The effect of salt and pH on block liposomes studied by cryogenic transmission electron microscopy

Recently, we have reported the discovery of block liposomes (BLs), a new class of liquid (chain-melted) vesicles, formed in mixtures of the curvature-stabilizing hexadecavalent cationic lipid MVLBG2, the neutral lipid 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC), and water with no added salt. BLs consist of connected spheres, pears, tubes, or rods. Unlike in typical liposome systems, where spherical vesicles, tubular vesicles, and cylindrical micelles are separated on the macroscopic scale, shapes remain connected and are separated only on the nanometer scale within a single BL. Here, we report structural studies of the effect of salt and pH on the BL phase, carried out using differential interference contrast microscopy (DIC) and cryogenic transmission electron microscopy (cryo-TEM). Addition of salt screens the electrostatic interactions; in low-salt conditions, partial screening of electrostatic interactions leads to a shape transition from BLs to bilamellar vesicles, while in the high-salt regime, a shape transition from BLs to liposomes with spherical morphologies occurs. This demonstrates that strong electrostatic interactions are essential for BL formation. Understanding the control of liposome shape evolution is of high interest because such shape changes play an important role in many intracellular processes such as endocytosis, endoplasmatic reticulum-associated vesiculation, vesicle recycling and signaling.     

O2 replenishment to fish nests: males adjust brood care to ambient conditions and brood development

Parental care through nest defense and maintenance enhancesoffspring success. In nature, obligate anemone-dwelling fishesand their nests of benthic eggs are protected against most predatorsby their host anemone; thus, parental care generally consistsof nest tending through fanning and mouthing. Tending in fishesis believed to oxygenate the eggs; however, a real-time linkbetween fanning and oxygenation is tenuous. This study investigatedwhether tending modified the oxygen microenvironment of theembryos and, subsequently, whether tending was modified accordingto ambient dissolved oxygen (DO), increasing metabolic demandsof developing embryos, and water temperature. There was a timelag of approximately 1 s between tending and increases in theamount of oxygen within the nest, demonstrating that DO is directlyaffected by parental tending. While there was evidence of biparentalcare, males invested more time tending embryos (40% initially)than did females (20–30%), and male investment increasedto 70% as embryo development progressed and embryonic metabolicdemands increased. Additionally, male fish adjusted tendingeffort on a diel cycle as ambient DO fluctuated: time spenttending was lowest between 1000 and 1400 h (35%), when ambientDO was highest, and increased throughout the day, reaching apeak of 70% between 2200 and 0200 h, when ambient DO was lowest.Increased water temperature reduced the number of tending boutsper minute throughout the day but did not influence any otheraspect of tending behavior. These results suggest that fishadjust tending behavior coincident to changing conditions inthe nest, both on a daily basis and throughout development ofthe embryos.     

Methyl‐CpG‐binding protein 2 polymorphisms and vulnerability to autism

The methyl‐binding protein gene, MECP2, is a candidate for involvement in autism through its implication as a major causative factor in Rett syndrome that has similarities to autism. Rare mutations in MECP2 have also been identified in autistic individuals. We have examined the possible broader involvement of MECP2 as a predisposing factor in the disorder. Analysis of polymorphic markers spanning the gene and comprising both microsatellites and single nucleotide polymorphisms (SNPs) by the transmission disequilibrium test in two collections of families (219 in total), one in the USA and one in the UK, has provided evidence for significant association (P = 0.009) for a three‐marker SNP haplotype of MECP2 with autism/autism spectrum disorders. This association is supported by association of both Single Sequence Repeat (SSR) and SNP single markers located at the 3′ end of the MECP2 locus and flanking sequence, the most significant being that of an indel marker located in intron 2 (P = 0.001 – Bonferroni corrected P = 0.006). This suggests that one or more functional variants of MECP2 existing at significant frequencies in the population may confer increased risk of autism/autism spectrum disorders and warrants further investigation in additional independent samples.     

Complex effects of grazing treatment on an annual in a species-poor grassland community

Abstract. The effects of grazing upon the establishment, survival, growth and reproduction of a grassland annual Geranium dissectum growing in a sward dominated by grasses were examined in a replicated grazing experiment with sheep. Seeds were sown in both summer and autumn, and grazing was controlled to produce two levels of grazing in winter, two levels in spring, and two in summer, combined in a 2 x 2 x 2 factorial experimental design. Higher intensities of grazing in the period immediately before emergence benefitted plant establishment, but subsequent survival showed many interactions between factors, demonstrating that under certain conditions and at certain times grazing was detrimental. It is suggested that the frequency of G. dissectum in the grassland was low because the heavy grazing conditions that foster seedling emergence also jeopardize subsequent survival. This may also be why productive grassland communities in general contain few palatable dicots.     

Differential Behavioural Effects of Silent Bared Teeth Display and Relaxed Open Mouth Display in Chimpanzees (Pan troglodytes)

This study examines the behavioural consequences of the silent bared teeth display (SBT) and the relaxed open mouth display (ROM) in the chimpanzee, and discusses functional similarities with smiling and laughing (respectively) in humans. Rates of affinitive behaviour increase (in relation to baseline levels) following SBT, suggesting that SBT is a signal of affinity. ROM is observed primarily during play, and dyadic play bouts are significantly longer when ROM is bidirectional, indicating that it may be a signal of play. Rates of affinitive behaviour also increased after ROM, suggesting that both displays may have a similar ultimate (evolutionary) function – social bonding; this could explain convergence of the two displays in humans.     

Analysis of rare high-DNA cell populations in serous effusions using continuous-motion imaging

The rare high-DNA cell sub-populations in a series of serous effusion specimens were analysed to determine whether such measurements could provide a basis for the improved diagnosis of malignancy. Monolayer specimens stained with gallocyanin chrome-alum were scanned with the CERVIFIP continuous-motion image analyser to locate and measure the highest-DNA cells in the sample. Two types of features were obtained for the detected sub-populations; firstly, 'percentile ploidy' values which characterise the ploidy levels above which specified proportions of the total cells are found; and secondly 'percentage abnormal' values which characterise the proportion of the cells diagnosed as malignant during examination by a cytopathologist. The classification accuracy for one or both of these features was then obtained by comparison with the clinical outcome of each patient. The results gave a classification error of 9/44 (20%) using the 0.01% percentile ploidy alone, 6/44 (14%) using the 75% percentage abnormal feature alone, but only 2/44 (5%) from a box discriminant using both features. It was therefore concluded that the analysis of the high-DNA cell population could be of value in the diagnosis of malignancy in serous effusion specimens.     

Protein B: a versatile bacterial Fc-binding protein selective for human IgA

Protein B, a selective bacterial IgA Fc-binding protein isolated from group B streptococci, has been used to quantify fluid phase and immobilized human IgA. Protein B detects both human IgA1 and IgA2 subclasses and is also reactive with secretory IgA. Protein B can be used immobilized to microtiter plates to capture IgA or following biotinylation as a tracer for fluid phase or immobilized human IgA. The studies presented here suggest protein B will prove to be a valuable reagent for quantitative immunochemical procedures involving human IgA antibodies and facilitate a variety of studies of IgA responses in man.