderating consumption of alcohol, exercising, reducing sodium intake, altering intake of calcium, magnesium and potassium, and reducing stress. Following these options will maintain or reduce the risk of hypertension. For people who already have hypertension, the options for controlling the condition are lifestyle modification, antihypertensive medications or a combination of these options; with no treatment, these people remain at risk for the complications of hypertension. OUTCOMES: The health outcomes considered were changes in blood pressure and in morbidity and mortality rates. Because of insufficient evidence, no economic outcomes were considered. EVIDENCE: A MEDLINE search was conducted for the period January 1996 to September 1996 for each of the interventions studied. Reference lists were scanned, experts were polled, and the personal files of the authors were used to identify other studies. All relevant articles were reviewed, classified according to study design and graded according to level of evidence. VALUES: A high value was placed on the avoidance of cardiovascular morbidity and premature death caused by untreated hypertension. BENEFITS, HARMS AND COSTS: Lifestyle modification by means of weight loss (or maintenance of healthy body weight), regular exercise and low alcohol consumption will reduce the blood pressure of appropriately selected normotensive and hypertensive people. Sodium restriction and stress management will reduce the blood pressure of appropriately selected hypertensive patients. The side effects of these therapies are few, and the indirect benefits are well known. There are certainly costs associated with lifestyle modification, but they were not measured in the studies reviewed. Supplementing the diet with potassium, calcium and magnesium has not been associated with a clinically important reduction in blood pressure in people consuming a healthy diet. RECOMMENDATIONS: (1) It is recommended that health care professionals determine the body mass index (weight in kilograms/[height in metres]2) and alcohol consumption of all adult patients and assess sodium consumption and stress levels in all hypertensive patients. (2) To reduce blood pressure in the population at large, it is recommended that Canadians attain and maintain a healthy body mass index. For those who choose to drink alcohol intake should be limited to 2 or fewer standard drinks per day (maximum of 14/week for men and 9/week for women). Adults should exercise regularly. (3) To reduce blood pressure in hypertensive patients, individualized therapy is recommended. This therapy should emphasize weight loss for overweight patients, abstinence from or moderation in alcohol intake, regular exercise, restriction of sodium intake and, in appropriate circumstances, individualized cognitive behaviour modification to reduce the negative effects of stress. VALIDATION: The recommendations were reviewed by all of the sponsoring organizations and by participants in a satellite symposium of the fourth international Conference on Preventive Cardiology. They are similar to those of the World Hypertension League and the Joint National committee, with the exception of the recommendations on stress management, which are based on new information. They have not been clinically tested. SPONSORS: The Canadian Hypertension Society, the Canadian Coalition for High Blood Pressure Prevention and Control, the Laboratory Centre for Disease Control at health Canada, and the Heart and Stroke Foundation of Canada.     

The phylogenetic distribution of a transposable dioxygenase from the Niagara River watershed

Horizontal gene transfer in the Bacteria has been demonstrated to occur under natural conditions. The ecological impact of gene transfer events depends on the new genetic material being expressed in recipient organisms, and on natural selection processes operating on these recipients. The phylogenetic distribution of cbaAB genes for chlorobenzoate 3,4-(4,5)-dioxygenase, which are carried within Tn5271 on the IncPβ plas-mid pBRC60, was investigated using isolates from freshwater microcosms and from the Niagara River watershed. The latter included isolates from surface water, groundwater and bioremediation reactor samples. The cbaAB genes have become integrated, through interspecific transfer, primarily into species of the β Proteobacteria (44/48 isolates). Only four isolates, identified as Pseudomonas fluorescens (3/48) and Xanthomonas maltophilia (1/48), belonged to the Γ Proteobacteria, despite the observation that pBRC60 was capable of mobilizing these genes into a wide range of β and Γ Proteobacteria in the laboratory. The natural host range correlated with the distribution of the meta-ring-fission pathway for metabolism of protocatechuates formed when the cbaAB genes were expressed (45/48 isolates). We proposed the hypothesis that natural selection has favoured recipients that successfully integrate the activity of the transferred dioxygenase with the conserved meta ring-fission pathway. The hypothesis was tested by transferring a plasmid construct containing the cbaAB genes into type strains representative of the β and γ Proteobacteria. The concept of applying mobile catabolic genes to probe the phylogenetic distribution of compatible degradative pathways is discussed.     

ELECTRON MICROSCOPIC DEMONSTRATION OF A DITHIOTHREITOL-LABILE VITELLINE COAT SURROUNDING THE UNFERTILIZED EGG OF COMANTHUS JAPONICA (ECHINODERMATA: CRINOIDEA)*

In Comanthus, the unfertilized egg is surrounded by a vitelline coat, which is separated from the underlying plasma membrane by a space several hundred Ångstroms wide. By electron microscopy, the vitelline coat is a distinct layer 100 to 150 Å thick, which consists of finely granular material of moderate electron density. Treatment for 3 min in 0.01 M dithiothreitol in sea water buffered to pH 9.2 almost completely removes the vitelline coat and causes the irregularly shaped egg to become spherical. After such DTT-treated eggs have been washed for 2 min in sea water, they cannot be fertilized, but they can undergo a cortical reaction when treated with ionophore A23187. This cortical reaction consists of the exocytosis of cortical granule material directly into the surrounding sea water. By several hours after DTT treatment, most of the eggs, whether exposed to ionophore or not, fragment into spheres of diverse sizes.     

Interactions between wheat (Triticum aestivum L.) cultivar, row spacing and density and the effect on weed suppression and crop yield

In 1995/1996 weed suppression ability of two wheat cultivars (Spark and Tonic) was investigated in conjunction with two row spacings (15 cm and 9 cm) and three sowing densities (125, 250 and 350 plants m^-2). Weed biomass was influenced initially by crop density, and following stem extension by both cultivar and density, although these factors did not interact. Tillering capacity was a poor predictor of weed suppression ability and Spark, the more profusely tillering cultivar, contained greater weed biomass than Tonic. The earlier stem extension of Tonic increased shading at 0–20 cm above ground level compared to Spark and this was believed to be the reason for reduced weed biomass. Row spacing did not influence weed suppression, but grain yield was reduced in 15 cm rows at a density of 350 plants m^-12 compared to 250 plants m^-12. This may be of importance to growers contemplating the use of wider row spacings for mechanical weeding.     

THE VIRTUE ETHICS APPROACH TO BIOETHICS

This paper discusses the viability of a virtue‐based approach to bioethics. Virtue ethics is clearly appropriate to addressing issues of professional character and conduct. But another major remit of bioethics is to evaluate the ethics of biomedical procedures in order to recommend regulatory policy. How appropriate is the virtue ethics approach to fulfilling this remit? The first part of this paper characterizes the methodology problem in bioethics in terms of diversity, and shows that virtue ethics does not simply restate this problem in its own terms. However, fatal objections to the way the virtue ethics approach is typically taken in bioethics literature are presented in the second section of the paper. In the third part, a virtue‐based approach to bioethics that avoids the shortcomings of the typical one is introduced and shown to be prima facie plausible. The upshot is an inviting new direction for research into bioethics' methodology.