Oral Candida colonization in patients with chronic periodontitis. Is there any relationship?

Background

Candida can be implicated in the pathology of chronic periodontitis.

Thermal ecology of two sympatric saxicolous lizards of the genus Phymaturus from the Payunia region (Argentina)

We evaluated the thermal biology of two sympatric saxicolous species of the genus Phymaturus, endemic from the Argentine Payunia region. Taking into account that the distributional range of Phymaturus roigorum (the largest species) is greater than the range of P. payuniae, we evaluated the habitat (type of rocks) used by these species. We recorded body temperature and operative temperatures in different habitats, and we determined the preferred body temperature in the laboratory. We compared the thermal quality of habitats occupied and not occupied by Phymaturus payuniae, and the accuracy and effectiveness of thermoregulation between species.     

Caspase-8 activity prevents type 2 cytokine responses and is required for protective T cell-mediated immunity against Trypanosoma cruzi infection

During Trypanosoma cruzi infection, T cells up-regulate caspase-8 activity. To assess the role of caspase-8 in T cell-mediated immunity, we investigated the effects of caspase-8 inhibition on T cells in viral FLIP (v-FLIP) transgenic mice. Compared with wild-type controls, increased parasitemia was observed in v-FLIP mice infected with T. cruzi. There was a profound decrease in expansion of both CD4 and CD8 T cell subsets in the spleens of infected v-FLIP mice. We did not find differences in activation ratios of T cells from transgenic or wild-type infected mice. However, the numbers of memory/activated CD4 and CD8 T cells were markedly reduced in v-FLIP mice, possibly due to defective survival. We also found decreased production of IL-2 and increased secretion of type 2 cytokines, IL-4 and IL-10, which could enhance susceptibility to infection. Similar, but less pronounced, alterations were observed in mice treated with the caspase-8 inhibitor, zIETD. Furthermore, blockade of caspase-8 by zIETD in vitro mimicked the effects observed on T. cruzi infection in vivo, affecting the generation of activated/memory T cells and T cell cytokine production. Caspase-8 is also required for NF-kappaB signaling upon T cell activation. Blockade of caspase-8 by either v-FLIP expression or treatment with zIETD peptide decreased NF-kappaB responses to TCR:CD3 engagement in T cell cultures. These results suggest a critical role for caspase-8 in the establishment of T cell memory, cell signaling, and regulation of cytokine responses during protozoan infection.     

The impact of Helicobacter pylori on atopic disorders in childhood

Background: The prevalence of Helicobacter pylori in Western populations has steadily decreased. This has been suggested as one of the factors involved in the recent increase of asthma and allergy. Some studies have reported a negative association between H. pylori and asthma and allergy, but data are inconsistent and there are a few studies in children. Aim: We investigated whether the prevalence of H. pylori was associated with asthma symptoms, allergic rhinitis, and atopic dermatitis in childhood. Methods: We determined IgG anti‐H. pylori and CagA antibodies in serum of Dutch children, who took part in the PIAMA birth cohort study. Serum was collected from 545 children, aged 7–9 years (Dutch ethnicity 91.5%). Symptoms of asthma and atopy were assessed by yearly questionnaires. Chi‐square tests and logistic regression were used. Results: We found 9%H. pylori and 0.9% CagA seropositivity. Twelve (5.9%) children with reported wheezing ever were H. pylori positive, compared to 37 (10.9%) of the non‐wheezers (p = .05). No significant differences in H. pylori prevalence were found between children with or without allergic rhinitis (8.5% vs 9.5%), atopic dermatitis (8.7% vs 9.2%), and physician‐diagnosed asthma (7.1% vs 9.4%). Multivariate analysis showed no significant associations between H. pylori seropositivity and wheezing (OR 0.52; 95% CI 0.25–1.06), allergic rhinitis (OR 0.96; 95% CI 0.51–1.81), atopic dermatitis (OR 1.05; 95% CI 0.56–1.98) or physician‐diagnosed asthma (OR 0.87; 95% CI 0.37–2.08). Conclusion: We found a borderline significantly lower H. pylori seropositivity in children with wheezing compared to non‐wheezers, but no association between H. pylori serum‐antibody status and allergic rhinitis, atopic dermatitis, or asthma.     

Population structure and phylogeography of the mistletoes Tristerix corymbosus and T. aphyllus (Loranthaceae) using chloroplast DNA sequence variation

The mistletoe Tristerix corymbosus (Loranthaceae) is present in the temperate forest and Chilean matorral biomes of Chile and northwest Patagonia. The closely related cactus-specific species, T. aphyllus, occurs only in the matorral biome. The population structure of these mistletoes was examined to determine whether the distribution of haplotypes corresponds mostly to geographic zone, biome, or other biotic factors. Samples from 108 individuals in 26 localities of T. corymbosus and 13 individuals in four localities of T. aphyllus were collected. Sequences were obtained from two chloroplast genome regions: the atpB-rbcL spacer and the trnL-F region. Haplotypes were analyzed using parsimony and Bayesian trees as well as parsimony networks. All methods placed the haplotypes in four clades, one of which corresponded to T. aphyllus and the others to T. corymbosus. Within T. corymbosus, the different clades did not correlate with biome, geographical region, host, or any apparent morphological feature of the mistletoe. The morphologically distinct cactus parasite T. aphyllus likely arose in sympatry from an unspecialized tree parasite, T. corymbosus, after a host switch. The present day haplotype distribution is complex and resulted from post-glaciation migrations from multiple Pleistocene refugia.     

