Oxidative damage to DNA related to survivorship and carotenoid-based sexual ornamentation in the common yellowthroat

Carotenoid-based sexual ornaments are hypothesized to be reliable signals of male quality, based on an allocation trade-off between the use of carotenoids as pigments and their use in antioxidant defence against reactive oxygen species. Carotenoids appear to be poor antioxidants in vivo, however, and it is not clear whether variation in ornament expression is correlated with measures of oxidative stress (OXS) under natural conditions. We used single-cell gel electrophoresis to assay oxidative damage to erythrocyte DNA in the common yellowthroat (Geothlypis trichas), a sexually dichromatic warbler in which sexual selection favours components of the males’ yellow ‘bib’. We found that the level of DNA damage sustained by males predicted their overwinter survivorship and was reflected in the quality of their plumage. Males with brighter yellow bibs showed lower levels of DNA damage, both during the year the plumage was sampled (such that yellow brightness signalled current OXS) and during the previous year (such that yellow brightness signalled past OXS). We suggest that carotenoid-based ornaments can convey information about OXS to prospective mates and that further work exploring the proximate mechanism(s) linking OXS to coloration is warranted.

Intestinal bacterial colonization induces mutualistic regulatory T cell responses

Mammals harbor a dense commensal microbiota in the colon. Regulatory T (Treg) cells are known to limit microbe-triggered intestinal inflammation and the CD4+ T cell compartment is shaped by the presence of particular microbes or bacterial compounds. It is, however, difficult to distinguish whether these effects reflect true mutualistic immune adaptation to intestinal colonization or rather idiosyncratic immune responses. To investigate truly mutualistic CD4+ T cell adaptation, we used the altered Schaedler flora (ASF). Intestinal colonization resulted in activation and de novo generation of colonic Treg cells. Failure to activate Treg cells resulted in the induction of T helper 17 (Th17) and Th1 cell responses, which was reversed by wild-type Treg cells. Efficient Treg cell induction was also required to maintain intestinal homeostasis upon dextran sulfate sodium-mediated damage in the colon. Thus, microbiota colonization-induced Treg cell responses are a fundamental intrinsic mechanism to induce and maintain host-intestinal microbial T cell mutualism.

[Thirty years of laser-assisted microvascular anastomosis (LAMA): what are the clinical perspectives?]

Since the first studies by Jain and Gorisch (1979), laser-assisted anastomoses have been steadily developed to a stage where clinical use is within reach. The laser-assisted vascular microanastomosis (LAMA) procedure is performed more quickly than conventional anastomosis, the surgically induced vessel damage is limited, and reduced bleeding after unclamping is observed.

Does a pulsed mode offer advantages over a continuous wave mode for excisional biopsies performed using a carbon dioxide laser?

Animal studies of excisional biopsies have shown less thermal damage when a carbon dioxide (CO(2)) laser (10.6 μm) is used in a char-free (CF) mode than in a continuous-wave (CW) mode. The authors' aim was to evaluate and compare clinical and histopathologic findings of excisional biopsies performed with CW and CF CO(2) laser (10.6 μm) modes.

Eosinophils in the gastrointestinal tract: friends or foes?

Eosinophils play an important role in the mucosal immune system of the gastrointestinal tract under resting and under inflammatory conditions. Under steady-state conditions, the mucosa of the digestive tract is the only organ harboring a substantial number of eosinophils, which, if need be, get activated and exert several effector and immunoregulatory functions. The precise function of these late-phase inflammatory cells is not yet completely understood. Nevertheless, it has recently been demonstrated that lipopolysaccharides from gram-negative bacteria activate eosinophils to rapidly release mitochondrial DNA in the extracellular space. Released mitochondrial DNA and eosinophil granule proteins form extracellular structures able to bind and inactivate bacteria. These findings suggest a novel mechanism of eosinophil-mediated innate immune responses that might be important in maintaining the intestinal barrier function. Moreover, eosinophils also play a crucial role in several inflammatory conditions, such as intestinal infections, immune-mediated inflammations and hypersensitivity reactions. Under chronic inflammatory conditions, the ability of the eosinophils to induce repair can lead to pathological sequelae in the tissue, such as esophageal remodeling in eosinophilic esophagitis. It is established that the uncontrolled eosinophilic inflammation induces fibrosis, esophageal wall thickening and strictures leading to damage that results in a loss of esophageal function. One potential mechanism of this remodeling is so-called 'epithelial mesenchymal transition', which is triggered by eosinophils and is potentially reversible under successful anti-eosinophil treatment. Therefore, eosinophils may act either as friends or as foes, depending on the microenvironment.

