The role of the anion in the reaction of reducing sugars with ammonium salts

Reactions of reducing sugars with ammonia and its compounds are important commercially, particularly in the preparation of flavors and caramel colors. However, such reactions generally produce a complex series of products ranging from simple molecules to complex polymeric materials, particularly since commercial systems generally involve mixtures of sugars as opposed to single sugars. This complexity has made understanding the mechanisms of such reactions difficult. Therefore, investigatory work has generally been focused on model systems. Herein we report one such study with model systems: the effects of the nature of the anion of the reactions of reducing sugars with ammonium salts. D-Glucose was reacted in aqueous solution with each of the following ammonium salts: acetate, bicarbonate, carbonate, chloride, citrate, formate, monohydrogenphosphate (DAP), sulfate, and sulfite. These reactions were carried out in a Parr bomb at 93 degrees C for 2.5 h. The initial pH of the reaction mixtures was adjusted to pH 8.0 at 25 degrees C. The resulting mixtures were analyzed by LC-MS, and the results were analyzed by comparing the product yields and distributions with those obtained with DAP. The major reaction product of interest was 2,6-deoxyfructosazine, as it had been shown to be a marker for the polymeric material formed from such reactions. It was found that ammonium salts of weak acids were much more effective in effecting the desired reactions than were those of strong acids; however, none was as effective as DAP.     

四种落叶松种子球蛋白免疫血清学的初步研究

本文对兴安落叶松、长白落叶松、华北落叶松和新疆落叶松种子的球蛋白进行了免疫血清学研究。通过双扩及免疫电泳分析,结果表明四种落叶松之间的抗原距离为零。这可提示用球蛋白进行免疫血清学方法不能鉴别这四个种。     

Esophageal tissue engineering: an in-depth review on scaffold design

Treatment of esophageal cancer often requires surgical procedures that involve removal. The current approaches to restore esophageal continuity however, are known to have limitations which may not result in full functional recovery. In theory, using a tissue engineered esophagus developed from the patient's own cells to replace the removed esophageal segment can be the ideal method of reconstruction. One of the key elements involved in the tissue engineering process is the scaffold which acts as a template for organization of cells and tissue development. While a number of scaffolds range from traditional non-biodegradable tubing to bioactive decellularized matrix have been proposed to engineer the esophagus in the past decade, results are still not yet favorable with many challenges relating to tissue quality need to be met improvements. The success of new esophageal tissue formation will ultimately depend on the success of the scaffold being able to meet the essential requirements specific to the esophageal tissue. Here, the design of the scaffold and its fabrication approaches are reviewed. In this paper, we review the current state of development in bioengineering the esophagus with particular emphasis on scaffold design.     

The variant senescence-associated secretory phenotype induced by centrosome amplification constitutes a pathway that activates hypoxia-inducible factor-1α

The senescence-associated secretory phenotype (SASP) can promote paracrine invasion while suppressing tumour growth, thus generating complex phenotypic outcomes. Likewise, centrosome amplification can induce proliferation arrest yet also facilitate tumour invasion. However, the eventual fate of cells with centrosome amplification remains elusive. Here, we report that centrosome amplification induces a variant of SASP, which constitutes a pathway activating paracrine invasion. The centrosome amplification-induced SASP is non-canonical as it lacks the archetypal detectable DNA damage and prominent NF-κB activation, but involves Rac activation and production of reactive oxygen species. Consequently, it induces hypoxia-inducible factor 1α and associated genes, including pro-migratory factors such as ANGPTL4. Of note, cellular senescence can either induce tumourigenesis through paracrine signalling or conversely suppress tumourigenesis through p53 induction. By analogy, centrosome amplification-induced SASP may therefore be one reason why extra centrosomes promote malignancy in some experimental models but are neutral in others.     

A bacterial type III effector targets plant vesicle-associated membrane proteins

The soilborne bacterial pathogen Ralstonia solanacearum is one of the most destructive plant pathogens worldwide, and its infection process involves the manipulation of numerous plant cellular functions. In this work, we found that the R. solanacearum effector protein RipD partially suppressed different levels of plant immunity triggered by R. solanacearum elicitors, including specific responses triggered by pathogen-associated molecular patterns and secreted effectors. RipD localized in different subcellular compartments in plant cells, including vesicles, and its vesicular localization was enriched in cells undergoing R. solanacearum infection, suggesting that this specific localization may be particularly relevant during infection. Among RipD-interacting proteins, we identified plant vesicle-associated membrane proteins (VAMPs). We also found that overexpression of Arabidopsis thaliana VAMP721 and VAMP722 in Nicotiana benthamiana leaves promoted resistance to R. solanacearum, and this was abolished by the simultaneous expression of RipD, suggesting that RipD targets VAMPs to contribute to R. solanacearum virulence. Among proteins secreted in VAMP721/722-containing vesicles, CCOAOMT1 is an enzyme required for lignin biosynthesis, and mutation of CCOAOMT1 enhanced plant susceptibility to R. solanacearum. Altogether our results reveal the contribution of VAMPs to plant resistance against R. solanacearum and their targeting by a bacterial effector as a pathogen virulence strategy.     

