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排序方式: 共有83条查询结果,搜索用时 15 毫秒
1.
Protective effects of manganese, cobalt, nickel, and barium against a calcium paradox in the isolated frog heart 总被引:1,自引:0,他引:1
The effect of inorganic slow channel blockers on the calcium paradox in the frog heart was examined. Addition of the divalent cations of manganese, cobalt, nickel, or barium during calcium depletion protected the frog heart against a calcium paradox. This protective effect was indicated by reduced protein release, maintenance of electrical activity, and recovery of mechanical activity during reperfusion. Tissue calcium determination results showed that in the control paradox in the absence of divalent cations, there is an efflux of calcium from myocardial cells during calcium depletion and a massive influx of calcium during the following reperfusion, leading to a calcium overload. Divalent cations protected frog myocardial cells, when present in the calcium-free perfusion medium, by reducing both calcium efflux during calcium depletion and the massive calcium influx during reperfusion. The effectiveness of the added divalent cations showed a strong dependence upon their ionic radius. The most potent inhibitors of the calcium paradox in the frog heart were the divalent cations having an ionic radius closer to the ionic radius of calcium. These results are discussed in terms of the possible mechanism involved in the protective effect of manganese, cobalt, nickel, and barium. 相似文献
2.
Basile Michaelidis Athanasios Papadopoulos Isidoros Beis 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1990,160(2):201-206
Summary The kinetic properties of PK and PFK were studied in aerobic versus 12-hours anoxic marine worms Hedistae(=Nereis) diversicolor and Diopatra neapolitana and earth worms Allolobophora calliginosa and Eisenia foetida. The total glycogen phosphorylase (a+b) activity and the percentage of active a form were also measured in the marine and earth worms under the same conditions. Anoxia exposure did not result in any significant changes of kinetic parameters of PK and total activities of glycogen phosphorylase from marine worms, but it altered the kinetic characteristics of PFK from H. diversicolor. Chromatographical studies showed that PK from both aerobic and anoxic marine worms is eluted from DEAE-cellulose as a single peak at 50 mM KCl. In contrast to marine worms, however, anoxia caused a marked change in kinetic properties of PK from both earth worms, resulting in a reduction of enzyme affinity for its substrate PEP. In addition, the enzyme existed in both earth worms in two distinct variants eluted from DEAE-cellulose column as peak I and peak II at 50 mM and 150 mM KCl, respectively. The ratio of enzyme units (peak I/peak II) was reduced significantly after 12 h of anoxia, indicating that these two peaks are interconvertible. Anoxia also caused a reduction of total glycogen phosphorylase activity in E. foetida and lowered the percentage of active a form of the enzyme by approximately 50% in both earth worms. Kinetic properties of PFK from both earth worms were not significantly affected by anoxia. However, their low Ka values for F-2,6-P2 imply that this effector may play an important role in PFK control in earth worms under anoxia.Abbreviations
F6P
fructose-6-phosphate
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FBP
fructose-1,6-bisphosphate
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F-2,6-P
fructose-2,6-bisphosphate
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PEP
phosphoenoylpruvate
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PFK
6-phosphofructo-1-kinase (E.C.2.7.1.11)
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PK
pyruvate kinase (E.C.2.7.1.40)
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Pi
inorganic phosphate
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PMSF
phenyl methylsulfonyl fluoride 相似文献
3.
The changes in the activities of the glycolytic enzymes were followed during the development of Ascaris lumbricoides eggs. The maximum catalytic capacities of the major catabolic pathways were estimated from the maximum activities of the nonequilibrium enzymes, and the results are compared with the changes in metabolic rate and the changes in carbohydrate and lipid utilization which occur during development. Although the onset of carbohydrate and lipid utilization was accompanied by an increase in the catalytic capacities of the corresponding pathways, there was no drop in the catalytic capacities of the pathways when the eggs became dormant, nor was there any change when the dormant egg was activited. 相似文献
4.
An auxin-dependent distal organizer of pattern and polarity in the Arabidopsis root 总被引:16,自引:0,他引:16
Sabatini S Beis D Wolkenfelt H Murfett J Guilfoyle T Malamy J Benfey P Leyser O Bechtold N Weisbeek P Scheres B 《Cell》1999,99(5):463-472
Root formation in plants involves the continuous interpretation of positional cues. Physiological studies have linked root formation to auxins. An auxin response element displays a maximum in the Arabidopsis root and we investigate its developmental significance. Auxin response mutants reduce the maximum or its perception, and interfere with distal root patterning. Polar auxin transport mutants affect its localization and distal pattern. Polar auxin transport inhibitors cause dramatic relocalization of the maximum, and associated changes in pattern and polarity. Auxin application and laser ablations correlate root pattern with a maximum adjacent to the vascular bundle. Our data indicate that an auxin maximum at a vascular boundary establishes a distal organizer in the root. 相似文献
5.
Aida M Beis D Heidstra R Willemsen V Blilou I Galinha C Nussaume L Noh YS Amasino R Scheres B 《Cell》2004,119(1):109-120
6.
7.
A deficit in brain serotonin is thought to be associated with deteriorated stress coping behaviour, affective disorders and exaggerated violence. We challenged this hypothesis in mice with a brain-specific serotonin depletion caused by a tryptophan hydroxylase 2 (TPH2) deficiency. We tested TPH2-deficient (Tph2−/–) animals in two social situations. As juveniles, Tph2−/− mice displayed reduced social contacts, whereas ultrasonic vocalizations (USVs) were unchanged within same-sex same-genotype pairings. Interestingly, juvenile females vocalized more than males across genotypes. Sexually naive adult males were exposed to fresh male or female urine, followed by an interaction with a conspecific, and re-exposed to urine. Although Tph2−/− mice showed normal sexual preference, they were hyper-aggressive towards their interaction partners and did not vocalize in response to sexual cues. These results highlight that central serotonin is essential for prosocial behaviour, especially USV production in adulthood, but not for sexual preference. 相似文献
8.
Demirayak S Beis R Karaburun AC Kayagil I Incesu Z Ucucu U 《Journal of enzyme inhibition and medicinal chemistry》2006,21(1):113-118
Some 1,5-diaryl-3-ethoxycarbonyl-2-methylpyrrole derivatives were obtained by reacting 1-aryl-3-ethoxycarbonylpent-1,4-diones and a suitable aniline derivative or sulfanilamide under Paal-Knorr pyrrole synthesis conditions. The cytotoxicity of the compounds was tested and all compounds, except for compound 2 h, showed a time-dependent increase in cytotoxic activity. Analgesic activities of the compounds were determined by using the tail-flick and tail-immersion methods; some of the compounds showed potent analgesic activity. 相似文献
9.
10.
In vivo cell biology: following the zebrafish trend 总被引:5,自引:0,他引:5
A deeper understanding of the mechanisms of cell behavior is essential if we want to comprehend how an organism develops and functions. Changes in cellular processes, including the orientation of cell divisions, cell shape, polarity, differentiation and migration, account for tissue rearrangements during development and homeostasis. The in vivo relevance of in vitro findings is being constantly debated and the need for in vivo systems becoming more pressing. The zebrafish (Danio rerio) might become the vertebrate system of choice for a wide spectrum of biological questions that need to be investigated in vivo at cellular and subcellular resolutions. Here, we discuss some recent studies in which the zebrafish was used to gain insight into cell-biological mechanisms. Although this model system has been predominantly appreciated for its amenability to forward genetics, current advances in imaging technology and an increasing number of transgenic lines are bringing it closer to its full potential. 相似文献