Randomized controlled trial of nasogastric tube use after esophagectomy: study protocol for the kinetic trial.

Esophagectomy is a complex and complication laden procedure. Despite centralization, variations in perioparative strategies reflect a paucity of evidence regarding optimal routines. The use of nasogastric (NG) tubes post esophagectomy is typically associated with significant discomfort for the patients. We hypothesize that immediate postoperative removal of the NG tube is non-inferior to current routines. All Nordic Upper Gastrointestinal Cancer centers were invited to participate in this open-label pragmatic randomized controlled trial (RCT). Inclusion criteria include resection for locally advanced esophageal cancer with gastric tube reconstruction. A pretrial survey was undertaken and was the foundation for a consensus process resulting in the Kinetic trial, an RCT allocating patients to either no use of a NG tube (intervention) or 5 days of postoperative NG tube use (control) with anastomotic leakage as primary endpoint. Secondary endpoints include pulmonary complications, overall complications, length of stay, health related quality of life. A sample size of 450 patients is planned (Kinetic trial: https://www.isrctn.com/ISRCTN39935085). Thirteen Nordic centers with a combined catchment area of 17 million inhabitants have entered the trial and ethical approval was granted in Sweden, Norway, Finland, and Denmark. All centers routinely use NG tube and all but one center use total or hybrid minimally invasive-surgical approach. Inclusion began in January 2022 and the first annual safety board assessment has deemed the trial safe and recommended continuation. We have launched the first adequately powered multi-center pragmatic controlled randomized clinical trial regarding NG tube use after esophagectomy with gastric conduit reconstruction.

Nitrogen narcosis and emotional processing during compressed air breathing.

BACKGROUND: Previous studies on nitrogen narcosis have focused on how it affects behavior, performance, and cognitive function. However, little is known about the effects of nitrogen narcosis on the emotional processing of external stimuli. METHOD: We presented 20 volunteers with images from the International Affective Picture System (IAPS) and categorized as unpleasant, neutral, or pleasant, while sitting in a hyperbaric chamber at the surface (101,3kPa) and at 39 m equivalent depth (496.4 kPa). The participants rated the images along three affective dimensions: valence (intrinsic attractiveness or aversiveness of a stimuli), arousal, and dominance. RESULTS: In the valence dimension there was no significant effect of increased pressure or interaction between increased pressure and image category. There was a significant interaction between image category and the pressure at which the images were viewed in the arousal dimension. The mean arousal rating score for unpleasant stimuli was 0.5 point (on a 9-point scale) lower at hyperbaric conditions and equal arousal rating score for neutral stimuli in general. DISCUSSION: The absence of any effect of pressure in the valence dimension suggests that divers have no impairment in their ability to determine the pleasantness or unpleasantness of different stimuli. Furthermore, this study suggests that the effects of nitrogen narcosis on the emotional processing of external stimuli are primarily evident in the arousal dimension. Although differences in arousal ratings were relatively small in magnitude, even a small alteration in emotional response to external stimuli might be important in the context of deep diving.

Substrate profiling of tobacco etch virus protease using a novel fluorescence-assisted whole-cell assay.

Site-specific proteolysis of proteins plays an important role in many cellular functions and is often key to the virulence of infectious organisms. Efficient methods for characterization of proteases and their substrates will therefore help us understand these fundamental processes and thereby hopefully point towards new therapeutic strategies. Here, a novel whole-cell in vivo method was used to investigate the substrate preference of the sequence specific tobacco etch virus protease (TEVp). The assay, which utilizes protease-mediated intracellular rescue of genetically encoded short-lived fluorescent substrate reporters to enhance the fluorescence of the entire cell, allowed subtle differences in the processing efficiency of closely related substrate peptides to be detected. Quantitative screening of large combinatorial substrate libraries, through flow cytometry analysis and cell sorting, enabled identification of optimal substrates for TEVp. The peptide, ENLYFQG, identical to the protease's natural substrate peptide, emerged as a strong consensus cleavage sequence, and position P3 (tyrosine, Y) and P1 (glutamine, Q) within the substrate peptide were confirmed as being the most important specificity determinants. In position P1', glycine (G), serine (S), cysteine (C), alanine (A) and arginine (R) were among the most prevalent residues observed, all known to generate functional TEVp substrates and largely in line with other published studies stating that there is a strong preference for short aliphatic residues in this position. Interestingly, given the complex hydrogen-bonding network that the P6 glutamate (E) is engaged in within the substrate-enzyme complex, an unexpectedly relaxed residue preference was revealed for this position, which has not been reported earlier. Thus, in the light of our results, we believe that our assay, besides enabling protease substrate profiling, also may serve as a highly competitive platform for directed evolution of proteases and their substrates.

