Oxygen radicals regulate many physiological processes, such as signaling, proliferation, and apoptosis, and thus play a pivotal role in pathophysiology and disease development. There are at least two thioredoxin reductase/ thioredoxin/peroxiredoxin systems participating in the cellular defense against oxygen radicals. At present, relatively little is known about the contribution of individual enzymes to the redox metabolism in different cell types. To begin to address this question, we generated and characterized mice lacking functional mitochondrial thioredoxin reductase (TrxR2). Ubiquitous Cre-mediated inactivation of TrxR2 is associated with embryonic death at embryonic day 13. TrxR2 ؊/؊ embryos are smaller and severely anemic and show increased apoptosis in the liver. The size of hematopoietic colonies cultured ex vivo is dramatically reduced. TrxR2-deficient embryonic fibroblasts are highly sensitive to endogenous oxygen radicals when glutathione synthesis is inhibited. Besides the defect in hematopoiesis, the ventricular heart wall of TrxR2 ؊/؊ embryos is thinned and proliferation of cardiomyocytes is decreased. Cardiac tissue-restricted ablation of TrxR2 results in fatal dilated cardiomyopathy, a condition reminiscent of that in Keshan disease and Friedreich's ataxia. We conclude that TrxR2 plays a pivotal role in both hematopoiesis and heart function.Reactive oxygen species (ROS)-generated mainly as a byproduct of the respiratory chain or by oxidases-are implicated in the pathogenesis and pathophysiology of a variety of human diseases such as cancer, cardiovascular, and degenerative disorders. A variety of cellular antioxidant systems control the balance of free intra-and extracellular oxygen radicals. Previous efforts have addressed the physiological role of superoxide dismutases, catalases, and glutathione (GSH) peroxidases in vivo, but the role of the thioredoxin/thioredoxin reductase/ peroxiredoxin system in ROS removal has only recently attracted attention.Thioredoxins are small redox-active proteins with an essential function in DNA metabolism and repair, transcription, and cell-cell communication (1). Acting through peroxiredoxins, they also efficiently protect cells from oxidative damage (27). Cytosolic (Trx1) and mitochondrial (Trx2) thioredoxins are required for proliferation and protection from apoptosis during early embryogenesis (26). Moreover, in chicken B cells, Trx2 is critically involved in the regulation of mitochondriondependent apoptosis (37). More recently, heart-specific overexpression of dominant-negative Trx1 was shown to be associated with increased oxidative stress and cardiac hypertrophy in mice (39).Trx activities are governed by thioredoxin reductases (TrxRs) that, in turn, use NADPH/H ϩ as the reducing agent (23). TrxRs are members of the pyridine nucleotide-disulfide oxidoreductase family, form homodimers, and possess two interacting redox-active centers. The C-terminal redox center contains a catalytically important selenocysteine (SeCys) (9,17,41). In mammals, three TrxRs...

Mice deficient for the major lysosomal aspartic proteinase cathepsin D, generated by gene targeting, develop normally during the first 2 weeks, stop thriving in the third week and die in a state of anorexia at day 26 +/− 1. An atrophy of the ileal mucosa first observed in the third week progresses towards widespread intestinal necroses accompanied by thromboemboli. Thymus and spleen undergo massive destruction with fulminant loss of T and B cells. Lysosomal bulk proteolysis is maintained. These results suggest, that vital functions of cathepsin D are exerted by limited proteolysis of proteins regulating cell growth and/or tissue homeostasis, while its contribution to bulk proteolysis in lysosomes appears to be non‐critical.

Lysosomal cysteine proteinases of the papain family are involved in lysosomal bulk proteolysis, major histocompatibility complex class II mediated antigen presentation, prohormone processing, and extracellular matrix remodeling. Cathepsin L (CTSL) is a ubiquitously expressed major representative of the papain-like family of cysteine proteinases. To investigate CTSL in vivo functions, the gene was inactivated by gene targeting in embryonic stem cells. CTSL-deficient mice develop periodic hair loss and epidermal hyperplasia, acanthosis, and hyperkeratosis. The hair loss is due to alterations of hair follicle morphogenesis and cycling, dilatation of hair follicle canals, and disturbed club hair formation. Hyperproliferation of hair follicle epithelial cells and basal epidermal keratinocytes-both of ectodermal origin-are the primary characteristics underlying the mutant phenotype. Pathological inflammatory responses have been excluded as a putative cause of the skin and hair disorder. The phenotype of CTSL-deficient mice is reminiscent of the spontaneous mouse mutant furless (fs). Analyses of the ctsl gene of fs mice revealed a G149R mutation inactivating the proteinase activity. CTSL is the first lysosomal proteinase shown to be essential for epidermal homeostasis and regular hair follicle morphogenesis and cycling.

