Properties and localization of bicarbonate-stimulated ATPase activity in rat brain

Abstract— A 20–30 per cent stimulation of ATPase activity by added NaHCO₃ was found in homogenates of a variety of mammalian tissues. The subcellular distribution of this (HCO₃^-)—stimulated activity was examined in detail using rat cerebral cortex. The stimulation was specific for the HCO₃^- ion and was predominantly localized in the mitochondrial subcellular fraction, in which a 2-fold stimulation by HCO₃^- was found. The effect of inhibitors supported the identification as the mitochondrial ATPase. Both sodium azide and thiocyanate were inhibitory. The effects of varying the Mg²⁺ concentration, HCO₃^- concentration, and pH were also studied. In the presence of HCO₃^- the K_m for ATP was reduced approximately 3-fold. There was no effect of HCO₃^- on the ma + K) ATPase or Mg²⁺ ATPase from the microsomal fraction of rat cerebral cortex. Our findings have been discussed in relation to previous work on HCO₃^- stimulation of ATPae activity in subcellular fractions from other tissues, as well as its possible relevance to the known effects of HCO₃^- and carbonic anhydrase on active ion transport.     

Seasonal variation in hypericin content of Hypericum perforatum L. (St. John's Wort)

Hypericin and pseudohypericin, bioactive constituents in St. John's Wort (Hypericum perforatum), have been determined in the soft tops of the plant that are most likely to be browsed by foraging livestock. In two consecutive seasons, the hypericin/pseudohypericin concentration in a broad leaf biotype varied from a winter minimum of less than 100 ppm to a summer maximum approaching 3000 ppm. In contrast the narrow leaf biotype increased from similar winter values to summer maxima approaching 5000 ppm. The latter biotype was slower in returning to low levels of hypericin/pseudohypericin.     

Promyelocytic Leukemia Protein Interacts with the Apoptosis-associated Speck-like Protein to Limit Inflammasome Activation

The apoptosis-associated speck-like protein containing a caspase-activating recruitment domain (ASC) is an essential component of several inflammasomes, multiprotein complexes that regulate caspase-1 activation and inflammation. We report here an interaction between promyelocytic leukemia protein (PML) and ASC. We observed enhanced formation of ASC dimers in PML-deficient macrophages. These macrophages also display enhanced levels of ASC in the cytosol. Furthermore, IL-1β production was markedly enhanced in these macrophages in response to both NLRP3 and AIM2 inflammasome activation and following bone marrow-derived macrophage infection with herpes simplex virus-1 (HSV-1) and Salmonella typhimurium. Collectively, our data indicate that PML limits ASC function, retaining ASC in the nucleus.     

Invasion of human epithelial cells by Campylobacter upsaliensis

Few data exist on the interaction of Campylobacter upsaliensis with host cells, and the potential for this emerging enteropathogen to invade epithelial cells has not been explored. We have characterized the ability of C. upsaliensis to invade both cultured epithelial cell lines and primary human small intestinal cells. Epithelial cell lines of intestinal origin appeared to be more susceptible to invasion than non-intestinal-derived cells. Of three bacterial isolates studied, a human clinical isolate, CU1887, entered cells most efficiently. Although there was a trend towards more efficient invasion of Caco-2 cells by C. upsaliensis CU1887 at lower initial inocula, actual numbers of intracellular organisms increased with increasing multiplicity of infection and with prolonged incubation period. Confocal microscopy revealed C. upsaliensis within primary human small intestinal cells. Both Caco-2 and primary cells in non-confluent areas of the infected monolayers were substantially more susceptible to infection than confluent cells. The specific cytoskeletal inhibitors cytochalasin B, cytochalasin D and vinblastine attenuated invasion of Caco-2 cells in a concentration-dependent manner, providing evidence for both microtubule- and microfilament-dependent uptake of C. upsaliensis. Electron microscopy revealed the presence of organisms within Caco-2 cell cytoplasmic vacuoles. C. upsaliensis is capable of invading epithelial cells and appears to interact with host cell cytoskeletal structures in order to gain entry to the intracellular environment. Entry into cultured primary intestinal cells ex vivo provides strong support for the role of host cell invasion during human enteric C. upsaliensis infection.     

Susceptibility to Invasive Meningococcal Disease: Polymorphism of Complement System Genes and Neisseria meningitidis Factor H Binding Protein

Background

Neisseria meningitidis can cause severe infection in humans. Polymorphism of Complement Factor H (CFH) is associated with altered risk of invasive meningococcal disease (IMD). We aimed to find whether polymorphism of other complement genes altered risk and whether variation of N. meningitidis factor H binding protein (fHBP) affected the risk association.

