Fluctuating salinity effect on Sphoeroides annulatus (Jenyns 1842) physiological responses

Euryhaline fish, such as the Bullseye puffer Sphoeroides annulatus (Jenyns 1842), experience sudden salinity changes in their natural environment, which is more common than the exception, so they must adapt to survive and cope with extreme salt conditions. Therefore, Bullseye puffer juveniles were exposed to short‐term stress (39 hr) by fluctuating salinity conditions (41, 35, 29, 23, 17, 11, 5, 11, 17, 23, 29, 35, 41 psu) with a 3‐hr interval between each point at 26 ± 1ºC in a respirometer chamber and acclimation reservoirs. Responses to oxygen consumption rate (OCR: 23–35 mg O₂ h^–1 kg^–1), ammonium excretion rate (AER: 1–1.85 mg NH4⁺ h^?1 kg^?1), oxygen‐nitrogen atomic ratio (O:N 17–30), osmoregulatory pattern (blood osmotic pressure from 342.4 to 332.8 mmol/kg) and changes in expression levels of Na⁺/K⁺‐ATPase in the gills (higher values at higher salinities) were measured. Although some signs of stress were detected below the iso‐osmotic point (11.4 psu), the puffer fish is a strong euryhaline fish that survives under these conditions. Nonetheless, it could recover when salinity returned to the initial acclimation point because Sphoeroides annulatus is able to live in a wide range of environments with wide natural salinity fluctuations; thus, a common practice in aquaculture has been to expose fish to low salinity for several reasons discussed in this study. This capacity reveals its high plasticity to saline adaptation from 41 to 5 psu an up from 5 to 41 psu, all in less than 2 days.     

Expression and functional characterization of glutamine synthetase from giant freshwater prawn (Macrobrachium rosenbergii) under osmotic stress

The freshwater prawn, Macrobrachium rosenbergii naturally lives in the freshwater, though it migrates to the brackish water environment during spawning that claimed to be resistant on a broad range of saline fluxes. However, little is known about the osmoregulatory patterns and the effect of an enzyme glutamine synthetase (GS) in M. rosenbergii under stress. Here, we described the identification and functional characterization of GS from M. rosenbergii (Mr‐GS) at molecular and protein levels. The identified Mr‐GS was comprised of 361 amino acids that phylogenetically shared the highest identity with other crustaceans and predicted to contain Gln‐synt_C and Gln‐synt_N domains at the respective terminal regions. Tissue distribution analysis in M. rosenbergii revealed that the Mr‐GS was highly expressed in muscle, and commonly existed in other examined tissues in the following order gills > heart > stomach > brain > haemolymph. Whereas, the mRNA of Mr‐GS was significantly up‐regulated in the muscle and gill tissues following challenges with either hyper (0 → 13‰), or hypo (13 → 0‰) osmotic stress at 3, 6 and 12 hr. Furthermore, the level of Glutamine concentration was positively correlated with the GS mRNA and protein expression patterns in hyper‐osmotic stress, whereas in hypo‐osmotic stress a slight decrease in the gills and maintained a level in the muscle tissues at 3, 6 and 12 hr post‐treatments. Our findings suggest that Mr‐GS potentially exhibited the osmoregulation responses in the gill and muscle tissues of M. rosenbergii throughout the time of osmotic stress, which will benefit for future study on osmoregulation.     

H9N2禽流感病毒全基因组密码子使用偏好性及影响因素分析

【目的】探究H9N2禽流感病毒(AIV)全基因组的密码子使用偏好性及影响因素。【方法】选取2010—2018年国内H9N2 AIV流行毒株的全基因组为研究对象,分析其碱基组成特性、最优密码子、密码子使用偏好性的影响因素以及病毒对宿主密码子使用模式的适应性。【结果】H9N2 AIV的全基因组中AU含量高于GC。大部分最优密码子以A或U结尾,有效密码子数(ENC)平均值为52.86,提示存在密码子使用偏好性但偏好性较低。密码子使用偏好性主要受到突变压力和自然选择的共同作用,其中自然选择(所占比例为61.79%～76.15%)作用大于突变压力(所占比例为23.85%～38.21%)。H9N2 AIV对人Homo sapiens的密码子适应指数平均值为0.739～0.741,提示H9N2AIV禽流感病毒可能已适应人类的密码子使用模式。【结论】本研究为H9N2 AIV的基因进化分析、已有疫苗的密码子优化和新型疫苗(密码子去优化疫苗)研制提供了理论依据。     

