Awake negative pressure reflex response of the genioglossus in OSA patients and normal subjects.

We hypothesized that the response of the genioglossus to negative pressure during wakefulness should be intact in obstructive sleep apnea (OSA) patients despite published evidence showing impairment of the response of palatal muscles (Mortimore IL and Douglas NJ. Am J Respir Crit Care Med 156: 867-873, 1997). Thus the response of the genioglossus to brief nasal negative pressure applications (NPAs) in early inspiration was compared between OSA patients and an age-matched group of normal subjects at two study sites (n = 11 per group in Long Beach, n = 14 per group in Boston). Subjects were studied in the sitting (Long Beach) or supine (Boston) posture, and the genioglossus electromyogram (EMGgg) was measured with an intraoral surface electrode (Long Beach) or intramuscular electrode (Boston). The response of the EMGgg was expressed as the percent change from baseline where the baseline EMGgg was the value at the onset of the NPA. In Long Beach, the EMGgg response was significantly higher in the OSA patients at a lower suction pressure of approximately 10 cmH(2)O (75.2 +/- 8.4 vs. 37.4 +/- 4.0% increase; P < 0.001) but not at a higher suction pressure of approximately 20 cmH(2)O. In Boston, the response in the OSA patients was also greater (107.2 +/- 25.9 vs. 46.3 +/- 8.3%; P < 0.05) at a suction pressure of approximately 13 cmH(2)O. We conclude that the response of the genioglossus to NPA during wakefulness is not impaired in OSA patients compared with normal subjects and is greater at low suction pressures.     

Conditions on the Mexican moulting grounds influence feather colour and carotenoids in Bullock's orioles (Icterus bullockii)

Carotenoid‐based plumage coloration plays a critical role for both inter‐ and intrasexual communication. Habitat and diet during molt can have important consequences for the development of the ornamental signals used in these contexts. When molt occurs away from the breeding grounds (e.g., pre‐alternate molt on the wintering grounds, or stopover molt), discerning the influence of habitat and diet can be particularly important, as these effects may result in important carryover effects that influence territory acquisition or mate choice in subsequent seasons. Several species of songbirds in western North America, including the Bullock's oriole (Icterus bullockii), migrate from the breeding grounds to undergo a complete prebasic (post‐breeding) molt at a stopover site in the region affected by the Mexican monsoon climate pattern. This strategy appears to have evolved several times independently in response to the harsh, food‐limited late‐summer conditions in the arid West, which contrast strongly with the high productivity driven by heavy rains that is characteristic of the Mexican monsoon region. Within this region, individuals may be able to optimize plumage coloration by molting in favourable areas characterized by high resource abundance. We used stable isotope analysis (δ¹³C, δ¹⁵N) to ask whether the diet and molt habitat/location of Bullock's orioles influenced their expression of carotenoid‐based plumage coloration as well as plumage carotenoid content and composition. Bullock's orioles with lower feather δ¹⁵N values acquired more colorful plumage (orange‐shifted hue) but had feathers with lower total carotenoid concentration, lower zeaxanthin concentration, and marginally lower canthaxanthin and lutein concentration. Examining factors occurring throughout the annual cycle are critical for understanding evolutionary and ecological processes. Here, we demonstrate that conditions experienced during a stopover molt, occurring hundreds to thousands of kilometers from the breeding grounds, influence the production of ornamental plumage coloration, which may carryover to influence inter‐ and intrasexual signaling in subsequent seasons.     

New insights into vegetation, climate and fire history of southern Brazil revealed by a 40,000 year environmental record from the State Park Serra do Tabuleiro

