Membrane phase behavior during cooling of stallion sperm and its correlation with freezability

Abstract

Stallion sperm exhibits great male-to-male variability in survival after cryopreservation. In this study, we have investigated if differences in sperm freezability can be attributed to membrane phase and permeability properties. Fourier transform infrared spectroscopy (FTIR) was used to determine supra and subzero membrane phase transitions and characteristic subzero membrane hydraulic permeability parameters. Sperm was obtained from stallions that show differences in sperm viability after cryopreservation. Stallion sperm undergoes a broad and gradual phase transition at suprazero temperatures, from 30–10°C, whereas freezing-induced dehydration of the cells causes a more severe phase transition to a highly ordered gel phase. Sperm from individual stallions showed significant differences in post-thaw progressive motility, percentages of sperm with abnormal cell morphology, and chromatin stability. The biophysical membrane properties evaluated in this study, however, did not show clear differences amongst stallions with differences in sperm freezability. Cyclodextrin treatment to remove cholesterol from the cellular membranes increased the cooperativity of the suprazero phase transition, but had little effects on the subzero membrane phase behavior. In contrast, freezing of sperm in the presence of protective agents decreased the rate of membrane dehydration and increased the total extent of dehydration. Cryoprotective agents such as glycerol decrease the amount of energy needed to transport water across cellular membranes during freezing.     

Freezing-induced cellular and membrane dehydration in the presence of cryoprotective agents

Abstract

FTIR and cryomicroscopy have been used to study mouse embryonic fibroblast cells (3T3) during freezing in the absence and presence of DMSO and glycerol. The results show that cell volume changes as observed by cryomicroscopy typically end at temperatures above ?15°C, whereas membrane phase changes may continue until temperatures as low as ?30°C. This implies that cellular dehydration precedes dehydration of the bound water surrounding the phospholipid head groups. Both DMSO and glycerol increase the membrane hydraulic permeability at subzero temperature and reduce the activation energy for water transport. Cryoprotective agents facilitate dehydration to continue at low subzero temperatures thereby decreasing the incidence of intracellular ice formation. The increased subzero membrane hydraulic permeability likely plays an important role in the cryoprotective action of DMSO and glycerol. In the presence of DMSO water permeability was found to be greater compared to that in the presence of glycerol. Two temperature regimes were identified in an Arrhenius plot of the membrane hydraulic permeability. The activation energy for water transport at temperature ranging from 0 to ?10°C was found to be greater than that below ?10°C. The non-linear Arrhenius behavior of Lp has been implemented in the water transport model to simulate cell volume changes during freezing. At a cooling rate of 1°C min^-1, ～5% of the initial osmotically active water volume is trapped inside the cells at ?30°C.     

Importance of Dietary Cholesterol for the Maturation of Mouse Brain Myelin

The effect of nil (control), 1% (CH-l) and 5% (CH-5) dietary cholesterol on the myelination of mouse brain, and its deposition in the heart and liver were investigated during infancy. Swiss Webstar female mice were given formulated diets from early gestation, and their pups were weaned on the same diet as that of the individual mothers up to 60 days after birth. The test diets increased the liver weight and cholesterol content compared to the control even in suckling pups (20 days), but did not significantly influence the heart weight until 60 days. The cholesterol content of the heart was not increased by the CH-l diet throughout the feeding period, but it did increase the mole ratio of major myelin lipids and hastened its maturation. Myelin cholesterol was 10% higher in 20-day-old suckling pups in the CH-5 group compared to the control. Data indicate that dietary cholesterol altered the brain myelination rate of weaning mice, and that the mother’s dietary cholesterol influenced myelination of the suckling pups.     

