Extracellular lipid droplets promote hemozoin crystallization in the gut of the blood fluke Schistosoma mansoni

Hemozoin (Hz) is a heme crystal produced upon hemoglobin digestion as the main mechanism of heme disposal in several hematophagous organisms. Here, we show that, in the helminth Schistosoma mansoni, Hz formation occurs in extracellular lipid droplets (LDs). Transmission electron microscopy of adult worms revealed the presence of numerous electron-lucent round structures similar to LDs in gut lumen, where multicrystalline Hz assemblies were found associated to their surfaces. Female regurgitates promoted Hz formation in vitro in reactions partially inhibited by boiling. Fractionation of regurgitates showed that Hz crystallization activity was essentially concentrated on lower density fractions, which have small amounts of pre-formed Hz crystals, suggesting that hydrophilic-hydrophobic interfaces, and not Hz itself, play a key catalytic role in Hz formation in S. mansoni. Thus, these data demonstrate that LDs present in the gut lumen of S. mansoni support Hz formation possibly by allowing association of heme to the lipid-water interface of these structures.     

Lipid-gramicidin interactions: dynamic structure of the boundary lipid by 2D-ELDOR

The use of 2D-electron-electron double resonance (2D-ELDOR) for the characterization of the boundary lipid in membrane vesicles of DPPC and gramicidin A' (GA) is reported. We show that 2D-ELDOR, with its enhanced spectral resolution to dynamic structure as compared with continuous-wave electron spin resonance, provides a reliable and useful way of studying lipid-protein interactions. The 2D-ELDOR spectra of the end-chain spin label 16-PC in DPPC/GA vesicles is composed of two components, which are assigned to the bulk lipids (with sharp auto peaks and crosspeaks) and to the boundary lipids (with broad auto peaks). Their distinction is clearest for higher temperatures and higher GA concentrations. The quantitative analysis of these spectra shows relatively faster motions and very low ordering for the end chain of the bulk lipids, whereas the boundary lipids show very high "y-ordering" and slower motions. The y-ordering represents a dynamic bending at the end of the boundary lipid acyl chain, which can then coat the GA molecules. These results are consistent with the previous studies by Ge and Freed (1999) using continuous-wave electron spin resonance, thereby supporting their model for GA aggregation and H(II) phase formation for high GA concentrations. Improved instrumental and simulation methods have been employed.     

Effects of Octadecanoylsucrose Derivatives on the Production of Inulinase by Apergillus niger SL-09

Summary The effect of the addition of octadecanoylsucrose esters to the growth medium on the production of inulinase by Aspergillus niger SL-09 was studied in batch culture using shake flasks. The activities of inulinase in vitro and in vivo formed by Aspergillus niger SL-09 was enhanced dramatically by the addition of sucrose ester S-770 to the medium, and it was confirmed that sucrose ester acted as a very efficient inducer for inulinase production. As a result, with the addition of 6 g sucrose ester l⁻¹ at the beginning of the culture, the enzyme activities were enhanced near 7-fold higher than that obtained in the basal medium.     

防烟叶霉变菌株对烟叶霉变的影响

为有效防止烟叶霉变,采用平板对峙培养的方法,就3个防烟叶霉变菌株对霉变菌的抑制作用进行了研究．结果表明,JMBl42、B112、B329对供试霉变菌皆表现出一定的抑制作用,对不同霉变菌的平均抑制率分别为51．6％、52．9％、53．7％．3个防烟叶霉变菌株分别以每mL 10^7、10^8、10^9 cfu(colony当当forming unit)13个浓度单独处理和每mL10。cfu浓度混合处理烟叶,结果表明,JMBl42菌株每mL10,cfu处理浓度效果最好,与对照差异极显著,其次为B112菌株每mL10^8cfu处理浓度,但它与对照差异不显著,B329菌株处理效果最差,混合施用结果与对照差异不显著．由此确定JMBl42菌株每mL10^9cfu处理浓度为仓储烟叶防霉变最佳处理参数、     

Allozyme variation in the diploid (A genome) populations ofScilla scilloides (Hyacinthaceae)

Allozyme variation at eleven loci encoding seven enzyme systems were examined in 20 populations of diploid (genome AA, 2n = 16)Scilla scilloides in China. In comparison with the average species of seed plants studied, populations of this species display a high amount of genetic variation (A = 2.0, P = 58.6%, H_o = 0.172, and H_e = 0.185). Allozyme variation pattern revealed predominant outcrossing within populations and considerable differentiation (F_ST = 0.314) among populations as well as between the subtropic and temperate regions. The wide distribution, long existence and outcrossing are presumably the main factors responsible for the high genetic diversity within populations. But the gravity dispersal of seeds and pollination by small insects set limits to the increase of genetic variation within populations and promote differentiation between populations and regions. In addition, allozyme variation does not distinguishS. scilloides var.albo-viridis and suggests that subtropic populations may be considered as a genetic entity.     