Methods

We undertook a case-control study with 309 European cases and 5,200 1958 Birth Cohort and National Blood Service cohort controls. We used additive model logistic regression, accepting P<0.05 as significant after correction for multiple testing. The effects of fHBP subfamily on the age at infection and severity of disease was tested using the independent samples median test and Student’s T test. The effect of CFH polymorphism on the N. meningitidis fHBP subfamily was investigated by logistic regression and Chi squared test.

Results

Rs12085435 A in C8B was associated with odds ratio (OR) of IMD (0.35 [95% CI 0.19–0.67]; P = 0.03 after correction). A CFH haplotype tagged by rs3753396 G was associated with IMD (OR 0.56 [95% CI 0.42–0.76], P = 1.6x10⁻⁴). There was no bacterial load (CtrA cycle threshold) difference associated with carriage of this haplotype. Host CFH haplotype and meningococcal fHBP subfamily were not associated. Individuals infected with meningococci expressing subfamily A fHBP were younger than those with subfamily B fHBP meningococci (median 1 vs 2 years; P = 0.025).

Discussion

The protective CFH haplotype alters odds of IMD without affecting bacterial load for affected heterozygotes. CFH haplotype did not affect the likelihood of infecting meningococci having either fHBP subfamily. The association between C8B rs12085435 and IMD requires independent replication. The CFH association is of interest because it is independent of known functional polymorphisms in CFH. As fHBP-containing vaccines are now in use, relationships between CFH polymorphism and vaccine effectiveness and side-effects may become important.     

Helminth Infection and Commensal Microbiota Drive Early IL-10 Production in the Skin by CD4+ T Cells That Are Functionally Suppressive

The skin provides an important first line of defence and immunological barrier to invasive pathogens, but immune responses must also be regulated to maintain barrier function and ensure tolerance of skin surface commensal organisms. In schistosomiasis-endemic regions, populations can experience repeated percutaneous exposure to schistosome larvae, however little is known about how repeated exposure to pathogens affects immune regulation in the skin. Here, using a murine model of repeated infection with Schistosoma mansoni larvae, we show that the skin infection site becomes rich in regulatory IL-10, whilst in its absence, inflammation, neutrophil recruitment, and local lymphocyte proliferation is increased. Whilst CD4⁺ T cells are the primary cellular source of regulatory IL-10, they expressed none of the markers conventionally associated with T regulatory (T_reg) cells (i.e. FoxP3, Helios, Nrp1, CD223, or CD49b). Nevertheless, these IL-10⁺ CD4⁺ T cells in the skin from repeatedly infected mice are functionally suppressive as they reduced proliferation of responsive CD4⁺ T cells from the skin draining lymph node. Moreover, the skin of infected Rag^-/- mice had impaired IL-10 production and increased neutrophil recruitment. Finally, we show that the mechanism behind IL-10 production by CD4⁺ T cells in the skin is due to a combination of an initial (day 1) response specific to skin commensal bacteria, and then over the following days schistosome-specific CD4⁺ T cell responses, which together contribute towards limiting inflammation and tissue damage following schistosome infection. We propose CD4⁺ T cells in the skin that do not express markers of conventional T regulatory cell populations have a significant role in immune regulation after repeated pathogen exposure and speculate that these cells may also help to maintain skin barrier function in the context of repeated percutaneous insult by other skin pathogens.     

Further Evidence of Lack of Pheromonal Inhibition among Queens of the Ant Leptothorax acervorum

Queens in some species of ant with several queens per colony are believed to inhibit one another's fecundity pheromonally. This paper describes a repeat of an experimental test of this idea in the multiple-queen ant Leptothorax acervorum. The three most fecund queens from a field-collected colony were housed together in an experimental nest. This was then filmed for 10 h per day over 36 consecutive days (i.e. for 360 h in total). Over the first 12 d, all queens were present in the colony. For the middle 12 d, the two most fecund queens were removed, but were returned for the final 12 d. The queen that was observed throughout the experiment failed to show a rise in fecundity when the other queens were removed. Instead, her egg-laying rate fell, although this drop was not significant. These results confirm previous findings that short-term, strong pheromonal inhibition of fecundity does not occur among L. acervorum queens. The phenomena of pheromonal inhibition in other species may be a result of workers treating queens differentially in response to rapid, short-term changes in the numbers of queens and eggs. If so, the results presented here could stem from the relative infrequency of such changes in L. acervorum.