Immunomodulating polysaccharide fractions of Menyanthes trifoliata L

Looking for new plant sources of immunomodulating agents polysaccharide-rich fractions (PS) from Menyanthes trifoliata L. (Menyanthaceae) have been isolated. The herb of Menyanthes trifoliata L. was sequentially extracted with water, 0.1 M NaOH, 8% CH3COOH, and 1 M NaOH. After dialysis and resolution on Biogel P-10 four homogenic (B-4, B-5, C-4, D-5) and two nonhomogenic (A-3 and D-4) PS were isolated. About 0.5% of PS over 3500 Da were found in the dry plant material. They were characterized through chemical analysis, NMR and vibrational spectroscopy. Speciation analysis of chosen metal/metaloid elements was performed and an exceptionally high concentration of Se was found in PS of a pure water extract (A-3). The biological tests on the immunomodulating influence with human blood-derived lymphocytes and granulocytes revealed that two fractions, B-4 and B-5, were strong stimulators of immune cells, whereas fractions D-5 and A-3 were found as potent suppressive and anti-inflammatory agents. The applied isolation procedures led to the separation of active compounds into stimulatory and inhibitory fractions.     

Reduced sensitivity of Niemann-Pick C1-deficient cells to θ-toxin (perfringolysin O): sequestration of toxin to raft-enriched membrane vesicles

-Toxin (perfringolysin O) binds to cell surface cholesterol and forms oligomeric pores that cause membrane damage. Both in cytotoxicity and cell survival assays, a mutant Chinese hamster ovary cell line NPC1(–) that lacked Niemann-Pick C1 showed reduced sensitivity to -toxin, compared with wild-type (wt) cells. BC is a derivative of -toxin that retains cholesterol-binding activity but lacks cytotoxicity. Confocal and electron microscopy revealed the presence of multiple vesicles which bound BC, both on the cell surface and in the extracellular space of these cells. BC binding to raft microdomains was verified by its resistance to 1% Triton X-100 at 4°C and recovery of bound BC in floating low-density fractions on sucrose density gradient fractionation. BC-labeled vesicles were abolished when NPC1(–) cells were depleted of lipoproteins and also when treated with a Rho-associated kinase inhibitor Y-27632. In addition, similar vesicles were observed in wt cells treated with progesterone. In parallel with these results, -toxin sensitivity of NPC1(–) cells was increased when cells were depleted of lipoproteins or treated with Y-27632, whereas that of wt cells was decreased by progesterone. Our findings suggest that sequestration of toxin to raft-enriched cell surface vesicles may underlie reduced sensitivity of NPC1-deficient cells to -toxin.     

Characterization of components of the mismatch repair machinery in Trypanosoma brucei

Mismatch repair is one of a number of DNA repair pathways that cells possess to deal with damage to their genome. Mismatch repair is concerned with the recognition and correction of incorrectly paired bases, which can be base-base mismatches or insertions or deletions of a few bases, and appears to have been conserved throughout evolution. Primarily, this is concerned with increasing the fidelity of DNA replication, but also has important roles in the regulation of homologous recombination and the correction of chemical damage. In this study, we describe five genes in the protistan parasite Trypanosoma brucei that are likely to be involved in nuclear mismatch repair. The predicted T. brucei mismatch repair genes are diverged compared with their likely counterparts in the other eukaryotes examined to date. To demonstrate that these do indeed encode a functional nuclear mismatch repair system, we made T. brucei null mutants in two of the genes, MSH2 and MLH1, that are likely to be central to the functioning of the mismatch repair machinery. These mutations resulted in increased rates of sequence variation at a number of microsatellite loci in the parasite genome, and led to increased tolerance to the alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine, both phenotypes consistent with mismatch repair impairment.     

Streptococcus alactolyticus is the dominating culturable lactic acid bacterium species in canine jejunum and feces of four fistulated dogs

Canine intestinal lactic acid bacterium (LAB) population in four fistulated dogs was cultured and enumerated using MRS agar. LAB levels ranging from 1.4x10(6) to 1.5x10(7) CFU ml(-1) were obtained in jejunal chyme. In the fecal samples 7.0x10(7) and 2.0x10(8) CFU g(-1) were detected. Thirty randomly selected isolates growing in the highest sample dilutions were identified to species level using numerical analysis of 16S and 23S rDNA restriction fragment length polymorphism patterns (ribotyping) and 16S rDNA sequence analysis. According to these results, Streptococcus alactolyticus was the dominant culturable LAB species in both feces and jejunal chyme. In addition, Lactobacillus murinus and Lactobacillus reuteri were detected.     

Poly(3-hydroxybutyrate) biosynthesis in the biofilm of Alcaligenes eutrophus, using glucose enzymatically released from pulp fiber sludge

Glucose, enzymatically released from pulp fiber sludge, was combined with inorganic salts and used as a growth medium for Alcaligenes eutrophus, a gram-negative strain producing poly(3-hydroxybutyrate) (PHB). By controlling the concentrations of the inorganic salts in the growth medium, almost 78% of the cell mass was converted to pure PHB. Efforts were made to find conditions for bacterial growth in the form of a biofilm on a cheap and reusable carrier. A number of positively charged carriers were tested, and the anion exchanger DEAE-Sephadex A-25 was chosen as a microcarrier for packed-bed biofilm cultures of A. eutrophus. Conditions for attachment, growth, and detachment were established. Biofilm formation on the microcarrier is strongly dependent on the ionic strength of the attachment medium. In order to achieve formation of the biofilm and its recovery from the microcarrier, the ionic strengths of the attachment and the detachment media were varied. Low ionic strength was tested for attachment, and high ionic strength was tested for detachment. Although biofilm formation in the packed-bed reactor is limited, the volumetric yield of cells based on the void volume of the packed bed is comparable with the batch culture yield.     

siRNAs and miRNAs: small RNA molecules for big tasks

Small RNAs have been recently discovered as important regulators of gene expression in Eukaryota. This review compares two categories of small RNAs existing in plants: short interfering RNAs (siRNAs) and microRNAs (miRNAs) and reveals similarities and differences between two intriguing processes: RNA degradation and translational repression directed by small RNAs. The disruption of miRNA-mediated regulation causes developmental abnormalities in plants, proving a fundamental role of miRNAs.     

Signal detection theory applied to three visual search tasks--identification, yes/no detection and localization

Adding distracters to a display impairs performance on visual tasks (i.e. the set-size effect). While keeping the display characteristics constant, we investigated this effect in three tasks: 2 target identification, yes-no detection with 2 targets, and 8-alternative localization. A Signal Detection Theory (SDT) model, tailored for each task, accounts for the set-size effects observed in identification and localization tasks, and slightly under-predicts the set-size effect in a detection task. Given that sensitivity varies as a function of spatial frequency (SF), we measured performance in each of these three tasks in neutral and peripheral precue conditions for each of six spatial frequencies (0.5-12 cpd). For all spatial frequencies tested, performance on the three tasks decreased as set size increased in the neutral precue condition, and the peripheral precue reduced the effect. Larger set-size effects were observed at low SFs in the identification and localization tasks. This effect can be described using the SDT model, but was not predicted by it. For each of these tasks we also established the extent to which covert attention modulates performance across a range of set sizes. A peripheral precue substantially diminished the set-size effect and improved performance, even at set size 1. These results provide support for distracter exclusion, and suggest that signal enhancement may also be a mechanism by which covert attention can impose its effect.