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  • 1985-1989  (6)
  • Maximum oxygen uptake  (3)
  • cactus  (3)
  • 1
    Digitale Medien
    Digitale Medien
    Significance of saguaro cactus alkaloids in ecology ofDrosophila mettleri, a soil-breeding, cactophilic drosophilid (1987)
    Springer
    Journal of chemical ecology 13 (1987), S. 2069-2081 
    Details
    ISSN: 1573-1561
    Schlagwort(e): Drosophila ; D. mojavensis ; D. nigrospiracula ; D. mettleri ; Diptera ; Drosophilidae ; cactus ; alkaloids ; viability ; development ; longevity ; host-plant relationships
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Drosophila mettleri is a soil-breeding, cactophilic drosophilid which lives in the Sonoran Desert. Several chemical constituents of cacti in this region have been identified as having major roles in insect-host plant relationships involvingDrosophila. For example, isoquinoline alkaloids, which are present in senita cactus, have been shown to be toxic to seven of the nine species tested. The two tolerant species areD. pachea, the normal resident, andD. mettleri. Necroses of senita cacti are often used as feeding substrates byD. mettleri adults, but this species has never been reared from senita rots. Soil, which have been soaked by juice from saguaro and cardón rots, are the typical breeding substrates of this species. The tissues of both of these cacti also contain alkaloids, chemically related to those in senita, but at much lower concentrations. Alkaloid concentration in saguaro-soaked soil was found to be 1.4–27 times the average concentration in fresh tissue. Alkaloids were extracted from saguaro tissue and used in tests of larva-to-adult viability, developmental rate, and adult longevity. Elevated concentrations of saguaro alkaloids had no significant effect on the longevity ofD. mettleri, but significantly reduced the longevity ofD. nigrospiracula andD. mojavensis, two nonsoil breeding cactophilic species. Viability and developmental rates of all three species were affected, but the effect onD. nigrospiracula was comparatively greater. It is argued that the adaptations that allowD. mettleri to utilize the saguaro soil niche also convey tolerance to alkaloids present in senita tissue. The ability to utilize senita necroses as feeding substrates represents an ecological advantage to D. mettleri, in that the density of potential feeding sites is increased as compared to species which are more specific in their host-plant relationships.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01012872
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  • 2
    Digitale Medien
    Digitale Medien
    Ecological aspects of cactus triterpene glycosides I. Their effect on fitness components ofDrosophila mojavensis (1989)
    Springer
    Journal of chemical ecology 15 (1989), S. 663-676 
    Details
    ISSN: 1573-1561
    Schlagwort(e): Drosophila ; Diptera ; Drosophilidae ; triterpene glycosides ; cactus ; fitness components ; host-plant relationships
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The effects of pentacyclic triterpene glycosides extracted from agria and organ pipe cacti on three fitness parameters of the cactophilic fruit fly,Drosophila mojavensis were tested. Triterpene glycosides from organ pipe increased development time and reduced larval viability while those from agria produced smaller adults (reduced fecundity). In addition, the microbial communities in the organ pipe saponin media were less dense than those in the media to which agria saponins had been added. The role of cactus triterpene glycosides in the ecology of thisDrosophila species is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01014709
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  • 3
    Digitale Medien
    Digitale Medien
    Coadaptation ofDrosophila and yeasts in their natural habitat (1986)
    Springer
    Journal of chemical ecology 12 (1986), S. 1037-1055 
    Details
    ISSN: 1573-1561
    Schlagwort(e): Drosophila ; Diptera ; Drosophilidae ; yeasts ; cactus ; community ecology ; mutualism ; coadaptation ; evolution ; alkaloids ; fatty acids ; sterols