Photosynthetic electron transport interaction of xanthorrhizol isolated from Iostephane heterophylla and its derivatives

A bioactivity-guided chemical study of Iostephane heterophylla (Asteraceae) led to the isolation of xanthorrhizol (1) as the compound that causes inhibition of ATP synthesis, H⁺-uptake and electron flow from water to methylviologen (basal, phosphorylating and uncoupled) in freshly lysed spinach chloroplasts, thus acting as an inhibitor of the Hill reaction. Acetyl (2), dihydro (3) and acetyl-dihydro (4) derivatives were synthesized. It was found that 4 was less active than 1 and 2 in ATP synthesis, whereas 3 was the most potent inhibitor of the Hill reaction and was also an inhibitor of H⁺-ATPase. Studies of the photosynthetic partial redox reactions from PQ to MV indicated that 1 partially inhibited the PQ pool, but that 3 did not. However, both inhibited the uncoupled electron transport in PSII from water to DCBQ. Uncoupled electron flow from water to silicomolybdate was completely inhibited by 3 and partially by 1. The reaction from DPC to DCPIP was inhibited by both 1 and 3. These results indicate that the inhibition site is located within PSII for 1 and 3 as was corroborated by fluorescence decay data.     

Key residues of loop 3 in the interaction with the interface residue at position 14 in triosephosphate isomerase from Trypanosoma brucei

Cysteine 14 is an interface residue that is fundamental for the catalysis and stability of homodimeric triosephosphate isomerase from Trypanosoma brucei (TbTIM). Its side chain is surrounded by a deep pocket of 11 residues that are part of loop 3 of the adjacent monomer. Mutation of this residue to serine (producing single mutant C14S) yields a wild-type-like enzyme that is resistant to the action of sulfhydryl reagents methylmethane thiosulfonate (MMTS) and 5,5-dithiobis(2-nitrobenzoate) (DTNB). This mutant enzyme was a starting point for probing by cysteine scanning the role of four residues of loop 3 in the catalysis and stability of the enzyme. Considering that the conservative substitution of either serine or alanine with cysteine would minimally alter the structure and properties of the environment of the residue in position 14, we made double mutants C14S/A69C, C14S/S71C, C14S/A73C, and C14S/S79C. Three of these double mutants were similar in their kinetic parameters to wild-type TbTIM and the single mutant C14S, but double mutant C14S/A73C showed a greatly reduced k cat. All enzymes had similar CD spectra, but all mutants had thermal stabilities lower than that of wild-type TbTIM. Intrinsic fluorescence was also similar for all enzymes, but the double mutants bound up to 50 times more 1-anilino-8-naphthalene sulfonate (ANS) and were susceptible to digestion with subtilisin. The double mutants were also susceptible to inactivation by sulfhydryl reagents. Double mutant C14S/S79C exhibited the highest sensitivity to MMTS and DTNB, bound a significant amount of ANS, and had the highest sensitivity to subtilisin. Thus, the residues at positions 73 and 79 are critical for the catalysis and stability of TbTIM, respectively.     

Molecular Bases of Caloric Restriction Regulation of Neuronal Synaptic Plasticity

Aging is associated with the decline of cognitive properties. This situation is magnified when neurodegenerative processes associated with aging appear in human patients. Neuronal synaptic plasticity events underlie cognitive properties in the central nervous system. Caloric restriction (CR; either a decrease in food intake or an intermittent fasting diet) can extend life span and increase disease resistance. Recent studies have shown that CR can have profound effects on brain function and vulnerability to injury and disease. Moreover, CR can stimulate the production of new neurons from stem cells (neurogenesis) and can enhance synaptic plasticity, which modulate pain sensation, enhance cognitive function, and may increase the ability of the brain to resist aging. The beneficial effects of CR appear to be the result of a cellular stress response stimulating the production of proteins that enhance neuronal plasticity and resistance to oxidative and metabolic insults; they include neurotrophic factors, neurotransmitter receptors, protein chaperones, and mitochondrial biosynthesis regulators. In this review, we will present and discuss the effect of CR in synaptic processes underlying analgesia and cognitive improvement in healthy, sick, and aging animals. We will also discuss the possible role of mitochondrial biogenesis induced by CR in regulation of neuronal synaptic plasticity.