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Most of the previous studies on the effects of iron deficiency on skeletal muscle respiratory capacity and work performance have been investigated in severe or moderate iron-deficiency anemia. We report here that even in mild iron deficiency where the hemoglobin concentration was 10 g/dl and the iron stores in livers and spleen were not completely depleted, a marked reduction in succinate dehydrogenase was observed in skeletal muscles but not in heart. Similarly, cytochrome oxidase activities were reduced. Although no significant change in glycerophosphate dehydrogenase was detected in the iron-deficient rats, exposure to cold in this group greatly reduced this enzyme activity. As cold acclimatization accelerates marrow erythropoiesis (20) which in turn, demands more iron, it seems that in the iron-insufficient state, this iron demand for marrow activity may persist at the expense of the tissue iron pool, resulting in a marked reduction in glycerophosphate dehydrogenase activities. Since succinate dehydrogenase plays a significant role in the impairment of mitochondrial function and early fatigue of iron-deficient muscle (11), the present study shows that even in mild iron deficiency, some loss of muscle functions could result as succinate dehydrogenase activities were greatly reduced. 相似文献
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X. M. Zhou P. H.-S. Jen 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2000,186(4):389-398
This study examines the role of neural inhibition in auditory spatial selectivity of inferior collicular neurons of the big
brown bat, Eptesicus fuscus, using a two-tone inhibition paradigm. Two-tone inhibition decreases auditory spatial response areas but increases the slopes
of directional sensitivity curves of inferior collicular neurons. Inferior collicular neurons have either directionally-selective
or hemifield directional sensitivity curves. A directionally-selective curve always has a peak which is at least 50% larger
than the minimum. A hemifield directional sensitivity curve rises from an ipsilateral angle by more than 50% and either reaches
a plateau or declines by less than 50% over a range of contralateral angles. Two-tone inhibition does not change directionally-selective
curves but changes most hemifield directional sensitivity curves into directionally-selective curves. Auditory spatial selectivity
determined both with and without two-tone inhibition increases with increasing best-excitatory frequency. Sharpening of auditory
spatial selectivity by two-tone inhibition is larger for neurons with smaller differences between excitatory and inhibitory
best frequencies. The effect of two-tone inhibition on auditory spatial selectivity increases with increasing inhibitory tone
intensity but decreases with increasing intertone interval. The implications of these findings in bat echolocation are discussed.
Accepted: 18 January 2000 相似文献
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Four Indica and five Japonica varieties of rice (Oryza sativa L.) were examined to elucidate their differences in photosynthetic activity and dark respiratory rate as influenced by leaf nitrogen levels and temperatures. The photosynthetic rates of single leaf showed correlations with total nitrogen and soluble protein contents in the leaves. Respiratory rate was also positively correlated with the leaf nitrogen content. When compared at the same level of leaf nitrogen or soluble protein content, the four Indica varieties and one of Japonica varieties, Tainung 67, which have some Indica genes derived from one of its parents, showed higher photosynthetic rates than the remaining four Japonica varieties. At the same photosynthetic rate, the Indica varieties showed lower respiratory rate than Japonica varieties. When the leaf temperature rose from 20°C to 30°C, the photosynthetic rate increased by 18 to 41%, whereas the respiratory rate increased by 100 to 150%. These increasing rates in response to temperature were higher in the Japonica than in the Indica varieties. In this respect, Tainung 67 showed the same behavior as of the other four Japonica varieties.Abbreviations 30/20 ratios
the ratios of photosynthetic and respiratory rates at 30°C to those at 20°C 相似文献
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Specific interaction of vinculin with alpha-actinin 总被引:33,自引:0,他引:33
D H Wachsstock J A Wilkins S Lin 《Biochemical and biophysical research communications》1987,146(2):554-560
Vinculin and alpha-actinin are cytoskeletal proteins present at focal contacts of the ventral surface of cultured fibroblasts. We labelled alpha-actinin with an acceptor fluorophore and vinculin with a donor. A mixture of vinculin and alpha-actinin showed a 28% quench, due to energy transfer, suggesting an interaction. Quench of vinculin was dependent on the concentration of alpha-actinin; Scatchard analysis gives a dissociation constant in the microM range. Quench was inhibited by excess unlabelled alpha-actinin, and by reaction of the acceptor protein with p-chloromercuribenzoate. We found that vinculin had a slightly greater elution volume in a gel filtration column equilibrated with alpha-actinin, indicating a higher effective Stokes radius due to the interaction of the two proteins. 相似文献
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