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141.
142.
Paradoxical helium and sulfur hexafluoride single-breath washouts in short-term vs. sustained microgravity 总被引:1,自引:0,他引:1
Lauzon Anne-Marie; Prisk G. Kim; Elliott Ann R.; Verbanck Sylvia; Paiva Manuel; West John B. 《Journal of applied physiology》1997,82(3):859-865
Lauzon, Anne-Marie, G. Kim Prisk, Ann R. Elliott, SylviaVerbanck, Manuel Paiva, and John B. West. Paradoxical helium andsulfur hexafluoride single-breath washouts in short-term vs. sustainedmicrogravity. J. Appl. Physiol. 82(3):859-865, 1997.During single-breath washouts in normal gravity (1 G), the phase III slope of sulfur hexafluoride(SF6) is steeper than that ofhelium (He). Two mechanisms can account for this:1) the higher diffusivity of Heenhances its homogeneous distribution; and2) the lower diffusivity ofSF6 results in a more peripherallocation of the diffusion front, where airway asymmetry is larger.These mechanisms were thought to be gravity independent. However, weshowed during the Spacelab Life Sciences-2 spaceflight that insustained microgravity (µG) theSF6-to-He slope difference isabolished. We repeated the protocol during short periods (27 s) of µG(parabolic flights). The subjects performed a vital-capacityinspiration and expiration of a gas containing 5% He-1.25%SF6-balanceO2. As in sustained µG, thephase III slopes of He and SF6decreased. However, during short-term µG, theSF6-to-He slope differenceincreased from 0.17 ± 0.03%/l in 1 G to 0.29 ± 0.06%/l inµG, respectively. This is contrary to sustained µG, in which theSF6-to-He slope difference decreased from 0.25 ± 0.03%/l in 1 G to 0.01 ± 0.06%/lin µG. The increase in phase III slope difference in short-term µGwas caused by a larger decrease of He phase III slope compared with that in sustained µG. This suggests that changes in peripheral gasmixing seen in sustained µG are mainly due to alterations in thediffusive-convective inhomogeneity of He that require >27 s of µGto occur. Changes in pulmonary blood volume distribution or cardiogenicmixing may explain the differences between the results found inshort-term and sustained µG. 相似文献
143.
Darquenne Chantal; Brand Peter; Heyder Joachim; Paiva Manuel 《Journal of applied physiology》1997,83(3):966-974
Darquenne, Chantal, Peter Brand, Joachim Heyder, and ManuelPaiva. Aerosol dispersion in human lung: comparison between numerical simulations and experiments for bolus tests.J. Appl. Physiol. 83(3): 966-974, 1997.Bolus inhalations of 0.87-µm-diameter particles wereadministered to 10 healthy subjects, and data were compared withnumerical simulations based on a one-dimensional model of aerosoltransport and deposition in the human lung (J. Appl.Physiol. 77: 2889-2898, 1994). Aerosol boluseswere inhaled at a constant flow rate into various volumetric lungdepths up to 1,500 ml. Parameters such as bolus half-width, mode shift, skewness, and deposition were used to characterize the bolus and todisplay convective mixing. The simulations described the experimental results reasonably well. The sensitivity of the simulations to different parameters was tested. Simulated half-width appeared to beinsensitive to altered values of the deposition term, whereas it wasgreatly affected by modified values of the apparent diffusion in thealveolar zone of the lung. Finally, further simulations were comparedin experiments with a fixed penetration volume and various flow rates.Comparison showed good agreement, which may be explained by the factthat half-width, mode shift, and skewness were little affected by theflow rate. 相似文献
144.
C. H. S. Carvalho N. Bohorova P. N. Bordallo L. L. Abreu F. H. Valicente W. Bressan E. Paiva 《Plant cell reports》1997,17(1):73-76
A total of 113 maize inbreds adapted to tropical conditions were evaluated for their tissue culture response. Additionally,
four media combinations of 15 or 30 μm dicamba with or without 88 μm AgNO3 were used to study the effect of dicamba and AgNO3 on type II callus production and plant regeneration from 42 of the inbred lines. Inbreds 48, 389 and 1345 of the populations
BR 105, BR 112, and Catete, respectively, showed a high capacity for type II callus production and plant regeneration. The
production of type II calli increased significantly when the concentration of dicamba was changed from 15 to 30 μm and when AgNO3 was added to the medium. A synergistic effect between 88 μm AgNO3 and 30 μm dicamba (CM-30Ag medium) was observed, leading to additional production of type II callus. Medium CM-30Ag allowed the best
tissue culture performance and plant regeneration capacity.
Received: 5 October 1996 / Revision received: 21 April 1997 / Accepted: 9 May 1997 相似文献
145.
To determine the extent of the role that gravity plays in dispersion and deposition during breath holds, we performed aerosol bolus inhalations of 1-microm-diameter particles followed by breath holds of various lengths on four subjects on the ground (1G) and during short periods of microgravity (microG). Boluses of approximately 70 ml were inhaled to penetration volumes (V(p)) of 150 and 500 ml, at a constant flow rate of approximately 0.45 l/s. Aerosol concentration and flow rate were continuously measured at the mouth. Aerosol deposition and dispersion were calculated from these data. Deposition was independent of breath-hold time at both V(p) in microG, whereas, in 1G, deposition increased with increasing breath hold time. At V(p) = 150 ml, dispersion was similar at both gravity levels and increased with breath hold time. At V(p) = 500 ml, dispersion in 1G was always significantly higher than in microG. The data provide direct evidence that gravitational sedimentation is the main mechanism of deposition and dispersion during breath holds. The data also suggest that cardiogenic mixing and turbulent mixing contribute to deposition and dispersion at shallow V(p). 相似文献
146.