The present study reveals palaeoenvironmental changes in the coastal southern Brazilian highlands during the last 39720 b.p., by the means of pollen, charcoal and multivariate data analyses. The isolated mountain range of Serra do Tabuleiro corresponds to the southern distribution limit of many tropical plant species and is therefore sensitive to climate change. Palaeoenvironmental reconstructions from the Ciama 2 core at 860 m a.s.l. indicate that Campos (subtropical grassland) covered extensive areas on the highlands throughout the recorded glacial period, thus suggesting cold and dry climatic conditions. The initial development of the Atlantic rainforest occurred after the glacial period, whereas plant diversity began to increase at the beginning of the Holocene due to climate change towards warmer and wetter conditions. At about 10400 cal. b.p., the Atlantic rainforest started to move over the slopes and Campos retracted. Multivariate data analysis showed a change of vegetation dynamics after 11200 cal. b.p. with the initial development of the Atlantic rainforest continuing until the mid-Holocene. Major vegetation changes, including the further expansion of the Atlantic rainforest and the initial development of the Araucaria forest in the higher regions of the Serra do Tabuleiro, occurred during the late Holocene after about 3600 cal. b.p. These changes reflect higher precipitation levels without an annual dry season. Multivariate data analysis reveals a clearly directional change of vegetation dynamics corresponding to the progressive expansion of the Atlantic rainforest from 3850 to 1600 cal. b.p. A second directional change of vegetation dynamics occurred from 320 to 160 cal. b.p. (a.d. 1630 to 1790) with a further development of the Atlantic rainforest and the partial replacement of Campos by Araucaria forest and Atlantic rainforest. Thereafter, an ecosystem disturbance, which resulted in forest opening, took place. Palaeofires probably did not occur during glacial times, whereas fire events, which were probably caused by Amerindians, were common in the Serra do Tabuleiro region from ca. 10400 until 3600 cal. b.p.     

Spider Trait Assembly Patterns and Resilience under Fire-Induced Vegetation Change in South Brazilian Grasslands

Disturbances induce changes on habitat proprieties that may filter organism''s functional traits thereby shaping the structure and interactions of many trophic levels. We tested if communities of predators with foraging traits dependent on habitat structure respond to environmental change through cascades affecting the functional traits of plants. We monitored the response of spider and plant communities to fire in South Brazilian Grasslands using pairs of burned and unburned plots. Spiders were determined to the family level and described in feeding behavioral and morphological traits measured on each individual. Life form and morphological traits were recorded for plant species. One month after fire the abundance of vegetation hunters and the mean size of the chelicera increased due to the presence of suitable feeding sites in the regrowing vegetation, but irregular web builders decreased due to the absence of microhabitats and dense foliage into which they build their webs. Six months after fire rosette-form plants with broader leaves increased, creating a favourable habitat for orb web builders which became more abundant, while graminoids and tall plants were reduced, resulting in a decrease of proper shelters and microclimate in soil surface to ground hunters which became less abundant. Hence, fire triggered changes in vegetation structure that lead both to trait-convergence and trait-divergence assembly patterns of spiders along gradients of plant biomass and functional diversity. Spider individuals occurring in more functionally diverse plant communities were more diverse in their traits probably because increased possibility of resource exploitation, following the habitat heterogeneity hypothesis. Finally, as an indication of resilience, after twelve months spider communities did not differ from those of unburned plots. Our findings show that functional traits provide a mechanistic understanding of the response of communities to environmental change, especially when more than one trophic level is considered.     

Upper airway muscle responsiveness to rising PCO(2) during NREM sleep.

Although pharyngeal muscles respond robustly to increasing PCO(2) during wakefulness, the effect of hypercapnia on upper airway muscle activation during sleep has not been carefully assessed. This may be important, because it has been hypothesized that CO(2)-driven muscle activation may importantly stabilize the upper airway during stages 3 and 4 sleep. To test this hypothesis, we measured ventilation, airway resistance, genioglossus (GG) and tensor palatini (TP) electromyogram (EMG), plus end-tidal PCO(2) (PET(CO(2))) in 18 subjects during wakefulness, stage 2, and slow-wave sleep (SWS). Responses of ventilation and muscle EMG to administered CO(2) (PET(CO(2)) = 6 Torr above the eupneic level) were also assessed during SWS (n = 9) or stage 2 sleep (n = 7). PET(CO(2)) increased spontaneously by 0.8 +/- 0.1 Torr from stage 2 to SWS (from 43.3 +/- 0.6 to 44.1 +/- 0.5 Torr, P < 0.05), with no significant change in GG or TP EMG. Despite a significant increase in minute ventilation with induced hypercapnia (from 8.3 +/- 0.1 to 11.9 +/- 0.3 l/min in stage 2 and 8.6 +/- 0.4 to 12.7 +/- 0.4 l/min in SWS, P < 0.05 for both), there was no significant change in the GG or TP EMG. These data indicate that supraphysiological levels of PET(CO(2)) (50.4 +/- 1.6 Torr in stage 2, and 50.4 +/- 0.9 Torr in SWS) are not a major independent stimulus to pharyngeal dilator muscle activation during either SWS or stage 2 sleep. Thus hypercapnia-induced pharyngeal dilator muscle activation alone is unlikely to explain the paucity of sleep-disordered breathing events during SWS.