The influence of larval density, food availability and habitat longevity on the life history and population growth rate of the midge Chironomus riparius

Despite long-standing interest in the forms and mechanisms of density dependence, these are still imperfectly understood. However, in a constant environment an increase in density must reduce per capita resource availability, which in turn leads to reduced survival, fecundity and somatic growth rate. Here we report two population experiments examining the density dependent responses under controlled conditions of an important indicator species, Chironomus riparius. The first experiment was run for 35 weeks and was started at low density with replicate populations being fed three different rations. Increased ration reduced generation time and increased population growth rate (pgr) but had no effect on survival, fecundity and female body weight in the first generation. In the second generation there was a six-fold increase in generation time, presumably due to the greatly reduced per capita resource availability as the estimated initial densities of the second generation were 300 times greater than the first. Juvenile survival to emergence, fecundity, adult body weight and pgr declined by 90%, 75%, 35% and 99%, respectively. These large between-generation effects may have obscured the effects of the threefold variation in ration, as only survival to emergence significantly increased with ration in the second generation. These results suggest that some chironomid larvae survive a reduction in resource availability by growing more slowly. In the ephemeral habitats sometimes occupied by C. riparius, the effects of population density may depend crucially on the longevity of the environment. A second experiment was therefore performed to measure pgr from six different starting densities over an eight-week period. The relationship between pgr and density was concave, viewed from above. At densities above 16 larvae per cm(2), less than 1% of the population emerged and no offspring were produced. Under the conditions of experiment 2 - an 8-week habitat lifespan carrying capacity was estimated as 8 larvae per cm(2).

Effect of honey feeding by thyrinteina arnobia males and females on their reproduction and longevity

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Rising longevity, education, savings, and growth

This paper examines the impact of declines in adult mortality on growth in an overlapping generations model. With public education and imperfect annuity markets, a decline in mortality affects growth through three channels. First, it raises the saving rate and thereby increases the rate of physical capital accumulation. Second, it reduces accidental bequests, lowers investment, and thereby lowers the rate of physical capital accumulation. Third, it may lead the median voter to increase the tax rate for public education initially but lower the tax rate in a later stage. Starting from a high mortality rate as found in many Third World populations, the net effect of a decline in mortality is to raise the growth rate. However, starting from a low mortality rate such as is found in most industrial populations, the net effect of a further decline in mortality is to reduce the growth rate. The findings appear consistent with recent empirical evidence. (C) 2002 Elsevier Science B.V All rights reserved.

A century of trends in adult human height

Being taller is associated with enhanced longevity, and higher education and earnings. We reanalysed 1472 population-based studies, with measurement of height on more than 18.6 million participants to estimate mean height for people born between 1896 and 1996 in 200 countries. The largest gain in adult height over the past century has occurred in South Korean women and Iranian men, who became 20.2 cm (95% credible interval 17.5–22.7) and 16.5 cm (13.3– 19.7) taller, respectively. In contrast, there was little change in adult height in some sub-Saharan African countries and in South Asia over the century of analysis. The tallest people over these 100 years are men born in the Netherlands in the last quarter of 20th century, whose average heights surpassed 182.5 cm, and the shortest were women born in Guatemala in 1896 (140.3 cm; 135.8– 144.8). The height differential between the tallest and shortest populations was 19-20 cm a century ago, and has remained the same for women and increased for men a century later despite substantial changes in the ranking of countries.

An interpretative phenomenological analysis of adult clients’ experience of My Career Chapter

This paper presents an investigation into the properties of a new narrative technique for career assessment and counselling, My Career Chapter: A Dialogical Autobiography. This technique is used to facilitate clients’ construction of a meaningful career-related autobiography. Previous research indicates the usefulness of My Career Chapter for adult clients and its alignment with recommendations for the development and application of qualitative assessment and counselling techniques. This study specifically commences research into the technique’s applicability for adolescents. A focus group, comprised of guidance counselling professionals whose work primarily pertained to the needs of adolescents, found that there is potential to develop a version of My Career Chapter that is suitable for adolescents.

A longitudinal study comparing bereavement phenomena in recently bereaved spouses, adult children and parents

Objective: The study investigated previous research findings and clinical impressions which indicated that the intensity of grief for parents who had lost a child was likely to be higher than that for widows/widowers, who in turn were likely to have more intense reactions than adult children losing a parent. Method: In order to compare the intensities of the bereavement reactions among representative community samples of bereaved spouses (n = 44), adult children (n = 40) and parents (n = 36), and to follow the course of such phenomena, a detailed Bereavement Questionnaire was administered at four time points over a 13-month period following the loss. Results: Measures based on items central to the construct of bereavement showed significant time and group differences in accordance with the proposed hypothesis. More global items associated with the construct of resolution showed a significant time effect, but without significant group differences. Conclusions: Evidence from this study supports the hypothesis that in non-clinical, community-based populations the frequency with which core bereavement phenomena are experienced is in the order: bereaved parents bereaved spouses bereaved adult children.

