Chain asymmetry alters thermotropic and barotropic properties of phospholipid bilayer membranes

The alignment of the sn-1 and sn-2 acyl chains at the terminal methyl ends generally produces significant influence on the thermodynamic properties of the bilayer phase transitions. We investigated the bilayer phase behavior of asymmetric phospholipids, myristoylpalmitoylphosphatidylcholine and palmitoylmyristoylphosphatidylcholine, by high-pressure light-transmittance and Prodan-fluorescence techniques and differential scanning calorimetry. Constructed temperature-pressure phase diagrams revealed that no stable phase can exist in the whole pressure range because of the formation of the most stable L_c phase. Nevertheless, the pretransition, the detection of which is severely hampered by the exceptionally prompt formation of the L_c phase, was successfully observed. Moreover, the effect of the total and difference of the sn-1 and sn-2 acyl chain lengths on minimal interdigitation pressure (MIP) was summarized in a MIP vs. chain-length inequivalence parameter plot, where the effect was proved to be classified in three zones depending on the alignment of both terminal methyl ends.     

The CARLIT method for the assessment of the ecological quality of European Mediterranean waters: Relevance,robustness and possible improvements

The application of the European Union (EU) Water Framework Directive (WFD) requires the assessment of the ecological status (ES) of coastal waters in order to detect environmental changes and implement management plans to prevent their further deterioration. The ES of a water body (WB) has to be assessed on the basis of the status of several biological indicators, referred to as biological quality elements (BQE), such as phytoplankton, macroalgae, seagrasses, macroinvertebrates and fish. We present the most extensive assessment ever undertaken of the ES of Mediterranean waters, by means of the CARLIT index, the most widely used index for the Mediterranean Sea. This index is based on the Ecological Quality Ratio (EQR) between a measured value of Ecological Quality (EQ) and a value corresponding to a reference site. This assessment is based on an extensive field study, covering the whole of the Mediterranean French coasts (including Corsica), 40 WBs and ∼2 970 kilometres of shore (at a 1/2 500 scale). The original Ballesteros CARLIT method is compared to the Nikolić modified method, and we have undertaken the challenge of developing an alternative new simplified CARLIT method. This simplified method, which requires less expert judgement, is easier to implement by local authorities, and provides results similar overall to those of the original method. Previous attempts, if any, to correlate EQRs with anthropogenic stressors (through pressure indices) were mainly based upon land uses or on comprehensive lists of stressors, some spatially very sporadic, temporally highly variable, non-representative of the WB and with the impact poorly established on species and communities. To date, the LUSI (Land Uses Simplified Index) and the MA-LUSI-WB have been the most widely used pressure indices. Here, we propose a new pressure index (HAPI) taking into consideration the possible shortcomings of previous indices. It takes into account the actual pressures at community levels considered by the CARLIT method. It accounts well for the EQR values of the study area, as evidenced by the high correlation coefficient between EQRs and HAPI, better than that of the other pressure indices. The present study provides a comprehensive view of the ES of the French Mediterranean coasts. Surprisingly, the picture is far less cause for concern than expected, although this could result from an artefact due to the focus on superficial waters and habitats inherent to the CARLIT method. Where two successive assessments were performed (23 WBs, 2007–2010 vs 2012–2015), the results were similar, which stresses the robustness of the method and/or the relative stability over time of the overall ES of the WBs, and suggests that the successive assessments could be carried out at low frequency.     

