Experimental Sepsis Impairs Humoral Memory in Mice

<div><p>Patients with sepsis are often immune suppressed, and experimental mouse models of sepsis also display this feature. However, acute sepsis in mice is also characterized by a generalized B cell activation and plasma cell differentiation, resulting in a marked increase in serum antibody concentration. Its effects on humoral memory are not clearly defined. We measured the effects of experimental sepsis on long-term immunological memory for a defined antigen: we induced colon ascendens stent peritonitis (CASP) 8 weeks after 2 rounds of immunization with ovalbumin. Four weeks later, the antigen-specific bone marrow plasma cell count had doubled in immunized non-septic animals, but remained unchanged in immunized septic animals. Sepsis also caused a decrease in antigen-specific serum antibody concentration. We conclude that sepsis weakens humoral memory by impeding the antigen-specific plasma cell pool’s development, which is not complete 8 weeks after secondary immunization.</p> </div

Bacterial dissemination and clearance during experimental sepsis.

<p>C57BL/6 mice were subjected to CASP (18G). At the indicated time points blood, spleen, peritoneal lavage, liver, lung, and kidney were harvested. Solid organs were homogenized with an ultrathorax. Liquids and organ suspensions were plated on agar-plates and incubated for 22 h, when cfus were enumerated. n=5-6 mice/group.</p

Experimental sepsis in OVA-immunized mice reduces OVA-specific IgG-ASCs.

<div><p>OVA-specific IgG-ASCs in spleen and bone marrow 2 and 4 wk after CASP (colon ascendens stent peritonitis) are shown here. C57BL/6 mice were immunized and boosted with OVA at 6 and 9 wk, respectively, and CASP was induced 8 wk after the secondary immunization. Control animals were either untreated, only immunized or only CASP induced. A combination of two independent experiments with the same trend is shown here. A statistical analysis was performed with the one-way ANOVA and Bonferroni’s post test for selected pairs. N = 10-18/group. </p> <p>*: p<0.05; **: p<0.01. </p></div

Experimental sepsis in OVA-immunized mice reduces OVA-specific serum IgG.

<div><p>OVA-specific serum-IgM and -IgG at 2 and 4 wk after CASP (colon ascendens stent peritonitis) are shown here (au = arbitrary units). C57BL/6 mice were immunized and boosted with OVA at 6 and 9 wk, respectively, and CASP was induced 8 wk after the secondary immunization. Control animals were either untreated, only immunized or only CASP induced. A combination of two independent experiments with the same trend is shown here. A statistical analysis was performed with the one-way ANOVA and Bonferroni’s post test for selected pairs. </p> <p>n=10-18/group. *: p<0.05; **: p<0.01.</p></div

Total serum IgG concentration tends to increase after experimental sepsis.

<p>Serum IgM and IgG concentrations 2 or 4 wk after CASP (colon ascendens stent peritonitis) are shown here. C57BL/6 mice were immunized and boosted with OVA at 6 and 9 wk, respectively, and CASP was induced 8 wk after the secondary immunization. Control animals were either untreated, only immunized or only CASP induced. A statistical analysis was performed with the one-way ANOVA and Bonferroni’s post test for selected pairs. n=10-18/group. A single experiment is shown here. </p

Linear, Hypervalent Se₃^4– Units and Unprecedented Cu₄Se₉ Building Blocks in the Copper(I) Selenide Ba₄Cu₈Se₁₃

Single-crystal and polycrystalline Ba₄Cu₈Se₁₃ were synthesized; the average crystal structure was solved by single-crystal X-ray diffraction, and the structural model was confirmed by a detailed electron microscopy study of polycrystalline Ba₄Cu₈Se₁₃. The title compound can be rationalized as (Ba²⁺)₄(Cu⁺)₈(Se^2–)₂(Se₂^2–)₄(Se₃^4–) and crystallizes in a new structure type (space group <i>C</i>2/<i>c</i> with <i>a</i> = 9.171(8) Å, <i>b</i> = 9.146(8) Å, <i>c</i> = 27.35(3) Å, β = 93.21(3)°, and <i>V</i> = 2291 ų). It contains unprecedented Cu₄Se₉ fragments with planar Cu rectangles. These fragments form two-dimensional layers via regular (2c-2e) Se–Se bonds. Two of these layers are then connected in the third dimension via linear, hypervalent Se₃^4– units, resulting in “sandwichlike”, layered building blocks, which are stacked along <i>c</i> and separated by Ba. Ba₄Cu₈Se₁₃ is the first example where Se₂^2– and Se₃^4– groups coexist. We were able to visualize the crystal structure by recording HAADF images, which clearly reveal the Cu₄Se₉ fragments and linear Se₃^4– units. The title compound is a charge-balanced semiconductor and possesses a large Seebeck coefficient (380 μV K^–1 at 200 K) and a low thermal conductivity (0.77 W m^–1 K^–1 at 200 K)two requirements for efficient thermoelectric materials

TRAIL-treatment improved survival of CASP.

