An automated differential scanning dilatometer.

A sensitive scanning dilatometer has been constructed which continuously records the apparent partial specific volume of small biological samples (10–100 mg) as a function of temperature. Changes in volume of 0.02 μl can be resolved. Tedious calibrations with their inherent errors are eliminated by employing a differential approach in which a recording electrobalance responds to the difference in buoyancy of identical sample and reference tubes. Agreement with the literature values for the specific volume of n-eicosane and the apparent partial specific volume of KCl was excellent. Apparent partial specific volumes obtained for dipalmitoyl lecithin, egg albumin, and bovine serum albumin agreed well with published values.     

Time- and dose-dependent influence of ouabain on the ultrastructure of optic neurones

The cardiac glycoside ouabain was injected into the eye-bulb of the teleost fish, Carassius carassius. Three doses of ouabain were used: 10(-4) M, 10(-5) M, 10(-6) M. The final concentrations in the vitreous body of the eye were approximately 3-10(-5) M, 3-10-6 M and 3-10-7 M, respectively. After 8 hrs, 1, 2, 4, 6 and 8 days the ultrastructural alterations of retinal ganglion cells, the optic axons near the bulb and the terminal segments in the optic tectum were studied. The high doses of ouabain induced an early necrobiosis of the cell bodies in the retina followed by degeneration in the nerve. This is characterized as a protracted form of Wallerian degeneration. The significance of the inhibition of Na+ -K+-activated ATPase at the perikaryal level for both the integrity of axonal morphology and the axonal flow is discussed.     

Cucurbit Powdery Mildew: First Insights for the Identification of the Causal Agent and Screening for Resistance of Squash Genotypes (Cucurbita moschata (Duchesne ex Lam.) Duchesne ex Poir.) in Mendoza,Argentina

The cucurbit powdery mildew (CPM) caused by different fungal species is a major concern for cucurbit crops around the world. In Argentina CPM constitutes the most common and damaging disease for cucurbits, especially for squash crops (Cucurbita moschata). The present study displays initial insights into the knowledge of the disease in western Argentina, including the determination of the prevalent species causing CPM, as well as the evaluation of the resistance of squash cultivars and breeding lines. Fungal colonies were isolated from samples collected in Mendoza province, Argentina. A field trial was also performed to assess the resistance of five squash accessions, including commercial cultivars and breeding lines. The severity of CPM was analyzed and epidemiological models were built based on empirical data. The morphological determinations and analysis with specific molecular markers confirmed Podosphaera xanthi as the prevalent causal agent of CPM in Mendoza. The results od the field trial showed differences in the resistance trait among the squash accessions. The advanced breeding line BL717/1 showed promising results as source of CPM resistance for the future development of open pollinated resistant cultivars, a crucial tool for an integrative control of the disease.     

基于SD的生态安全指标阈值的确定及应用——以上海崇明岛为例

结合区域复合生态系统的特点,建立由经济、人口、资源、环境和生态5个子系统71个参数构成的上海崇明岛区域生态安全的系统动力学模型,并以变量"净GDP"为参考依据,通过情景仿真进行生态安全趋势分析和方案比较,确定生态安全的指标阈值;通过系统模拟对阈值进行验证,认为阈值在反映系统动态发展趋势上,是一定发展模式下的生态安全的特征参照系。这一尝试克服了目前生态安全指标阈值的研究中以参照法为主的静态性缺憾。将确定的阈值应用于崇明岛生态安全的评价和因子分析中,发现由于崇明岛生态岛的定位和生态保障措施的实施,近几年生态安全综合得分呈现逐步提高的特点,但目前(2007年)得分为0.523,仍处于中等水平;并以阈值为标准的因子检验发现各主要安全因子差异较大,主要的制约因子主要体现为环境治污水平和能源利用等方面。     

大肠杆菌共表达LeGGPS2、LePSY1和crtI基因合成番茄红素

利用大肠杆菌研究番茄红素的合成,不仅可以获得副产物少的高产菌株,而且可以探讨基因或基因簇的功能。文中将番茄LeGGPS2和LePSY1的cDNA序列,及欧文氏菌crtI的编码序列分别添加上核糖体结合位点后,以单独或组合的方式受控于T7启动子和终止子,在大肠杆菌菌株BL21(DE3)中进行表达和诱导番茄红素合成。结果显示,仅T7::crtI-LeGGPS2-LePSY1三价基因共表达时才能合成番茄红素,且将种子液以1∶50接种于含3%蔗糖的LB培养基(pH 6.8)中,于37℃摇8 h左右的对数生长后期加IPTG至80μmol/L,30℃诱导表达5 h的发酵条件下,获得2.124 mg/g DCW的番茄红素。该结果既验证了原核化的番茄LeGGPS2和LePSY1基因及与crtI基因协同作用的功能,又为在番茄质体中建立独立的番茄红素合成途径奠定了基础。     

Global stability of Gause-type predator-prey systems

In this paper, we present some global stability results obtained from comparison analysis, Bendixson-Dulac criterion or limit cycle stability analysis for the general Gause-type predator-type systems.Research supported in part by a FGIA grant from the Arizona State University Research Fund AMS (MOS) subject classifications. Primary 34C05; secondary 34C25, 92A15.     

Acetic acid and acidification accelerate chronological and replicative aging in yeast

Comment on: Murakami C, et al. Cell Cycle 2012; 11:3087-96.