Glutamine deprivation alters the origin and function of cancer cell exosomes.

Exosomes are secreted extracellular vesicles carrying diverse molecular cargos, which can modulate recipient cell behaviour. They are thought to derive from intraluminal vesicles formed in late endosomal multivesicular bodies (MVBs). An alternate exosome formation mechanism, which is conserved from fly to human, is described here, with exosomes carrying unique cargos, including the GTPase Rab11, generated in Rab11-positive recycling endosomal MVBs. Release of Rab11-positive exosomes from cancer cells is increased relative to late endosomal exosomes by reducing growth regulatory Akt/mechanistic Target of Rapamycin Complex 1 (mTORC1) signalling or depleting the key metabolic substrate glutamine, which diverts membrane flux through recycling endosomes. Vesicles produced under these conditions promote tumour cell proliferation and turnover and modulate blood vessel networks in xenograft mouse models in vivo. Their growth-promoting activity, which is also observed in vitro, is Rab11a-dependent, involves ERK-MAPK-signalling and is inhibited by antibodies against amphiregulin, an EGFR ligand concentrated on these vesicles. Therefore, glutamine depletion or mTORC1 inhibition stimulates release from Rab11a compartments of exosomes with pro-tumorigenic functions, which we propose promote stress-induced tumour adaptation.

Can surgical skills be taught using technological advances online? A comparative study of online and face-to-face surgical skills training.

INTRODUCTION: Online teaching has rapidly emerged as a viable alternative to traditional face-to-face education. How to teach surgical skills in the online environment, however, has not yet been fully established nor evaluated. METHODS: An international 1-day online surgical skills course consisting of lectures, pre-recorded virtual workshops, live demonstrations and along with surgical skills teaching in breakout rooms was organised. Based on existing learning theories, new methods were developed to deliver skills teaching online. Simultaneously, traditional in-person surgical skills teaching was also conducted and used as a benchmark. Skills development was assessed by trained demonstrators and self-reported competency scores were compared between the online and face-to-face event. RESULTS: 553 delegates from 20 different countries attended the online course. Of these, 64 were trained in breakout rooms with a 1:5 demonstrator-to-delegate ratio whilst the remaining 489 delegates participated in didactic skills development sessions. In a separate face-to-face course, 20 delegates were trained with traditional methods. Demonstrators rated the competency of delegates for suturing, tendon repair and vascular anastomosis. There was no significant difference in the competency ratings of delegates receiving online teaching or face-to-face teaching (p = 0.253, p = 0.084, p = 1.00, respectively). The development of the same skills to "articulation" were not different between formats (p = 0.841, p = 0.792, p = 1.00, respectively). Post course self-rated competency scores improved for all technical skills (p < 0.001). Small group sessions, both online and face-to-face, received higher satisfaction ratings compared to large group sessions in terms of clarity of instructions, answers to questions and demonstrator feedback. Overall feedback on teaching quality, however, was equivalent across both groups. DISCUSSION: Online teaching of surgical skills for early training years is an appropriate alternative to face-to-face teaching.

Ultrasensitive detection of waste products in water using fluorescence emission cavity-enhanced spectroscopy.

Clean water is paramount to human health. In this article, we present a technique for detection of trace amounts of human or animal waste products in water using fluorescence emission cavity-enhanced spectroscopy. The detection of femtomolar concentrations of urobilin, a metabolic byproduct of heme metabolism that is excreted in both human and animal waste in water, was achieved through the use of an integrating cavity. This technique could allow for real-time assessment of water quality without the need for expensive laboratory equipment.

Ultraviolet (250-550 nm) absorption spectrum of pure water.

Data for the spectral light absorption of pure water from 250 to 550 nm have been obtained using an integrating cavity made from a newly developed diffuse reflector with a very high UV reflectivity. The data provide the first scattering-independent measurements of absorption coefficients in the spectral gap between well-established literature values for the absorption coefficients in the visible (>400 nm) and UV (<200 nm). A minimum in the absorption coefficient has been observed in the UV at 344 nm; the value is 0.000811±0.000227 m-1.

