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Metabolism Rate (metabolism + rate)

Distribution by Scientific Domains

Life Sciences	80%

Selected Abstracts

Insight into the Metabolism Rate of Quinone Analogues from Molecular Dynamics Simulation and 3D-QSMR Methods

CHEMICAL BIOLOGY & DRUG DESIGN, Issue 4 2007
Hai-Feng Chen
Molecular dynamics simulation was applied to investigate the metabolism mechanism for quinone analogues. Favourable hydrogen bonds between ligand and NQO1, and parallel orientation between ligand and flavin adenine dinucleotide could explain the difference of metabolism rate (in ,mol/min/mg) for quinone analogues. This is consistent with the experimental observation (Structure 2001;9:659,667). Then Support Vector Machines was used to construct quantitative structure,metabolism rate model. The model was evaluated by 14 test set compounds. Some descriptors selected by Support Vector Machine, were introduced into standard fields of three-dimensional quantitative structure,metabolism relationship to improve the statistical parameters of three-dimensional quantitative structure,metabolism relationship models. The results show that the inclusion of highest occupied molecular orbital and lowest unoccupied molecular orbital is meaningful for three-dimensional quantitative structure,metabolism relationship models. These in silico absorption, distribution, metabolism and excretion models are helpful in making quantitative prediction of their metabolic rates for new lead compounds before resorting in vitro and in vivo experimentation. [source]

The effect of long-term exercise on glucose metabolism and peripheral insulin sensitivity in Standardbred horses

EQUINE VETERINARY JOURNAL, Issue S36 2006
E. de GRAAF-ROELFSEMA
Summary Reasons for performing study: To study the possible long-term effect of improved glucose tolerance in horses after long-term training, as the impact of exercise training on glucose metabolism is still unclear in the equine species. It is not known whether there is a direct long-term effect of training or if the measurable effect on glucose metabolism is the residual effect of the last exercise session. Objectives: To determine the chronic effect on glucose metabolism and peripheral insulin sensitivity of long-term training in horses by use of the euglycaemic hyperinsulinaemic clamp technique. Methods: Eleven Standardbred horses were acclimatised to running on the high-speed treadmill for 4 weeks (Phase 1) followed by training for 18 weeks with an alternating endurance (, 60% HRmax) high intensity training programme (, 80% HRmax) (Phase 2). Training frequency was 4 days/week. At the end of Phase 1, a euglycaemic hyperinsulinaemic clamp was performed 72 h after the last bout of exercise in all horses. At the end of Phase 2, the horses were clamped 24 h or 72 h after the last bout of exercise. Results: Glucose metabolism rate did not change significantly after 18 weeks of training, measured 72 h after the last exercise bout (0.018 ± 0.009 and 0.022 ± 0.006 mmol/kg bwt/min, respectively). Peripheral insulin sensitivity also did not change significantly following training (7.6 ± 5.7 times 10,6 and 8.0 ± 3.1 times 10,6, respectively). The same measurements 24 h after the last bout of exercise showed no significant differences. Conclusions: Results indicated that long-term training in Standardbreds neither changed glucose metabolism or insulin sensitivity 72 h after the last bout of exercise. Potential relevance: The fact that the beneficial effect of increased insulin sensitivity after acute exercise diminishes quickly in horses and no long-term effects on insulin sensitivity after chronic exercise have as yet been found in horses, implies that exercise should be performed on a regular basis in horses to retain the beneficial effect of improved insulin sensitivity. [source]

Insight into the Metabolism Rate of Quinone Analogues from Molecular Dynamics Simulation and 3D-QSMR Methods

Annual cycle and inter-annual variability of gross primary production and ecosystem respiration in a floodprone river during a 15-year period

FRESHWATER BIOLOGY, Issue 5 2006
URS UEHLINGER
Summary 1. Temporal variation in ecosystem metabolism over a 15-year period (1986,2000) was evaluated in a seventh order channelised gravel bed river (mean annual discharge 48.7 m3 s,1) of the Swiss Plateau. The river is subject to frequent disturbance by bed-moving spates. Daily integrals of gross primary production (GPP) and ecosystem respiration (ER) were calculated based on single-station diel oxygen curves. 2. Seasonal decomposition of the time series of monthly metabolism rates showed that approximately 50% of the variation of GPP and ER can be attributed to season. Annual GPP averaged 5.0 ± 0.6 g O2 m,2 day,1 and showed no long-term trend. 3. Ecosystem respiration, averaging 6.2 ± 1.4 g O2 m,2 day,1, declined from 8.8 to 4.1 g O2 m,2 day,1 during the 15-year period. This significant trend paralleled a decline in nitrate and soluble reactive phosphorus concentrations, and the biochemical oxygen demand discharged by sewage treatment facilities upstream of the study reach. The ratio of GPP to ER (P/R) increased from 0.53 to about 1 as consequence of ER reduction. 4. Bed moving spates reduced GPP by 49% and ER by 19%. Postspate recovery of GPP was rapid between spring and autumn and slow during winter. Recovery of ER lacked any seasonal pattern. Annual patterns of daily GPP and to a minor extent of daily ER can be described as a sequence of recovery periods frequently truncated by spates. 5. The study showed that disturbance by frequent bed-moving spates resulted in major stochastic variation in GPP and ER but annual patterns were still characterised by a distinct seasonal cycle. It also became evident that stream metabolism is a suitable method to assess effects of gradual changes in water quality. [source]

Whole ecosystem metabolic pulses following precipitation events

FUNCTIONAL ECOLOGY, Issue 5 2008
G. D. Jenerette
Summary 1Ecosystem respiration varies substantially at short temporal intervals and identifying the role of coupled temperature- and precipitation-induced changes has been an ongoing challenge. To address this challenge we applied a metabolic ecological theory to identify pulses in ecosystem respiration following rain events. Using this metabolic framework, precipitation-induced pulses were described as a reduction in metabolic activation energy after individual precipitation events. 2We used this approach to estimate the responses of 237 individual events recorded over 2 years at four eddy-covariance sites in southern AZ, USA. The sites varied in both community type (woody and grass dominated) and landscape position (riparian and upland). We used a nonlinear inversion procedure to identify both the parameters for the pre-event temperature sensitivity and the predicted response of the temperature sensitivity to precipitation. By examining multiple events we evaluated the consistency of pulses between sites and discriminated between hypotheses regarding landscape position, event distributions, and pre-event ecosystem metabolism rates. 3Over the 5-day post-event period across all sites the mean precipitation effect was attributed to 6·1 g CO2 m,2 of carbon release, which represented a 21% increase in respiration over the pre-event steady state trajectory of carbon loss. Differences in vegetation community were associated with differences in the integrated magnitude of pulse responses, while differences in topographic position were associated with the initial peak pulse rate. In conjunction with the differences between sites, the individual total pulse response was positively related to the drying time interval and metabolic rates prior to the event. The quantitative theory presented provides an approach for understanding ecosystem pulse dynamics and helps characterized the dependence of ecosystem metabolism on both temperature and precipitation. [source]