Upright LBPP application attenuates elevated postexercise resting thresholds for cutaneous vasodilation and sweating.

We evaluated postexercise venous pooling as a factor leading to previously reported increases in the postexercise esophageal temperature threshold for cutaneous vasodilation (ThVD) and sweating (ThSW). Six subjects were randomly exposed to lower body positive pressure (LBPP) and to no LBPP after an exercise and no-exercise treatment protocol. The exercise treatment consisted of 15 min of upright cycling at 65% of peak oxygen consumption, and the no-exercise treatment consisted of 15 min upright seated rest. Immediately after either treatment, subjects donned a liquid-conditioned suit used to regulate mean skin temperature and then were positioned within an upright LBPP chamber. The suit was first perfused with 20 degrees C water to control and stabilize skin and core temperature before whole body heating. Subsequently the skin was heated ( approximately 4.0 degrees C/h) until cutaneous vasodilation and sweating occurred. Forearm skin blood flow and arterial blood pressure were measured noninvasively and were used to calculate cutaneous vascular conductance during whole body heating. Sweat rate response was estimated from a 5.0-cm2 ventilated capsule placed on the upper back. Postexercise ThVD and ThSW were both significantly elevated (0.27 +/- 0.04 degrees C and 0.25 +/- 0.04 degrees C, respectively) compared with the no-exercise trial without LBPP (P < 0.05). However, the postexercise increases in both ThVD and ThSW were reversed with the application of LBPP. Our results support the hypothesis that the postexercise warm thermal responses of cutaneous vasodilation and sweating are attenuated by baroreceptor modulation via lower body venous pooling.     

Stroma-forming endophyte Epichloë glyceriae provides wound-inducible herbivore resistance to its grass host

Fungal endophyte-grass associations are diverse and complex. Some endophytes (e.g. Neotyphodium spp.) reproduce asexually by growing vegetatively into host seeds and many of these vertically-transmitted endophytes form mutualisms with their hosts by providing high levels of alkaloids, such as lolines, that reduce herbivore performance. Additionally, Neotyphodium coenophialum provides wound-inducible herbivore resistance through increased production of lolines. Neotyphodium likely evolved from Epichloë spp. which are sexually reproducing endophytes that are transmitted horizontally to the next host generation through production of stromata (fruiting bodies), which sterilize host grasses. We asked if wound-inducible resistance like that in N . coenophialum also occurs in the ancestral, sexually reproducing Epichloë glyceriae , which infects Glyceria striata . Host grasses were damaged by fall armyworm caterpillars, artificially cut, or left undamaged. An aphid bioassay tested the plant's toxicity to herbivores, expression of lolc (a gene in the loline biosynthesis pathway) was quantified using real-time RT-PCR, and loline concentration was quantified using gas chromatography and mass spectrometry. Artificially-damaged plants supported fewer live aphids, had greater lolc mRNA expression, and greater loline concentration than undamaged plants. Herbivore-damaged plants supported intermediate performance by aphids, low lolc mRNA expression, and minimal loline concentration. Our study is the first to demonstrate sexual endophytes can produce lolines following wounding. This suggests wound-induced responses are ancestral within the Epichloë / Neotyphodium clade and reveals a trait of grass endophytes that may have predisposed them for the evolution of defensive mutualisms with their hosts.