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71.
72.
Dispersed from a dry film into buffer (5 mM phosphate, 0.15 M NaCl, pH 7.4), the liponucleotide 1-β-d-arabinofuranosylcytosine 5′-diphosphate l-1,2-diacylglycerol (ara-CDPdiacylglycerol) spontaneously forms vesicles which are several microns in diameter and probably unilamellar. Their average size immediately begins to decrease, and after 2 h none can be seen in the light microscope. During 1–2 days in unstirred solutions at 25°C, the vesicles are transformed to spherical or nearly spherical micelles having an apparent partial specific volume of 0.835 ml·g?1, a maximum possible aggregation number of about 150, and an anhydrous radius of about 37 Å. The critical micelle concentration (CMC) is about 10 μM in buffer and 20 μM in distilled water, but micelle-monomer equilibration requires at least 1 week at a total concentration of 66 μM. This exceedingly slow equilibration is unique among reported detergents. The standard enthalpy and entropy of micellization are ?13 kJ·mol?1 and 87 J·mol?1·K?1, respectively. These values are within the range reported for other detergents. Sonication accelerates the vesicle-micelle transformation to 30 min. 相似文献
73.
Erythrocytic cell kinetics were studied in normal dog bone marrow, at the transition between younger cells that are able to synthesize DNA, and more mature nucleated normoblasts which have lost this ability. the rate of progression out of the first group was compared to that into the second, after necessary adjustments of group sizes. No significant discrepancy was detected within the limits of resolution of autoradiographic cytokinetic analysis.
It is concluded that 'ineffective' red cell production in the normal dog, if it occurs at all, can only be very small in quantity. 相似文献
It is concluded that 'ineffective' red cell production in the normal dog, if it occurs at all, can only be very small in quantity. 相似文献
74.
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76.
Victor Ambros 《Current biology : CB》2021,31(4):R212-R214
77.
Victor Melnikov Falk Pollehne Natalia Minkina Lidia Melnik 《Journal of fish biology》2021,99(4):1393-1402
Understanding what environmental drivers influence marine predator–prey relationships can be key to managing and protecting ecosystems, especially in the face of future climate change risks. This is especially important in environments such as the Black Sea, where strong biogeochemical gradients can drive marine habitat partitioning and ecological interactions. We used underwater video recordings in the north-eastern Black Sea in November 2013 to observe the distribution and behaviour of the Black Sea sprat (Sprattus sprattus phalericus, Risso 1827) and its zooplankton prey. Video recordings have shown that the Black Sea sprat S. sprattus phalericus tolerates severely hypoxic waters near the redoxcline. The school was distributed in the 33–96 m layer [oxygen concentration (O2) 277–84 μmol L−1]. Some individuals were observed to leave the school and descended 20 m deeper for foraging on copepods in the 119–123 m layer (O2 12–10 μmol L−1). Zooplankton appeared concentrated on the upper boundary of the suboxic zone (O2 < 10 μmol L−1). No zooplankton were observed below O2 6–7 μmol L−1 (128 m). Understanding the ability of this species to tolerate low oxygen waters is crucial to predicting future responses to natural and anthropogenic changes in hypoxia. 相似文献
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79.
N-acetylcysteine Protects Mice from Lethal Endotoxemia by Regulating the Redox State of Immune Cells
The excessive production of reactive oxygen species (ROS) associated with inflammation leads to oxidative stress, which is involved with the high mortality from several diseases such as endotoxic shock and can be controlled to a certain degree by antioxidants. The immune cells use ROS in order to support their functions and, therefore, need adequate levels of antioxidant defenses in order to avoid the harmful effect of an excessive ROS production. In the present work, the effect of the administration of the antioxidant N-acetylcysteine (NAC) on the redox state of peritoneal macrophages and lymphocytes from mice with lethal endotoxic shock (100 mg/kg i.p. of lipopolysaccharide, LPS), was studied. In both types of immune cells at 0, 2, 4, 12 and 24 h after LPS injection, an increase of ROS, of the proinflammatory cytokine tumor necrosis factor alpha (TNFα), the lipid peroxidation (malonaldehyde levels, MDA), inducible nitric oxide synthase (iNOS) expression and the oxidized/reduced glutathione (GSSG/GSH) ratio, as well as a decrease of enzymatic antioxidant defenses, such as superoxide dismutase (SOD) and catalase (CAT) activity, was observed. The injection of NAC (150 mg/kg i.p. at 30 min after LPS injection) decreased the ROS, the TNFα the MDA levels, iNOS expression and the GSSG/GSH ratio, and increased the antioxidant defenses in both macrophages and lymphocytes. Moreover, the NAC treatment prevented the activation of nuclear translocation of the nuclear factor κB (NF-κB), which regulates ROS, inflammatory cytokines and antioxidant levels. Our present results provide evidence that both cell types have a relevant role in the pathogenesis of endotoxic shock, and that NAC, by improving the redox state of these immune cells, could increase mouse survival. Thus, antioxidants could offer an alternative treatment of human endotoxic shock. 相似文献
80.
John S. Driscoll Victor E. Marquez Jacqueline Plowman 《Nucleosides, nucleotides & nucleic acids》2013,32(5-6):1131-1133
Abstract CPE-C is a potent antitumor and antiviral agent. It is active against a variety of preclinical murine and human xenograft tumor models in vivo as well as DNA and RNA viruses in vitro. 相似文献