Studies on Water Movement Into and Out of Grapevine Fruits During the Ripening

The experiment was carried out during the ripening of grape (Vitis vinifera L. and V. vinifera × V. labrusca) fruits using the technique of dye tracing and measurement of water potential. Under the natural conditions of sufficient soil water supply and those of a high evapotranspiration potentiality on clear days, the water in fruits was transfered, during the morning and afternoon, out of the clusters and into the xylem of shoots; but the fruits capture water in the late afternoon and evening from the xylem of shoots. The diurnal variations of the water exchange between fruits and the xylem of shoots have been described and these variations seemed to be relevant not only to the differences of water potential between leaves and fruits but also to the hydraulic status of fruits. Under the mild water stress, the variations of the diurnal "fruits-shoots" water exchange were similar to those under the conditions of ample water supply, but the rate of "fruits-shoots" water exchange in the lightly stressed vine was decreased as compared with the fully watered vines. After a certain period of severe water stress, the fruits possessed a great capacity of conserving their water and an equilibrium in water potential was set up between leaves and fruits so that the fruits did not lose any more water. Under a sudden severe water stress, the fruits lost water at a higher outflux rate than when the water supply was sufficient. However, this water loss ceased rapidly. The water flowing out from the fruits was privileged to pass in the lateral shoots located above and on the same side of the fruits, and then the water might enter the primary shoot leaves situated above and on the same side of the fruits. Water captured by the fruits of the well watered vines in the evening came from the roots while under severe stress water might be obtained from the roots and also from the leaves as well. The fruit cell water potential, solute potential and pressure potential were different from those of leaves, mainly in the more important differences of water potential necessitated for the volume changes of fruit cell after incipient plasmolysis in com parison with leaves. Finally the relationships between water exchange and water potential dif ferences between "fruits-shoots", associated with the fruits hydraulic status, have been discussed. The possible relationships between water "sink-source" of fruits and the fruit development have been analysed.     

Pressure reduction affects growth and morphology of Chlamydomonas reinhardtii

Cellular perception of pressure is a largely unknown field in microalgae research although it should be addressed for optimization of a photobioreactor design regarding typically occurring pressure cycles. Also for the purpose of using microalgae as basic modules for material cycles in controlled ecological life support systems, the absence of pressure in outer space or the low absolute pressures on other planets is an abiotic factor that needs to be considered for design of integrated microalgae‐based modules. The aim of this work is to study the effects of lowered pressure and pressure changes on photosynthesis as well as morphology. Two Chlamydomonas reinhardtii wild‐type strains were exposed to controlled pressure patterns during batch cultivations. Sudden pressure changes should test for existing threshold values for cell survival to mimic such events during space missions. Algae were grown inside a 2 L photobioreactor with an integrated vacuum pump ensuring constant pressures down to 700 mbar. Cultivation samples were analyzed for OD₇₅₀, cell dry weight, and morphology via light microscope. Chlamydomonas reinhardtii CC‐1690 cells showed decreased growth rates, higher carbon dioxide uptake rates, and unchanged oxygen production rates at lower pressures. For sudden pressures changes in the range of 300 mbar no fatal threshold was determined. This study shows that pressure reduction affects growth, gas exchange rates, and morphology. Within the tested pressure range no fatal threshold value was reached.     

The kinetics of the main phase transition of aqueous dispersions of phospholipids induced by pressure jump and monitored by raman spectroscopy

The sensitivity of the melting transition temperature of aqueous dispersions of dipalmitoyl- and distearoylphosphatidylcholine to hydrostatic pressure is used to allow measurement of the rates of isothermal freezing and melting of the lipids by rapidly changing the pressure. The degree of order of the lipids is measured by monitoring a ratio of two points in the Raman spectrum of the lipids which changes sharply at the melting temperature. Use of this Raman order ratio allows correlation between the order of the sample and the rates of transition in a manner which is impossible by monitoring only turbidity. Our longest relaxation times range upwards from a few seconds for both compounds. The freezing rates are slowest when the samples are initially fully melted, and the melting rates are slowest when the samples are initially frozen. These results imply that nucleation of the growing phase dominates the kinetics of both freezing and melting.     