Granulocyte death regulation by naturally occurring autoantibodies

Programmed cell death (PCD) plays a central role in the regulation of granulocytes that are key effector cells of the innate immune system. Granulocytes are produced in high amounts in the bone marrow. A safe elimination of granulocytes by cell death (apoptosis) is essential to maintain the numbers of these cells balanced. In many acute and chronic inflammatory diseases, delayed apoptosis is one mechanism that contributes to accumulation of neutrophil and eosinophil granulocytes at the site of inflammation. On the other hand, a safe elimination of granulocytes by cell death is required to avoid unwanted tissue damage for instance by secretion of toxic products from these cells. Recent evidence shows that humans produce an array of naturally occurring autoantibodies (NAbs) with the capacity to regulate granulocyte death, including agonistic and antagonistic NAbs that bind to the receptors Fas, Siglec-8, and Siglec-9. Together with other factors, these various NAbs exhibit different properties in terms of the form of cell death they induce, the molecular signaling pathways they engage, as well as the efficacy or potency by which they induce cell death. Moreover, several regulatory mechanisms seem to exist that control their biological activity. Novel insights support the concept of granulocyte death regulation by NAbs, which might have important implications for our understanding of the pathogenesis and treatment of inflammatory diseases, including many autoimmune and allergic disorders.

Loss of astrocyte polarization upon transient focal brain ischemia as a possible mechanism to counteract early edema formation

Brain edema is the main cause of death from brain infarction. The polarized expression of the water channel protein aquaporin-4 (AQP4) on astroglial endfeet surrounding brain microvessels suggests a role in brain water balance. Loss of astrocyte foot process anchoring to the basement membrane (BM) accompanied by the loss of polarized localization of AQP4 to astrocytic endfeet has been shown to be associated with vasogenic/extracellular edema in neuroinflammation. Here, we asked if loss of astrocyte polarity is also observed in cytotoxic/intracellular edema following focal brain ischemia after transient middle cerebral artery occlusion (tMCAO). Upon mild focal brain ischemia, we observed diminished immunostaining for the BM components laminin α4, laminin α2, and the proteoglycan agrin, in the core of the lesion, but not in BMs in the surrounding penumbra. Staining for the astrocyte endfoot anchorage protein β-dystroglycan (DG) was dramatically reduced in both the lesion core and the penumbra, and AQP4 and Kir4.1 showed a loss of polarized localization to astrocytic endfeet. Interestingly, we observed that mice deficient for agrin expression in the brain lack polarized localization of β-DG and AQP4 at astrocytic endfeet and do not develop early cytotoxic/intracellular edema following tMCAO. Taken together, these data indicate that the binding of DG to agrin embedded in the subjacent BM promotes polarized localization of AQP4 to astrocyte endfeet. Reduced DG protein levels and redistribution of AQP4 as observed upon tMCAO might therefore counteract early edema formation and reflect a beneficial mechanism operating in the brain to minimize damage upon ischemia.