Stem cell regulatory gene expression in human adult dental pulp and periodontal ligament cells undergoing odontogenic/osteogenic differentiation

Introduction During development and regeneration, odontogenesis and osteogenesis are initiated by a cascade of signals driven by several master regulatory genes. Methods In this study, we investigated the differential expression of 84 stem cell–related genes in dental pulp cells (DPCs) and periodontal ligament cells (PDLCs) undergoing odontogenic/osteogenic differentiation. Results Our results showed that, although there was considerable overlap, certain genes had more differential expression in PDLCs than in DPCs. CCND2, DLL1, and MME were the major upregulated genes in both PDLCs and DPCs, whereas KRT15 was the only gene significantly downregulated in PDLCs and DPCs in both odontogenic and osteogenic differentiation. Interestingly, a large number of regulatory genes in odontogenic and osteogenic differentiation interact or crosstalk via Notch, Wnt, transforming growth factor β (TGF-β)/bone morphogenic protein (BMP), and cadherin signaling pathways, such as the regulation of APC, DLL1, CCND2, BMP2, and CDH1. Using a rat dental pulp and periodontal defect model, the expression and distribution of both BMP2 and CDH1 have been verified for their spatial localization in dental pulp and periodontal tissue regeneration. Conclusions This study has generated an overview of stem cell–related gene expression in DPCs and PDLCs during odontogenic/osteogenic differentiation and revealed that these genes may interact through the Notch, Wnt, TGF-β/BMP, and cadherin signalling pathways to play a crucial role in determining the fate of dental derived cell and dental tissue regeneration. These findings provided a new insight into the molecular mechanisms of the dental tissue mineralization and regeneration

Cellular senescence and longevity of osteophyte-derived mesenchymal stem cells compared to patient-matched bone marrow stromal cells

This study aimed to determine the cellular aging of osteophyte-derived mesenchymal cells (oMSCs) in comparison to patient-matched bone marrow stromal cells (bMSCs). Extensive expansion of the cell cultures was performed and early and late passage cells (passages 4 and 9, respectively) were used to study signs of cellular aging, telomere length, telomerase activity, and cell-cycle-related gene expression. Our results showed that cellular aging was more prominent in bMSCs than in oMSCs, and that oMSCs had longer telomere length in late passages compared with bMSCs, although there was no significant difference in telomere lengths in the early passages in either cell type. Telomerase activity was detectable only in early passage oMSCs and not in bMSCs. In osteophyte tissues telomerase-positive cells were found to be located perivascularly and were Stro-1 positive. Fifteen cell-cycle regulator genes were investigated and only three genes (APC, CCND2, and BMP2) were differentially expressed between bMSC and oMSC. Our results indicate that oMSCs retain a level of telomerase activity in vitro, which may account for the relatively greater longevity of these cells, compared with bMSCs, by preventing replicative senescence. J. Cell. Biochem. 108: 839-850, 2009. (c) 2009 Wiley-Liss, Inc.

The potential for a web based intervention to improve young adult passenger safety

Young drivers aged 17-24 are consistently overrepresented in motor vehicle crashes. Research has shown that a young driver’s crash risk increases when carrying similarly aged passengers, with fatal crash risk increasing two to three fold with two or more passengers. Recent growth in access to and use of the internet has led to a corresponding increase in the number of web based behaviour change interventions. An increasing body of literature describes the evaluation of web based programs targeting risk behaviours and health issues. Evaluations have shown promise for such strategies with evidence for positive changes in knowledge, attitudes and behaviour. The growing popularity of web based programs is due in part to their wide accessibility, ability for personalised tailoring of intervention messages, and self-direction and pacing of online content. Young people are also highly receptive to the internet and the interactive elements of online programs are particularly attractive. The current study was designed to assess the feasibility for a web based intervention to increase the use of personal and peer protective strategies among young adult passengers. An extensive review was conducted on the development and evaluation of web based programs. Year 12 students were also surveyed about their use of the internet in general and for health and road safety information. All students reported internet access at home or at school, and 74% had searched for road safety information. Additional findings have shown promise for the development of a web based passenger safety program for young adults. Design and methodological issues will be discussed.

Towards a cognitive-behavioural intervention for adult grief reactions

Published accounts of behavioural interventions for grief have relied on exposure and habituation to grief cues as the primary strategy. Such an approach is excessively narrow, since it does not adequately confront the challenges that are posed by a bereavement. Many people cope with a bereavement by themselves, and for those, intervention may well be counterproductive. A cognitive-behavioural intervention, following models for depression/anxiety, can assist vulnerable individuals obtain a more rapid or complete adjustment. The proposed approach differs from dynamic treatments by placing less emphasis on defensive behavior, insight, and interpretation and more emphasis on training of coping skills.