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Spatial resource subsidies can alter bottom-up and top-down forces of community regulation across ecosystem boundaries. Most subsidies are temporally variable, and recent theory has suggested that consumer-resource dynamics can be stabilized if the peak timing of a subsidy is desynchronized with that of prey productivity in the recipient ecosystem. However, magnitude of consumer responses per se could depend on the subsidy timing, which may be a critical component for community dynamics and ecosystem processes., The aim of this study was to test (i) whether a recipient consumer (cutthroat trout) responds differently to a resource subsidy occurring early in its growing season than to a subsidy occurring late in the season and, if this is the case, (ii) whether the timing-dependent consumer response has cascading effects on communities and ecosystem functions in streams., To test those hypotheses, we conducted a large-scale field experiment, in which we directly manipulated the timing of augmentation of the terrestrial invertebrates that enter stream (i.e. peak timing of June-August vs. August-October), keeping constant the total amounts of the invertebrates entered., We found large increases in the individual growth rate and population biomass of the cutthroat trout, in response to the early resource pulse, but not to the late pulse. This timing-dependent consumer response cascaded down to reduce benthic invertebrates and leaf breakdown rate, and increased water nutrient concentrations. Furthermore, the early resource pulse resulted in higher maturity rate of the cutthroat trout in the following spring, demonstrating the importance of the subsidy timing on long-term community dynamics via the consumer's numerical response., Our results emphasize the need to acknowledge timing-dependent consumer responses in understanding the effects of subsidies on communities and ecosystem processes. Elucidating the mechanisms by which consumers effectively exploit pulsed subsidies is an important avenue to better understand community dynamics in spatially coupled ecosystems. [ABSTRACT FROM AUTHOR]

Context Recent case reports detail the successful use of temozolomide in the management of aggressive pituitary tumours. O6-methylguanine-DNA methyltransferase (MGMT) is a DNA repair protein that counteracts the effect of temozolomide. Objective To study MGMT expression in pituitary tumours and consider whether MGMT expression is associated with response to temozolomide therapy in aggressive pituitary tumours. Patients We report two patients with aggressive pituitary tumours treated with temozolomide, one who responded to temozolomide and the other who did not. MGMT expression was assessed in a further 88 archived pituitary tumour samples. Design MGMT expression was assessed by immunohistochemistry. MGMT promoter methylation was studied by methylation-specific polymerase chain reaction (MSP), sequencing of MGMT was performed and loss of heterozygosity (LOH) analysis undertaken. Results Low MGMT expression and MGMT promoter methylation were found in the pituitary tumour of the patient who responded to temozolomide. Conversely, high MGMT expression was seen in the patient demonstrating a poor response to temozolomide. Eleven out of 88 archived tumour samples (13%) had low MGMT expression. Prolactinomas were more likely to have low MGMT expression compared with other pituitary tumour subtypes ( P < 0·001). There was no significant difference in MGMT expression between invasive and noninvasive tumours, or between recurrent and nonrecurrent tumours. A significant inverse correlation was found between MGMT expression and promoter methylation ( P = 0·012). Conclusion MGMT expression as assessed by immunohistochemistry may predict response to temozolomide therapy in patients with aggressive pituitary tumours. MGMT promoter methylation is likely to explain low MGMT expression in some, but not all, pituitary tumours. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented related to plasma free metanephrines.

A response by Kristen A. Campbell and colleagues to a letter to the editor regarding their article "The Half-Lives of Plasma Free Metanephrines" in the 2011 issue is presented.