The objective was to evaluate total serum bile acids (SBA) as a biological marker of hepatotoxicity in car painters exposed to organic solvents and to compare their performance with classic biochemical parameters of liver function. SBA were analysed in a selected group of workers (n=57) occupationally exposed to a mixture of organic solvents and in a control group (n=51). In addition, aspartate aminotransferase (AST), alanine aminotransferase (ALT), total bilirubin (TB), gamma-glutamyltransferase (GGT) and alkaline phosphatase (ALP) were determined in the two groups. Urinary hippuric acid was measured in all samples. Statistical analysis of the data revealed a significant increase in the concentration of SBA, AST, ALP and TB in exposed workers compared with controls (Mann-Whitney, p=0.05). However, SBA was the parameter most frequently altered in exposed workers and showed higher significance between the two groups (chi-square test) compared with the upper limit of the reference range (8 micromol l(-1)). In conclusion, SBA can be considered to be a sensitive parameter of hepatotoxicity induced by organic solvents than the traditional tests and it can be used as an biological marker of subclinical liver injury. 相似文献
147.
Evidence for low‐level hybridization between two allochronic populations of the pine processionary moth,Thaumetopoea pityocampa (Lepidoptera: Notodontidae)
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Christian Burban Mathieu Gautier Raphael Leblois Julie Landes Helena Santos Maria‐Rosa Paiva Manuela Branco Carole Kerdelhue 《Biological journal of the Linnean Society. Linnean Society of London》2016,119(2):311-328
Divergence between populations sharing the same habitat can be initiated by different reproductive times, leading to allochronic differentiation. A spatially localized allochronic summer population (SP) of the pine processionary moth Thaumetopoea pityocampa, recently discovered in Portugal, occurs in sympatry with the local winter population (WP). We examined the level of genetic differentiation between the two populations and estimated the current gene flow within the spatial framework of their co‐occurrence. Mitochondrial data indicated that the two sympatric populations were genetically closer than other WP populations. Conversely, microsatellite genotyping uncovered greater differentiation between the two sympatric populations than between allopatric ones. While male trapping confirmed that reproduction of SP and WP occurred at distinct times, clustering approaches demonstrated the presence of a few LateSP individuals emerging within the WP flight period, although genetically identified as SP. We also identified rare recent hybridization events apparently occurring mainly in the margins of the current SP range. The ongoing gene flow detected between the ancestral and the emerging allochronic populations revealed an incomplete reproductive isolation, which must therefore be taken into account and integrated with studies focussed on ecological drivers, so that a complete understanding of the ongoing speciation process might be achieved. 相似文献
148.
Patrícia Gonçalves‐Souza Eduardo Gomes Gonçalves Elder Antônio Sousa Paiva 《Botanical journal of the Linnean Society. Linnean Society of London》2016,180(2):229-240
Extrafloral nectaries (EFNs) are involved in animal–plant interactions that lead to protection against herbivory. The presence of EFNs in Araceae is rare, besides Philodendron, there is report for only two other genera. With the aim to investigate the occurrence of EFNs in Philodendron and to describe the distribution patterns and structural organization of these glands, 75 Philodendron spp. were examined, 16 of which were selected for study by light microscopy. Three Homalomena spp. were also examined for EFNs, but these were not found. Philodendron martianum was employed as a model for additional study using scanning and transmission electron microscopy. The studied EFNs showed a high degree of structural similarity. They were present in the prophyll, leaf and spathe, becoming functional in young organs. In surface view, EFNs consisted of small areas and showed one or more stomata through which secretions were released. The secretory cells formed a globular region surrounded by ground parenchyma. In P. martianum, nectariferous parenchyma cells exhibited typical features of cells with high metabolism related to nectar secretion. These results allow us to infer that EFNs have a widespread occurrence in Philodendron, and they remain an exclusive character for this group. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2016, 180 , 229–240. 相似文献
149.
Description and Phylogeny of Urostyla grandis wiackowskii subsp. nov. (Ciliophora,Hypotricha) from an Estuarine Mangrove in Brazil
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Thiago da Silva Paiva Chen Shao Noemi Mendes Fernandes Bárbara do Nascimento Borges Inácio Domingos da Silva‐Neto 《The Journal of eukaryotic microbiology》2016,63(2):247-261
Interphase specimens, aspects of physiological reorganization and divisional morphogenesis were investigated in a strain of a hypotrichous ciliate highly similar to Urostyla grandis Ehrenberg, 1830 (type species of Urostyla), collected from a mangrove area in the estuary of the Paraíba do Sul river (Rio de Janeiro, Brazil). The results revealed that albeit interphase specimens match with the known morphologic variability in U. grandis, morphogenetic processes have conspicuous differences. Parental adoral zone is entirely renewed during morphogenesis, and marginal cirri exhibit a unique combination of developmental modes, in which left marginal rows originate from multiple anlagen arising from innermost left marginal cirral row, whereas right marginal ciliature originates from individual within‐row anlagen. Based on such characteristics, a new subspecies, namely U. grandis wiackowskii subsp. nov. is proposed, and consequently, U. grandis grandis Ehrenberg, 1830 stat. nov. is established. Bayesian and maximum‐likelihood analyses of the 18S rDNA unambiguously placed U. grandis wiackowskii as adelphotaxon of a cluster formed by other U. grandis sequences. The implications of such findings to the systematics of Urostyla are discussed. 相似文献
150.