Single incision laparoscopic approach for infected necrotizing pancreatitis: A case report.

INTRODUCTION: Approximately 5% of patients with acute pancreatitis develop infected necrotizing pancreatitis, with reported mortality rates up to 32%. Surgical interventions are postponed as long as possible, but if surgical debridement is needed the optimal approach has not been found yet. CASE PRESENTATION: A 47-year-old male was referred to our tertiary centre with infected necrotizing pancreatitis. Two months after initial presentation and repeated percutaneous drainage, surgical retroperitoneal debridement of the necrotic tissue was performed using a single incision laparoscopic surgery (SILS) port. Postoperatively, percutaneous drainage was performed two more times, but no additional surgical interventions were needed. The patient was discharged one month after the surgical procedure. DISCUSSION AND CONCLUSION: This is the first report of a minimally invasive technique using a SILS port for debridement of necrotizing pancreatitis. The ability to create a stable pneumo-retroperitoneum leads to optimal visualisation, better haemostasis, more space to operate in, better instrument handling, and better tissue control.

Postoperative microcirculatory perfusion and endothelial glycocalyx shedding following cardiac surgery with cardiopulmonary bypass.

We investigated microcirculatory perfusion disturbances following cardiopulmonary bypass in the early postoperative period and whether the course of these disturbances mirrored restoration of endothelial glycocalyx integrity. We performed sublingual sidestream dark field imaging of the microcirculation during the first three postoperative days in patients who had undergone on-pump coronary artery bypass graft surgery. We calculated the perfused vessel density, proportion of perfused vessels and perfused boundary region. Plasma was obtained to measure heparan sulphate and syndecan-1 levels as glycocalyx shedding markers. We recruited 17 patients; the mean (SD) duration of non-pulsatile cardiopulmonary bypass was 103 (18) min, following which 491 (29) ml autologous blood was transfused through cell salvage. Cardiopulmonary bypass immediately decreased both microcirculatory perfused vessel density; 11 (3) vs. 16 (4) mm.mm-2 , p = 0.052 and the proportion of perfused vessels; 92 (5) vs. 69 (9) %, p < 0.0001. The proportion of perfused vessels did not increase after transfusion of autologous salvaged blood following cardiopulmonary bypass; 72 (7) %, p = 0.19 or during the first three postoperative days; 71 (5) %, p < 0.0001. The perfused boundary region increased after cardiopulmonary bypass; 2.2 (0.3) vs. 1.9 (0.3) µm, p = 0.037 and during the first three postoperative days; 2.4 (0.3) vs. 1.9 (0.3) µm, p = 0.003. Increased plasma heparan sulphate levels were inversely associated with the proportion of perfused vessels during cardiopulmonary bypass; R = -0.49, p = 0.02. Plasma syndecan-1 levels were inversely associated with the proportion of perfused vessels during the entire study period; R = -0.51, p < 0.0001. Our study shows that cardiopulmonary bypass-induced acute microcirculatory perfusion disturbances persist in the first three postoperative days, and are associated with prolonged endothelial glycocalyx shedding. This suggests prolonged impairment and delayed recovery of both microcirculatory perfusion and function after on-pump cardiac surgery.

Vasculotide, an angiopoietin-1 mimetic, reduces pulmonary vascular leakage and preserves microcirculatory perfusion during cardiopulmonary bypass in rats.

