世居及移居高原青少年最大有氧能力的特征

本文报道海拔３４１７ｍ和４２８０ｍ地区世居藏族和移居汉族青少年运动状态下心肺功能的对比研究。结果显示：３４１７ｍ和４２８０ｍ世居藏族的最大氧耗量、无氧阈值及最大心输出量都明显大于汉族,血氧饱和度（Ｓａｏ２）随运动负荷的增加而降低。海拔３４１７ｍ藏、汉族的△Ｓａｏ２分别为７．４６％和１０．０３％,４２８０ｍ处为８．５７％和１３．７５％,最大心率随海拔升高而下降。研究提示,藏族青少年有较高的最大有氧能力,反映了他们对低氧环境的适应优势。     

Pitfalls in the sample preparation and analysis of N-acylethanolamines

N-acylethanolamines (NAEs) are a group of lipid mediators synthesized in response to a number of physiological and pathological stimuli. Because of the low tissue concentrations of NAEs, analyses often include liquid extraction followed by solid-phase extraction and subsequent quantitation by LC/MS or GC/MS. Reported levels of NAEs vary considerably, however, and often no explanation is given for these discrepancies. Brought on by difficulties encountered during method development, the effects of using four different brands of silica-containing solid phase extraction (SPE) columns and five different brands of chloroform for sample preparation were investigated. Considerable variation in the retention and recoveries of seven NAEs and 2-arachidonoylglycerol existed between the SPE columns. Furthermore, it was found that some chloroforms contained quantifiable amounts of N-palmitoylethanolamine and N-stearoylethanolamine. Finally, it was found that use of one of the chloroforms resulted in a loss of N-oleoylethanolamine from solution due to addition of chlorine to the ω-9 bond. The identity of this reaction product was confirmed by LC-MS/MS and NMR. It is recommended that these aspects of sample preparation and analysis should be thoroughly validated during method development and the relevant information on specific brands used be reported in future communications in order to better estimate the validity of reported quantitative data.     

The phylogeny of the ant tribe Formicini (Hymenoptera: Formicidae) with the description of a new genus

Abstract. The holarctic ant tribe Formicini is revised, the new genus Bajcaridris described, and possible phylogenetic relationships are discussed. The subgenus Iberoformica is synonymized with Formica. A synopsis, diagnosis and keys to the genera are provided.     

Circular dichroism spectra of human hemoglobin reveal a reversible structural transition at body temperature

Previously we have shown that human red blood cells (RBCs) undergo a sudden change from blocking to passing through a 1.3±0.2-µm micropipette when applying an aspiration pressure of 2.3 kPa at a critical transition temperature (T_c=36.4±0.3 °C). Low-shear viscosity measurements suggested that changes in the molecular properties of hemoglobin might be responsible for this effect. To evaluate structural changes in hemoglobin at the critical temperature, we have used circular dichroism (CD) spectroscopy. The thermal denaturation curves of human hemoglobin A (HbA) and hemoglobin S (HbS) upon heating between 25 and 60 °C were non-linear and showed accelerated denaturation between 35 and 39 °C with a midpoint at 37.2±0.6 °C. The transition was reversible below 39 °C and independent of solution pH (pH 6.8–7.8). It was also independent of the oxygenation state of hemoglobin, since a sample that was extensively deoxygenated with N₂ showed a similar transition by CD. These findings suggest that a structural change in hemoglobin may enable the cellular passage phenomenon as well as the temperature-dependent decrease in viscosity of RBC solutions.     

Hypochlorous acid and human blood low density lipoproteins modified by hypochlorous acid increase erythrocyte adhesion to endothelial cells