新疆日光温室前屋面的风载数值模拟分析

【目的】 对日光温室前屋面风载大小和变化趋势进行模拟,可辅助前屋面骨架结构优化设计和前屋面实际风载计算,为提前预测和防灾功能提供科学依据。【方法】 将日光温室墙体、保温被和骨架等结构简化,使用UG 软件对日光温室进行造型,将模型与空气进行布尔求差,得到整体模型,将整体模型导入到ANSYS ICEM中,进行网格划分,得到保温被4种工作状态薄膜风压。再通过Y向的9条曲线画出不同条件下风压变化对比曲线。【结果】 在无保温被和保温被全铺时,薄膜最南侧风压最高,约1.014×10⁵Pa,往北侧风压逐渐降低,脊高位置风压最小约1.010×10⁵Pa。由于最南侧风遇到薄膜阻碍,造成风压的升高,而北侧接近日光温室顶端,风速快,而风速快的位置风压小。在保温被全卷及半卷时,也是最南侧风压较最高,约1.014×10⁵Pa,往北有风压的降低,总体屋面风压变化比较小,约1.013×10⁵Pa。只是保温被半卷时,在保温被卷放位置会有风压的突变为1.012×10⁵Pa。【结论】 无保温被、保温被全铺、保温被全卷及保温被半卷4种情况南侧风压较大且相差不大,但越往北侧,保温被全卷或半卷会造成薄膜风压的升高,尤其是顶部的突然升高。保温被全铺是最佳防风方案。南侧风压高,南侧前屋面钢骨架拱形段的性能对日光温室结构稳定性和安全性至关重要,设计和建设时需要着重计算和核验。     

Asystole associated with cerebrospinal fluid collection in a 3-month-old foal under general anaesthesia

A 3-month-old colt foal presented to the Philip Leverhulme Equine Hospital for investigation of progressive neurological signs. Diagnostic investigation included cerebrospinal fluid collection, which was performed under general anaesthesia. During this procedure, severe bradycardia which progressed to asystole occurred. Initial resuscitation was successful; however, the foal had clinical signs consistent with cerebral hypoxia post-resuscitation and was euthanased the following day due to deterioration of neurological function. Asystole was presumed due to a Cushing-type reflex as a result of changes in intracranial pressure during the sampling procedure.     

鲜食玉米果穗收获负压除杂装置参数优化与试验

针对现有鲜食玉米收获机在收获果穗时，果穗中含有茎叶等杂质，影响运输、贮存和后续加工等问题，采用轴流风机负压除杂技术去除果穗中的茎秆和茎叶等杂质，同时在除杂装置内增加动、定刀，切碎杂质，便于后续的打包回收利用，并对风机负压除杂装置进行了性能分析和参数优化。通过对动、定刀进行动力学分析，对动、定刀数和刀间隙进行分析，确定了该装置的风机转速范围为1326~1573r/min，动、定刀间隙20mm，定刀数为3~8。采用二次回归正交组合试验方案，以风机转速、定刀数、喂入量为试验因素，以果穗含杂率和茎秆切碎长度合格率为试验指标进行台架试验，通过分析各因素对指标贡献率，得到影响茎秆切碎长度合格率的主次顺序为喂入量、风机转速、定刀数，影响果穗含杂率的主次顺序为风机转速、喂入量、定刀数。建立了参数优化数学模型，利用Optimization模块优化得出，当风机转速为1524r/min、单排定刀数为4、喂入量为7.6kg/s时，茎秆切碎长度合格率为96.8%，果穗含杂率为0.69%。对优化后的参数组合进行了5组验证试验，得到茎秆切碎长度合格率平均值为96.2%，果穗含杂率平均值为0.71%。相比于传统收获机，该装置使果穗含杂率降低了23.3%，说明该优化参数能够满足鲜食玉米果穗收获和茎叶青贮相关技术要求。     

速溶薏米粉的制备及其特性研究

以超高压改性与高压均质相结合为关键技术制备速溶薏米粉，并对速溶薏米粉营养成分及其特性进行了测定。结果表明，制备的速溶薏米粉主要营养成分保存较好，抗性淀粉含量显著增加，休止角较小，堆积密度较大，结块率较小，冲调性和蛋白质分散性较好，消化率较低，香气风味及色泽等稍逊于常见谷物粉，但口感较好，为薏米冲调食品的开发提供依据。     