BACKGROUND: Cardiopulmonary bypass (CPB) during cardiac surgery impairs microcirculatory perfusion and is paralleled by vascular leakage. The endothelial angiopoietin/Tie2 system controls microvascular leakage. This study investigated whether targeting Tie2 with the angiopoietin-1 mimetic vasculotide reduces vascular leakage and preserves microcirculatory perfusion in a rat CPB model. METHODS: Rats were subjected to 75 min of CPB after treatment with vasculotide or phosphate buffered solution as control or underwent a sham procedure. Microcirculatory perfusion and leakage were assessed with intravital microscopy (n=10 per group) and Evans blue dye extravasation (n=13 per group), respectively. Angiopoietin-1, -2, and Tie2 protein and gene expression were determined in plasma, kidney, and lung. RESULTS: CPB immediately impaired microcirculatory perfusion [5 (4-8) vs 10 (7-12) vessels per recording, P=0.002] in untreated CPB rats compared with sham, which persisted after weaning from CPB. CPB increased circulating angiopoeietin-1, -2, and soluble Tie2 concentrations and reduced Tie2 messenger ribonucleic acid (mRNA) expression in kidney and lung. Moreover, CPB increased Evans blue dye leakage in kidney [12 (8-25) vs 7 (1-12) µg g-1, P=0.04] and lung [and 23 (13-60) vs 6 (4-16) µg g-1, P=0.001] compared with sham. Vasculotide treatment preserved microcirculatory perfusion during and after CPB. Moreover, vasculotide treatment reduced Evans blue dye extravasation in lung compared with CPB control [18 (6-28) µg g-1vs 23 (13-60) µg g-1, P=0.04], but not in kidney [10 (3-23) vs 12 (8-25) µg g-1, P=0.38]. Vasculotide did not affect circulating or mRNA expression of angiopoietin-1, -2, and Tie2 concentrations compared with untreated CPB controls. CONCLUSIONS: Treatment with the angiopoietin-1 mimetic vasculotide reduced pulmonary vascular leakage and preserved microcirculatory perfusion during CPB in a rat model.

Determination of Total Biotin by Liquid Chromatography Coupled with Immunoaffinity Column Cleanup Extraction: Multilaboratory Testing, Final Action 2016.02.

Single- and multilaboratory testing data have provided systematic scientific evidence that a simple, selective, accurate, and precise method can be used as a potential candidate reference method for dispute resolution in determining total biotin in all forms of infant, adult, and/or pediatric formula. Using LC coupled with immunoaffinity column cleanup extraction, the method fully meets the intended purpose and applicability statement in AOAC Standard Method Performance Requirement 2014.005. The method was applied to a cross-section of infant formula and adult nutritional matrixes, and acceptable precision and accuracy were established. The analytical platform is inexpensive, and the method can be used in almost any laboratory worldwide with basic facilities. The immunoaffinity column cleanup extraction is the key step to successful analysis.

Improving recognition and referral of patients with an increased familial risk of colorectal cancer: results from a randomized controlled trial.

AIM: Only 12-49% of colorectal cancer (CRC) patients and their first-degree relatives with an increased familial CRC risk are referred for cancer prevention measures (surveillance colonoscopies or genetic counselling). The study was performed to evaluate the effectiveness and feasibility of a novel strategy to improve the uptake of genetic counselling for high risk individuals and surveillance colonoscopy for moderate risk groups. METHOD: Eighteen hospitals participated in a clustered randomized controlled trial. Patients in nine hospitals received usual care (group A). Nine other hospitals received the novel strategy (group B) including access to a website for patients and clinicians, patient-targeted brochures and clinician-targeted education and pocket referral cards. Data before and after dissemination of the strategy were collected from questionnaires and medical records. RESULTS: Data were complete for 358 (44%) of 820 CRC patients and 50 (36%) of 137 clinicians before dissemination of the strategy and 392/862 patients (45%) and 47/137 clinicians (34%) after. Referral for cancer prevention measures was assessed at a median of 8 (2-12) months after CRC diagnosis in groups A and B before the dissemination of the strategy and in group A after. In group B referral was assessed at a median of 9 (4-11) months after the dissemination of the strategy. Uptake of genetic counselling by high risk patients was equal in groups A and B, being 33% before and 15% after (P = 0.003). Uptake of surveillance colonoscopy by moderate risk relatives did not change significantly (group A, 36% before vs 41% after; group B, 33% before vs 19% after). In group B 94/140 patients (67%) and 25/72 clinicians (35%) visited the website and 34/140 (24%) patients read the brochure. Patients valued clinicians' information as most useful, followed by the patient brochure. Clinicians preferred pocket cards and education. CONCLUSION: Our strategy did not improve referral for cancer prevention measures. Although the newly offered strategy elements were appreciated, patients preferred clinicians' advice regarding referral for cancer prevention measures. It may be useful to aim future interventions at healthcare professionals rather than patients to improve the prevention of familial cancer.

An optimized software framework for real-time, high-throughput tracking of spherical beads.

