Particle-bubble attachment in yeast flotation by colloidal gas aphrons

Flotation of microorganisms by colloidal gas aphrons (CGAs) is recognised as an inexpensive and effective method of separation. CGAs are micro-sized gas bubbles of 25 7m in average diameter and each is encapsulated in an aqueous shell of surfactant solution. High flotation efficiency can be achieved when colloidal gas aphrons are employed in a dilute suspension containing yeast cells. Under certain experimental conditions, the adsorption of yeast on the aphrons follows the Langmuir model. With changes in the pH and feed concentration, the mechanism of bubble attachment and detachment changes from a monolayer to a multilayer adsorption.     

活性氧对外源IAA诱导的ACC合酶活性的影响

本文试图从活性氧的角度阐明外源IAA诱导ACC合酶活性的机制.绿豆(Phaseolus radiatus L.)幼苗的乙烯产生及ACC合酶活性从萌发的第5天开始上升,到第10天达到高峰,接着下降.10 μmol/L的外源IAA能明显促进绿豆幼苗乙烯的产生及ACC合酶的活性,同时也促进了超氧阴离子自由基(O(-)/(*)2)、过氧化氢(H2O2)的产生.显示外源IAA诱导的ACC合酶的活性与其诱导的活性氧的产生具有某种相关性.外源O(-)/(*)2处理能明显提高绿豆幼苗的乙烯产生速率及ACC合酶的活性,而外源H2O2无论对乙烯产生或ACC合酶的活性均没有明显的作用.外加O(-)/(*)2的清除剂SOD对绿豆幼苗乙烯的产生及ACC合酶活性的提高有一定的抑制作用,而外源过氧化氢酶却没有明显的作用.为此我们可以得出结论:外源IAA诱导的绿豆幼苗ACC合酶活性的提高可能是由于其诱导的O(-)/(*)2产生的升高引起的,这可能也是高等植物中调控乙烯生物合成的机制之一;而IAA诱导的H2O2产率的升高并不是其诱导ACC合酶活性升高的原因.     

Chromosome homology in the climbing rats,genus tylomys (Rodentia: Cricetidae)

The climbing rats (Tylomys spp.) have diploid numbers of 52 (T. panamensis), 42 (T. nudicaudus), 40 (T. n. gymnurus) and 36 (T. n. villai). Using G-band analysis we found that the variations are mainly of the Bobertsonian type, and practically all changes can be traced. G-banding also revealed that biarmed chromosomes with similar morphology may be composed of different components. Such conclusions were verified also by analysis of the chromosomes of interspecific hybrids. C-band staining showed that the constitutive heterochromatin of Tylomys is mainly located in the centromeric regions and the sex chromosomes, a situation similar to that of Microtus agrestis. In one specimen of T. panamensis, however, an additional terminal heterochromatic segment was found in one member of the large metacentric pair. Our data underline that in mammalian cytotaxonomy studies both C- and G-band (or C- and Q-band) techniques must be applied to gain maximal information.     

癌基因iASPP的克隆、表达与纯化

iASPP是新近发现的高度保守的p53相关基因,其蛋白产物定位于细胞核内,具有结合NFκBp65亚基和p53功能,进而抑制NFκB的转录调节和p53对凋亡的调节功能。利用RTPCR方法从人白血病细胞系U937中克隆出癌基因iASPP,将其克隆至原核表达载体pET28a(+)中,成功构建iASPP表达载体PIAF,重组质粒读码框和序列与预期一致。在IPTG诱导下,重组载体大肠杆菌Rosetta(DE3)菌株,表达产物经SDSPAGE和Westernblot方法分析证实系iASPP融合蛋白。利用Ni离子鳌合层析的方法纯化iASPP融合蛋白,经SDSPAGE鉴定其纯度超过80%。     

2��-O Methylation of the Viral mRNA Cap by West Nile Virus Evades Ifit1-Dependent and -Independent Mechanisms of Host Restriction In Vivo

Prior studies have shown that 2′-O methyltransferase activity of flaviviruses, coronaviruses, and poxviruses promotes viral evasion of Ifit1, an interferon-stimulated innate immune effector protein. Viruses lacking 2′-O methyltransferase activity exhibited attenuation in primary macrophages that was rescued in cells lacking Ifit1 gene expression. Here, we examined the role of Ifit1 in restricting pathogenesis in vivo of wild type WNV (WNV-WT) and a mutant in the NS5 gene (WNV-E218A) lacking 2′-O methylation of the 5′ viral RNA cap. While deletion of Ifit1 had marginal effects on WNV-WT pathogenesis, WNV-E218A showed increased replication in peripheral tissues of Ifit1 ^−/− mice after subcutaneous infection, yet this failed to correlate with enhanced infection in the brain or lethality. In comparison, WNV-E218A was virulent after intracranial infection as judged by increased infection in different regions of the central nervous system (CNS) and a greater than 16,000-fold decrease in LD₅₀ values in Ifit1 ^−/− compared to wild type mice. Ex vivo infection experiments revealed cell-type specific differences in the ability of an Ifit1 deficiency to complement the replication defect of WNV-E218A. In particular, WNV-E218A infection was impaired in both wild type and Ifit1 ^−/− brain microvascular endothelial cells, which are believed to participate in blood-brain barrier (BBB) regulation of virus entry into the CNS. A deficiency of Ifit1 also was associated with increased neuronal death in vivo, which was both cell-intrinsic and mediated by immunopathogenic CD8⁺ T cells. Our results suggest that virulent strains of WNV have largely evaded the antiviral effects of Ifit1, and viral mutants lacking 2′-O methylation are controlled in vivo by Ifit1-dependent and -independent mechanisms in different cell types.     

Survival adaptations of threeEuphorbia spp. in arid ecosystem

Three species ofEuphorbia (E. granulata, E. prostrata andE. hirta) exhibited both morphological and physiological adaptations in dry environmental conditions. High bound water, thick cuticle, dense hair covering and low stomatal index are some of the survival adaptations they developed under water stress conditions of the Indian arid zone.     

Temperature-Dependent Electrical and Ultrastructural Characterizations of Porcine Skin upon Electroporation

The mechanism of high-voltage pulse-induced permeabilization of the stratum corneum, the outer layer of the skin, is still not completely understood. It has been suggested that joule heating resulting from the applied pulse may play a major role in disrupting the stratum corneum. In this study, electrical and ultrastructural measurements were conducted to examine the temperature dependence of the pulse-induced permeabilization of the stratum corneum. The stratum corneum resistance was measured using a vertical diffusion holder, with the stratum corneum placed between two electrode-containing chambers. The stratum corneum resistance was reduced manyfold during the applied pulse. The extent of resistance reduction increased with pulse voltage until reaching a threshold value, above which the resistance reduction was less dependent on the pulse voltage. The stratum corneum was more susceptible to permeabilization at high temperature, the threshold voltage being lower. The stratum corneum resistance recovered within milliseconds after a single 0.3-ms pulse. High-temperature samples had a more prolonged recovery time. Using time-resolved freeze fracture electron microscopy, aggregates of lipid vesicles were observed in all samples pulsed above the threshold voltage. The sizes and fractional areas occupied by aggregates of lipid vesicles at 4°C and at 25°C were measured at different time points after the applied pulse. Aggregates of vesicles persisted long after the electric resistance was recovered. After pulsing at the same voltage of 80 V, samples at 4°C were found to have slightly more extensive aggregate formation initially, but recovered more rapidly than those at 25°C. The more rapid recovery of the 4°C samples was likely due to a lower supra-threshold voltage. Viscoelastic instability propagation created by the pulse may also play a role in the recovery of the aggregates.