pH-sensitive liposomes mediate cytoplasmic delivery of encapsulated macromolecules

AbstractNegatively charged liposomes are endocytosed by the coated vesicle system and accumulate in acidic intracellular vesicles. Liposomes that become unstable at acidic pH improve cytoplasmic delivery of membraneimpermeant macromolecules such as calcein (CAL) and FITC dextran (18 or 40 kDa). Oleic acid (OA): phosphatidylethanolamine (PE) (3:7 mole ratio) liposomes become permeable to CAL at pH < 7.0. Control liposomes of phosphatidylserine : PE or OA : phosphatidylcholine are stable at pH 4–8. OA:PE liposomes promote cytoplasmic delivery of encapsulated CAL to CV-1 cells, as evidenced by the emergence of diffuse, cytoplasmic CAL fluorescence. Delivery requires metabolic energy and is partially inhibited by chloroquine or monensin, which raise the pH of intracellular vesicles

Silicon fractionation in Mollic Fluvisols along the Central Elbe River, Germany

Quantification of Si in its different forms in soil is a prerequisite to understand the geochemical distribution and fate of Si along with their driving biogeochemical processes. However, different Si fractions in floodplain soils have not been quantified yet, and little is known about the processes driving Si fractionation in these soils. The aim of this study was to clarify the processes that drive formation and distribution of Si among fractions in floodplain soils. We obtained and quantified these fractions using a sequential Si extraction method (Georgiadis et al., 2013) in three Mollic Fluvisols along the Central Elbe River. The highest Si proportion apart from the residual fraction was found in minerogenic amorphous silica (up to 5.6% of total Si), followed by Si occluded in pedogenic oxides and hydroxides (up to 0.7% of total Si). Silicon from biogenic amorphous silica amounted to 0.02-0.6% of total Si. The smallest proportion of Si was found in the mobile Si fraction and made up about 0.01% of the total Si. The results of this study demonstrate the importance of the soil water budget on the accumulation of easy-to-mobilise Si, Si occluded in pedogenic oxides and hydroxides and amorphous silica. Reductive dissolution of Fe and Mn oxides may induce Si release into the soil solution, subsequent oxidizing conditions may induce Si accumulation by adsorption, co-precipitation and occlusion of Si on/with newly formed Fe and Mn oxides. Accumulation of bio-opal after flooding may induce larger amounts of biogenic amorphous silica in floodplain soils than in terrestrial soils. Finally, floodplain soils may accumulate larger amounts of Si bound to occluded particulate SOM than terrestrial soils, which experience less input of particulate SOM than floodplain soils

Theory of tunable pH sensitive vesicles of anionic and cationic lipids or anionic and neutral lipids

The design of vesicles which become unstable at an easily tuned value of pH is of great interest for targeted drug delivery. We present a microscopic theory for two forms of such vesicles. A model of lipids introduced by us previously is applied to a system of ionizable, anionic lipid, and permanently charged, cationic lipid. We calculate the pH at which the lamellar phase becomes unstable with respect to an inverted hexagonal one, a value which depends continuously on the system composition. Identifying this instability with that displayed by unilamellar vesicles undergoing fusion, we obtain very good agreement with the recent experimental data of Hafez et al., Biophys. J. 2000 79: 1438-1446, on the pH at which fusion occurs vs. vesicle composition. We explicate the mechanism in terms of the role of the counter ions. This understanding suggests that a system of a neutral, non lamellar forming lipid stabilized by an anionic lipid would serve equally well for preparing tunable, pH sensitive vesicles. Our calculations confirm this. Further, we show that both forms of vesicle have the desirable feature of exhibiting a regime in which the pH at instability is a rapidly varying function of the vesicle composition.Comment: five figures, to appear in Biophys.