Robust algorithm for brain magnetic resonance image (MRI) classification based on GARCH variances series

In this paper, a robust algorithm for disease type determination in brain magnetic resonance image (MRI) is presented. The proposed method classifies MRI into normal or one of the seven different diseases. At first two-level two-dimensional discrete wavelet transform (2D DWT) of input image is calculated. Our analysis show that the wavelet coefficients of detail sub-bands can be modeled by generalized autoregressive conditional heteroscedasticity (GARCH) statistical model. The parameters of GARCH model are considered as the primary feature vector. After feature vector normalization, principal component analysis (PCA) and linear discriminant analysis (LDA) are used to extract the proper features and remove the redundancy from the primary feature vector. Finally, the extracted features are applied to the K-nearest neighbor (KNN) and support vector machine (SVM) classifiers separately to determine the normal image or disease type. Experimental results indicate that the proposed algorithm achieves high classification rate and outperforms recently introduced methods while it needs less number of features for classification.     

汶川地震转运与震区住院患者回顾性对比分析

目的:探讨汶川地震转运与震区住院伤病员的特点和疾病谱.方法:采用“军卫一号“医院信息系统,收集整理三所军队医院收治汶川地震伤病员的诊疗信息.对比转运与震区住院伤病员的入院时间、基本情况和诊疗信息的差异.结果:震后第2日震区住院伤病员入院人数最多,为394人;前4日占震后10日内入院人数的80.6％.全部住院伤病员男性730人,占56.5％,女性562人,占43.5％;汉族占95％,羌族、藏族及其他民族占5％;已婚占76.4％;手术率为36.5％;住院天数的中位数为12天;治愈好转率为96.5％,病死率为1％.转运与震区住院伤病员的性别、年龄组、民族、手术与否和治疗结果构成差异具有统计学意义(P＜0.05);震区住院伤病员组的住院天数中位数低于转运住院伤病员组(P＜0.00l).按照出院第一诊断,损伤或中毒住院伤病员占81.5％;其他疾病前五位为消化系统疾病、呼吸系统疾病、肌肉骨骼和结缔组织疾病、循环系统疾病、症状和体征.结论:地震等灾害后应尽早(灾后3-5天)转运伤病员.震区一线医院和接收转运伤病员医院应科学、合理设置床位、安排陪护人员、招募志愿者.地震第一阶段医疗救援完成后,救援重点应转向内科和慢性疾病,并提前做好应医疗准备.     

Brain structure and spatial sensitivity profile assessing by near‐infrared spectroscopy modeling based on 3D MRI data

The goal of this study is to prove that the light propagation in the head by used the 3‐D optical model from in vivo MRI data set can also provide significant characteristics on the spatial sensitivity of cerebral cortex folding geometry based on Monte Carlo simulation. Thus, we proposed a MRI based approach for 3‐D brain modeling of near‐infrared spectroscopy (NIRS). In the results, the spatial sensitivity profile of the cerebral cortex folding geometry and the arrangement of source‐detector separation have being necessarily considered for applications of functional NIRS. The optimal choice of source‐detector separation is suggested within 3–3.5 cm by the received intensity with different source‐detector separations and the ratio of received light from the gray and white matter layer is greater than 50%. Additionally, this study has demonstrated the capability of NIRS in not only assessing the functional but also detecting the structural change of the brain by taking advantage of the low scattering and absorption coefficients observed in CSF of sagittal view. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Real‐time mid‐infrared imaging of living microorganisms

The speed and efficiency of quantum cascade laser‐based mid‐infrared microspectroscopy are demonstrated using two different model organisms as examples. For the slowly moving Amoeba proteus, a quantum cascade laser is tuned over the wavelength range of 7.6 µm to 8.6 µm (wavenumbers 1320 cm^–1 and 1160 cm^–1, respectively). The recording of a hyperspectral image takes 11.3 s whereby an average signal‐to‐noise ratio of 29 is achieved. The limits of time resolution are tested by imaging the fast moving Caenorhabditis elegans at a discrete wavenumber of 1265 cm^–1. Mid‐infrared imaging is performed with the 640 × 480 pixel video graphics array (VGA) standard and at a full‐frame time resolution of 0.02 s (i.e. well above the most common frame rate standards). An average signal‐to‐noise ratio of 16 is obtained. To the best of our knowledge, these findings constitute the first mid‐infrared imaging of living organisms at VGA standard and video frame rate.