The ability of hypochlorous acid (HOCl) (anion form - hypochlorite, OCl-) and HOCl/OCl- -modified human blood low density lipoproteins (HOCl-LDLs) to stimulate erythrocyte adhesion to endothelial cell monolayers was studied. LDLs were modified by incubating at different HOCl/OC- concentrations. This led to a damage of proteins and lipids. We found (1) a more than 20-fold decrease of LDL fluorescence intensity (extinction at 285 nm, emission at 340 nm), (2) accumulation of secondary (TBA-reactive substances) and final (Schiff bases) products of lipid peroxidation, and (3) increase in the electrophoretic mobility of LDLs. Preincubation of endothelial cells (ECs) with HOCI/OCl- (up to 50 microM) enhanced erythrocyte adhesion to the EC monolayer. Preincubation of ECs with HOCl-LDLs (up to 250 microM of HOCI//OCl- during LDL modification) (1) caused an increase in the cholesterol/phospholipid molar ratio in EC and (2) enhanced adhesion of erythrocytes to endothelium. Application of HOCl/OCl- at concentrations above 50 microM or treatment of LDLs with 500 microM HOCl resulted in the cytotoxic effect on ECs and led to a decrease in the molar cholesterol/phospholipid ratio in ECs and adhesion of erythrocytes to endothelium. The results suggest that HOCl/OCl- at physiological concentrations stimulates the adhesion of blood cells to the endothelium and cholesterol accumulation in the vessel wall ECs either directly or due to LDL modification. Both effects could be important in the development of many vascular diseases.     

Temperature transitions of protein properties in human red blood cells.

Human red blood cells (RBC) undergo a sudden change from blocking to passing through 1.3 +/- 0.2-micrometer micropipettes at a transition temperature (Tc) of 36.4 degrees C. For resealed RBC ghosts this transition occurs at 28.3 degrees C (Tg). These findings are attributed to an elastomeric transition of hemoglobin from being gel-like to a fluid and to an elastomeric transition of membrane proteins such as spectrin. Spectrin shows a uniform distribution along the aspirated RBC tongue above Tg in contrast to the linear gradient below Tg.     

Effects of Selenium Supplementation on Antioxidant Defense and Glucose Homeostasis in Experimental Diabetes Mellitus

The objective of this study was to investigate the effects of different forms of Se supplementation on the antioxidant defense and glucose homeostasis in experimental diabetes. Sodium selenate (SS) or selenomethionine (SM) were administered (2 μmol Se kg⁻¹ day⁻¹) via orogastric route to streptozotocine (STZ)-induced diabetic rats in addition to basal diet for 12 weeks. Glucose levels in whole blood, glutathione peroxidase (GSH-Px) activity in erythrocytes, Se and fructosamine levels in plasma were evaluated monthly. Plasma Se levels increased significantly in all diabetic groups compared to basal measurements, being more prominent in SM group [p(SM₃/SM₀) = 0.018]. The increase in GSH-Px activities was significant at the end of the second month in SS [p(SS₂/SS₀) = 0.028], whereas at the end of the third month in SM the value was lower [p(SM₃/SM₀) = 0.018] and the unsupplemented diabetic control (DC) groups, p(DC₃/DC₀) = 0.012. Glucose increased significantly only in DC group. Fructosamine increased gradually in all diabetic groups, being significant in DC and SS groups. At the end of the third month, highest fructosamine levels were observed in SS group, which were significantly higher than the SM group [p(SM/SS) = 0.010]. In conclusion, Se augmented the antioxidant defense by increasing GSH-Px activity and this effect was more prominent when Se was supplemented as SM, which exerted positive effects also on glucose homeostasis.     

Changes in brain levels of N-acylethanolamines and 2-arachidonoylglycerol in focal cerebral ischemia in mice

The N -acylethanolamines (NAEs) and 2-arachidonoylglycerol (2-AG) are bioactive lipids that can modulate inflammatory responses and protect neurons against glutamatergic excitotoxicity. We have used a model of focal cerebral ischemia in young adult mice to investigate the relationship between focal cerebral ischemia and endogenous NAEs. Over the first 24 h after induction of permanent middle cerebral artery occlusion, we observed a time-dependent increase in all the investigated NAEs, except for anandamide. Moreover, we found an accumulation of 2-AG at 4 h that returned to basal level 12 h after induction of ischemia. Accumulation of NAEs did not depend on regulation of N -acylphosphatidylethanolamine-hydrolyzing phospholipase D or fatty acid amide hydrolase. Treatment with the fatty acid amide hydrolase inhibitor URB597 (cyclohexyl carbamic acid 3'-carbamoyl-biphenyl-3-yl ester; 1 mg/kg; i.p.) 1.5 h before arterial occlusion decreased the infarct volume in our model system. Our results suggest that NAEs and 2-AG may be involved in regulation of neuroprotection during focal cerebral ischemia in mice.