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The mutualistic interactions of cactophilicDrosophila and their associated yeasts in the Sonoran Desert are studied as a system which has evolved within the framework of their host cactus stem chemistry. Because theDrosophila-yeast system is saphrophytic, their responses are not thought to directly influence the evolution of the host. Host cactus stem chemistry appears to play an important role in determining where cactophilicDrosophila breed and feed. Several chemicals have been identified as being important. These include sterols and alkaloids of senita as well as fatty acids and sterol diols of agria and organpipe cactus. Cactus chemistry appears to have a limited role in directly determining the distribution of cactus-specific yeasts. Those effects which are known are due to unusual lipids of organpipe cactus and triterpene glycosides of agria and organpipe cactus.Drosophilayeast interactions are viewed as mutualistic and can take the form of (1) benefits to theDrosophila by either direct nutritional gains or by detoxification of harmful chemicals produced during decay of the host stem tissue and (2) benefits to the yeast in the form of increased likelihood of transmission to new habitats. Experiments on yeast-yeast interactions in decaying agria cactus provide evidence that the yeast community is coadapted. This coadaptation among yeasts occurs in two manners: (1) mutualistic increases in growth rates (which are independent of the presence ofDrosophila larvae) and (2) stabilizing competitive interactions when growth reaches carrying capacity. This latter form is dependent on larval activity and results in benefits to the larvae present. In this sense, the coadapted yeast community is probably also coadapted with respect to itsDrosophila vector.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01638995
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  • 4
    Digitale Medien
    Digitale Medien
    The effects of dietary manipulation upon the respiratory exchange ratio as a predictor of maximum oxygen uptake during fixed term maximal incremental exercise in man (1989)
    Springer
    European journal of applied physiology 58 (1989), S. 722-727 
    Details
    ISSN: 1439-6327
    Schlagwort(e): Respiratory exchange ratio ; Maximum oxygen uptake ; Dietary manipulation ; Maximal incremental exercise
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary This study examined the effects of dietary manipulation upon the respiratory exchange ratio ( $$R = \dot V_{{\text{CO}}_{\text{2}} } /\dot V_{{\text{O}}_{\text{2}} } $$ ) as a predictor of maximum oxygen uptake ( $$\dot V_{{\text{O}}_{{\text{2}} {\text{max}}} } $$ ). Seven healthy males performed fixed term maximal incremental treadmill exercise after an overnight fast on three separate occasions. The first test took place after the subjects had consumed their normal mixed diet (45±5% carbohydrate (CHO)) for a period of three days. This test protocol was then repeated after three days of a low CHO diet (3±2% CHO), and again after three days of a high CHO diet (61±5% CHO). Respiratory gases were continuously monitored during each test using an online system. No significant changes in mean exercise oxygen uptake ( $$\dot V_{{\text{O}}_{\text{2}} } $$ ), $$\dot V_{{\text{O}}_{{\text{2}} {\text{max}}} } $$ or maximum functional heart rate (FHRmax) were found between tests. Mean exercise carbon dioxide output ( $$\dot V_{{\text{CO}}_{\text{2}} } $$ ) and R were significantly lower than normal after the low CHO diet (bothp〈0.001) and significantly higher than normal after the high CHO diet (bothp〈0.05). Moreover, compared with the normal CHO diet, the R-time relationship during exercise was at all times significantly (p〈0.001) shifted to the right after the low CHO diet, and shifted to the left, being significantly so (p〈0.05) over the final 5 min of exercise, after the high CHO diet. As a result, predictions of $$\dot V_{{\text{O}}_{{\text{2}} {\text{max}}} } $$ based on the R-time relationship were similar to recorded $$\dot V_{{\text{O}}_{{\text{2}} {\text{max}}} } $$ after the normal CHO dietary condition (-1.5±1.9%), but higher after the low CHO diet (+14.8±3.9%,p〈0.001) and lower after the high CHO diet (−7.0±4.5%,p〈0.01). These results indicate that dietary manipulation can significantly affect respiratory gas exchanges during fixed term maximal incremental exercise, and by doing so can significantly influence predictions of $$\dot V_{{\text{O}}_{{\text{2}} {\text{max}}} } $$ based on R.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00637383
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  • 5
    Digitale Medien
    Digitale Medien
    The respiratory $$\dot V_{CO_2 } /\dot V_{O_2 }$$ exchange ratio during maximum exercise and its use as a predictor of maximum oxygen uptake (1988)
    Springer
    European journal of applied physiology 57 (1988), S. 714-719 
    Details
    ISSN: 1439-6327
