Themes in songs written by clients with traumatic brain injury: Differences across the Lifespan

This study aimed to identify age differences in the themes of songs written by patients with traumatic brain injury (TBI). Lyrics from 82 songs written by 11 female and 20 male patients aged between 5 and 60 years were categorised into eight themes and 24 categories. Incidence of categories and themes were calculated and compared across six age brackets. Results suggest that children, early adolescent, and middle adolescent patients with TBI focus on memories to a substantially greater degree than older patients. Early and late adolescent patient groups are most likely to be self-reflective, and to raise concerns about the future, when compared with other patient groups. (author abstract)

Modelling cell lifespan and proliferation: is likelihood to die or to divide independent of age?

In cell lifespan studies the exponential nature of cell survival curves is often interpreted as showing the rate of death is independent of the age of the cells within the population. Here we present an alternative model where cells that die are replaced and the age and lifespan of the population pool is monitored until a, steady state is reached. In our model newly generated individual cells are given a determined lifespan drawn from a number of known distributions including the lognormal, which is frequently found in nature. For lognormal lifespans the analytic steady-state survival curve obtained can be well-fit by a single or double exponential, depending on the mean and standard deviation. Thus, experimental evidence for exponential lifespans of one and/or two populations cannot be taken as definitive evidence for time and age independence of cell survival. A related model for a dividing population in steady state is also developed. We propose that the common adoption of age-independent, constant rates of change in biological modelling may be responsible for significant errors, both of interpretation and of mathematical deduction. We suggest that additional mathematical and experimental methods must be used to resolve the relationship between time and behavioural changes by cells that are predominantly unsynchronized.

Genotypic consistency in the expression of leaf water potential in rice (Oryza sativa L.)

Early work has shown variation in the grain yield of rice cultivars grown under water stress conditions to be associated with the plant water status, mainly with the maintenance of high leaf water potential (LWP) at flowering and grain filling stage. Considerable variation for LWP among rice varieties has been recorded. The present work was designed to investigate genotypic consistency in water potential within the plant and under canopy manipulation to vary plant water requirement. In a glasshouse experiment, with six rice genotypes, a consistent water potential gradient from stem base to leaf tip has been observed. Leaf tip water potential has been found as the minimum LWP that can be recorded at any time of stress. Genotypes with similar canopy size could maintain different levels of LWP under stress conditions. In a field experiment, with four selected lines, four canopy sizes and two canopy mixture treatments were introduced prior to the imposition of control, mild and severe water stress conditions. It was found that the line differences in LWP and relative water content (RWC) were expressed under both mild and severe stress conditions, regardless of canopy size, tiller number and whether they were mixed with another line with different capacity to maintain LWP. Although there were some differences among canopy size treatments for radiation interception in three water conditions, canopy manipulation (plant size) within a line did not affect the expression of LWP and hence genotypic variation in LWP was maintained. Under both glasshouse and field conditions, lines that maintained high LWP had larger xylem diameter and stem areas than those that had low LWP. The results indicated that the size of the vascular bundles could influence the maintenance of plant water relations under water deficit. (c) 2005 Elsevier B.V. All rights reserved.

Is the distribution of Fiji leaf gall in Australian sugarcane explained by variation in the vector Perkinsiella saccharicida?

Fiji leaf gall (FLG) is an important virally induced disease in Australian sugarcane. It is confined to southern canegrowing areas, despite its vector, the delphacid planthopper Perkinsiella saccharicida, occurring in all canegrowing areas of Queensland and New South Wales. This disparity between distributions could be a result of successful containment of the disease through quarantine and/or geographical barriers, or because northern Queensland populations of Perkinsiella may be poorer vectors of the disease. These hypotheses were first tested by investigating variation in the ITS2 region of the rDNA fragment among eastern Australian and overseas populations of Perkinsiella. The ITS2 sequences of the Western Australian P. thompsoni and the Fijian P. vitiensis were distinguishable from those of P. saccharicida and there was no significant variation among the 26P. saccharicida populations. Reciprocal crosses of a northern Queensland and a southern Queensland population of P. saccharicida were fertile, so they may well be conspecific. Single vector transmission experiments showed that a population of P. saccharicida from northern Queensland had a higher vector competency than either of two southern Queensland populations. The frequency of virus acquisition in the vector populations was demonstrated to be important in the vector competency of the planthopper. The proportion of infected vectors that transmitted the virus to plants was not significantly different among the populations tested. This study shows that the absence of FLG from northern Queensland is not due to a lack of vector competency of the northern population of P. saccharicida.

