167 research outputs found
Amyloidosis in Heart Failure
No full textPurpose: Amyloidosis represents an increasingly recognized but still frequently missed cause of heart failure. In the light of many effective therapies for light chain (AL) amyloidosis and promising new treatment options for transthyretin (ATTR) amyloidosis, awareness among caregivers needs to be raised to screen for amyloidosis as an important and potentially treatable differential diagnosis. This review outlines the diversity of cardiac amyloidosis, its relation to heart failure, the diagnostic algorithm, and therapeutic considerations that should be applied depending on the underlying type of amyloidosis. Recent Findings: Non-biopsy diagnosis is feasible in ATTR amyloidosis in the absence of a monoclonal component resulting in higher detection rates of cardiac ATTR amyloidosis. Biomarker-guided staging systems have been updated to facilitate risk stratification according to currently available biomarkers independent of regional differences, but have not yet prospectively been tested. Novel therapies for hereditary and wild-type ATTR amyloidosis are increasingly available. The complex treatment options for AL amyloidosis are improving continuously, resulting in better survival and quality of life. Mortality in advanced cardiac amyloidosis remains high, underlining the importance of early diagnosis and treatment initiation. Summary: Cardiac amyloidosis is characterized by etiologic and clinical heterogeneity resulting in a frequently delayed diagnosis and an inappropriately high mortality risk. New treatment options for this hitherto partially untreatable condition have become and will become available, but raise challenges regarding their implementation. Referral to specialized centers providing access to extensive and targeted diagnostic investigations and treatment initiation may help to face these challenges
Caspase-8 and caspase-7 sequentially mediate proteolytic activation of acid sphingomyelinase in TNF-R1 receptosomes
No full textWe previously demonstrated that tumour necrosis factor (TNF)-induced ceramide production by endosomal acid sphingomyelinase (A-SMase) couples to apoptosis signalling via activation of cathepsin D and cleavage of Bid, resulting in caspase-9 and caspase-3 activation. The mechanism of TNF-mediated A-SMase activation within the endolysosomal compartment is poorly defined. Here, we show that TNF-induced A-SMase activation depends on functional caspase-8 and caspase-7 expression. The active forms of all three enzymes, caspase-8, caspase-7 and A-SMase, but not caspase-3, colocalize in internalized TNF receptosomes. While caspase-8 and caspase-3 are unable to induce activation of purified pro-A-SMase, we found that caspase-7 mediates A-SMase activation by direct interaction resulting in proteolytic cleavage of the 72-kDa pro-A-SMase zymogen at the non-canonical cleavage site after aspartate 253, generating an active 57 kDa A-SMase molecule. Caspase-7 down modulation revealed the functional link between caspase-7 and A-SMase, confirming proteolytic cleavage as one further mode of A-SMase activation. Our data suggest a signalling cascade within TNF receptosomes involving sequential activation of caspase-8 and caspase-7 for induction of A-SMase activation by proteolytic cleavage of pro-A-SMase
Data from: Physiological and social consequences of gastrointestinal nematode infection in a nonhuman primate
No full textGastrointestinal nematodes are intensely studied models for host-pathogen interactions in wildlife, yet consequences of infections are not fully understood. Among the potential costs of nematode infection are physiological changes caused by immune system activation, reduction or reallocation of available energy, as well as potential social consequences in terms of decreased social activity or avoidance of infected individuals. We used experimental anthelmintic treatment to investigate effects of strongyle nematode infection in Barbary macaques (Macaca sylvanus), comparing 56 treated to 17 untreated individuals. Deworming success was monitored by coproscopy and infection probability estimated from patch occupancy models. Increasing strongyle infection probabilities were associated with increased fecal glucocorticoid metabolite levels and slightly