Additive manufacturing of cellulose-based materials with continuous, multidirectional stiffness gradients.

Functionally graded materials (FGMs) enable applications in fields such as biomedicine and architecture, but their fabrication suffers from shortcomings in gradient continuity, interfacial bonding, and directional freedom. In addition, most commercial design software fail to incorporate property gradient data, hindering explorations of the design space of FGMs. Here, we leveraged a combined approach of materials engineering and digital processing to enable extrusion-based multimaterial additive manufacturing of cellulose-based tunable viscoelastic materials with continuous, high-contrast, and multidirectional stiffness gradients. A method to engineer sets of cellulose-based materials with similar compositions, yet distinct mechanical and rheological properties, was established. In parallel, a digital workflow was developed to embed gradient information into design models with integrated fabrication path planning. The payoff of integrating these physical and digital tools is the ability to achieve the same stiffness gradient in multiple ways, opening design possibilities previously limited by the rigid coupling of material and geometry.

A novel rapid additive manufacturing concept for architectural composite shell construction inspired by the shell formation in land snails.

State-of-the-art rapid additive manufacturing (RAM)-specifically fused filament fabrication (FFF)-has gained popularity among architects, engineers and designers for the quick prototyping of technical devices, the rapid production of small series and even the construction scale fabrication of architectural elements. The spectrum of producible shapes and the resolution of detail, however, are determined and constrained by the layer-based nature of the fabrication process. These aspects significantly limit FFF-based approaches for the prefabrication and in situ fabrication of free-form shells at the architectural scale. Snails exhibit a shell building process that suggests ways to overcome these limits. They produce a soft, pliable proteinaceous film-the periostracum-which later hardens and serves, among other functions, as a form-giving surface for an inner calcium carbonate layer. Snail shell formation behavior is interpreted from a technical point of view to extract potentially useful aspects for a biomimetic transfer. A RAM concept for the continuous extrusion of thin free-form composite shells inspired by the snail shell formation is presented.

[Ophthalmic Plastic Surgery of Exposure Keratopathy in the Intensive Care Unit]. / Okuloplastische Chirurgie bei Expositionskeratopathie auf der Intensivstation.

Critically ill patients in the intensive care unit (ICU) may develop eye problems, due to impaired ocular protective mechanisms or direct involvement of the eye in severe systemic diseases. If eye infections or ocular surface disorders are not identified in time, endophthalmitis or corneal ulcer may develop and can cause permanent functional injuries of the eye. A retrospective analysis was performed and a total of 283 complete intensive care courses of treatment were evaluated, taking into account ophthalmic medical consultations for frequent cardinal symptoms. The most common cardinal symptoms were lagophthalmus (exposure keratopathy), chemosis, redness and periorbital haematoma. The following predisposing risk factors for the onset of ocular complications during intensive care treatment were detected: chemosis (p < 0.001), redness (p = 0.007), lagophthalmus (p = 0.001), ventilation (p < 0.001), use of muscle relaxants (p < 0.001), cardiovascular (p < 0.001), and neurological diseases (p < 0.001). In 71.7 % of ICU patients, additional treatment was prescribed during the eye consultation. This includes special eye care treatment (6.0 %) and/or drug therapy (64.0 %), as well as oculoplastic surgery in 4,3 % of critically ill patients. The most common oculoplastic-surgical procedure in the ICU was lid adhesion to achieve adequate protection of the corneal surface in patients with severe exposure keratopathy. Oculoplastic surgery is the method of choice for protecting the cornea in critically ill patients, when conservative options such as hypoallergenic adhesive tape or a moisture chamber are not sufficient to protect the ocular surface. The main challenges are to pay attention to the indication and performance in due time, and to avoid permanent loss of function through transparency reduction or irregular astigmatism in post-recovery patients.

[Immunologic, alloantigen-dependent factors in chronic graft rejection]. / Immunologische, alloantigenabhängige Faktoren in der chronischen Transplantatabstossung.

BACKGROUND: The pathogenesis of chronic renal allograft rejection is still speculative. Amongst other factors immune-mediated graft injury is proposed. Since the allo-antigen is specifically recognized by the variable (V) alpha and beta chains of the T-cell receptor, a restricted T-cell repertoire might support the notion of allo-antigen involvement in chronic rejection. METHODS: By the means of semiquantitative polymerase chain reaction the V beta families 1-20 were assessed in allograft biopsies with histologically confirmed chronic and acute rejection. At the same time the V beta repertoire was analyzed in PBMC. RESULT: The intragraft V beta repertoire was limited to 1 to 3 dominant V beta families in chronic and acute rejection. The response was highly individual and did not correlate to the type or degree of HLA mismatches. The T-cell repertoire in PBMC was polyclonal and did not reflect the immune response in the graft. CONCLUSION: The finding of a restricted V beta repertoire in both forms of rejection might indicate an immunological basis not only for acute, but also for ongoing chronic rejection. Tailor-made antibodies against the dominant V beta clones might provide a tool for selective immunosuppression in both entities of rejection targeting only those T cells which were activated by allo-antigens.

