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151.
Inorganic iron rarely exceeds 10−4 molar concentration in the stomach after a meal. Natural sugars, ascorbic acid, citric acid, and amino-acids form iron complexes, and if they are present in the meal complexing occurs when the gastric contents are neutralized. In their absence an iron complex is formed with gastric mucopolysaccharide, which acts as a carrier, stable at neutral pH. Iron can be detached from this carrier at neutral pH by some low molecular weight substances, of which citric acid, ascorbic acid, and cysteine are particularly effective at low concentrations. Under normal circumstances most of the iron released from food in the stomach becomes bound to the mucopolysaccharide carrier. 相似文献
152.
Gretchen A Casazza Kevin A Jacobs Sang-Hoon Suh Benjamin F Miller Michael A Horning George A Brooks 《Journal of applied physiology》2004,97(1):302-309
We examined the effects of menstrual cycle phase and oral contraceptive (OC) use on triglyceride mobilization during 90 min of rest and 60 min of leg ergometry exercise at 45 and 65% peak O(2) uptake (Vo(2 peak)) in eight moderately physically active, eumenorrheic women (24.8 +/- 1.2 yr). Subjects were tested during the follicular phase (FP) and the luteal phase (LP) before OC use and during the inactive phase (IP) and high-dose phase (HP) after 4 complete mo of OC use. Glycerol rate of appearance (R(a)), a measure of triglyceride mobilization, was determined in a 3-h postabsorptive state using a primed constant infusion of [1,1,2,3,3-(2)H]glycerol. Before OC use (BOC), there were no significant differences between FP and LP in any of the variables studied. Dietary composition, exercise patterns, plasma glycerol concentrations, growth hormone concentrations, and exercise respiratory exchange ratio did not change with OC use. However, 4 mo of OC use significantly (P < 0.05) increased glycerol R(a) in HP during exercise at 45% Vo(2 peak) (6.2 +/- 0.2, 6.5 +/- 0.4, and 7.7 +/- 1.1 micromol.kg(-1).min(-1) for BOC, IP, and HP, respectively) and in IP and HP at 65% Vo(2 peak) (6.6 +/- 0.1, 8.2 +/- 0.6, and 8.1 +/- 0.7 micromol.kg(-1).min(-1) for BOC, IP, and HP, respectively). Plasma cortisol concentrations were significantly higher with OC use at rest and during exercise at 45 and 65% Vo(2 peak). In summary, although fluctuations of endogenous ovarian steroids have little effect on triglyceride mobilization, the synthetic ovarian steroids found in OCs increase triglyceride mobilization and plasma cortisol concentrations in exercising women. We conclude that the hierarchy of effects of ovarian steroids and their analogs on triglyceride mobilization in exercising women is as follows: energy flux > OC use > recent carbohydrate nutrition, menstrual cycle effects. 相似文献
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Popper Arthur N. Hawkins Anthony D. Jacobs Fred Jacobson Paul T. Johnson Peter Krebs Justin 《Reviews in Fish Biology and Fisheries》2020,30(4):605-622
Reviews in Fish Biology and Fisheries - Downstream movements of some freshwater fishes, including eels, are adversely affected by the presence of hydroelectric structures and other anthropic... 相似文献
156.
Daniel J. Karst Kevin Ramer Erik H. Hughes Canping Jiang Pieter J. Jacobs Fernie G. Mitchelson 《Biotechnology progress》2020,36(6):e3040
Mammalian cells were grown to high density in a 3,000 L culture using perfusion with hollow fibers operated in a tangential flow filtration mode. The high-density culture was used to inoculate the production stage of a biomanufacturing process. At constant permeate flux operation, increased transmembrane pressures (TMPs) were observed on the final day of the manufacturing batches. Small scale studies suggested that the filters were not irreversibly fouled, but rather exposed to membrane concentration polarization that could be relieved by tangential sweeping of the hollow fibers. Studies were undertaken to analyze parameters that influence the hydrodynamic profile within hollow fibers; including filter area, cell density, recirculation flow rate, and permeate flow rate. Results indicated that permeate flow rate had the greatest influence on modulating TMP. Further evaluation showed a significant decrease in TMP when permeate flow was reduced, and this occurred without any negative effect on cell growth or viability. Hence, a 30% reduction of permeate flow rate was implemented at manufacturing scale. A stable operation was achieved as TMP was successfully reduced by 75% while preserving all critical factors for performance in the perfusion bioreactor. 相似文献
157.
Pluymaekers N. A. H. A. Dudink E. A. M. P. Weijs B. Vernooy K. Hartgerink D. E. J. Jacobs J. S. Erküner Ö. Marcks N. G. H. M. van Cauteren Y. J. M. Dinh T. ter Bekke R. M. A. Sels J. E. M. W. Delnoij T. S. R. Geyik Z. Driessen R. G. H. Linz D. K. den Uijl D. W. Crijns H. J. G. M. Luermans J. G. L. M. 《Netherlands heart journal》2021,29(5):255-261
Netherlands Heart Journal - The current standard of care for acute atrial fibrillation (AF) focuses primarily on immediate restoration of sinus rhythm by cardioversion, although AF often terminates... 相似文献
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Frigeir Grímsson Silvia Ulrich Mario Coiro Shirley A. Graham Bonnie F. Jacobs Ellen D. Currano Alexandros Xafis Reinhard Zetter 《Ecology and evolution》2021,11(10):5164
Fossil pollen believed to be related to extant Hagenia abyssinica were discovered in the early Miocene (21.73 Ma) Mush Valley paleoflora, Ethiopia, Africa. Both the fossil and extant pollen grains of H. abyssinica were examined with combined light microscopy, scanning electron microscopy, and transmission electron microscopy to compare the pollen and establish their relationships. Based on this, the fossil pollen grains were attributed to Hagenia. The presence of Hagenia in the fossil assemblage raises the questions if its habitat has changed over time, and if the plants are/were wind pollinated. To shed light on these questions, the morphology of extant anthers was also studied, revealing specialized hairs inside the anthers, believed to aid in insect pollination. Pollen and anther morphology are discussed in relation to the age and origin of the genus within a molecular dated phylogenetic framework, the establishment of complex topography in East Africa, other evidence regarding pollination modes, and the palynological record. The evidence presented herein, and compiled from the literature, suggests that Hagenia was an insect‐pollinated lowland rainforest element during the early Miocene of the Mush Valley. The current Afromontane habitat and ambophilous (insect and wind) pollination must have evolved in post‐mid‐Miocene times. 相似文献
160.
R.Y. Kwon C.R. Jacobs 《Computer methods in biomechanics and biomedical engineering》2013,16(4):407-418
We propose a class of microstructurally informed models for the linear elastic mechanical behaviour of cross-linked polymer networks such as the actin cytoskeleton. Salient features of the models include the possibility to represent anisotropic mechanical behaviour resulting from anisotropic filament distributions, and a power law scaling of the mechanical properties with the filament density. Mechanical models within the class are parameterized by seven different constants. We demonstrate a procedure for determining these constants using finite element models of three-dimensional actin networks. Actin filaments and cross-links were modelled as elastic rods, and the networks were constructed at physiological volume fractions and at the scale of an image voxel. We show the performance of the model in estimating the mechanical behaviour of the networks over a wide range of filament densities and degrees of anisotropy. 相似文献