Different extracellular domains of the neural cell adhesion molecule (N-CAM) are involved in different functions

The neural cell adhesion molecule (N-CAM) engages in diverse functional roles in neural cell interactions. Its extracellular part consists of five Ig-like domains and two fibronectin type III homologous (type III) repeats. To investigate the functional properties of the different structural domains of the molecule in cell interactions and signal transduction to the cell interior, we have synthesized, in a bacterial expression system, the individual domains and tandem sets of individual domains as protein fragments. These protein fragments were tested for their capacity to influence adhesion and spreading of neuronal cell bodies, promote neurite outgrowth, and influence cellular migration patterns from cerebellar microexplants in vitro. Ig-like domains I and II and the combined type III repeats I-II were most efficient for adhesion of neuronal cell bodies, when coated as substrates. Neurite outgrowth was best on the substrate-coated combined type III repeats I-II, followed by the combined Ig-like domains I-V and Ig-like domain I. Spreading of neuronal cell bodies was best on substrate-coated combined type III repeats I-II, followed by Ig-like domain I and the combined Ig-like domains I-V. The cellular migration pattern from cerebellar microexplant cultures plated on a mixture of laminin and poly-L-lysine was modified by Ig-like domains I, III, and IV, while Ig-like domains II and V and the combined type III repeats I-II did not show significant modifications, when added as soluble fragments. Outgrowth of astrocytic processes from the explant core was influenced only by Ig-like domain I. Metabolism of inositol phosphates was strongly increased by Ig-like domain I and less by the Ig-like domains II, III, IV, and V, and not influenced by the combined type III repeats I-II. Intracellular concentrations of Ca2+ and pH values were increased only by the Ig-like domains I and II. Intracellular levels of cAMP and GMP were not influenced by any protein fragment. These experiments indicate that different domains of N-CAM subserve different functional roles in cell recognition and signal transduction, and are functionally competent without nervous system-derived carbohydrate structures.

Fast iterative algorithm for metal artifact reduction in X-ray CT

RATIONALE AND OBJECTIVES

The reduction of metal artifacts in x-ray computed tomography (CT) has important clinical applications. An iterative method adapted from the expectation maximization (EM) formula for emission CT was shown to be effective for metal artifact reduction, but its computational speed is slow. The goal of this project was to accelerate that iterative method for metal artifact reduction.

MATERIALS AND METHODS

Using the row-action/ordered-subset (EM) formula for emission CT as a basis, the authors developed a fast iterative algorithm for metal artifact reduction. In each iteration of this algorithm, both reprojection from an intermediate image and backprojection from discrepancy data are performed.

RESULTS

The feasibility of the fast iterative algorithm was demonstrated in numerical and phantom experiments. In comparison with the nonaccelerated iterative algorithm, the speed of iterative metal artifact reduction is improved by an order of magnitude given image quality in terms of visual inspection, I-divergence in the projection domain, and the euclidean distance in the image domain.

CONCLUSION

The fast iterative algorithm corrects intermediate reconstruction according to subsets of projections and produces satisfactory image quality at a much faster speed than the previously published iterative algorithm. This algorithm has important potential in clinical applications, such as orthopedic, oncologic, and dental imaging.

Characterization and mitigation of gene expression burden in mammalian cells

Despite recent advances in circuit engineering, the design of genetic networks in mammalian cells is still painstakingly slow and fraught with inexplicable failures. Here, we demonstrate that transiently expressed genes in mammalian cells compete for limited transcriptional and translational resources. This competition results in the coupling of otherwise independent exogenous and endogenous genes, creating a divergence between intended and actual function. Guided by a resource-aware mathematical model, we identify and engineer natural and synthetic miRNA-based incoherent feedforward loop (iFFL) circuits that mitigate gene expression burden. The implementation of these circuits features the use of endogenous miRNAs as elementary components of the engineered iFFL device, a versatile hybrid design that allows burden mitigation to be achieved across different cell-lines with minimal resource requirements. This study establishes the foundations for context-aware prediction and improvement of in vivo synthetic circuit performance, paving the way towards more rational synthetic construct design in mammalian cells.