Effect of laser soldering irradiation on covalent bonds of pure collagen

Laser tissue welding and soldering is being increasingly used in the clinical setting for defined surgical procedures. The exact induced changes responsible for tensile strength are not yet fully investigated. To further improve the strength of the bonding, a better understanding of the laser impact at the subcellular level is necessary. The goal of this study was to analyze whether the effect of laser irradiation on covalent bonding in pure collagen using irradiances typically applied for tissue soldering. Pure rabbit and equine type I collagen were subjected to laser irradiation. In the first part of the study, rabbit and equine collagen were compared using identical laser and irradiation settings. In the second part of the study, equine collagen was irradiated at increasing laser powers. Changes in covalent bonding were studied indirectly using the sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) technique. Tensile strengths of soldered membranes were measured with a calibrated tensile force gauge. In the first experiment, no differences between the species-specific collagen bands were noted, and no changes in banding were found on SDS-PAGE after laser irradiation. In the second experiment, increasing laser irradiation power showed no effect on collagen banding in SDS-PAGE. Finally, the laser tissue soldering of pure collagen membranes showed virtually no determinable tensile strength. Laser irradiation of pure collagen at typical power settings and exposure times generally used in laser tissue soldering does not induce covalent bonding between collagen molecules. This is true for both rabbit and equine collagen proveniences. Furthermore, soldering of pure collagen membranes without additional cellular components does not achieve the typical tensile strength reported in native, cell-rich tissues. This study is a first step in a better understanding of laser impact at the molecular level and might prove useful in engineering of combined collagen-soldering matrix membranes for special laser soldering applications.

Statin therapy induces ultrastructural damage in skeletal muscle in patients without myalgia

Muscle pain and weakness are frequent complaints in patients receiving 3-hydroxymethylglutaryl coenzymeA (HMG CoA) reductase inhibitors (statins). Many patients with myalgia have creatine kinase levels that are either normal or only marginally elevated, and no obvious structural defects have been reported in patients with myalgia only. To investigate further the mechanism that mediates statin-induced skeletal muscle damage, skeletal muscle biopsies from statin-treated and non-statin-treated patients were examined using both electron microscopy and biochemical approaches. The present paper reports clear evidence of skeletal muscle damage in statin-treated patients, despite their being asymptomatic. Though the degree of overall damage is slight, it has a characteristic pattern that includes breakdown of the T-tubular system and subsarcolemmal rupture. These characteristic structural abnormalities observed in the statin-treated patients were reproduced by extraction of cholesterol from skeletal muscle fibres in vitro. These findings support the hypothesis that statin-induced cholesterol lowering per se contributes to myocyte damage and suggest further that it is the specific lipid/protein organization of the skeletal muscle cell itself that renders it particularly vulnerable.

TRAIL receptor-mediated JNK activation and Bim phosphorylation critically regulate Fas-mediated liver damage and lethality

TNF-related apoptosis-inducing ligand (TRAIL) is a member of the TNF family with potent apoptosis-inducing properties in tumor cells. In particular, TRAIL strongly synergizes with conventional chemotherapeutic drugs to induce tumor cell death. Thus, TRAIL has been proposed as a promising future cancer therapy. Little, however, is known regarding what the role of TRAIL is in normal untransformed cells and whether therapeutic administration of TRAIL, alone or in combination with other apoptotic triggers, may cause tissue damage. In this study, we investigated the role of TRAIL in Fas-induced (CD95/Apo-1-induced) hepatocyte apoptosis and liver damage. While TRAIL alone failed to induce apoptosis in isolated murine hepatocytes, it strongly amplified Fas-induced cell death. Importantly, endogenous TRAIL was found to critically regulate anti-Fas antibody-induced hepatocyte apoptosis, liver damage, and associated lethality in vivo. TRAIL enhanced anti-Fas-induced hepatocyte apoptosis through the activation of JNK and its downstream substrate, the proapoptotic Bcl-2 homolog Bim. Consistently, TRAIL- and Bim-deficient mice and wild-type mice treated with a JNK inhibitor were protected against anti-Fas-induced liver damage. We conclude that TRAIL and Bim are important response modifiers of hepatocyte apoptosis and identify liver damage and lethality as a possible risk of TRAIL-based tumor therapy.