Robust commercial diffuse reflector for UV-VIS-NIR applications.

We report the development and testing of a new commercially available diffuse reflecting material with reflectivities in the visible comparable to industry-leading products. This new diffuse reflector consists of solid quartz in which there is a dense distribution of tiny pockets of air. The multiple reflections by the quartz-air interfaces of these air pockets transforms a highly transmissive base material into a highly diffuse reflecting material.

Diffuse reflecting material for integrating cavity spectroscopy, including ring-down spectroscopy.

We report the development of a diffuse reflecting material with measured reflectivity values as high as 0.99919 at 532 nm and 0.99686 at 266 nm. This material is a high-purity fumed silica, or quartz powder, with particle sizes on the order of 40 nm. We demonstrate that this material can be used to produce surfaces with nearly Lambertian behavior, which in turn can be used to form the inner walls of high-reflectivity integrating cavities. Light reflecting off such a surface penetrates into the material. This means there will be an effective "wall time" for each reflection off the walls in an integrating cavity. We measure this wall time and show that it can be on the order of several picoseconds. Finally, we introduce a technique for absorption spectroscopy in an integrating cavity based on cavity ring-down spectroscopy. We call this technique integrating cavity ring-down spectroscopy.

Stress-induced Rab11a-exosomes induce amphiregulin-mediated cetuximab resistance in colorectal cancer.

Exosomes are secreted vesicles made intracellularly in the endosomal system. We have previously shown that exosomes are not only made in late endosomes, but also in recycling endosomes marked by the monomeric G-protein Rab11a. These vesicles, termed Rab11a-exosomes, are preferentially secreted under nutrient stress from several cancer cell types, including HCT116 colorectal cancer (CRC) cells. HCT116 Rab11a-exosomes have particularly potent signalling activities, some mediated by the epidermal growth factor receptor (EGFR) ligand, amphiregulin (AREG). Mutant activating forms of KRAS, a downstream target of EGFR, are often found in advanced CRC. When absent, monoclonal antibodies, such as cetuximab, which target the EGFR and block the effects of EGFR ligands, such as AREG, can be administered. Patients, however, inevitably develop resistance to cetuximab, either by acquiring KRAS mutations or via non-genetic microenvironmental changes. Here we show that nutrient stress in several CRC cell lines causes the release of AREG-carrying Rab11a-exosomes. We demonstrate that while soluble AREG has no effect, much lower levels of AREG bound to Rab11a-exosomes from cetuximab-resistant KRAS-mutant HCT116 cells, can suppress the effects of cetuximab on KRAS-wild type Caco-2 CRC cells. Using neutralising anti-AREG antibodies and an intracellular EGFR kinase inhibitor, we show that this effect is mediated via AREG activation of EGFR, and not transfer of activated KRAS. Therefore, presentation of AREG on Rab11a-exosomes affects its ability to compete with cetuximab. We propose that this Rab11a-exosome-mediated mechanism contributes to the establishment of resistance in cetuximab-sensitive cells and may explain why in cetuximab-resistant tumours only some cells carry mutant KRAS.

Is motion analysis a valid tool for assessing laparoscopic skill?