Distribution of Iron in Sphaerotilus and the Associated Inhibition

The distribution of iron between the sheaths and the cells of iron-inhibited Sphaerotilus cultures was determined. The experiment was conducted with different soluble iron forms as inhibitors. The growth inhibition was found to be related to the iron sorbed by the cells rather than by the sheaths. At the 90% inhibition level, iron sorbed by the cells ranged from 13 to 15 mg/g of organism for all three inhibitors tested. For 50% inhibition, the iron sorbed by the cells ranged from 7 to 8 mg/g of organism. The iron sorbed by the sheaths varied widely, ranging from 23 to 118 mg/g of organism at the 90% inhibition level and from 11 to 61 mg/g at the 50% inhibition level. The degree of inhibition is closely related to the amount of iron sorbed by the cells, which in turn is a function of the type of iron compound or complex used. The solubility of the iron is a major consideration.     

Mechanism of enteroviral inactivation by ozone

The mechanism of enteroviral inactivation by ozone was investigated with poliovirus 1 (Mahoney) as the model virus. Ozone was observed to alter two of the four polypeptide chains present in the viral protein coat of poliovirus 1. However, the alteration of the protein coat did not significantly impair virus adsorption or alter the integrity of the virus particle. Damage to the viral RNA after exposure to ozone was demonstrated by velocity sedimentation analysis. It was concluded that the damage to the viral nucleic acid is the major cause of poliovirus 1 inactivation by ozone.     

Fertilization and early cleavage in vitro of ageing bovine oocytes after maturation in culture

Bovine follicular oocytes cultured for 20 to 48 hours were inseminated with frozen thawed spermatozoa. Significantly higher penetration rates (94 to 100% vs 86 to 94%: P < 0.05) and proportions of polyspermy (35 to 78% vs 22 to 45%: P < 0.01) were obtained for oocytes cultured continuously for 24 hours with spermatozoa than for those separated from spermatozoa 8 hours after insemination. The most prominent effect of ageing of oocytes on early events of penetration was observed in the incidence of polyspermy rather than in the penetration rate and the proportion of pronuclear plus cleaved oocytes: the proportion of polyspermic oocytes significantly increased (P < 0.05) in oocytes inseminated after 28 to 48 hours of culture (36 to 78%) compared with those cultured for 20 to 24 hours (22 to 35%) for maturation. Culture experiments for early development of penetrated oocytes indicated that no significant differences were observed in the proportions of oocytes cleaved to the two- to four-cell stage 48 hours after insemination among those cultured for 20 to 40 hours for maturation. However, further cleavage to the four- to sixteen-cell stage 72 to 96 hours after insemination was greatly inhibited as ageing of oocytes proceeded from 28 hours in culture for maturation.     

Kinetics of formation of humic substances in activated sludge systems and their effect on flocculation

Humic substances were isolated during batch aeration studies with activated sludge and a complex waste source, by using concentration and separation techniques that employ reverse osmosis, ultrafitration, and gel permeation chromatography. The study suggests that the formation of high molecular weight humic substances may occur after the removal of the readily available carbon source. The amount of refractory material finally present in the solution will depend on its adsorptive properties toward bacterial cells. The adsorptive characteristics may be determined by the magnitude of the carbohydrate fraction present in the humic substances. If the carbohydrate content decreases, adsorption onto the cells may decrease resulting in an impairment of both the floe formation and settleability of the sludge floes. Decreased adsorption will result in a higher total organic carbon content and an increase in color bearing materials in the effluent.     

Comparative Study of Different Iron Compounds in Inhibition of Sphaerotilus Growth

The effectiveness of iron compounds on growth inhibition of Sphaerotilus species was compared. In this study, two strains of Sphaerotilus were tested with different iron concentrations in a synthetic sewage (S-medium) as formulated by Lackey and Wattie (Sewage Works J. 12:669-684, 1940). For both strains, >80% inhibition of the maximum respiration rate was obtained by the following levels of soluble iron concentrations at pH 6.0: iron citrate, 20 mg/liter as Fe; iron cysteine, 5 mg/liter as Fe; and ferrous sulfate, 10 mg/liter as Fe. At a pH of 6.7 with iron citrate (20 mg/liter as Fe), inhibition of both strains was in excess of 50%. Insoluble iron compounds, such as iron hydroxides and ferrous carbonate, were found to be much less effective than the soluble iron compounds as inhibitors of these two strains. Aged iron hydroxide (500 mg/liter as Fe) produced a 70% inhibition in the maximum respiration rate while fresh iron hydroxide (52 mg/liter as Fe) and ferrous carbonate (500 mg/liter as Fe) produced a 20% inhibition. Chemical analyses of the iron-inhibited Sphaerotilus strains showed a close relationship between the inhibition of the organism's growth and the amount of iron sorbed by the organism.