Crystal structure of the platelet glycoprotein Ib(alpha) N-terminal domain reveals an unmasking mechanism for receptor activation

Glycoprotein Ib (GPIb) is a platelet receptor with a critical role in mediating the arrest of platelets at sites of vascular damage. GPIb binds to the A1 domain of von Willebrand factor (vWF-A1) at high blood shear, initiating platelet adhesion and contributing to the formation of a thrombus. To investigate the molecular basis of GPIb regulation and ligand binding, we have determined the structure of the N-terminal domain of the GPIb(alpha) chain (residues 1-279). This structure is the first determined from the cell adhesion/signaling class of leucine-rich repeat (LRR) proteins and reveals the topology of the characteristic disulfide-bonded flanking regions. The fold consists of an N-terminal beta-hairpin, eight leucine-rich repeats, a disulfide-bonded loop, and a C-terminal anionic region. The structure also demonstrates a novel LRR motif in the form of an M-shaped arrangement of three tandem beta-turns. Negatively charged binding surfaces on the LRR concave face and anionic region indicate two-step binding kinetics to vWF-A1, which can be regulated by an unmasking mechanism involving conformational change of a key loop. Using molecular docking of the GPIb and vWF-A1 crystal structures, we were also able to model the GPIb.vWF-A1 complex.

Myofibroblasts induce ectopic activity in cardiac tissue

Focal ectopic activity in cardiac tissue is a key factor in the initiation and perpetuation of tachyarrhythmias. Because myofibroblasts as present in fibrotic remodeled myocardia and infarct scars depolarize cardiomyocytes by heterocellular electrotonic interactions via gap junctions in vitro, we investigated using strands of cultured ventricular cardiomyocytes coated with myofibroblasts, whether this interaction might give rise to depolarization-induced abnormal automaticity. Whereas uncoated cardiomyocyte strands were invariably quiescent, myofibroblasts induced synchronized spontaneous activity in a density dependent manner. Activations appeared at spatial myofibroblast densities >15.7% and involved more than 80% of the preparations at myofibroblast densities of 50%. Spontaneous activity was based on depolarization-induced automaticity as evidenced by: (1) suppression of activity by the sarcolemmal K(ATP) channel opener P-1075; (2) induction of activity in current-clamped single cardiomyocytes undergoing depolarization to potentials similar to those induced by myofibroblasts in cardiomyocyte strands; and (3) induction of spontaneous activity in cardiomyocyte strands coated with connexin 43 transfected Hela cells but not with communication deficient HeLa wild-type cells. Apart from unveiling the mechanism underlying the hallmark of monolayer cultures of cardiomyocytes, ie, spontaneous electromechanical activity, these findings open the perspective that myofibroblasts present in structurally remodeled myocardia following pressure overload and infarction might contribute to arrhythmogenesis by induction of ectopic activity.

Solder doped polycaprolactone scaffold enables reproducible laser tissue soldering

BACKGROUND AND OBJECTIVES: In this in vitro feasibility study we analyzed tissue fusion using bovine serum albumin (BSA) and Indocyanine green (ICG) doped polycaprolactone (PCL) scaffolds in combination with a diode laser as energy source while focusing on the influence of irradiation power and albumin concentration on the resulting tensile strength and induced tissue damage. MATERIALS AND METHODS: A porous PCL scaffold doped with either 25% or 40% (w/w) of BSA in combination with 0.1% (w/w) ICG was used to fuse rabbit aortas. Soldering energy was delivered through the vessel from the endoluminal side using a continuous wave diode laser at 808 nm via a 400 microm core fiber. Scaffold surface temperatures were analyzed with an infrared camera. Optimum parameters such as irradiation time, radiation power and temperature were determined in view of maximum tensile strength but simultaneously minimum thermally induced tissue damage. Differential scanning calorimetry (DSC) was performed to measure the influence of PCL on the denaturation temperature of BSA. RESULTS: Optimum parameter settings were found to be 60 seconds irradiation time and 1.5 W irradiation power resulting in tensile strengths of around 2,000 mN. Corresponding scaffold surface temperature was 117.4+/- 12 degrees C. Comparison of the two BSA concentration revealed that 40% BSA scaffold resulted in significant higher tensile strength compared to the 25%. At optimum parameter settings, thermal damage was restricted to the adventitia and its interface with the outermost layer of the tunica media. The DSC showed two endothermic peaks in BSA containing samples, both strongly depending on the water content and the presence of PCL and/or ICG. CONCLUSIONS: Diode laser soldering of vascular tissue using BSA-ICG-PCL-scaffolds leads to strong and reproducible tissue bonds, with vessel damage limited to the adventitia. Higher BSA content results in higher tensile strengths. The DSC-measurements showed that BSA denaturation temperature is lowered by addition of water and/or ICG-PCL.