Nutrient deficiencies in greater yam and their effects on leaf nutrient concentrations

This paper describes the first systematic study of nutritional deficiencies of greater yam (Dioscorea alata). Yam plants (cv. 'Mahoa'a') were propagated from tuber discs and grown in nutrient solution, with nutrients supplied following a modified programmed nutrient-addition method. After an establishment period of four weeks, deficiencies of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), boron (B), manganese (Mn), copper (Cu), zinc (Zn), and molybdenum (Mo) were induced by omitting the relevant nutrient from the solution. Foliar symptoms were recorded photographically. Notably, deficiencies of the mobile macronutrients failed to induce senescence of oldest leaves, while vine growth and younger leaves were affected. Leaf blades of the main stem were sampled in sequence and analyzed chemically, providing the distribution of each nutrient from youngest to oldest leaves in both adequately supplied and deficient plants. The nutrient-concentration profiles, together with the visible symptoms, indicated that little remobilization of mobile macronutrients had occurred. For both macro- and micronutrients, young leaves gave the best separation of nutrient concentrations between well-nourished and deficient plants.

Strong and weak lifespan extension: What is most feasible and likely?

Recent advances in biomedical science indicate that it may eventually be possible to intervene in the biological process of human ageing. This paper overviews the current state of the science of lifespan extension and promising future directions. It is uncertain whether 'strong' lifespan extension - the extension of human life beyond the maximum 122 years so far observed - will become a reality. It is more likely that cumulative effects of numerous scientific and biomedical advances in the treatment of common disease will produce 'weak' lifespan extension - the extension of average life expectancy. The practical application of molecular, genetic and nanomaterials research may also lead to advances in life expectancy. It is not too early to begin to consider the policy implications of either form of lifespan extension.

What does the community think about lifespan extension technologies? The need for an empirical base for ethical and policy debates

Objectives: This paper examines public understandings of possibilities for increasing life expectancy, interest in taking up lifespan-extending interventions, and motivations influencing these intentions. Methods: Structured interviews were conducted with 31 adults, aged 50 and over. Results: Participants believed that technological advances would increase life expectancy but questioned the value of quantity over quality of life. Life in itself was not considered valuable without the ability to put it to good use. Participants would not use technologies to extend their own lifespan unless the result would also enhance their health. Conclusions: These findings may not be generalisable to the general public but they provide the first empirical evidence on the plausibility of common assumptions about public interest in 'anti-ageing' interventions. Surveys of the views of representative samples of the population are needed to inform the development of a research agenda on the ethical, legal and social implications of lifespan extension.

Cutting management of multipurpose tree legumes: effects on green herbage production, leaf retention and water-use-efficiency during the dry season in Timor, Indonesia

Edible herbage production and water-use-efficiency of three tree legumes (Leucaena leucocephala cv. Tarramba, L. pallida x L. leucocephala (KX2) and Gliricidia sepium), cut at different times of the year (February, April, June and uncut) were compared in a semi-arid area of Timor Island, Indonesia. Cutting in the early and mid dry-season (April and June) resulted in higher total leaf production (P< 0.05) and water-use-efficiency (P< 0.05), than cutting late in the wet-season (February) or being left uncut. For the leucaena treatments removing leaf in the early to mid dry-season reduced transpiration, saving soil water for subsequent regrowth as evidenced by the higher relative water contents of leaves from these treatments. This cutting strategy can be applied to local farming conditions to increase the supply of feed for livestock during the dry season.

Towards developing reliable models of leaf area on grapevines (Vitis vinifera L.)

A field study in three vineyards in southern Queensland (Australia) was carried out to develop predictive models for individual leaf area and shoot leaf area of two cultivars (Cabernet Sauvignon and Shiraz) of grapevines (Vitis Vinifera L.). Digital image analysis was used to measure leaf vein length and leaf area. Stepwise regressions of untransformed and transformed models consisting of up to six predictor variables for leaf area and three predictor variables for shoot leaf area were carried out to obtain the most efficient models. High correlation coefficients were found for log10 transformed individual leaf and shoot leaf area models. The significance of predictor variables in the models varied across vineyards and cultivars, demonstrating the discontinuous and heterogeneous nature of vineyards. The application of this work in a grapevine modeling environment and in a dynamic vineyard management context are discussed. Sample sizes for quantification of individual leaf areas and areas of leaves on shoots are proposed based on target margins of errors of sampled data.