Affinity recovery of eight HER2-binding affibody variants using an anti-idiotypic affibody molecule as capture ligand.

Affibody molecules generated by combinatorial protein engineering to bind the human epidermal growth factor receptor 2 (HER2) have in earlier studies proven to be promising tracers for HER2-mediated molecular imaging of cancer. Amino acid extensions either at the N- or C-terminus of these Z(HER2) affibody molecules, have been successfully employed for site-specific radiolabeling of the tracer candidates. Hexahistidyls or other tags, which would be convenient for recovery purposes, should be avoided since they could negatively influence the tumor targeting efficacy and biodistribution properties of the tracer. Using a new ß-lactamase-based protein fragment complementation assay (PCA), an affibody molecule was isolated which bound a Z(HER2) affibody molecule with sub-micromolar affinity, but not unrelated affibody molecules. This suggests that the interacting area include the HER2-binding surface of Z(HER2). This novel anti-idiotypic affibody molecule Z(E01) was produced in Escherichia coli, purified, and chemically coupled to a chromatography resin in order to generate an affibody-based affinity column, suitable for recovery of different variants of Z(HER2) affibody molecules, having a common binding surface for HER2. Eight such Z(HER2) affibody molecules, designed for future radioimaging investigations, having different C-terminal peptide extensions aimed for radioisotope ((99m)Tc)-chelation, were successfully produced and recovered in a single step to high purity using the anti-idiotypic affibody ligand for the affinity purification. These results clearly suggest a potential for the development of anti-idiotypic affibody-based resins for efficient recovery of related variants of a target protein that might have altered biochemical properties, thus avoiding the cumbersome design of specific recovery schemes for each variant of a target protein.

Affinity maturation of a TNFalpha-binding affibody molecule by Darwinian survival selection.

The introduction of different methodologies for the construction and screening of complex protein libraries has provided powerful means in protein engineering for the development of molecules with desired traits. A challenge faced in many situations is to adapt a given methodology for efficient and rapid identification of the most interesting variants present in a library. In the present study, the concept of Darwinian selection based on a growth advantage for clones having the desired trait has been investigated. Using a beta-lactamase-based PCA (protein fragment complementation assay), affinity maturation of a TNFalpha (tumour necrosis factor alpha)-binding Affibody molecule with an initial 2 nM affinity for the target has been performed. Initial characterization of the PCA system, based on the affinity-driven reconstitution of beta-lactamase activity in the periplasm of cells harbouring a library member showing affinity for a co-expressed target protein, showed that the system was responsive to promoter induction level, interaction affinity and applied selection pressure. Using combinatorial protein engineering principles, a 107 library of second-generation Affibody molecules was constructed and subjected to selection of improved variants by library growth in liquid culture. The results show that, after a pre-selection step on semi-solid medium to eliminate non-binding variants, present in the majority, two rounds of selection in liquid culture resulted in an enrichment for binders showing up to 8-fold higher affinity for the TNFalpha target than the ancestral variant. Biosensor analyses showed that the major factor for the improved affinity could be attributed to reduced off-rate constants.

Strategies to improve photostabilities in ultrasensitive fluorescence spectroscopy.