The term mesocrystal has been widely used to describe crystals that form by oriented assembly, and that exhibit nanoparticle substructures. Using calcite crystals co-precipitated with polymers as a suitable test case, this article looks critically at the concept of mesocrystals. Here we demonstrate that the data commonly used to assign mesocrystal structure may be frequently misinterpreted, and that these calcite/polymer crystals do not have nanoparticle substructures. Although morphologies suggest the presence of nanoparticles, these are only present on the crystal surface. High surface areas are only recorded for crystals freshly removed from solution and are again attributed to a thin shell of nanoparticles on a solid calcite core. Line broadening in powder X-ray diffraction spectra is due to lattice strain only, precluding the existence of a nanoparticle sub-structure. Finally, study of the formation mechanism provides no evidence for crystalline precursor particles. A re-evaluation of existing literature on some mesocrystals may therefore be required.

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Dilated cardiomyopathy is a frequent cause of heart failure and is associated with high mortality. Progressive remodeling of the myocardium leads to increased dimensions of heart chambers. The role of intracellular proteolysis in the progressive remodeling that underlies dilated cardiomyopathy has not received much attention yet. Here, we report that the lysosomal cysteine peptidase cathepsin L (CTSL) is critical for cardiac morphology and function. Oneyear-old CTSL-deficient mice show significant ventricular and atrial enlargement that is associated with a comparatively small increase in relative heart weight. Interstitial fibrosis and pleomorphic nuclei were found in the myocardium of the knockout mice. By electron microscopy, CTSL-deficient cardiomyocytes contained multiple large and apparently fused lysosomes characterized by storage of electron-dense heterogeneous material. Accordingly, the assessment of left ventricular function by echocardiography revealed severely impaired myocardial contraction in the CTSL-deficient mice. In addition, echocardiographic and electrocardiographic findings to some degree point to left ventricular hypertrophy that most likely represents an adaptive response to cardiac impairment. The histomorphological and functional alterations of CTSL-deficient hearts result in valve insufficiencies. Furthermore, abnormal heart rhythms, like supraventricular tachycardia, ventricular extrasystoles, and first-degree atrioventricular block, were detected in the CTSL-deficient mice.

We investigated the influence of the porosity of the growth medium on the crystallization of calcium carbonate in hydrogels with different gelatin solid contents (2.5, 5, and 10 wt %). In all experiments, the precipitate consisted of calcite with occasional occurrences of some vaterite and aragonite. The calcite grew as compact radial intergrowths of crystals that show rhombohedral external faces. The crystal surfaces consist of identical 1−10 μm sized rhombohedral sub-blocks. Electron backscatter diffraction (EBSD) uncovered the radial intergrowth structure of the aggregates. EBSD also documented the internal microscale mosaicity and mesocrystal-like constitution of the gel-grown calcite. Raman spectroscopy and thermogravimetric analysis confirmed the presence of gelatin within the crystals. It reached up to ∼2 mass % in the calcite-gelatin composites that formed in hydrogels with 10 wt % gelatin content. Calcite morphology and mosaicity varied with the gelatin content of the hydrogel, such that an increase in gelatin content initiated the growth of smaller crystal aggregates having progressively rougher surfaces, increasing amounts of incorporated gel, and increasing degrees of misorientation in the internal mosaic structure. Apart from biospecific morphology, the gel growth experiment successfully mimics many characteristics of calcite biomineralization such as formation of a hierarchical hybrid composite, crystal mosaicity, and mesocrystal-like constitution.

Crack extension under static loading in pseudoplastic and pseudoelastic binary NiTi shape memory alloy (SMA) compact tension (CT) specimens was examined. Two material compositions of 50.3 at.% Ni (martensitic/pseudoplastic) and 50.7 at.% Ni (austenitic/ pseudoelastic) were investigated. The SMAs were characterized using differential scanning calorimetry to identify the phase transformation temperatures and tensile testing to characterize the stress-strain behavior. A miniature CT specimen was developed, which yields reliable critical fracture mechanics parameters. At 295 K, cracks propagate at similar stress intensities of 30 AE 5 MPa ffiffiffiffi m p into martensite and pseudoelastic austenite. Integrating the miniature CT specimen into a small test device which can be fitted into a scanning electron microscope shows that this is due to cracks propagating into regions of detwinned martensite in both materials. Investigating a pseudoelastic miniature CT specimen in a synchrotron beam proves that martensite forms in front of the crack in the center of the CT specimen, i.e. under plane strain conditions.