BACKGROUND: The use of simulation for laparoscopic training has led to the development of objective tools for skills assessment. Motion analysis represents one area of focus. This study was designed to assess the evidence for the use of motion analysis as a valid tool for laparoscopic skills assessment. METHODS: Embase, MEDLINE and PubMed were searched using the following domains: (1) motion analysis, (2) validation and (3) laparoscopy. Studies investigating motion analysis as a tool for assessment of laparoscopic skill in general surgery were included. Common endpoints in motion analysis metrics were compared between studies according to a modified form of the Oxford Centre for Evidence-Based Medicine levels of evidence and recommendation. RESULTS: Thirteen studies were included from 2,039 initial papers. Twelve (92.3 %) reported the construct validity of motion analysis across a range of laparoscopic tasks. Of these 12, 5 (41.7 %) evaluated the ProMIS Augmented Reality Simulator, 3 (25 %) the Imperial College Surgical Assessment Device (ICSAD), 2 (16.7 %) the Hiroshima University Endoscopic Surgical Assessment Device (HUESAD), 1 (8.33 %) the Advanced Dundee Endoscopic Psychomotor Tester (ADEPT) and 1 (8.33 %) the Robotic and Video Motion Analysis Software (ROVIMAS). Face validity was reported by 1 (7.7 %) study each for ADEPT and ICSAD. Concurrent validity was reported by 1 (7.7 %) study each for ADEPT, ICSAD and ProMIS. There was no evidence for predictive validity. CONCLUSIONS: Evidence exists to validate motion analysis for use in laparoscopic skills assessment. Valid parameters are time taken, path length and number of hand movements. Future work should concentrate on the conversion of motion data into competency-based scores for trainee feedback.

Investigating the collection and assessment of patient-reported outcome data amongst unplanned surgical hospital admissions: a feasibility study.

BACKGROUND: Randomised controlled trials (RCTs) in surgery can be challenging to conduct, and trials in the emergency surgical setting when patients have unplanned hospital admissions are particularly difficult. One area of challenge is capturing baseline patient-reported outcome (PRO) data. This study examined the feasibility and optimal methods for the collection of baseline and follow-up PRO data in the setting of unplanned surgical hospital admissions. METHODS: Clinically stable adult patients with unplanned admissions through the day and night under the care of general surgeons at two acute NHS trusts were approached during working week days and asked to complete validated PRO measures (European Quality of Life-5 Dimension, Short Form-12, and Gastrointestinal Quality of Life Index) on admission and 6 weeks following discharge. Feasibility of PRO data collection was determined by the proportions of admitted patients eligible and recruited and by questionnaire-response rates at baseline and follow up. Reasons for non-recruitment and non-completion of questionnaires were sought and recorded. RESULTS: There were 276 admissions, of whom 235 (85.1 %) were eligible. Reasons for ineligibility were the following: age under 18 years old (n = 5, 1.8 %), non-surgical presenting complaint (n = 6, 2.2 %) and clinical instability (n = 30, 10.9 %). One hundred and sixty-six patients (70.6 %) were recruited (98 female, 59.0 %); median age 53, range 19-100). Common reasons for non-recruitment included patients being discharged home before approached by researchers (n = 29, 12.3 %) or declining participation because they felt unwell (n = 15, 6.4 %). The most common reason for admission to the hospital was abdominal pain (n = 120, 72.3 % recruited patients), of whom 50 (30.1 %) required operative intervention. Baseline PRO data was obtained from 153 patients (93.3 %), and 74 (48.4 %) returned follow-up questionnaires. CONCLUSIONS: Collection of baseline PRO data amongst unplanned admissions in general surgery is feasible. Methods for optimising retention and follow up are needed.

Bright emission from a random Raman laser.

Random lasers are a developing class of light sources that utilize a highly disordered gain medium as opposed to a conventional optical cavity. Although traditional random lasers often have a relatively broad emission spectrum, a random laser that utilizes vibration transitions via Raman scattering allows for an extremely narrow bandwidth, on the order of 10 cm(-1). Here we demonstrate the first experimental evidence of lasing via a Raman interaction in a bulk three-dimensional random medium, with conversion efficiencies on the order of a few percent. Furthermore, Monte Carlo simulations are used to study the complex spatial and temporal dynamics of nonlinear processes in turbid media. In addition to providing a large signal, characteristic of the Raman medium, the random Raman laser offers us an entirely new tool for studying the dynamics of gain in a turbid medium.