Given the particular importance of dye photostability for single-molecule and fluorescence fluctuation spectroscopy investigations, refined strategies were explored for how to chemically retard dye photobleaching. These strategies will be useful for fluorescence correlation spectroscopy (FCS), fluorescence-based confocal single-molecule detection (SMD) and related techniques. In particular, the effects on the addition of two main categories of antifading compounds, antioxidants (n-propyl gallate, nPG, ascorbic acid, AA) and triplet state quenchers (mercaptoethylamine, MEA, cyclo-octatetraene, COT), were investigated, and the relevant rate parameters involved were determined for the dye Rhodamine 6G. Addition of each of the compound categories resulted in significant improvements in the fluorescence brightness of the monitored fluorescent molecules in FCS measurements. For antioxidants, we identify the balance between reduction of photoionized fluorophores on the one hand and that of intact fluorophores on the other as an important guideline for what concentrations to be added for optimal fluorescence generation in FCS and SMD experiments. For nPG/AA, this optimal concentration was found to be in the lower micromolar range, which is considerably less than what has previously been suggested. Also, for MEA, which is a compound known as a triplet state quencher, it is eventually its antioxidative properties and the balance between reduction of fluorophore cation radicals and that of intact fluorophores that defines the optimal added concentration. Interestingly, in this optimal concentration range the triplet state quenching is still far from sufficient to fully minimize the triplet populations. We identify photoionization as the main mechanism of photobleaching within typical transit times of fluorescent molecules through the detection volume in a confocal FCS or SMD instrument (<1-20 ms), and demonstrate its generation via both one- and multistep excitation processes. Apart from reflecting a major pathway for photobleaching, our results also suggest the exploitation of the photoinduced ionization and the subsequent reduction by antioxidants for biomolecular monitoring purposes and as a possible switching mechanism with applications in high-resolution microscopy.

Improved solubility of TEV protease by directed evolution.

The efficiency and high specificity of tobacco etch virus (TEV) protease has made it widely used for cleavage of recombinant fusion proteins. However, the production of TEV protease in E. coli is hampered by low solubility. We have subjected the gene encoding TEV protease to directed evolution to improve the yield of soluble protein. Libraries of mutated genes obtained by error-prone PCR and gene shuffling were introduced into the Gateway cloning system for facilitated transfer between vectors for screening, purification, or other applications. Fluorescence based in vivo solubility screening was carried out by cloning the libraries into a plasmid encoding a C-terminal GFP fusion. Mutant genes giving rise to high GFP fluorescence intensity indicating high levels of soluble TEV-GFP were subsequently transferred to a vector providing a C-terminal histidine tag for expression, purification, and activity tests of mutated TEV. We identified a mutant, TEV(SH), in which three amino acid substitutions result in a five-fold increase in the yield of purified protease with retained activity.

Safety and efficacy of valsartan versus enalapril in heart failure patients.

Although a cornerstone in the treatment of heart failure, angiotensin-converting enzyme inhibitors are under-used, partly due to side effects. If proven at least similarly efficacious to angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers may replace them due to their superior tolerability. We aimed to compare the efficacy and safety of valsartan and enalapril in heart failure patients stabilised on an angiotensin-converting enzyme inhibitor. We randomised 141 patients (mean 68 years, 74% males) with stable mild/moderate heart failure and left ventricular ejection fraction 0.45 or less, to valsartan 160 mg q.d. (n=70) or enalapril 10 mg b.i.d. (n=71) for 12 weeks. Changes in 6-min-walk test (primary efficacy variable), patients' wellbeing and left ventricular size and function did not differ significantly between the treatment groups. Valsartan was significantly non-inferior to enalapril in walk test distance change: least-square means treatment difference +1.12 m (95% confidence interval -21.9 to 24.1), non-inferiority P<0.001. Left ventricular size (P<0.001) and function (P=0.048) improved significantly only in the valsartan group. Fewer patients experienced adverse events in the valsartan group (50%) than in the enalapril group (63%), although statistically non-significant. Valsartan is similarly efficacious and safe to enalapril in patients with stable, mild/moderate heart failure, previously stabilised on an angiotensin-converting enzyme inhibitor and directly switched to study medication.