Mice lacking the gene encoding for MMP-9 and resistance artery reactivity

OBJECTIVES: To define the link between the deletion of gene encoding for metalloproteinase 9 and resistance artery reactivity, we studied in vitro smooth muscle and endothelial cell function in response to pressure, shear stress, and pharmacological agents. BACKGROUND: Matrix metalloproteinases play a crucial role in the regulation of extracellular matrix turnover and structural artery wall remodeling. METHODS: Resistance arteries were isolated from mice lacking gene encoding for MMP-9 (KO) and their control (WT). Hemodynamic, pharmacology approaches, and Western blot analysis were used in this study. RESULTS: The measurement of blood pressure in vivo was similar in KO and WT mice. Pressure-induced myogenic tone, contractions to angiotensin-II and phenylephrine were similar in both groups. The inhibition of MMP2/9 ((2R)-2-[(4-biphenylylsulfonyl) amino]-3-phenylpropionic acid) significantly decreased myogenic tone in WT and had no effect in KO mice. Relaxation endothelium-dependent (flow-induced- dilation 41.3+/-0.6 vs. 21+/-1.6 at 10 microl/min in KO and WT mice, respectively, P<0.05) and eNOS expression were increased in KO compared to WT mice. The inhibition of eNOS with L-NAME significantly decreased endothelium response to shear stress, which was more pronounced in KO mice resistance arteries (-26.83+/-2.5 vs. -15.84+/-2.3 at 10 microl/min in KO and WT, respectively, P<0.05). However, the relaxation to exogenous nitric oxide-donor was similar in both groups. CONCLUSION: Our study provides evidence of a selective effect of MMP-9 on endothelium function. Thus, MMP-9 gene deletion specifically increased resistance artery dilation endothelium-dependent and eNOS expression. Based on our results, MMP-9 could be a potential therapeutic target in cardiovascular disease associated with resistance arteries dysfunction.     

Copy number variations of obesity relevant loci associated with body mass index in young Chinese

Obesity is one of the most complex human diseases that are widely concerned and studied. More recently, copy number variations (CNVs) emerge as another important genetic marker to influence various human diseases. To elucidate the relationship between obesity and CNVs, this current study selected obesity-related candidate CNVs and analyzed their association with body mass index (BMI). Results showed that a CNV locus, 8q24.3, was significantly different (P = 0.0070) in CNV frequency between the obese and healthy controls in a young eastern Chinese cohort, while no statistical significance was observed in other seven candidate loci including well reported 10q11.22 and 16p11.2 loci. The association of 8q24.3 CNVs with BMI of the subjects only showed marginal significance, while the copy number (CN) of 5p15.33 had a significant correlation with the BMI of the subject. These results suggested that 8q24.3 CN gains was associated with obesity, and 5p15.33 might also contribute to obesity pathogenesis, highlighting the importance of these CNVs for obesity risks, as well as providing new evidence for CNVs in the pathology of common diseases.     

经胸右心室穿刺法测量大鼠右心室压力的研究

目的:探索一种技术简单、操作方便、重复性好、容易掌握的大鼠右心室压力测量方法。方法:取健康Sprague Dawley大鼠20只,随机分为实验组(n=10),对照组(n=10)。实验组使用一次性静脉输液针(0.45×13.5 mm)经胸直接穿刺右心室测量右心室压力,对照组使用右心导管,经颈外静脉沿右心房插入右心室测量右心室压力。比较两者操作时间、成功率、右心室压力等指标。结果:实验组从麻醉开始到成功测出右心室压力的时间5.10±1.32 min,对照组为25.21±10.30 min(P0.05)。两种方法所检测到的右心室收缩压、右心室舒张压、右心室平均压无统计学差异(P0.05)。实验组大鼠成功率100%,对照组60%(P0.05)。结论:经胸右心室穿刺法能准确、快速穿刺到右心室并能准确测量右心室压力。     

肾盂灌注冲洗对肾脏功能和结构的影响

目的:探讨经皮肾镜碎石术肾盂灌注冲洗压对肾脏结构和功能的影响。方法:建立20头活体猪高压肾盂冲洗模型,建立24F肾造瘘通道,分别在0mmHg(作自身对照,只造瘘不灌注)、150mmHg、200mmHg、250mmHg、300mmHg压力下各冲洗30分钟。术中取肾组织送病理检查,监测肾单位光镜和电镜下的形态学改变;术后5天留取尿标本,应用免疫比浊测定法(ITM)检测尿微量白蛋白(ALB)和β2-微球蛋白(β2-MG);并于术后第5天再次取肾组织行病理检查观察肾单位的形态学改变。结果:所有灌注组术后都出现尿蛋白的增高,术后第1天和术前相比,都有显著差异(P<0.01)。形态学观察:当肾盂灌注冲洗压在150-200mmHg时,光镜下观察见肾小囊腔轻度扩张,压力超过250mmHg,肾小囊腔见红细胞和蛋白渗出物,肾小管扩张。电镜下见肾近曲小管上皮细胞内空泡形成,微绒毛排列杂乱、稀疏、部分微绒毛脱落。结论:肾盂灌注冲洗安全压不应超过200mmHg。