Limited T-cell repertoire in renal allograft and allogeneic melanoma transmitted by the graft.

In a patient with metastatic melanoma transmitted by the renal allograft, HLA serves as an alloantigen per se and is associated with tumor antigens at the same time. The influence of this antigeneic pattern on the Vbeta T-cell repertoire in an allogeneic melanoma, allograft, and peripheral blood mononuclear cells (PBMC) was assessed by polymerase chain reaction. Vbeta13.1 and 19 were found in both the melanoma and the graft. Vbeta14 was detected only in the melanoma and Vbeta6 was detected only in the kidney. PBMC revealed an unrestricted Vbeta pattern. Markers for cytotoxic activity of T cells--granzyme B and perforin--were not expressed during immunosuppressive therapy as clinically reflected in a nonrejecting allograft and in a progressing melanoma. In vitro PBMC proliferated to recombinant interleukin-2, whereas recombinant interferon-gamma did not augment this response. Initiation of immune therapy, in addition to discontinuation of immunosuppression, might support the rejection of the allogeneic tumor by dominant Vbeta T cells.

Restricted T cell V beta repertoire in renal allografts during acute and chronic rejection.

Allo-MHC specific antigen recognition might not only be involved in acute, but also in chronic rejection. The clonotypic specificity of the T-cell receptor to recognize all-MHC is located in the variable (V) alpha and beta chain. A restricted T-cell receptor repertoire could support an immunological basis for chronic rejection. The novel feature of this study is that V beta repertoire was assessed in ongoing chronic rejection before end-stage renal failure and in acute rejection. V beta s 1 to 20 were quantitated by PCR in PBMC and biopsies of rejecting renal allografts. The V beta pattern in PBMC demonstrated a polyclonal distribution. However, the intragraft V beta repertoire was restricted to 1 to 3 dominant V betas and highly individual in 9 of 12 patients. Number and type of the HLA mismatch and the time interval between transplantation and biopsy did not correlate to the V beta distribution. The individual response is attributed to genetic predisposition factors of the recipient. Therefore, the restriction of the V beta repertoire indicates allo-MHC dependent immune processes not only in acute, but also in ongoing chronic rejection. Tailor-made antibodies against dominant V betas might offer specific individual immunosuppression in treating both acute and ongoing chronic rejection.

Characterisation of a new allele of pale cress and its role in greening in Arabidopsis thaliana.

A recessive mutant with white leaves was identified in a screen of a population of T-DNA-tagged Arabidopsis thaliana plants. The mutation is lethal, but plants develop almost to maturity under sterile conditions. The white areas in leaves are devoid of developed chloroplasts, but the plants frequently develop green sectors which contain green chloroplasts. Molecular characterisation of the affected gene revealed that the mutant is allelic to pale cress (pac), a recently described mutation, and was therefore named pac-2. Sequencing of cDNAs and the genomic region revealed several noteworthy features of this genetic locus. In pac-2 the T-DNA had inserted in the region of the promoter and abolished transcription of the PAC gene completely. Cytokinin induced greening in mature, white homozygous pac-2 plants, and therefore is likely to be responsible for the greening observed in callus and shoots induced on roots from such plants. However, the PAC transcript was found to be absent in both white leaves and green callus. Thus, since cytokinin induced greening in the absence of PAC RNA this plant hormone appears to be able to bypass PAC function.

[Left cerebral ischemia in mitral valve aneurysm]. / Linkszerebrale Ischämie bei Mitralklappenaneurysma.

An anterior mitral leaflet aneurysm was detected by two-dimensional echocardiography using the transesophageal approach in a 53-year-old patient with cerebral ischemic event. The transesophageal examination allowed a clear description of the aneurysm which was confirmed during surgery. This case demonstrates that transesophageal echocardiography is the method of choice in evaluation of distinct valvular lesions. The importance of TEE examination in patients with a neurological history is evident.

High rates of Ac/Ds germinal transposition in Arabidopsis suitable for gene isolation by insertional mutagenesis.

Overexpression of the Activator (Ac) transposase gene in Arabidopsis thaliana resulted in a minimal germinal transposition frequency of 27% in which independent Dissociation (Ds) transposition events were observed. Molecular analysis of 45 F1 generation Ac/Ds plants indicated that high rates of somatic excision had occurred, and independent germinal insertions were identified in F2 generation progeny plants. A tandem cauliflower mosaic virus (CaMV) promoter fused to two different Ac coding sequences significantly increased the rate of Ds transposition. The CaMV-Ac fusions activated single and multiple copies of two different Ds elements, DsDHFR and Ds35S-1, and reciprocal crosses resulted in similar transposition frequencies. The improved rate of independent germinal transposition observed makes Arabidopsis an ideal system for insertional mutagenesis.