定量泵负载敏感系统卸荷压力冲击抑制研究

定量泵负载敏感系统在快速卸荷时容易出现压力冲击现象,对系统的可靠性和寿命产生较大危害。三通压力补偿阀是定量泵负载敏感系统中关键的调压元件,本文以三通压力补偿阀为切入点,建立定量泵负载敏感系统功率键合图模型,基于键合图模型推导系统的状态方程,建立Matlab动态仿真模型,探讨系统卸荷压力冲击的抑制方案。基于系统仿真模型,首先对系统卸荷压力冲击的仿真与试验进行对比,验证了仿真模型的正确性;然后,针对三通压力补偿阀的系统压力腔阻尼、阀芯直径、Ls腔阻尼、阀口锥角等关键参数,对卸荷压力冲击影响规律进行仿真;最后,基于关键参数对卸荷压力冲击影响规律的分析,提出了一种"小阀芯、双阀口"型三通压力补偿阀结构优化方案,并对其卸压冲击抑制效果进行了仿真和试验。结果表明,该方案可以有效抑制卸荷压力冲击,优化后系统卸压冲击压差比原系统降低了89%,卸荷压力降低了20%,进一步实现了节能。     

The impact of foliar fertilizers on growth and biochemical responses of Thymus vulgaris to salinity stress

Salinity reduces plant biomass and may lead to death when severe. To cope with the negative effects of this stress, plant species present specific physiological or biochemical responses. In this work, we hypothesized that spraying salt-stressed thyme leaves with K⁺ and Ca²⁺ could mitigate the negative effects of salinity on plant growth and metabolism. To test this hypothesis, we grew thyme plants under salinity stress for two and four weeks before applying foliar sprays. Also, to test the effect of stress relief, treated plants were allowed two weeks of recovery after four weeks of salt stress. In general, after two and four weeks of salinity stress, the leaf fresh weight of thyme plants was reduced by 31 and 43%, respectively. Salinity also decreased the relative water content, water, and osmotic potentials and led to ion imbalances and nutrient deficiencies. Salinity altered concentration of some essential oils, but leaf antioxidant contents remained fairly stable, except for a significant increase for plants under NaCl?+?KCl two weeks after treatment. Our results indicated that stressed plants accumulated significantly more soluble sugars and amino acids in comparison with the control. Foliar sprays with KCl and CaCl₂ reversed the negative effects of salinity on plant biomass and induced the accumulations of compatible solutes. Moreover, concentrations of some essential oils and gallic acid increased in sprayed plants, but these effects were dependent on the type and duration of the treatment. Overall, spraying leaves with K⁺ and Ca²⁺ was able to mitigate salinity stress in Thymus vulgaris even during the recovery period.     

Diversity in daytime and night‐time transpiration dynamics in barley indicates adaptation to drought regimes across the Middle‐East

A challenge to breeding drought‐tolerant barley in the Middle‐East is that precipitation and evaporative demand patterns dictate opposite water use strategies (conservative vs. risk‐taking). To characterize these strategies, we examined high‐resolution, whole‐plant transpiration rate (TR) responses to increasing vapour pressure deficit (VPD) and nocturnal TR (TR_N) dynamics among 25 local barley genotypes, using a novel phenotyping system. These traits were specifically selected because they exist under modalities enabling the expression of both strategies. The genotypes were selected from locations spread across a large aridity gradient represented by temperature and precipitation data spanning 30 years. Here, we uncovered a substantial diversity in TR responses to VPD where slopes of the linear responses correlated negatively with local maximal temperatures, pointing to opposite drought tolerance strategies. Low canopy conductance (low slopes) was associated with higher aridity, likely to enable water‐saving, while higher conductance was associated with wetter areas, likely to enable a more aggressive water use to maximize physiological activity. TR_N was highly diverse and represented up to 15% of maximal daytime TR, pointing to the possibility of increasing water‐saving by reducing TR_N. Furthermore, we detected pre‐dawn variation in TR_N that negatively correlated with local precipitation, indicating that a tighter circadian control is associated with adaptation to drought, consistently with a circadian resonance mechanism. These findings indicate that canopy conductance and TR_N are potentially beneficial to design drought‐tolerant barley germplasm adapted to different drought regimes taking place in the Middle‐East.