    Schlagwort(e): Respiratory $$\dot V_{CO_2 } /\dot V_{O_2 }$$ exchange ratio ; Incremental exercise ; Treadmill ; Maximum oxygen uptake ; Prediction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The purpose of this study was to define carefully the dynamic relationship between oxygen uptake (as% $$\dot V_{O_{2\max } }$$ ) and the respiratory $$\dot V_{CO_2 } /\dot V_{O_2 }$$ exchange ratio (R) during maximum progressive treadmill exercise in trained and untrained men, and to determine if this relationship could be used to predict $$\dot V_{{\text{O}}_{{\text{2max}}} } $$ . Respiratory gases were continuously monitored and the % $$\dot V_{{\text{O}}_{{\text{2max}}} } $$ /R time profile calculated at 15 sec intervals over the final 5 min of each test. Young sedentary men (controls,n = 122) and over −60y sedentary men (n = 30) shared the same % $$\dot V_{{\text{O}}_{{\text{2max}}} } $$ /R relationship but the latter group had lower R values at $$\dot V_{{\text{O}}_{{\text{2max}}} } $$ (1.06±0.03 vs 1.08±0.03,P〈0.01) than controls. Endurance trained men (n = 45) had a lower % $$\dot V_{{\text{O}}_{{\text{2max}}} } $$ /R relationship and higher R at $$\dot V_{O_{2\max } }$$ (1.11±0.02,P〈 0.001), team athletes (n = 98) had a lower% $$\dot V_{O_{2\max } }$$ /R relationship but lower R at $$\dot V_{O_{2\max } }$$ (1.06±0.03,P〈0.001) and the weight trained (n = 19) had a higher% $$\dot V_{O_{2\max } }$$ /R relationship and lower R at $$\dot V_{O_{2\max } }$$ (1.01±0.02,P〈 0.001) all compared to controls. From the % $$\dot V_{O_{2\max } }$$ /R time profile, the following formulae were devised for the estimation of $$\dot V_{O_{2\max } }$$ ( $$\dot V_{O_{2\max } }$$ R): Young Sedentary, $$\dot V_{O_{2\max } }$$ R = $$\dot V_{O_2 }$$ R (3.000 −1.874 R); Over −60y Sedentary, $$\dot V_{O_{2\max } }$$ R = $$\dot V_{O_2 }$$ R (3.457-2.345 R); Endurance Trained, $$\dot V_{O_{2\max } }$$ = $$\dot V_{O_2 }$$ R (1.980–0.912 R); Team Athletes, $$\dot V_{O_{2\max } }$$ R = $$\dot V_{O_2 }$$ R (2.805−1.726 R); Weight Trained, $$\dot V_{O_{2\max } }$$ R = $$\dot V_{O_2 }$$ R (4.236−3.191 R). Comparison of recorded $$\dot V_{O_{2\max } }$$ and the estimated $$\dot V_{O_{2\max } }$$ R values showed no significant differences in any of the groups examined (r = 0.89–0.90,p〈 0.001). These results suggest the R response to maximum incremental exercise may be influenced by different types of physical training, and that specific formulae derived from the % $$\dot V_{O_{2\max } }$$ /R relationship can provide a precise estimate of $$\dot V_{O_{2\max } }$$ for individuals.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01075993
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  • 6
    Digitale Medien
    Digitale Medien
    The effects of previous severe exercise upon the respiratory $$\dot V_{CO_2 } /\dot V_{O_2 }$$ exchange ratio as a predictor of maximum oxygen uptake (1988)
    Springer
    European journal of applied physiology 57 (1988), S. 720-725 
    Details
    ISSN: 1439-6327
    Schlagwort(e): Respiratory $$\dot V_{CO_2 } /\dot V_{O_2 }$$ exchange ratio ; Maximum oxygen uptake ; Maximum exercise ; Prediction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The present study examined the effect of previous severe exercise upon (i) respiratory exchange during maximal exercise, and (ii) the respiratory $$\dot V_{CO_2 } /\dot V_{O_2 }$$ exchange ratio (R) as a predictor of maximum oxygen uptake ( $$\dot V_{O_{2\max } }$$ )- Thirteen healthy males performed a progressive treadmill test to $$\dot V_{O_{2\max } }$$ : at rest (T1); after a 1 h run on the level treadmill at a speed corresponding 82.4±7.3% of their $$\dot V_{O_{2\max } }$$ (T2); after 1 h recovery (T3); and after 24 h recovery (T4). Respiratory gases were continuously monitored. No changes in average work $$\dot V_{O_2 }$$ , $$\dot V_{O_{2\max } }$$ or maximum heart rate were found between trials. Average work $$\dot V_{CO_2 }$$ was lower in T2 (2.055±0.093 l·min−1,p〈0.001), T3 (2.080±0.087 l·min−1,p〈0.001) and T4 (2.337±0.154 l·min−1, NS) compared with T1 (2.360±0.147 l·min−1). This resulted in lower average R values in T2 (0.81±0.02,P〈0.001), T3 (0.83±0.02,P〈0.001) and T4 (0.94±0.02, NS) in relation to T1 (0.95±0.02). Analysis of the % $$\dot V_{O_{2\max } }$$ /R relationship over the final 5 min of each test showed a shift to the left during T2 (p〈0.001), T3 (p〈0.001) and T4 (NS) compared with T1. As a result predictions of $$\dot V_{O_{2\max } }$$ based on R ( $$\dot V_{O_{2\max } }$$ R) were similar to recorded $$\dot V_{O_{2\max } }$$ in T1 (+0.6%) and T4 (+2.2%). But higher in T2 (+8.7%,p〈0.001) and T3 (+6.9%,p〈0.001). The present results show that previous severe exercise can significantly affect respiratory exchange at rest and during maximum incremental exercise, and by doing so can significantly influence predictions of $$\dot V_{O_{2\max } }$$ based on R.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01075994
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