     

应用分子标记技术改良京作1号的稻瘟病抗性

稻瘟病是危害水稻产量的重要生物胁迫之一。实践证明,解决这一问题的最有效方法是培育具广谱、持久稻瘟病抗性的品种并推广种植。本研究以优质、高产、感稻瘟病的京作1号为轮回亲本,与稻瘟病抗性基因Pi9、Pigm和pi21的供体材料进行杂交、回交和复交,结合分子标记辅助选择和农艺性状筛选,培育不同的单基因导入系和聚合系。苗期人工接种多个稻瘟病菌的结果显示,Pi9抗性改良系的抗性频率达到100%,Pigm抗性改良系平均为90%,均极显著高于轮回亲本京作1号的抗性频率,且农艺性状与京作1号基本一致。pi21抗性改良系的抗性水平与京作1号没有明显差异,单株产量极显著低于京作1号。与轮回亲本相比,Pi9和pi21聚合系的抗性频率极显著提高,达到93.33%,但单株产量明显降低。研究结果证实了Pi9和Pigm基因在大幅度提高抗瘟性的同时对主要农艺性状影响小,都具有较大的育种利用价值。基因pi21抗谱较窄,抗性不强,且可能存在对产量的负效应,不宜单独用来改良水稻品种的稻瘟病抗性,需要与抗性强的主基因聚合,通过多次回交和自交打破该基因与产量的不利连锁累赘。     

Transmission in near‐infrared optical windows for deep brain imaging

Near‐infrared (NIR) radiation has been employed using one‐ and two‐photon excitation of fluorescence imaging at wavelengths 650–950 nm (optical window I) for deep brain imaging; however, longer wavelengths in NIR have been overlooked due to a lack of suitable NIR‐low band gap semiconductor imaging detectors and/or femtosecond laser sources. This research introduces three new optical windows in NIR and demonstrates their potential for deep brain tissue imaging. The transmittances are measured in rat brain tissue in the second (II, 1,100–1,350 nm), third (III, 1,600–1,870 nm), and fourth (IV, centered at 2,200 nm) NIR optical tissue windows. The relationship between transmission and tissue thickness is measured and compared with the theory. Due to a reduction in scattering and minimal absorption, window III is shown to be the best for deep brain imaging, and windows II and IV show similar but better potential for deep imaging than window I.

     

Automation of Mode Locking in a Nonlinear Polarization Rotation Fiber Laser through Output Polarization Measurements

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a new and inexpensive procedure to force mode locking in a pre-adjusted nonlinear polarization rotation fiber laser. This procedure is based on the detection of a sudden change in the output polarization state when mode locking occurs. This change is used to command the alignment of the intra-cavity polarization controller in order to find mode-locking conditions. More specifically, the value of the first Stokes parameter varies when the angle of the polarization controller is swept and, moreover, it undergoes an abrupt variation when the laser enters the mode-locked state. Monitoring this abrupt variation provides a practical easy-to-detect signal that can be used to command the alignment of the polarization controller and drive the laser towards mode locking. This monitoring is achieved by feeding a small portion of the signal to a polarization analyzer measuring the first Stokes parameter. A sudden change in the read out of this parameter from the analyzer will occur when the laser enters the mode-locked state. At this moment, the required angle of the polarization controller is kept fixed. The alignment is completed. This procedure provides an alternate way to existing automating procedures that use equipment such as an optical spectrum analyzer, an RF spectrum analyzer, a photodiode connected to an electronic pulse-counter or a nonlinear detecting scheme based on two-photon absorption or second harmonic generation. It is suitable for lasers mode locked by nonlinear polarization rotation. It is relatively easy to implement, it requires inexpensive means, especially at a wavelength of 1550 nm, and it lowers the production and operation costs incurred in comparison to the above-mentioned techniques.