The relationship between plasma lactate parameters, W-peak and 1-h cycling performance in women

Purpose: The relationship between six descriptors of lactate increase, peak (V) over dot O-2,W-peak, and 1-h cycling performance were compared in 24 trained, female cyclists (peak (V) over dot O-2 = 48.11 +/- 6.32 mL . kg(-1) . min(-1)). Methods: The six descriptors of lactate increase were: 1) lactate threshold (LT; the power output at which plasma lactate concentration begins to increase above the resting level during an incremental exercise test), 2) LT1 (the power output at which plasma lactate increases by 1 mM or more), 3) LTD (the lactate threshold calculated by the D-max method), 4) LTMOD (the lactate threshold calculated by a modified D-max method), 5) L4 (the power output at which plasma lactate reaches a concentration of 4 mmol-L-1), and 6) LTLOG (the power output at which plasma lactate concentration begins to increase when the log([La-]) is plotted against the log (power output)). Subjects first completed a peak (V) over dot O-2 test on a cycle ergometer. Finger-tip capillary blood was sampled within 30 s of the end of each 3-min stage for analysis of plasma lactate. Endurance performance was assessed 7 d later using a 1-h cycle test (OHT) in which subjects were directed to achieve the highest possible average power output. Results: The mean power output (W) for the OHT (+/- SD) was 183.01 +/- 18.88, and for each lactate variable was: LT (138.54 +/- 46.61), LT1 (179.17 +/- 27.25), LTLOG (143.97 +/- 45.74), L4 (198.09 +/- 33.84), LTD (178.79 +/- 24.07), LTMOD (212.28 +/- 31.75). Average power output during the OHT was more strongly correlated with all plasma lactate parameters (0.61 < r < 0.84) and W-peak (r = 0.81) than with peak (V) over dot O-2 (r = 0.55). The six lactate parameters were strongly correlated with each other (0.54 < r < 0.91) and of the six lactate parameters, LTD correlated best with endurance performance (r = 0.84). Conclusions: It was concluded that plasma lactate parameters and W-peak provide better indices of endurance performance than peak (V) over dot O-2 and that, of the six descriptors of lactate increase measured in this study, LTD is most strongly related to 1-h cycling performance in trained, female cyclists.

Foraging and vein-cutting behaviour of Euploea core corinna (W.S. Macleay) (Lepidoptera : Nymphalidae) caterpillars feeding on latex-bearing leaves

Caterpillars of Euploea core corinna (W. S. Macleay) sever leaf veins prior to feeding on their latex-bearing host plants, which restricts the flow of latex at feeding sites. The severing of leaf veins by insects feeding on latex-bearing plants is commonly referred to as 'sabotaging' and is thought to be an evolved response by the insect to counter the negative effects of feeding on latex-rich leaves. Sabotaging behaviour is described for all instars of E. core corinna, with particular attention given to neonates. Vein cutting by neonate E. core corinna caterpillars can occur within 2 h of hatching, with most caterpillars establishing feeding sites within 10 h. Commonly, first instars cut an are-shaped row of leaf side-veins parallel to the leaf margin, but they may also cut the leaf mid-rib in a fashion similar to older instar larvae. From a sample of 50 E. core corinna larvae, representing all instars, we found that the diameters of the veins cut by caterpillars are closely correlated to larval head width (r=0.90). Through manipulative experiments, we demonstrate for the first time that sabotaging behaviour in neonate caterpillars imposes no detectable short-term physiological costs on those caterpillars.

Historical overfishing and the recent collapse of coastal ecosystems

Ecological extinction caused by overfishing precedes all other pervasive human disturbance to coastal ecosystems, including pollution, degradation of water quality, and anthropogenic climate change. Historical abundances of large consumer species were fantastically large in comparison with recent observations. Paleoecological, archaeological, and historical data show that time lags of decades to centuries occurred between the onset of overfishing and consequent changes in ecological communities, because unfished species of similar trophic level assumed the ecological roles of overfished species until they too were overfished or died of epidemic diseases related to overcrowding. Retrospective data not only help to clarify underlying causes and rates of ecological change, but they also demonstrate achievable goals for restoration and management of coastal ecosystems that could not even be contemplated based on the limited perspective of recent observations alone.

Progress in integrated assessment and modelling

Environmental processes have been modelled for decades. However. the need for integrated assessment and modeling (IAM) has,town as the extent and severity of environmental problems in the 21st Century worsens. The scale of IAM is not restricted to the global level as in climate change models, but includes local and regional models of environmental problems. This paper discusses various definitions of IAM and identifies five different types of integration that Lire needed for the effective solution of environmental problems. The future is then depicted in the form of two brief scenarios: one optimistic and one pessimistic. The current state of IAM is then briefly reviewed. The issues of complexity and validation in IAM are recognised as more complex than in traditional disciplinary approaches. Communication is identified as a central issue both internally among team members and externally with decision-makers. stakeholders and other scientists. Finally it is concluded that the process of integrated assessment and modelling is considered as important as the product for any particular project. By learning to work together and recognise the contribution of all team members and participants, it is believed that we will have a strong scientific and social basis to address the environmental problems of the 21st Century. (C) 2002 Elsevier Science Ltd. All rights reserved.

Spatial bias and temporal lag in tactile space perception

Constructing a veridical spatial map by touch poses at least two problems for a perceptual system. First, as the hand is moved through space, the locations of features may be displaced if there is an uncorrected lag between the moment the hand encounters a feature and the time that feature is encoded on a spatial map. Second, due to the sequential nature of the process, some form of memory, which itself may be subject to spatial distortions, is required for integration of spatial samples. We investigated these issues using a task involving active haptic exploration with a stylus swept back and forth in the horizontal plane at the wrist. Remembered locations of tactile targets were shifted towards the medial axis of the forearm, suggesting a central tendency in haptic spatial memory, while evidence for a displacement of perceived locations in the direction of sweep motion was consistent with processing delays.