Numerous biophysical techniques such as magnetic tweezers, flow stretching assays, or tethered particle motion assays rely on the tracking of spherical beads to obtain quantitative information about the individual biomolecules to which these beads are bound. The determination of these beads' coordinates from video-based images typically forms an essential component of these techniques. Recent advances in camera technology permit the simultaneous imaging of many beads, greatly increasing the information that can be captured in a single experiment. However, computational aspects such as frame capture rates or tracking algorithms often limit the rapid determination of such beads' coordinates. Here, we present a scalable and open source software framework to accelerate bead localization calculations based on the CUDA parallel computing framework. Within this framework, we implement the Quadrant Interpolation algorithm in order to accurately and simultaneously track hundreds of beads in real time using consumer hardware. In doing so, we show that the scatter derived from the bead tracking algorithms remains close to the theoretical optimum defined by the Cramer-Rao Lower Bound. We also explore the trade-offs between processing speed, size of the region-of-interests utilized, and tracking bias, highlighting in passing a bias in tracking along the optical axis that has previously gone unreported. To demonstrate the practical application of this software, we demonstrate how its implementation on magnetic tweezers can accurately track (with ∼1 nm standard deviation) 228 DNA-tethered beads at 58 Hz. These advances will facilitate the development and use of high-throughput single-molecule approaches.

Easy-to-use online referral test detects most patients with a high familial risk of colorectal cancer.

AIM: Currently only 12-30% of individuals with a high risk of Lynch syndrome, the most common hereditary colorectal cancer (CRC) syndrome, are referred for genetic counselling. We assessed the sensitivity, usability and user experiences of a new online referral test aimed at improving referral of high-risk individuals for genetic counselling. METHOD: Sensitivity was assessed by entering pedigree data from high-risk individuals (i.e. Lynch syndrome mutation carriers) into the referral test to determine whether genetic counselling was recommended. For usability, we assessed nonmedical staff members' ability to determine referral, according to guidelines, in seven fictive clinical cases using the referral test after minimal training. Real-life users answered questions about their experience with the referral test. RESULT: Sensitivity of the referral test was 91% for mutation carriers with CRC (n = 164) and 73% for all affected and nonaffected mutation carriers (n = 420). Nonmedical staff members (n = 20) determined referral according to guidelines in 84% of cases using the referral test. Ten per cent (256/2470) of real-life users provided feedback about experiences; of those, 71% reported that the referral test increased reassurance, certainty about their familial risk and/or certainty about referral. CONCLUSION: The referral test has a high sensitivity in detecting individuals with a high risk of Lynch syndrome and is suitable for use in clinical practice. Widespread use of the referral test should improve cancer prevention in high-risk patients and their relatives.

B cell lymphoma and myeloma in murine Gaucher's disease.

Multiple myeloma and B cell lymphoma are leading causes of death in Gaucher's disease but the nature of the stimulus driving the often noted clonal expansion of immunoglobulin-secreting B cells and cognate lymphoid malignancy is unknown. We investigated the long-term development of B cell malignancies in an authentic model of non-neuronopathic Gaucher's disease in mice: selective deficiency of ß-glucocerebrosidase in haematopoietic cells [Gba(tm1Karl/tm1Karl)Tg(Mx1-cre)1Cgn/0, with excision of exons 9-11 of the murine GBA1 gene, is induced by poly[I:C]. Mice with Gaucher's disease showed visceral storage of ß-glucosylceramide and greatly elevated plasma ß-glucosylsphingosine [median 57.9 (range 19.8-159) nm; n = 39] compared with control mice from the same strain [median 0.56 (range 0.04-1.38) nm; n = 29] (p < 0.0001). Sporadic fatal B cell lymphomas developed in 11 of 21 GD mice (6-24 months) but only two of eight control animals developed tumours by age 24 months. Unexpectedly, most mice with overt lymphoma had absent or few Gaucher cells but local inflammatory macrophages were present. Eleven of 39 of Gaucher mice developed monoclonal gammopathy, but in the control group only one animal of 25 had clonal immunoglobulin abnormalities. Seven of 10 of the B cell lymphomas were found to secrete a monoclonal paraprotein and the lymphomas stained intensely for pan-B cell markers; reactive T lymphocytes were also present in tumour tissue. In the Gaucher mouse strain, it was notable that, as in patients with this disease, CD138(+) plasma cells frequently surrounded splenic macrophages engorged with glycosphingolipid. Our strain of mice, with inducible deficiency of ß-glucocerebrosidase in haematopoietic cells and a high frequency of sporadic lethal B cell malignancies, faithfully recapitulates human Gaucher's disease: it serves as a tractable model to investigate the putative role of bioactive sphingolipids in the control of B cell proliferation and the pathogenesis of myelomatosis-the most prevalent human cancer associated with this disorder.