Hip damage occurs at the zone of femoroacetabular impingement

Although current concepts of anterior femoroacetabular impingement predict damage in the labrum and the cartilage, the actual joint damage has not been verified by computer simulation. We retrospectively compared the intraoperative locations of labral and cartilage damage of 40 hips during surgical dislocation for cam or pincer type femoroacetabular impingement (Group I) with the locations of femoroacetabular impingement in 15 additional hips using computer simulation (Group II). We found no difference between the mean locations of the chondrolabral damage of Group I and the computed impingement zone of Group II. The standard deviation was larger for measures of articular damage from Group I in comparison to the computed values of Group II. The most severe hip damage occurred at the zone of highest probability of femoroacetabular impact, typically in the anterosuperior quadrant of the acetabulum for both cam and pincer type femoroacetabular impingements. However, the extent of joint damage along the acetabular rim was larger intraoperatively than that observed on the images of the 3-D joint simulations. We concluded femoroacetabular impingement mechanism contributes to early osteoarthritis including labral lesions. LEVEL OF EVIDENCE: Level II, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Integration of computational models and experimental characterization to study internal frost damage in cementitious materials

The objective of this doctoral research is to investigate the internal frost damage due to crystallization pore pressure in porous cement-based materials by developing computational and experimental characterization tools. As an essential component of the U.S. infrastructure system, the durability of concrete has significant impact on maintenance costs. In cold climates, freeze-thaw damage is a major issue affecting the durability of concrete. The deleterious effects of the freeze-thaw cycle depend on the microscale characteristics of concrete such as the pore sizes and the pore distribution, as well as the environmental conditions. Recent theories attribute internal frost damage of concrete is caused by crystallization pore pressure in the cold environment. The pore structures have significant impact on freeze-thaw durability of cement/concrete samples. The scanning electron microscope (SEM) and transmission X-ray microscopy (TXM) techniques were applied to characterize freeze-thaw damage within pore structure. In the microscale pore system, the crystallization pressures at sub-cooling temperatures were calculated using interface energy balance with thermodynamic analysis. The multi-phase Extended Finite Element Modeling (XFEM) and bilinear Cohesive Zone Modeling (CZM) were developed to simulate the internal frost damage of heterogeneous cement-based material samples. The fracture simulation with these two techniques were validated by comparing the predicted fracture behavior with the captured damage from compact tension (CT) and single-edge notched beam (SEB) bending tests. The study applied the developed computational tools to simulate the internal frost damage caused by ice crystallization with the two dimensional (2-D) SEM and three dimensional (3-D) reconstructed SEM and TXM digital samples. The pore pressure calculated from thermodynamic analysis was input for model simulation. The 2-D and 3-D bilinear CZM predicted the crack initiation and propagation within cement paste microstructure. The favorably predicted crack paths in concrete/cement samples indicate the developed bilinear CZM techniques have the ability to capture crack nucleation and propagation in cement-based material samples with multiphase and associated interface. By comparing the computational prediction with the actual damaged samples, it also indicates that the ice crystallization pressure is the main mechanism for the internal frost damage in cementitious materials.