<p>This effect was abrogated by depleting neutrophils. A: Survival of CASP is depicted as Kaplan Meier curves. Mice were treated with anti-Ly6G 24 hrs before CASP induction (anti-Ly6G) to deplete neutrophils. Controls received appropriate isotype controls (isotype). Neutrophil-depleted (anti-Ly6G, TRAIL) and untreated mice (TRAIL) received TRAIL (1 µg/g (wt/wt)) 1 h, 24 h and 48 h after CASP intravenously. TRAIL treatment significantly improved survival of sepsis in previously untreated mice (p<0.001). However, TRAIL-treatment was ineffective in Ly6G-depleted mice. B: Depletion of neutrophils was confirmed via FACS analyses. Representative data 48 hrs after neutrophil depletion are shown. The oval indicates neutrophils detected via CD11b+Ly6Cmed expression.</p

TRAIL-treatment led to induction of apoptosis in neutrophils in sepsis.

<p>A) Spleens, livers and lungs of septic saline-treated (CASP+saline) and septic TRAIL-treated (CASP+TRAIL) were analyzed 20 h after induction of CASP. Sections were stained for Ly6G. Ly6G-positive cells of respective organs (n = 5/group for each organ) were counted in three HPFs and the mean was calculated. The number of neutrophils per HPF is depicted. Box plots and outliers are shown. The infiltration of neutrophils within the septic organs is significantly decreased by TRAIL-treatment in sepsis. Results are representative of two independent experiments. B) The number of apoptotic cells within the spleen, liver and lungs was determined by immunohistochemistry (n = 5/group for each organ, mean of 3 HPFs). TUNEL-straining was performed 20 hours after CASP. Box plots and outliers are shown. TRAIL-treatment decreased the number of apoptotic cells. Results are representative of two experiments performed independently. C) Apoptotic neutrophils were detected by staining Ly6G and TUNEL. The number of apoptotic neutrophils within the respective septic organs 20 hrs after induction of CASP was counted in three HPFs and the mean was calculated (n = 5/group for each organ). Additionally, the number of total apoptotic cells per HPF was counted. The ratio of apoptotic neutrophils over all apoptotic cells was calculated for each HPF. Box plots and outliers are depicted. TRAIL-treatment increased the fraction of apoptotic neutrophils 20 hrs after induction of CASP within the septic organs. D) Representative immunohistochemical analysis of Ly6G (green) and TUNEL (red) in spleens of septic mice 20 hrs after induction of CASP with (right) and without (left) TRAIL-treatment. Apoptotic neutrophils appear yellow. *p<0.05.</p

TRAIL-treatment did not influence cell viability <i>in vitro</i>.

<p>LPS-stimulation increased TRAIL-expression by splenocytes. A: Cultures of splenocytes were stimulated with TRAIL (100 ng/ml) for 48 hours. Cell viability was determined using a CellTiter Blue Assay. Box plots and outliers are depicted. TRAIL-stimulation did not alter the viability of splenocytes. n = 5/group; results are representative of two independently performed experiments. B: Cultures of splenocytes were stimulated with LPS (1 µg/ml) for 24 hours. TRAIL-expression was determined by FACS analyses. Isotype controls were used for background staining. Box plots and representative histograms of FACS analyses are shown. LPS stimulation significantly increased the expression of TRAIL on the cell surface of splenocytes. One of two experiments in which similar results were obtained is shown. *: p<0.05.</p

Nanostructures in Te/Sb/Ge/Ag (TAGS) Thermoelectric Materials Induced by Phase Transitions Associated with Vacancy Ordering

Te/Sb/Ge/Ag (TAGS) materials with rather high concentrations of cation vacancies exhibit improved thermoelectric properties as compared to corresponding conventional TAGS (with constant Ag/Sb ratio of 1) due to a significant reduction of the lattice thermal conductivity. There are different vacancy ordering possibilities depending on the vacancy concentration and the history of heat treatment of the samples. In contrast to the average α-GeTe-type structure of TAGS materials with cation vacancy concentrations <∼3%, quenched compounds like Ge_0.53Ag_0.13­Sb_0.27□_0.07Te₁ and Ge_0.61Ag_0.11­Sb_0.22□_0.06Te₁ exhibit “parquet-like” multidomain nanostructures with finite intersecting vacancy layers. These are perpendicular to the pseudocubic ⟨111⟩ directions but not equidistantly spaced, comparable to the nanostructures of compounds (GeTe)_<i>n</i>­Sb₂Te₃. Upon heating, the nanostructures transform into long-periodically ordered trigonal phases with parallel van der Waals gaps. These phases are slightly affected by stacking disorder but distinctly different from the α-GeTe-type structure reported for conventional TAGS materials. Deviations from this structure type are evident only from HRTEM images along certain directions or very weak intensities in diffraction patterns. At temperatures above ∼400 °C, a rock-salt-type high-temperature phase with statistically disordered cation vacancies is formed. Upon cooling, the long-periodically trigonal phases are reformed at the same temperature. Quenched nanostructured Ge_0.53Ag_0.13­Sb_0.27□_0.07Te₁ and Ge_0.61Ag_0.11­Sb_0.22□_0.06Te₁ exhibit ZT values as high as 1.3 and 0.8, respectively, at 160 °C, which is far below the phase transition temperatures. After heat treatment, i.e., without pronounced nanostructure and when only reversible phase transitions occur, the ZT values of Ge_0.53Ag_0.13­Sb_0.27□_0.07Te₁ and Ge_0.61Ag_0.11­Sb_0.22□_0.06Te₁ with extended van der Waals gaps amount to 1.6 at 360 °C and 1.4 at 410 °C, respectively, which is at the top end of the range of high-performance TAGS materials