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Highlights • Method enables investigation of amyloid-β oligomer stoichiometry without requiring extrinsic fluorescent probes. • Uses single-molecule stepwise photobleaching in vitro. • Unveils heterogeneity within populations of oligomers. • Assays oligomer-induced dysregulation of intracellular Ca2+ homeostasis in living cells., A major hallmark of Alzheimer’s disease is the misfolding and aggregation of the amyloid- β peptide (Aβ). While early research pointed towards large fibrillar- and plaque-like aggregates as being the most toxic species, recent evidence now implicates small soluble Aβ oligomers as being orders of magnitude more harmful. Techniques capable of characterizing oligomer stoichiometry and assembly are thus critical for a deeper understanding of the earliest stages of neurodegeneration and for rationally testing next-generation oligomer inhibitors. While the fluorescence response of extrinsic fluorescent probes such as Thioflavin-T have become workhorse tools for characterizing large Aβ aggregates in solution, it is widely accepted that these methods suffer from many important drawbacks, including an insensitivity to oligomeric species. Here, we integrate several biophysics techniques to gain new insight into oligomer formation at the single-molecule level. We showcase single-molecule stepwise photobleaching of fluorescent dye molecules as a powerful method to bypass many of the traditional limitations, and provide a step-by-step guide to implementing the technique in vitro. By collecting fluorescence emission from single Aβ(1–42) peptides labelled at the N-terminal position with HiLyte Fluor 555 via wide-field total internal reflection fluorescence (TIRF) imaging, we demonstrate how to characterize the number of peptides per single immobile oligomer and reveal heterogeneity within sample populations. Importantly, fluorescence emerging from Aβ oligomers cannot be easily investigated using diffraction-limited optical microscopy tools. To assay oligomer activity, we also demonstrate the implementation of another biophysical method involving the ratiometric imaging of Fura-2-AM loaded cells which quantifies the rate of oligomer-induced dysregulation of intracellular Ca2+ homeostasis. We anticipate that the integrated single-molecule biophysics approaches highlighted here will develop further and in principle may be extended to the investigation of other protein aggregation systems under controlled experimental conditions.

Our study used near-infrared spectroscopy (NIRS) to measure muscle oxidative capacity (mVmax) in the medial gastrocnemius, vastus lateralis, biceps brachii, and wrist flexor muscles in Cross-country (LEG-T) and Swimmer/Rowers (WHOLE-T) and controls. Young male adults: cross-country LEG-Tners (n=6) and swimmers/rowers (n=5), moderately fit (CONTROL, n=7) were tested. mVmax was measured as the rate of post-exercise recovery of oxygen consumption after a short bout of exercise using NIRS. Whole-body peak oxygen uptake (VO2peak) was determined during a continuous treadmill protocol. The lower limb muscles had 42% higher mVmax than upper limb muscles in all subjects, with significant differences in 10 of 12 pairwise comparisons (p< 0.05). The LEG-T group had higher mVmax values in both legs than CONTROL group (p< 0.05), while the WHOLE-T group had higher mVmax in the vastus lateralis (p = 0.048). There were no differences in the arm muscles of between the groups. The combined mVmax of both leg muscles in all groups correlated with VO2peak (r2=0.597). Muscle oxidative capacity was consistent with training status, and leg mitochondrial capacity correlated with maximal whole body oxidative capacity. These results support the use of NIRS measurements to characterize oxidative capacity in skeletal muscles of athletic populations.

690 Background: Downstaging of pancreatic adenocarcinoma in patients presenting with nonmetastatic, unresectable disease has proven to be associated with improved clinical outcomes. Efforts at rescuing these patients to become surgical candidates are commonly attempted with a combination of systemic and radiation strategies. In this study, we aimed to determine tumor downsizing in patients that underwent neoadjuvant systemic therapy followed by a curative-intended surgical resection. Methods: A retrospective review of consecutive patients that underwent surgical resection for pancreatic adenocarcinoma following a course of neoadjuvant therapy was performed. Basic demographics, endoscopic ultrasound (EUS) findings, chemotherapy regimens and duration, rates of radiotherapy, type of surgical procedure and pathologic results were recorded. Tumor response to neoadjuvant therapy was established by correlating EUS- to pathologic tumor dimensions. Analysis of the data was done using Mann-Whitney U test, Pearson correlation and Chi-square when indicated. Results: A total of 97 patients were analyzed; 40 underwent neoadjuvant chemotherapy (13 patients also received concurrent radiation therapy). In those 57 patients that were resected upfront, EUS tended to underestimate tumor sizes significantly compared to pathologic dimensions, with an average difference between dimensions of 0.66 cm (p = 0.0004). Within the group treated with neoadjuvant chemotherapy, 90% of patients had downsizing at an average of 8% of tumor size. There were no differences in rates of tumor downsizing between FOLFIRINOX or Gemcitabine/Nac-paclitaxel treated patients. In addition, there were no correlations in margin status (R0) based on chemotherapy used, with both regimens achieving a similar rate of R0 resections (mean 61%). The type of chemotherapy regimen used did not affect the ratio of positive lymph nodes harvested. Conclusions: In patients that present with borderline resectable pancreatic adenocarcinoma, a course of neoadjuvant therapy results in tumor downsizing in a significant number allowing for margin negative resections. These results were seen regardless of the chemotherapeutic regimens utilized.

A multicenter study evaluates a new technique for transurethral ultrasonic ureterolithotripsy utilizing a solid-wire probe. The transverse vibrations of the probe cause greater stone disintegration. A small ureteroscope is used and a basket is not required. There was a 96.6 per cent success rate in 118 cases. This technique has significantly improved ultrasonic lithotripsy. It has proved to be useful for upper ureteral stones not amenable to extracorporeal shock-wave lithotripsy and lower ureteral stones including “steinstrasse”.