Biomedical subjects

Norbert Wagner

Publications and source records attributed to Norbert Wagner.

12 recordsLinked to original sources

PubMed2006

An upflow microbial fuel cell with an interior cathode: assessment of the internal resistance by impedance spectroscopy.

An upflow microbial fuel cell (UMFC) system with a U-shaped cathode inside the anode chamber was developed and produced a maximum volumetric power of 29.2 W/m3 at a volumetric loading rate of 3.40 kg COD/(m3 day) and an operating temperature of 35 degrees C while feeding sucrose continuously. The Coulombic efficiency decreased from 51.0% to 10.6% with the increase in the volumetric loading rate from 0.57 to 4.29 kg COD/(m3 day). In addition, the lab-scale UMFC maintained soluble chemical oxygen demand (COD) removal efficiencies exceeding 90% and volatile fatty acid concentrations of approximately 40 mg/L, indicating efficient wastewater treatment. The analysis of impedance spectroscopy, generated by fitting experimental data into an equivalent circuit, revealed that at a volumetric loading rate of 3.40 kg COD/(m3 day) the overall internal resistance was 17.13 omega. This internal resistance was composed of electrolyte resistance (8.62 omega), charge-transfer resistance (7.05 omega), and diffusion resistance (1.46 omega). Electrolyte resistance dominated throughout the entire range of loading rates. In addition, impedance spectroscopy demonstrated that both the anodic and the cathodic charge-transfer resistances were important limiting factors. To further improve the power output of the UMFC, we must reduce the electrolyte resistance by optimizing reactor configuration, reduce the anode charge-transfer resistances by selecting superior anodic microbiota, and reduce the cathodic charge-transfer resistance by exploring sustainable and efficient catalysts.

Bacteria↗

PubMed2006

Adult murine hematopoiesis can proceed without beta1 and beta7 integrins.

The function of alpha4beta1 and alpha4beta7 integrins in hematopoiesis is controversial. While some experimental evidence suggests a crucial role for these integrins in retention and expansion of progenitor cells and lymphopoiesis, others report a less important role in hematopoiesis. Using mice with a deletion of the beta1 and the beta7 integrin genes restricted to the hematopoietic system we show here that alpha4beta1 and alpha4beta7 integrins are not essential for differentiation of lymphocytes or myelocytes. However, beta1beta7 mutant mice displayed a transient increase of colony-forming unit (CFU-C) progenitors in the bone marrow and, after phenylhydrazine-induced anemia, a decreased number of splenic erythroid colony-forming units in culture (CFUe's). Array gene expression analysis of CD4(+)CD8(+) double-positive (DP) and CD4(-)CD8(-) double-negative (DN) thymocytes and CD19(+) and CD4(+) splenocytes did not provide any evidence for a compensatory mechanism explaining the mild phenotype. These data show that alpha4beta1 and alpha4beta7 are not required for blood cell differentiation, although in their absence alterations in numbers and distribution of progenitor cells were observed.

Anemia, Hemolytic↗

PubMed2006

ICAM-1-dependent pathways regulate colonic eosinophilic inflammation.

Eosinophilic inflammation is a common feature of numerous eosinophil-associated gastrointestinal (EGID) diseases. Central to eosinophil migration into the gastrointestinal tract are the integrin-mediated interactions with adhesion molecules. Although the mechanisms regulating eosinophil homing into the small intestine have begun to be elucidated, the adhesion pathways responsible for eosinophil trafficking into the large intestine are unknown. We investigated the role of adhesion pathways in eosinophil recruitment into the large intestine during homeostasis and disease. First, using a hapten-induced colonic injury model, we demonstrate that in contrast to the small intestine, eosinophil recruitment into the colon is regulated by a beta7 -integrin addressin cell adhesion molecule-1-independent pathway. Characterization of integrin expression on colonic eosinophils by flow cytometry analysis revealed that colonic CC chemokine receptor 3+ eosinophils express the intercellular adhesion molecule-1 (ICAM-1) counter-receptor integrins alphaL, alphaM, and beta2. Using ICAM-1-deficient mice and anti-ICAM-1 neutralizing antibodies, we show that hapten-induced colonic eosinophilic inflammation is critically dependent on ICAM-1. These studies demonstrate that beta2 -integrin/ICAM-1-dependent pathways are integral to eosinophil recruitment into the colon during GI inflammation associated with colonic injury.