Alpine and cross-country skiing after total hip replacement: 2 cohorts of 50 patients each, one active, the other inactive in skiing, followed for 5-10 years

2 groups of 50 patients each, matched for age, weight, height, gender and type of implant, were clinically and radiographically examined after THR. Group A regularly carried out alpine skiing and/or cross-country skiing, while group B did no winter sports. At 5 years, no signs of loosening were found in group A, whereas 5/60 implants in group B had signs of loosening, mostly of the femoral component (p < 0.05). At 10 years, 30 patients remained in group A and 27 in group B. No new cases of loosening were found in group B, but 2/30 cases in group A. There was a higher (p < 0.05) average wear rate in group A (2.1 mm) than in group B (1.5 mm). The wear rate was particularly high (3-4 mm) in physically very active patients in group A with localized osteolysis at the interface. It seems likely that in an even longer follow-up, the number of cases of aseptic loosening would be greater in group A than group B. Our findings, combined with the results of previously-published biomechanical studies, do not provide any evidence that controlled alpine and/ or cross-country skiing has a negative effect on the acetabular or femoral component of hip replacements. The results of the biomechanical studies indicate, however, that it is advantageous to avoid short-radius turns on steep slopes or moguls.

A reduction in severe hypoglycaemia in type 1 diabetes in a randomized crossover study of continuous intraperitoneal compared with subcutaneous insulin infusion

AIM

Continuous intraperitoneal insulin infusion (CIPII) with the DiaPort system using regular insulin was compared to continuous subcutaneous insulin infusion (CSII) using insulin Lispro, to investigate the frequency of hypoglycemia, blood glucose control, quality of life, and safety.

METHODS

In this open, randomized, controlled, cross-over, multinational, 12-month study, 60 type 1 diabetic patients with frequent hypoglycemia and/or HbA1c > 7.0% with CSII were randomized to CIPII or CSII. The aim was to obtain the best possible blood glucose while avoiding hypoglycemia.

RESULTS

The frequency of any hypoglycemia was similar (CIPII 118.2 (SD 82.6) events / patient year, CSII 115.8 (SD 75.7) p = 0.910). The incidence of severe hypoglycemia with CSII was more than twice the one with CIPII (CIPII 34.8 events / 100 patient years, CSII 86.1, p = 0.013). HbA1c, mean blood glucose, and glucose fluctuations were not statistically different. Treatment-related severe complications occurred mainly during CIPII: port infections (0.47 events / patient year), abdominal pain (0.21 events / patient year), insulin underdelivery (0.14 events / patient year). Weight gain was greater with CSII (+ 1.5 kg vs. - 0.1 kg, p = 0.013), quality of life better with CIPII.

CONCLUSIONS

In type 1 diabetes CIPII with DiaPort reduces the number of severe episodes of hypoglycemia and improves quality of life with no weight gain. Because of complications, indications for CIPII must be strictly controlled. CIPII with DiaPort is an alternative therapy when CSII is not fully successful and provides an easy method of intraperitoneal therapy.

Fasciculation of granule cell neurites is responsible for the perpendicular orientation of small inhibitory interneurons in mouse cerebellar microexplant cultures in vitro

To study the cellular and molecular mechanisms involved in the perpendicular orientation of stellate and/or basket cells to the direction of fasciculating granule cell neurites, we have used cultures of microexplants from early postnatal mouse cerebellum that show this cellular behaviour in vitro. When these cultures were maintained in the presence of antibodies to the neural cell adhesion molecules L1 and N-CAM or immunoglobulin-like domains I, II and IV of N-CAM, the resulting decrease or increase in the fasciculation of granule cell neurites changed the perpendicular orientation and morphology of the small inhibitory interneurons. Additives which did not perturb fasciculation did not affect the perpendicular orientation and morphology of stellate and/or basket cells. Furthermore, when perturbation of fasciculation was prevented, neither L1 nor N-CAM antibodies modified the positioning or morphology of interneurons. These observations indicate that ordered fasciculation of granule cell neurites is an important parameter in the perpendicular orientation and elaboration of the typical morphology of the small cerebellar inhibitory interneurons.

