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C Zinner M Krueger JL Reed M Kohl-Bareis H-C Holmberg B Sperlich 《Biology of sport / Institute of Sport》2016,33(1):71-76
In this study, we tested the hypothesis that breathing hyperoxic air (FinO2 = 0.40) while exercising in a hot environment exerts negative effects on the total tissue level of haemoglobin concentration (tHb); core (Tcore) and skin (Tskin) temperatures; muscle activity; heart rate; blood concentration of lactate; pH; partial pressure of oxygen (PaO2) and carbon dioxide; arterial oxygen saturation (SaO2); and perceptual responses. Ten well-trained male athletes cycled at submaximal intensity at 21°C or 33°C in randomized order: first for 20 min while breathing normal air (FinO2 = 0.21) and then 10 min with FinO2 = 0.40 (HOX). At both temperatures, SaO2 and PaO2, but not tHb, were increased by HOX. Tskin and perception of exertion and thermal discomfort were higher at 33°C than 21°C (p < 0.01), but independent of FinO2. Tcore and muscle activity were the same under all conditions (p > 0.07). Blood lactate and heart rate were higher at 33°C than 21°C. In conclusion, during 30 min of submaximal cycling at 21°C or 33°C, Tcore, Tskin and Tbody, tHb, muscle activity and ratings of perceived exertion and thermal discomfort were the same under normoxic and hyperoxic conditions. Accordingly, breathing hyperoxic air (FinO2 = 0.40) did not affect thermoregulation under these conditions. 相似文献
43.
S. Goss D. Fresneau J. L. Deneubourg J. -P. Lachaud J. Valenzuela-Gonzalez 《Oecologia》1989,80(1):65-69
Summary A model of individual foraging in social insects as presented that formalises the dynamics of foraging and concentrates on the collective rather than the individual benefit, quantifying the relationships between a colony's foraging area, number of foragers and foraging energy budget and the food sources' rate of arrival, disappearance and capture. A series of experiments, in which a number of prey were offered to colonies of the individually foraging antPachycondyla (ex-Neoponera) apicalis confirm the hypotheses implicit in the model and measured the rates of capture and competition. 60 days observation of 3P. apicalis colonies' foraging activity are summarised and used in conjunction with the model to obtain estimations of the density and rate of arrival of available prey in the foraging area. We examine how a colony's foraging benefit may be influenced by its foraging area, the number of foragers, and the forager/non-forager ratio and show that a colony's jocial structure strongly limits its potential foraging benefit. Within these limits,P. apicalis does not appear to be an optimal forager. 相似文献
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Ultrastructural localization of the high molecular weight proteins associated with in vitro-assembled brain microtubules 总被引:51,自引:30,他引:21
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Microtubules isolated from brain extracts by in vitro assembly (1, 19, 23) are composed principally of two tubulins and two high molecular weight proteins (microtubule-associated proteins [MAPS] 1 and 2) (2,5,7,20). Recently, it was demonstrated that in vitro-assembled brain microtubules (neurotubules) are coated with filaments (5, 7) which are similar to the filaments attached to neurotubules in situ (4, 15, 21, 24, 25), and it was suggested that the filaments are composed of the higher molecular weight MAPs (5, 7, 12). In this study, microtubules were assembled in the presence and absence of the MAPs, and thin sections of the microtubules were examined by electron microscopy. The results show that the filaments only occur on microtubules assembled in the presence of the MAPs and it is therefore concluded that the filaments are composed of the high molecular weight MAP's. 相似文献
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Intracavernous injection of 20 μg of prostaglandin E1 (PGE1) was carried out in 130 impotent patients. The erectile response was compared to the results of arteriological investigations including nocturnal penile tumescence and rigidity monitoring (NPTR) in 59 patients. The response of 60 patients positively categorized as exclusively psychogenic or vasculogenic was also compared to the pattern of the response to 80 mg of papaverine observed in a previous study by the same authors. The PGE1 test may not discriminate psychogenic from wholly organic patients since its results are not correlated to those of NPTR. It helps for the screening of vasculogenic impotence. Lack of response or a partly rigid response is consistent with this actiology but is not specific for it. A fully response makes it unlikely. Compared to papaverine, PGE1 induces less non rigid responses in psychogenic patients (15% versus 35% with papaverine) and more fully rigid responses in vasculogenic patients (respectively 12% and 5 %). Consequently the specificity of the PGE1 test is higher but its sensitivity lower than that of papaverine so that there is no clear difference in the effectiveness of the tests. Nevertheless the PGE1 test should be preferred, because it is safer. Prolonged erections occured in only 5 patients, and all ceased spontaneously. However 4 presented severely painful erections. 相似文献
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Self-organized asymmetries in ant foraging: a functional response to food type and colony needs 总被引:9,自引:0,他引:9
The dominant paradigm to explain asymmetries in the spatialdistribution of foraging animals is that they track the spatialheterogeneity of their environment. However, in social insects,endogenous spatial asymmetries can emerge within a uniformenvironment as an outcome from the self-organizing processof trail recruitment. We studied how self-organized asymmetries
contribute to the exploitation of different food sources (carbohydrateor proteins) in colonies of the aphid-tending ant Lasius nigervarying in their nutritional needs (presence or absence ofbrood). Colonies with brood fed on sucrose sources exhibita higher mobilization of foragers than the other experimentalgroups. Foraging patterns differ greatly according to food
type: colonies strongly focus their activity on only one dropletof sucrose, whereas they show a rather homogeneous distributionof foragers between proteinaceous sources. In addition, thepresence of brood in the colony enhances the asymmetry of collectiveforaging for both types of food. These spatial differencesin self-organized foraging patterns allow efficient exploitationof natural resources and play a role in the competitive strategy
of this widespread palearctic ant. 相似文献