Fluorescent probe for high-throughput screening of membrane protein expression.

Screening of protein variants requires specific detection methods to assay protein levels and stability in crude mixtures. Many strategies apply fluorescence-detection size-exclusion chromatography (FSEC) using green fluorescent protein (GFP) fusion proteins to qualitatively monitor expression, stability, and monodispersity. However, GFP fusion proteins have several important disadvantages; including false-positives, protein aggregation after proteolytic removal of GFP, and reductions in protein yields without the GFP fusion. Here we describe a FSEC screening strategy based on a fluorescent multivalent NTA probe that interacts with polyhistidine-tags on target proteins. This method overcomes the limitations of GFP fusion proteins, and can be used to rank protein production based on qualitative and quantitative parameters. Domain boundaries of the human G-protein coupled adenosine A2a receptor were readily identified from crude detergent-extracts of a library of construct variants transiently produced in suspension-adapted HEK293-6E cells. Well expressing clones of MraY, an important bacterial infection target, could be identified from a library of 24 orthologs. This probe provides a highly sensitive tool to detect target proteins to expression levels down to 0.02 mg/L in crude lysate, and requires minimal amounts of cell culture.

Familial colorectal cancer risk assessment needs improvement for more effective cancer prevention in relatives.

AIM: Twelve to thirty % of colorectal cancer (CRC) patients and relatives with an increased familial risk of CRC are referred for preventive measures. New guidelines recommend genetic counselling for high-risk families and surveillance colonoscopy for moderate-risk families. Assessment of familial risk of CRC and referral rates for these preventive measures were determined 1 year after the introduction of new guidelines. METHOD: Assessment of familial risk of CRC and referral for preventive measures were measured in clinical practice among 358 patients with CRC in 18 hospitals using medical records and questionnaires. Additionally, a knowledge survey was performed among 312 clinicians. RESULTS: Sixty-seven % of patients with an increased familial risk (n = 65/97) were referred for preventive measures, as were 23% (61/261) of low-risk patients. The uptake of genetic counselling in high-risk families was 33% (12/36). The uptake of surveillance colonoscopy in moderate-risk families was 34% (21/61). In the knowledge survey clinicians correctly determined familial risk in 55% and preventive measures in 65% of cases. CONCLUSION: Currently 67% of individuals with an increased familial risk of CRC were referred for preventive measures. Only one-third were referred in accordance with guidelines.

Age at onset of non-affective psychosis in relation to cannabis use, other drug use and gender.

BACKGROUND: Cannabis use is associated with an earlier age at onset of psychotic illness. The aim of the present study was to examine whether this association is confounded by gender or other substance use in a large cohort of patients with a non-affective psychotic disorder. METHOD: In 785 patients with a non-affective psychotic disorder, regression analysis was used to investigate the independent effects of gender, cannabis use and other drug use on age at onset of first psychosis. RESULTS: Age at onset was 1.8 years earlier in cannabis users compared to non-users, controlling for gender and other possible confounders. Use of other drugs did not have an additional effect on age at onset when cannabis use was taken into account. In 63.5% of cannabis-using patients, age at most intense cannabis use preceded the age at onset of first psychosis. In males, the mean age at onset was 1.3 years lower than in females, controlling for cannabis use and other confounders. CONCLUSIONS: Cannabis use and gender are independently associated with an earlier onset of psychotic illness. Our findings also suggest that cannabis use may precipitate psychosis. More research is needed to clarify the neurobiological factors that make people vulnerable to this precipitating effect of cannabis.

Cannabis and cognitive performance in psychosis: a cross-sectional study in patients with non-affective psychotic illness and their unaffected siblings.