Animals↗

PubMed2005

Isomers among the carbon sulfides C4S6--synthesis and crystal structures of alpha,alpha-C4S6, alpha,beta-C4S6, and of a second polymorph of the diiodine adduct alpha,beta-C4S6.I2.

The reaction of the alpha and beta forms of C3S5(2-) with thiophosgene yields two isomeric carbon sulfides alpha,alpha-C4S6 and alpha,beta-C4S6, respectively. The crystal structures of both compounds could be determined for the first time. Both structures are made up of almost planar molecules. The alpha,alpha-isomer (1,3-dithiolo-(4,5-d)-1,3-dithol-2,5-dithione) is D2h-symmetric, while the alpha,beta-isomer is approximately Cs-symmetric. In the molecules of both isomers the two different C3S5 units are retained without significant alterations of structural parameters. alpha,alpha-C4S6 is unstable with respect to alpha,beta-C4S6. The molecular rearrangement can be induced by a short thermal treatment at 150 degrees C. Significant differences are found in the mass spectra fragmentation patterns. Only alpha,beta-C4S6 shows an intense signal for C3S2+ and is therefore a potential source for the synthesis of carbon subsulfide via flash vacuum pyrolysis. Only alpha,beta-C4S6 forms a stable adduct with I2. alpha,beta-C4S6.I2 was already known (F. L. Lu, K. M. Keshavarz-K, G. Srdanov, R. H. Jacobson and F. Wudl, J. Org. Chem., 1989, 54, 2165, ), but a second polymorph is formed on crystallisation from a different solvent. The two polymorphic forms do not show differences in the structures of the individual molecules but show a different packing pattern. alpha,beta-C4S6.I2 is remarkably thermally stable. Thermal analysis shows that I2 cleavage occurs in that temperature region above 200 degrees C when C-S bonds are broken and CS2 and I2 are simultaneously liberated. Performed at 270 degrees C thermolysis of alpha,beta-C4S6.I2 yields under cleavage of I2 and CS2 a black polymeric carbon sulfide (CS)x which is probably a mixture of graphitic carbon and unidentified amorphous polymeric carbon sulfides.

Journal Article↗

PubMed2003

Lymphocyte homing to bronchus-associated lymphoid tissue (BALT) is mediated by L-selectin/PNAd, alpha4beta1 integrin/VCAM-1, and LFA-1 adhesion pathways.

Bronchus-associated lymphoid tissue (BALT) participates in airway immune responses. However, little is known about the lymphocyte-endothelial adhesion cascades that recruit lymphocytes from blood into BALT. We show that high endothelial venules (HEVs) in BALT express substantial levels of VCAM-1, in marked contrast to HEVs in other secondary lymphoid tissues. BALT HEVs also express the L-selectin ligand PNAd. Anti-L-selectin, anti-PNAd, and anti-LFA-1 mAbs almost completely block the homing of B and T lymphocytes into BALT, whereas anti-alpha4 integrin and anti-VCAM-1 mAbs inhibit homing by nearly 40%. alpha4beta7 integrin and MAdCAM-1 are not involved. Importantly, we found that mAbs against alpha4 integrin and VCAM-1 significantly block the migration of total T cells (80% memory phenotype) but not naive T and B cells to BALT. These results suggest that an adhesion cascade, which includes L-selectin/PNAd, alpha4beta1 integrin/VCAM-1, and LFA-1, targets specific lymphocyte subsets to BALT. This high level of involvement of alpha4beta1 integrin/VCAM-1 is unique among secondary lymphoid tissues, and may help unify lymphocyte migration pathways and immune responses in BALT and other bronchopulmonary tissues.

Animals↗

PubMed2003

Mice with neonatally induced inactivation of the vascular cell adhesion molecule-1 fail to control the parasite in Toxoplasma encephalitis.