Realizing Antithetic Integral Feedback Control in Mammalian Cells

Genetic circuit engineering has emerged as a powerful methodology to program the behavior of mammalian cells to respond to internal and external cues. This approach is now used to develop new therapeutics and improve production processes. However, genetic interaction networks are complex and hard to engineer rationally. Moreover, a design may fail, and it may not be possible to identify the root cause of its breakdown. Introducing designated regulatory circuitry in the form of integral feedback can introduce performance guarantees by ensuring robust and precise operation.

Diya - A universal light illumination platform for multiwell plate cultures

Recent progress in protein engineering has established optogenetics as one of the leading external non-invasive stimulation strategies, with many optogenetic tools being designed for in vivo operation. Characterization and optimization of these tools require a high-throughput and versatile light delivery system targeting micro-titer culture volumes. Here, we present a universal light illumination platform - Diya, compatible with a wide range of cell culture plates and dishes. Diya hosts specially designed features ensuring active thermal management, homogeneous illumination, and minimal light bleedthrough. It offers light induction programming via a user-friendly custom-designed GUI. Through extensive characterization experiments with multiple optogenetic tools in diverse model organisms (bacteria, yeast, and human cell lines), we show that Diya maintains viable conditions for cell cultures undergoing light induction. Finally, we demonstrate an optogenetic strategy for in vivo biomolecular controller operation. With a custom-designed antithetic integral feedback circuit, we exhibit robust perfect adaptation and light-controlled set-point variation using Diya.

[UV exposure in Switzerland: time- and topography-associated factors important for the skin]

The intensity of UV-A and UV-B-radiation in Switzerland shows big differences that result from the various altitudes, the season and the time of the day. Additionally the intensity of UV-radiation is influenced by other factors like aerosols, cloudiness and ozone. In higher altitudes there is an additional enhancement by reflection of snow. The most important consequences of the UV-radiation for the population are, however, relevant in spring and summer time during the bathing season and during the late winter season for ski tourists. On a day with a clear sky in summer the UV-radiation can reach maximum values for UV-A of 45 W/m2 and for UV-B of 0.175 W/m2. The ratio of UV-A/UV-B shows an annual course with a maximum in winter of about 500 and a minimum of about 220 in summer. The possible effects on health by extensive UV-exposition are photoageing, skin cancer, inflammation processes and cataract. In Switzerland about 5000 new melanoma cases in men and about 4000 in women occur per year. In contrast to other environmental factors like pollen UV-radiation has the big advantage that the personal exposition can be controlled. Therefore, it is very essential that the general rules of a judicious behaviour such as avoiding the sun at noon, always wearing a hat, shirt and trousers as well as sunglasses with UV-filter are often reiterated.

Multi-Layer Autocatalytic Feedback Enables Integral Control Amidst Resource Competition and Across Scales

Integral feedback control strategies have proven effective in regulating protein expression in unpredictable cellular environments. These strategies, grounded in model-based designs and control theory, have advanced synthetic biology applications. Autocatalytic integral feedback controllers, utilizing positive autoregulation for integral action, are one class of simplest architectures to design integrators. This class of controllers offers unique features, such as robustness against dilution effects and cellular growth, as well as the potential for synthetic realizations across different biological scales, owing to their similarity to self-regenerative behaviors widely observed in nature. Despite this, their potential has not yet been fully exploited. One key reason, we discuss, is that their effectiveness is often hindered by resource competition and context-dependent couplings. This study addresses these challenges using a multilayer feedback strategy. Our designs enabled population-level integral feedback and multicellular integrators, where the control function emerges as a property of coordinated interactions distributed across different cell populations coexisting in a multicellular consortium. We provide a generalized mathematical framework for modeling resource competition in complex genetic networks, supporting the design of intracellular control circuits. The use of our proposed multilayer autocatalytic controllers is examined in two typical control tasks that pose significant relevance to synthetic biology applications: concentration regulation and ratiometric control. We define a ratiometric control task and solve it using a variant of our controller. The effectiveness of our controller motifs is demonstrated through a range of application examples, from precise regulation of gene expression and gene ratios in embedded designs to population growth and coculture composition control in multicellular designs within engineered microbial ecosystems. These findings offer a versatile approach to achieving robust adaptation and homeostasis from subcellular to multicellular scales.