BACKGROUND: The relationship between cannabis use and cognitive functioning in patients with psychosis has yielded contradictory findings. In individuals at genetic high risk for psychosis, information is sparse. The aim of this study was to assess the association between recency and frequency of cannabis use and cognitive functioning in patients with psychosis and their unaffected siblings. METHOD: We conducted a cross-sectional study in 956 patients with non-affective psychosis, 953 unaffected siblings, and 554 control subjects. Participants completed a cognitive test battery including assessments of verbal learning, set shifting, sustained attention, processing speed, working memory, acquired knowledge, reasoning and problem solving and social cognition. Cannabis use was assessed by urinalysis and by the Composite International Diagnostic Interview. Using random-effect regression models the main effects of cannabis (recency and frequency) and the interaction with status (patient, sibling, control) on cognitive functioning were assessed. RESULTS: Current cannabis use was associated with poorer performance on immediate verbal learning, processing speed and working memory (Cohen's d -0.20 to -0.33, p<0.005). Lifetime cannabis use was associated with better performance on acquired knowledge, facial affect recognition and face identity recognition (Cohen's d+0.17 to +0.33, p<0.005). There was no significant interaction between cannabis and status on cognitive functioning. CONCLUSIONS: Lifetime cannabis-using individuals might constitute a subgroup with a higher cognitive potential. The residual effects of cannabis may impair short-term memory and processing speed.

Motivational interviewing and interaction skills training for parents to change cannabis use in young adults with recent-onset schizophrenia: a randomized controlled trial.

BACKGROUND: Cannabis use by people with schizophrenia has been found to be associated with family distress and poor clinical outcomes. Interventions to reduce drug use in this patient group have had limited efficacy. This study evaluated the effectiveness of a novel intervention for parents of young adults with recent-onset schizophrenia consisting of family-based motivational interviewing and interaction skills (Family Motivational Intervention, FMI) in comparison with routine family support (RFS). METHOD: In a trial with 75 patients who used cannabis and received treatment for recent-onset schizophrenia, 97 parents were randomly assigned to either FMI (n=53) or RFS (n=44). Assessments were conducted at baseline and 3 months after completion of the family intervention by an investigator who remained blind throughout the study about the assignment of the parents. RESULTS: At follow-up, patients' frequency and quantity of cannabis use was significantly more reduced in FMI than in RFS (p<0.05 and p<0.04 respectively). Patients' craving for cannabis was also significantly reduced in FMI whereas there was a small increase in RFS (p=0.01). There was no difference between FMI and RFS with regard to patients' other substance use and general level of functioning. Both groups showed significant improvements in parental distress and sense of burden. CONCLUSIONS: Training parents in motivational interviewing and interaction skills is feasible and effective in reducing cannabis use among young adults with recent-onset schizophrenia. However, FMI was not more effective than RFS in increasing patients' general level of functioning and in reducing parents' stress and sense of burden.

Adding familial risk assessment to faecal occult blood test can increase the effectiveness of population-based colorectal cancer screening.

BACKGROUND: The Dutch Health Council recently recommended the introduction of a colorectal cancer (CRC) screening programme by faecal occult blood testing (FOBT) for individuals aged 55-75 at population risk of CRC. Individuals at an increased familial CRC risk (≥ 2 times population risk) should be identified at a younger age, so they and their relatives can receive earlier, more intensive surveillance instead of FOBT. AIMS: To determine the percentage of participants with a positive FOBT in a CRC screening programme with an increased familial CRC risk. METHODS: In a population-based study, 10,569 individuals aged 50-75 received an FOBT. Individuals with a positive FOBT were invited for colonoscopy and familial risk assessment. Participants with an average familial CRC risk were compared to those with an increased risk. Increased familial CRC risk was defined as a cumulative lifetime risk of CRC of at least 10%. RESULTS: Of 6001 participants, 430 had a positive FOBT, of whom 324 (63% males; mean age 63 years) completed colonoscopy and familial risk assessment. CRC (n=22) and/or advanced adenomas (n=122) were found in 133 participants. Familial CRC risk was increased in 6% of participants with a positive FOBT. No significant differences were found between participants with an average versus an increased familial CRC risk. CONCLUSION: Six percent of participants with a positive FOBT had an increased familial CRC risk. Identifying at-risk participants enables them and their relatives to undergo regular colonoscopies. Adding familial risk assessment to FOBT screening may thus prevent a substantial number of CRCs.