Searching for Lyme borreliosis in Australia: Results of a canine sentinel study

Background: Lyme borreliosis is a common tick-borne disease of the northern hemisphere that is caused by bacterial spirochaetes of the Borrelia burgdorferi (sensu lato) (Bbsl) complex. To date, there has been no convincing evidence for locally-acquired Lyme borreliosis on the Australian continent and there is currently a national debate concerning the nature and distributions of zoonotic tick-transmitted infectious disease in Australia. In studies conducted in Europe and the United States, dogs have been used as sentinels for tick-associated illness in people since they readily contact ticks that may harbour zoonotic pathogens. Applying this principle, we used a combination of serological assays to test dogs living in tick 'hot spots' and exposed to the Australian paralysis tick, Ixodes holocyclus, for evidence of exposure to B. burgdorferi (s.l.) antigens and other vector-borne pathogens. Results: Altogether, 555 dogs from four demographic groups were recruited into this study. One dog had evidence of exposure to Anaplasma spp. but no other dog was positive in screening tests. A total of 122 dogs (22.0%) had a kinetic ELISA (KELA) unit value > 100, and one dog with a high titre (399.9 KELA units) had been vaccinated against B. burgdorferi (sensu stricto) before travelling to Australia. Older dogs and those with a history of tick paralysis were significantly more likely to have a KELA unit value > 100. Line immunoassay analysis revealed moderate-to-weak (equivocal) bands in 27 (4.9%) dogs. Conclusions: Except for a single dog presumed to have been exposed to Anaplasma platys, infection with Anaplasma spp. B. burgdorferi (s.l.), Ehrlichia spp., and Dirofilaria immitis, was not detected in the cohort of Australian dogs evaluated in this study. These results provide further evidence that Lyme borreliosis does not exist in Australia but that cross-reacting antibodies (false positive results) are common and may be caused by the transmission of other tick-associated organisms

Effect of amoxicillin‐clavulanic acid on clinical scores, intestinal microbiome, and amoxicillin‐resistant Escherichia coli in dogs with uncomplicated acute diarrhea

Background Despite limited evidence of efficacy, antibiotic treatment is still frequently prescribed in dogs with uncomplicated acute diarrhea (AD). Objective To assess whether amoxicillin‐clavulanic acid has a clinical benefit, an effect on the fecal microbiome, and the proportion of amoxicillin‐resistant Escherichia coli in dogs with AD. Animals Sixteen dogs with AD of <3 days duration. Methods Prospective, placebo‐controlled, double‐blinded study. Clinical scores were compared between client‐owned dogs randomly assigned to an antibiotic (AG) or a placebo (PG) group. The intestinal microbiome was analyzed using quantitative PCR assays. Amoxicillin‐resistant fecal E. coli were assessed semiquantitatively with microbiological methods. Results There was no difference in clinical recovery between treated dogs or controls (CADS index day 10: AG group median: 2 (range: 1‐3; CI [1.4; 2.6]); PG group median: 1.6 (range: 1‐3; CI [1.1; 2.4]); P > .99). All dogs gained normal clinical scores (CADS index ≤3) after 1 to 6 days (median 2 days) after presentation. There was no significant difference in the fecal dysbiosis index (during treatment: AG mean −2.6 (SD 3.0; CI [−5.1; 0.0]); PG mean −0.8 (SD 4.0; CI [−4.2; 2.5]; P > .99) or its bacterial taxa. The proportion of resistant fecal E. coli increased (to median: 100%; range: 35%‐100%) during treatment with amoxicillin‐clavulanic acid and was still increased (median: 10%; range 2%‐67%) 3 weeks after treatment, both of which were significantly higher proportions than in the placebo group for both time points (during treatment AG median 100% versus PG median 0.2% (P < .001); after treatment AG median 10% versus PG median 0.0% (P = .002)). Conclusions and Clinical Importance Our study suggests that treatment with amoxicillin‐clavulanic acid confers no clinical benefit to dogs with AD, but predisposes the development of amoxicillin‐resistant E. coli , which persist for as long as 3 weeks after treatment. These findings support international guideline recommendations that dogs with diarrhea should not be treated with antimicrobials unless there are signs of sepsis

Worms:Pernicious parasites or allies against allergies?