decreased activity, and had no significant effect on energy balance quantified as urinary C-peptide levels. The frequency to approach into close spatial proximity of a partner was predicted by the partner’s, but not focal individual’s infection status, with a tendency towards infected individuals being approached less frequently. Although effects were weak, they suggest a co-occurrence of sickness and avoidance behavior, both possibly shaping social interaction patterns with potential consequences for an individual’s social relationships. This study adds to the growing body of research on the complex interactions of sociality, health and fitness in a group living species
O processo de Cayley-Dickson e as álgebras de Jordan
No full textNeste trabalho apresentaremos um algoritmo que nos permite fazer a construção de álgebras, chamado de processo de Cayley-Dickson e, com ele, veremos que é possível construir as ´álgebras dos Reais (R), Complexos (C), Quaternizo (H) e Octônios (O), de dimensões 1, 2, 4 e 8, que representam todas as álgebras de divisão normandas e com composição, a menos de isomorfismos. Em seguida, introduziremos o conceito de Álgebras de Jordan, que foram apresentadas a matemática pelo físico Pascual Jordan na tentativa de descobrir uma nova configuração algébrica para Mecânica Quântica. Falaremos especialmente sobre as Álgebras de Jordan Formalmente Reais. Por fim, faremos uma análise apresentando resultados que associa diretamente estas álgebras
Accumulation of peripheral autoreactive B cells in the absence of functional human regulatory T cells
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Dreidimensionale Strukturbestimmung des Glycin-Betain Transporters BetP mittels Kryo-Elektronen Kristallographie
No full textThe soil bacterium Corynebacterium glutamicum has five secondary transporters for compatible solutes allowing it to cope with osmotic stress. The most abundant of them, the transporter BetP, performs a high affinity uptake of glycine-betain when encountering hyperosmotic stress. BetP belongs to the betaine/carnitine/choline/transporter (BCCT) family, and is predicted to have twelve transmembrane helices with both termini facing the cytoplasm. The goal of this thesis is to facilitate understanding of BetP function by determining a three dimensional (3D) model of its structure. Two-dimensional (2D) crystallization of wild-type (WT) BetP has been successfully performed by reconstitution into a mixture of E. coli lipids and bovine cardiolipin, which resulted in vesicular crystals diffracting to 7.5 Å resolution (Ziegler, Morbach et al. 2004). Diffraction patterns of these crystals however showed unfocused spots, generally due to high mosaicity. Better results were obtained by using the constitutively active mutant BetPdeltaC45 in which the first 45 amino acids of the positively charged C-terminus were removed. BetPdeltaC45 crystals obtained under the same conditions for BetP WT were concluded to be pseudo crystals, based on the inconsistence of symmetry. These crystals had BetPdeltaC45 molecules randomly up/downwards inserted into membrane crystals, and cannot be used for structure determination, even though they diffracted up to 7 Å. The problem of pseudo crystal formation could be solved by changing the lipids used for 2D crystallization to a native lipid extract from C. glutamicum cells. This change of lipids improved the crystals to well-ordered packing with exclusive p121_b symmetry. To understand the role of lipids in crystal packing and order, lipids were extracted at different stages during crystallization, and identified by using multiple precursor ion scanning mass spectrometry. The results show that phosphatidyl glycerol (PG) 16:0-18:1 is the most dominant lipid species in C. glutamicum membranes, and that BetP has a preference for the fatty acid moieties 16:0-18:1. Crystallization with synthetic PG 16:0-18:1 proved that an excess of this lipid prevents pseudo crystal formation, but these crystals did not reach the quality as previously achieved by using the C. glutamicum lipids. Apart from the effect of lipids in crystallinity, the concentration and type of salts influenced crystal growth and morphology. High salt conditions (>400 mM LiCl or KCl) yielded tubular crystals, whereas low salt conditions (<300 mM