Under various inflammatory conditions, cell adhesion molecules are up-regulated in the central nervous system (CNS) and may contribute to the recruitment of leukocytes to the brain. In the present study, the functional role of vascular cell adhesion molecule (VCAM)-1 in Toxoplasma encephalitis (TE) was addressed using VCAM(flox/flox MxCre) mice. Neonatal inactivation of the VCAM-1 gene resulted in a lack of induction of VCAM-1 on cerebral blood vessel endothelial cells, whereas the constitutive expression of VCAM-1 on choroid plexus epithelial cells and the ependyma was unaffected; in these animals, resistance to T. gondii was abolished, and VCAM(flox/flox MxCre) mice died of chronic TE caused by a failure to control parasites in the CNS. Although leukocyte recruitment to the CNS was unimpaired, the B cell response was significantly reduced as evidenced by reduced serum levels of anti-T. gondii-specific IgM and IgG antibodies. Furthermore, the frequency and activation state of intracerebral T. gondii-specific T cells were decreased, and microglial activation was markedly reduced. Taken together, these data demonstrate the crucial requirement of VCAM-1-mediated immune reactions for the control of an intracerebral infectious pathogen, whereas other cell adhesion molecules can efficiently compensate for VCAM-1-mediated homing across cerebral blood vessels.

Animals↗

PubMed2003

Oral prion infection requires normal numbers of Peyer's patches but not of enteric lymphocytes.

Prion pathogenesis following oral exposure is thought to involve gut-associated lymphatic tissue, which includes Peyer's patches (PPs) and M cells. Recruitment of activated B lymphocytes to PPs requires alpha(4)beta(7) integrin; PPs of beta 7(-/-) mice are normal in number but are atrophic and almost entirely devoid of B cells. Here we report that minimal infectious dose and disease incubation after oral exposure to logarithmic dilutions of prion inoculum were similar in beta 7(-/-) and wild-type mice, and PPs of both beta 7(-/-) and wild-type mice contained 3-4 log LD(50)/g prion infectivity > or =125 days after challenge. Despite marked reduction of B cells, M cells were present in beta 7(-/-) mice. In contrast, mice deficient in both tumor necrosis factor and lymphotoxin-alpha (TNF alpha(-/-) x LT alpha(-/-)) or in lymphocytes (RAG-1(-/-), mu MT), in which numbers of PPs are reduced in number, were highly resistant to oral challenge, and their intestines were virtually devoid of prion infectivity at all times after challenge. Therefore, lymphoreticular requirements for enteric and for intraperitoneal uptake of prions differ from each other. Although susceptibility to prion infection following oral challenge correlates with the number of PPs, it is remarkably independent of the number of PP-associated lymphocytes.

Animals↗

PubMed2002

Monoclonal antibody against beta7 integrins, but not beta7 deficiency, attenuates intestinal allograft rejection in mice.

BACKGROUND: beta7 integrins mediate homing and retention of lymphocytes to the normal and inflamed small bowel in a tissue-selective fashion. In the present study, we investigated the expression of beta7 integrins after small bowel transplantation (SBT) and tested the effects of blocking beta7-mediated pathways by using monoclonal antibody (mAb) or knockout mice. METHODS: Heterotopic SBT from BALB/c to C57BL/6 (B6) was used as a surgical model. Expression of beta7 integrins was measured on recipient lymphocytes (CD4 and CD8 ) in spleen, blood, and mesenteric lymph nodes (MLN) using flow cytometry. To analyze the effects of blocking beta7 integrins on graft survival, either beta7-deficient B6 or wild-type B6 mice that were treated with mAb against beta7 were studied. RESULTS: After allogeneic SBT, there were markedly increased levels of alpha4beta7 recipient CD8 lymphocytes in MLN, blood, and spleen as early as 3 days postoperatively. In contrast, alpha4beta7 integrin levels in isograft recipients were similar to those of normal mice. Mean survival time of intestinal allografts was not affected by beta7 deficiency (7.3+/-1 days) compared with wild-type mice (7.5+/-0.8 days). However, mAb against beta7 integrins significantly prolonged graft survival (12.8+/-1 days) compared with treatment with control mAb (7.3+/-1 days, <0.001). Histologic changes of SBT rejection were significantly attenuated when mice were given mAb against beta7. CONCLUSION: As indicated by the increased levels of alpha4beta7 CD8 lymphocytes, activation of this integrin contributes to the immune response in SBT rejection. Furthermore, blocking beta7 integrins with mAb provides a suitable target for immunosuppressive therapy. The discrepancy in survival data obtained by mAb and beta7 deficiency may be a result of the more rapid activation of compensatory mechanisms in the knockout mice.

Animals↗

PubMed2002

Beta7 integrins contribute to skin graft rejection.