Host-parasite interactio

Trans-Atlantic exchanges have shaped the population structure of the Lyme disease agent Borrelia burgdorferi sensu stricto

The origin and population structure of Borrelia burgdorferi sensu stricto (s.s.), the agent of Lyme disease, remain obscure. This tick-transmitted bacterial species occurs in both North America and Europe. We sequenced 17 European isolates (representing the most frequently found sequence types in Europe) and compared these with 17 North American strains. We show that trans-Atlantic exchanges have occurred in the evolutionary history of this species and that a European origin of B. burgdorferi s. s. is marginally more likely than a USA origin. The data further suggest that some European human patients may have acquired their infection in North America. We found three distinct genetically differentiated groups: i) the outgroup species Borrelia bissettii, ii) two divergent strains from Europe, and iii) a group composed of strains from both the USA and Europe. Phylogenetic analysis indicated that different genotypes were likely to have been introduced several times into the same area. Our results demonstrate that irrespective of whether B. burgdorferi s. s. originated in Europe or the USA, later trans-Atlantic exchange(s) have occurred and have shaped the population structure of this genospecies. This study clearly shows the utility of next generation sequencing to obtain a better understanding of the phylogeography of this bacterial species

Exposure to Leptospira spp. and associated risk factors in the human, cattle and dog populations in Bhutan

Leptospirosis is a neglected worldwide zoonotic bacterial disease with a high prevalence in subtropical and tropical countries. The prevalence of Leptospira spp. in humans, cattle and dogs is unknown in Bhutan. Therefore, we sought to find out whether humans, cattle or dogs had been infected in the past with leptospires by measuring antibodies in the serum. We therefore collected blood from 864 humans >/=13 years of age, 130 bovines and 84 dogs from different rural and urban areas in Bhutan and tested the serum for antibodies specific for leptospires with a screening of enzyme-linked immunosorbent assays (ELISA) and a confirmatory microscopic agglutination test (MAT). In humans, 17.6% were seropositive by ELISA and 1.6% by MAT. The seropositivity was stronger in bovines (36.9%) and dogs (47.6%). "Having had a fever recently" (OR 5.2, p = 0.004), "working for the military" (OR 26.6, p = 0.028) and "being unemployed" (OR 12.9, p = 0.041) (reference category = housemaker) were statistically significantly associated with seropositivity when controlled for the effects of other risk factors. However, due to the small number of positive test results, the findings on risk factors should be interpreted with caution. Based on the serogroups found in the three species, dogs could be a source of infection for humans, or dogs and humans are exposed to the same environmental risk factors Clinical leptospirosis in humans and domestic animals should be investigated by testing blood and urine for the presence of leptospires by molecular methods (qPCR)

Self-assembly of ordered wurtzite/rock salt heterostructures—A new view on phase separation in MgxZn1−xO

The self-assembled formation of ordered, vertically stacked rocksalt/wurtzite Mg x Zn 1−xO heterostructures by planar phase separation is shown. These heterostructures form quasi “natural” two-dimensional hetero-interfaces between the different phases upon annealing of MgO-oversaturated wurtzite Mg x Zn 1−xO layers grown by plasma-assisted molecular beam epitaxy on c-plane sapphire substrates. The optical absorption spectra show a red shift simultaneous with the appearance of a cubic phase upon annealing at temperatures between 900 °C and 1000 °C. Transmission electron microscopy reveals that these effects are caused by phase separation leading to the formation of a vertically ordered rock salt/wurtzite heterostructures. To explain these observations, we suggest a phase separation epitaxy model that considers this process being initiated by the formation of a cubic (Mg,Zn)Al2O4 spinel layer at the interface to the sapphire substrate, acting as a planar seed for the epitaxial precipitation of rock salt Mg x Zn 1−xO. The equilibrium fraction x of magnesium in the resulting wurtzite (rock salt) layers is approximately 0.15 (0.85), independent of the MgO content of the as-grown layer and determined by the annealing temperature. This model is confirmed by photoluminescence analysis of the resulting layer systems after different annealing temperatures. In addition, we show that the thermal annealing process results in a significant reduction in the density of edge- and screw-type dislocations, providing the possibility to fabricate high quality templates for quasi-homoepitaxial growth