Testing the sediment-trapping paradigm of seagrass: Do seagrasses influence nutrient status and sediment structure in tropical intertidal environments?

Seagrass meadows are considered important for sediment trapping and sediment stabilisation. Deposition of fine sediments and associated adsorbed nutrients is considered an important part of the chemical and biological processes attributed to seagrass communities. This paradigm was based on work in temperate regions on Zostera marina and in tropical regions on Thalassia testudinum, two species that maintain relatively high biomass, stable meadows. The current study investigates this concept for three species of intertidal tropical seagrass meadows in northeastern Australia. Sediment structure and nutrient status did not differ between vegetated and unvegated habitats in intertidal areas within the central region of the Great Barrier Reef World Heritage Area. The 'trapping' functions that have been attributed to seagrasses need to be re-assessed for a variety of locations and species before they can be accepted as dogma. In tropical Australia, intertidal meadows are predominantly ephemeral and comprised of structurally small species of low biomass. Consequently, sediment trapping within these meadows is largely insignificant.

Spatio-temporal evaluation of neck muscle activation during postural perturbations in healthy subjects

The purpose of this study was to examine the spatio-temporal activation of the sternocleidomastoid (SCM) and cervical extensor (CE) muscles with respect to the deltoid muscle onset during rapid voluntary upper limb movement in healthy volunteers. The repeatability and reliability of the spatio-temporal aspects of the myoelectric signals were also examined. Ten subjects performed bilateral and unilateral rapid upper limb flexion, abduction and extension in response to a visual stimulus. EMG onsets and normalised root mean square (nRMS) values were calculated for the SCM and CE muscles. Subjects attended three testing sessions over non-consecutive days allowing the repeatability and reliability of these measures to be assessed. The SCM and CE muscles demonstrated feed-forward activation (activation within 50 ms of deltoid onset) during rapid arm movements in all directions. The sequence and magnitude of neck muscle activation displayed directional specificity, however, the neck flexor and extensor muscles displayed co-activation during all perturbations. EMG onsets demonstrated high repeatability in terms of repeated measure precision (nSEM in the range 1.9-5.7%). This was less evident for the repeatability of nRMS values. The results of this study provide a greater understanding of cervical neuromotor control strategies. During bilateral and unilateral upper limb perturbations, the SCM and CE muscles demonstrate feed-forward co-activation. It seems apparent that feed-forward activation of neck muscles is a mechanism necessary to achieve stability for the visual and vestibular systems, whilst ensuring stabilisation and protection of the cervical spine. (C) 2004 Elsevier Ltd. All rights reserved.

Trends for in situ and invasive melanoma in Queensland, Australia, 1982-2002

Objectives Queensland, the north-eastern state of Australia, has the highest incidence of melanoma in the world. Control measures started earlier here than probably anywhere else in the world; early detection programmes started in the 1960s and primary prevention in the 1980s. Data from the population-based Queensland Cancer Registry therefore provide an internationally unique data source with which to assess trends for in situ and invasive melanomas and to consider the implications for early detection and primary prevention. Methods We used Poisson regression to estimate the annual percentage change in rates across 21 years of incidence data for in situ and invasive lesions, stratified by age and sex. Joinpoint analyses were used to assess whether there had been a statistically significant change in the trends. Results In situ melanomas increased by 10.4% (95% CI: 10.1%, 11.1%) per year among males and 8.4% (7.9%, 8.9%) per year among females. The incidence of invasive lesions also increased, but not as quickly; males 2.6% (2.4%, 2.8%), females 1.2% (0.9%, 1.5%). Valid data on thickness was only available for 1991 to 2002 and for this period thin-invasive lesions were increasing faster than thick-invasive lesions (for example, among males: thin 3.8%, thick 2.0%). We found some suggestive evidence of lower proportionate increase for the most recent years for both in-situ and invasive lesions, but this did not achieve statistical significance. Among people younger than 35 years, the incidence of invasive melanoma was stable and there was a suggestion of a birth cohort effect from about 1958. Mortality rates were stable across all ages, and there was a suggestion of decreasing rates among young women, although this did not achieve statistical significance. Conclusion Age-standardised incidence is continuing to increase and this, in combination with a shift to proportionately more in situ lesions, suggests that the stabilisation of mortality rates is due, in large part, to earlier detection. For primary prevention, after a substantial period of sustained effort in Queensland, there is some suggestive, but not definitive, evidence that progress is being made. Incidence rates are stabilising in those younger than 35 years and the proportionate increase for both in situ and invasive lesions appears to be lower for the most recent period compared with previous periods. However, even taking the most favourable view of these trends, primary prevention is unlikely to lead to decreases in the overall incidence rate of melanoma for at least another 20 years. Consequently, the challenge for primary prevention programmes will be to maintain momentum over the long term. If this can be achieved, the eventual public-health benefits are likely to be substantial.