杭州石荠苧生态学特性研究

 杭州石荠苧(Mosla hangchowensis)的种子完全靠风传播,但由于种子大,传播距离不远;种子在冬季休眠,春天(2月末3月初)萌发,种子萌发率很低,尤其是水选上层种子,主要原因是质量差。杭州石荠苧的营养期从3月初到8月上旬,株高在8月中旬以前基本为匀速增加,早期生长极为缓慢。形态和生殖力的环境可塑性极强,自然生长的植株冠幅变动在4～5616cm2之间。杭州石荠苧在自然生境中有时形成单优群落,通常与其它植物伴生。由于早期生长慢,限制了其在群落中的竞争能力,在土壤条件好的地方绝大部分被排挤掉,只是由于其极强的耐旱能力才在高温、干旱、土少的生境中得以存活。 将同属不濒危的华荠苧与之比较,其种子小于杭州石荠苧,但萌发率却高于杭州石荠苧。华荠苧的植株较矮,花色不如杭州石荠苧鲜艳,同在路边生长,不像杭州石荠苧那样容易被人采摘;华荠苧的根较杭州石荠苧的根深,抗雨水冲刷能力较强。华荠苧在自然生境中植株投入生殖的比例大于杭州石荠苧。     

Loss of viability during freeze–thaw of intact and adherent human embryonic stem cells with conventional slow-cooling protocols is predominantly due to␣apoptosis rather than cellular necrosis

Summary A major challenge in the widespread application of human embryonic stem (hES) cells in clinical therapy and basic scientific research is the development of efficient cryopreservation protocols. Conventional slow-cooling protocols utilizing standard cryoprotectant concentrations i.e. 10% (v/v) DMSO, yield extremely low survival rates of <5% as reported by previous studies. This study characterized cell death within frozen–thawed hES colonies that were cryopreserved under standard conditions. Surprisingly, our results showed that immediately after post-thaw washing, the overwhelming majority of hES cells were viable (≈98%), as assessed by the trypan blue exclusion test. However, when the freshly-thawed hES colonies were incubated within a 37 °C incubator, there was observed to be a gradual reduction in cell viability over time. The kinetics of cell death was drastically slowed-down by keeping the freshly-thawed hES colonies at 4 °C, with >90% of cells remaining viable after 90 min of incubation at 4 °C. This effect was reversible upon re-exposing the cells to physiological temperature. The vast majority of low temperature-exposed hES colonies gradually underwent cell death upon incubation for a further 90 min at 37 °C. Terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end-labeling (TUNEL) assay confirmed apoptosis-induced nuclear DNA fragmentation in frozen–thawed hES cells after incubation at 37 °C for 90 min. Expression of active caspase-3 enzyme, which is another prominent marker of apoptosis, was confirmed by immunocytochemical staining, while transmission electron microscopy showed typical ultrastructural features of apoptosis such as chromatin condensation and margination to the nuclear membrane. Hence, our results demonstrated that apoptosis instead of cellular necrosis, is the major mechanism of the loss of viability of cryopreserved hES cells during freeze–thawing with conventional slow-cooling protocols.     

Tricyclic dihydroquinazolinones as novel 5-HT2C selective and orally efficacious anti-obesity agents

Agonists of the 5-HT_2C receptor have been shown to suppress appetite and reduce body weight in animal models as well as in humans. However, agonism of the related 5-HT_2B receptor has been associated with valvular heart disease. Synthesis and biological evaluation of a series of novel and highly selective dihydroquinazolinone-derived 5-HT_2C agonists with no detectable agonism of the 5-HT_2B receptor is described. Among these, compounds (+)-2a and (+)-3c were identified as potent and highly selective agonists which exhibited weight loss in a rat model upon oral dosing.