LiCl, NaCl or KCl) led to formation of up to 10 µm large sheet-like crystals. The intermediate concentration gave a mixture of sheet-like and tubular crystals. In terms of resolution, sheets diffracted better than tubes. The sheet-like crystals used for 3D map reconstruction were obtained from a dialysis buffer containing 200 mM NaCl combined with using C. glutamicum lipids. Electron microscopic images were taken from frozen-hydrated crystals using a helium-cooled JEOL 300 SFF microscope or a liquid nitrogen-cooled FEI Tecnai G2 microscope at 300 kV, which allowed optimal data collection and minimized radiation damage to the sample. More than 1000 images of tilt angles up to 50° were taken and evaluated using optical diffraction of a laser beam. The best 200 images were processed with the MRC image processing software package, and 79 images from different tilt angles were merged to the final data set used for calculation of a 3D map at a planar resolution of 8 Å. The structure shows BetPdeltaC45 as a trimer with each monomer consisting of 12 transmembrane alpha-helices. Protein termini and loop regions could not be determined due to the limited resolution of the map. Six of the twelve helices line a central cavity forming a potential substrate-binding chamber. Each monomer shows a central cavity in different sizes and shapes. Thus, the constitutively active BetPdeltaC45 thus forms an unusual asymmetric homotrimer. BetP most likely reflects three different conformational states of secondary transporters: the cytoplasmically open (C), the occluded (O), and the periplasmically open (P) states. The C and O states are similar to BetP WT projection structure, while the P state is discrepant and highly flexible due to the shape and size of the central cavity as well as the lowest intensity of the density. The observation of the P state corresponds well to the constitutively active property of BetPdeltaC45. For the high resolution structure of the C and O states are available, this work presents the first structural information of the P state of a secondary transporter.Thema dieser Arbeit sind die Struktur/Funktionsprinzipien des osmoaktiven Betaintransporters BetP aus Corynebacterium glutamicum, eines Proteins aus der Familie der Betain/Carnitine/Cholin Transporter (BCCT) welches das kompatible Solut Betain unter Ausnutzung eines Natriumgradienten in die Zelle importiert. Gleichzeitig dient BetP auch als Osmolaritäts- und Temperatursensor der die Menge an importierten Solut ohne Umwege anpassen kann, wenn es z.B. als Folge von Überflutungen oder Dürren zu starken Schwankungen in der Wasseraktivität des bakteriellen Lebensraums kommt. Zum besseren Verständnis von osmoregulatorischen Sekundärtransportern und der BCCT Proteinfamilie wurde die dreidimensionale (3D) Struktur von BetP mittels Elektronenkristallographie bestimmt. Der BetP Wildtyp und eine konstitutiv aktive Mutante mit einem um 45 Aminosäuren gekürzten C-Terminus (BetPdeltaC45) wurden in E. coli überexprimiert und mittels Streptavidin-Affinitätschromatographie aufgereinigt. Die C-terminal gekürzte Mutante wurde gewählt da sie konstitutiv aktiv ist und Betain weitestgehend unabhängig von der Osmolarität der Umgebung über die Membran transportiert, was sie hervorragend geeignet macht den aktiven Zustand von BetP strukturell zu charakterisieren. Sowohl der BetP Wildtyp als auch die BetPdeltaC45 Mutante formten die für die Elektronenkristallographie nötigen zweidimensionalen (2D) Kristalle. Die Entfernung des positiv geladenen C-Terminus in der BetPdeltaC45 Mutante hatte jedoch einen starken Effekt auf die Kristallisierung und führte reproduzierbar zur Bildung von besser geordneten Kristallen mit niedrigerer Mosaizität. Die BetPdeltaC45 Mutante wurde daher für die weitere Optimierung und die 3D Strukturaufklärung verwendet. Neben dem Protein, sind die verwendeten Lipide für die Bildung von geordneten 2D Kristallen von entscheidender Bedeutung. Während der Optimierung wurde BetPdeltaC45 mittels dreier verschiedener Lipidpreparationen kristallisiert. Zum besseren Verständnis des Lipideinflusses auf das Kristallisationsverhalten wurden außerdem Lipidextrakte aus verschiedenen Stadien der Kristallisation hergestellt und die enthaltenen Lipide mittels quantitativer Massenspektrometrie bestimmt. Die