BACKGROUND: Because integrins alpha4beta7 and alphaEbeta7 contribute to epidermotropism of T-cells during skin inflammation, we sought to study their role in skin allograft rejection. METHODS: Wild-type (WT) (beta7+/+) and beta7 gene knockout (beta7-/-) C57BL/6 (H-2(b)) mice and SJL/J (H-2(s)) mice served as donors and recipients of allogeneic skin grafts. An anti-integrin beta7 subunit mAb (FIB504.64) was used to treat WT beta7+/+ C57BL/6 recipients of skin grafts from SJL/J mice. RESULTS: WT C57BL/6 recipients acutely rejected skin from SJL/J mice in 13 days. In contrast, the survival of SJL/J skin on either beta7-/- gene knockout or WT C57BL/6 recipients treated with anti-beta7 subunit mAb, was prolonged by 6 to 7 additional days (P<0.01). The survival of skin allografts from either beta7-/- or beta7+/+ C57BL/6 mice received by SJL/J recipients was not prolonged (P >0.05). CONCLUSIONS: Beta7 integrins contribute to skin graft rejection, in accord with their role in mediating the epidermotropism of T-cells during skin inflammation.

Animals↗

PubMed2002

Neonatal infection with a milk-borne virus is independent of beta7 integrin- and L-selectin-expressing lymphocytes.

Mouse mammary tumor virus (MMTV) is acquired by neonates through milk and first infects lymphocytes in Peyer's patches. We show here that newborn mice lacking beta7 integrin or L-selectin were infected with MMTV at wild-type levels in both their lymphoid and mammary tissues. Superantigen-mediated activation and cognate T cell deletion were also unimpaired in both types of null mice. A large proportion of neonatal Peyer's patch lymphocytes in wild-type mice were beta7 and beta1 integrin low and both populations increased in response to MMTV infection. These results suggest that adhesion molecules other than beta7 integrin or L-selectin play a role in lymphocyte homing in the gut, peripheral lymph nodes and mammary gland in response to MMTV infection.

Animals↗

PubMed2002

T cell homeostatic proliferation elicits effective antitumor autoimmunity.

Development of tumor immunotherapies focuses on inducing autoimmune responses against tumor-associated self-antigens primarily encoded by normal, unmutated genes. We hypothesized that such responses could be elicited by T cell homeostatic proliferation in the periphery, involving expansion of T cells recognizing self-MHC/peptide ligands. Herein, we demonstrate that sublethally irradiated lymphopenic mice transfused with autologous or syngeneic T cells showed tumor growth inhibition when challenged with melanoma or colon carcinoma cells. Importantly, the antitumor response depended on homeostatic expansion of a polyclonal T cell population within lymph nodes. This response was effective even for established tumors, was characterized by CD8(+) T cell-mediated tumor-specific cytotoxicity and IFN-gamma production, and was associated with long-term memory. The results indicate that concomitant induction of the physiologic processes of homeostatic T cell proliferation and tumor antigen presentation in lymph nodes triggers a beneficial antitumor autoimmune response.

Animals↗

PubMed2001

Enterocyte expression of the eotaxin and interleukin-5 transgenes induces compartmentalized dysregulation of eosinophil trafficking.

Eosinophils accumulate in the gastrointestinal tract in a number of medical disorders, but the mechanisms involved are largely unknown. To understand the significance of cytokine expression by enterocytes, enterocyte transgenic mice that overexpressed the eosinophil-selective cytokines eotaxin and interleukin (IL)-5 were generated. Transgenic mice, generated by utilizing the rat intestinal fatty acid-binding protein promoter (Fabpi), overexpressed the mRNA for these cytokines in the small intestine. Overexpression of IL-5 resulted in marked increases of eosinophils in the bone marrow and blood, whereas eotaxin overexpression resulted in similar levels compared with nontransgenic control mice. In contrast, both IL-5 and eotaxin transgenic mice had significant accumulation of eosinophils in the gastrointestinal mucosa compared with control mice. Eotaxin-induced gastrointestinal eosinophilia was substantially higher than that induced by IL-5 and was especially prominent within the lamina propria of the villi. Interestingly, genetic rescue of eotaxin deficiency (by transgenic overexpression of eotaxin in eotaxin gene-targeted mice) resulted in significant restoration of gastrointestinal eosinophil levels. Finally, the intestinal eosinophilia induced by the eotaxin transgene was beta(7) integrin-dependent. Taken together, these results demonstrate that expression of eotaxin and IL-5 in intestinal epithelium induces compartmentalized dysregulation of eosinophil trafficking and the important role of the beta(7) integrin in gastrointestinal allergic responses.

Animals↗