Ergebnisse zeigen die Präferenz von BetP für 16:0-18:1 Fettsäurereste und das eine an diesen Resten reiche Lipidmischung die Bildung von Pseudokristallen verhindert. Die besten Kristallisationsergebnisse wurden mit dem nativen C. glutamicum Lipidextrakt erzielt. Die mit dieser Lipidmischung gezüchteten Kristalle formten großflächig kristallin geordnete Platten, die besonders für die Aufnahme von 3D Daten geeignet sind. Wichtiger noch als die Größe war der höhere Ordnungsgrad, welcher die Datenaufnahme bis zu einer Auflösung von 7-8 Å erlaubte und damit die Identifizierung von Transmembranhelices, den grundsätzlichen Strukturbausteinen von Membranproteinen ermöglicht. Zur Bestimmung der 3D Struktur von BetPdeltaC45 wurden elektronenkristallographische Aufnahmen von mehr als 200 Kristallen aufgenommen und die zur Strukturaufklärung nötigen Phasen und Amplituden mittels Bildbearbeitung extrahiert. Die 3D Information wurde aus zwischen 0 und 50 Grad gekippten Aufnahmen der 2D Kristalle gewonnen. Alle Daten wurden unter Einhaltung der p121_b Symmetrie zu einem einheitlichen Datensatz vereinigt, der mit einem mittlerem Phasenresidual von 20.4° eine hohe Qualität aufzeigt. Amplituden und Phasen dieses Datensatzes wurden für die Errechnung einer 3D Dichtekarte verwendet. Die bestimmte Dichte hat eine planare Auflösung von 8 Å und zeigt BetP als Trimer mit 12 länglichen Dichten pro Monomer, welche den 12 mittels Hydrophobizitätsplot vorhergesagten Transmembranhelices zugeordnet wurden. Interessanterweise ist die Anordnung dieser Dichten unterschiedlich für alle drei Monomere, wie eindeutig mittels Analyse einer Kreuzkorrelations-Dichtekarte zwischen den Monomeren und anhand der möglichen Kristallsymmetrien gezeigt werden konnte. Die Unterschiede dieses äußerst ungewöhnlichen asymmetrischen Homotrimers konzentrieren sich um einen von vier Helices umrahmten Hohlraum mit unterschiedlich großen Eintrittsöffnungen für jedes Monomer. Basierend auf der Anordnung des BetP asymmetrischen Homotrimers und bekannten biochemischen Daten wurde ein Modell erstellt in dem sich die Substratbindungstellen in den zentralen Hohlräumen befinden und in dem jedes Monomer des asymmetrischen Homotrimers einen unterschiedlichen Aktivierungszustand einnimmt. Die drei Aktivierungszustände wurden als die cytoplasmatisch offene, die geschlossene und periplastisch offene Konformation von sekundären Transportern interpretiert. Die vorliegende Arbeit liefert die ersten Strukturinformationen für einen Transporter der BCCT Familie und die periplastisch offene Konformation eines Sekundärtransporters und liefert damit wichtige Bausteine für das bessere Verständnis dieser für alle Zellen überlebenswichtigen Klasse von Transportern
Lentiviral-mediated gene therapy restores B cell tolerance in Wiskott-Aldrich syndrome patients
No full textWiskott-Aldrich syndrome (WAS) is an X-linked immunodeficiency characterized by microthrombocytopenia, eczema, and high susceptibility to developing tumors and autoimmunity. Recent evidence suggests that B cells may be key players in the pathogenesis of autoimmunity in WAS. Here, we assessed whether WAS protein deficiency (WASp deficiency) affects the establishment of B cell tolerance by testing the reactivity of recombinant antibodies isolated from single B cells from 4 WAS patients before and after gene therapy (GT). We found that pre-GT WASp-deficient B cells were hyperreactive to B cell receptor stimulation (BCR stimulation). This hyperreactivity correlated with decreased frequency of autoreactive new emigrant/transitional B cells exiting the BM, indicating that the BCR signaling threshold plays a major role in the regulation of central B cell tolerance. In contrast, mature naive B cells from WAS patients were enriched in self-reactive clones, revealing that peripheral B cell tolerance checkpoint dysfunction is associated with impaired suppressive function of WAS regulatory T cells. The introduction of functional WASp by GT corrected the alterations of both central and peripheral B cell tolerance checkpoints. We conclude that WASp plays an important role in the establishment and maintenance of B cell tolerance in humans and that restoration of WASp by GT is able to restore B cell tolerance in WAS patients
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