Plasma globotriaosylsphingosine: diagnostic value and relation to clinical manifestations of Fabry disease.

Fabry disease is an X-linked lysosomal storage disorder due to deficiency of alpha-Galactosidase A, causing accumulation of globotriaosylceramide and elevated plasma globotriaosylsphingosine (lysoGb3). The diagnostic value and clinical relevance of plasma lysoGb3 concentration was investigated. All male and adult female patients with classical Fabry disease could be discerned by an elevated plasma lysoGb3. In young pre-symptomatic Fabry heterozygotes, lysoGb3 levels can be normal. Individuals carrying the R112H and P60L mutations, without classical Fabry symptoms, showed no elevated plasma lysoGb3. Multiple regression analysis showed that there is no correlation of plasma lysoGb3 concentration with total disease severity score in Fabry males. However, plasma lysoGb3 concentration did correlate with white matter lesions (odds ratio: 6.1 per 100 nM lysoGb3 increase (95% CI: 1.4-25.9, p=0.015). In females, plasma lysoGb3 concentration correlated with overall disease severity. Furthermore, plasma lysoGb3 level was related to left ventricular mass (19.5+/-5.5 g increase per 10 nM lysoGb3 increase; p=0.001). In addition, it was assessed whether lifetime exposure to lysoGb3 correlates with disease manifestations. Male Fabry patients with a high lysoGb3 exposure (>10,000 U), were moderately or severely affected, only one mildly. Female patients with a low exposure (<1000 U) were asymptomatic or mildly affected. A large proportion of the females with an exposure >1000 U showed disease complications. Plasma lysoGb3 is useful for the diagnosis of Fabry disease. LysoGb3 is an independent risk factor for development of cerebrovascular white matter lesions in male patients and left ventricular hypertrophy in females. Disease severity correlates with exposure to plasma lysoGb3.

Implicit and explicit affective associations towards cannabis use in patients with recent-onset schizophrenia and healthy controls.

BACKGROUND: Cannabis use is common in patients with recent-onset schizophrenia and this is associated with poor disease outcome. More insight in the cognitive-motivational processes related to cannabis use in schizophrenia may inform treatment strategies. The present study is the first known to compare implicit and explicit cannabis associations in individuals with and without psychotic disorder. METHOD: Participants consisted of 70 patients with recent-onset psychotic disorder and 61 healthy controls with various levels of cannabis use. Three Single-Category Implicit Association Tests (SC-IAT) were used to assess 'relaxed', 'active' and 'negative' implicit associations towards cannabis use. Explicit expectancies of cannabis use were assessed with a questionnaire using the same words as the SC-IAT. RESULTS: There were no differences in implicit associations between patients and controls; however, patients scored significantly higher on explicit negative affect expectancies than controls. Both groups demonstrated strong negative implicit associations towards cannabis use. Explicit relaxed expectancies were the strongest predictors of cannabis use and craving. There was a trend for implicit active associations to predict craving. CONCLUSIONS: The findings indicate that patients suffering from schizophrenia have associations towards cannabis similar to controls, but they have stronger negative explicit cannabis associations. The strong negative implicit associations towards cannabis could imply that users of cannabis engage in a behaviour they do not implicitly like. Explicit relaxing expectancies of cannabis might be an important mediator in the continuation of cannabis use in patients and controls.

Reasons for cannabis use and effects of cannabis use as reported by patients with psychotic disorders.

BACKGROUND: Cannabis is one of the most commonly used substances in patients with a psychotic disorder and is associated with a higher risk of psychotic relapses. Identifying reasons for cannabis use and subjective effects in patients with psychotic disorders can provide insight into the functions of cannabis use, and this may lead to targeted interventions. METHODS: A literature search of the PubMed and PsycINFO databases for articles published from 1985 till 2008 was carried out to review studies that examined self-reported reasons for cannabis use and self-reported effects of cannabis use in patients with psychotic disorders. RESULTS: Only a few studies were found that specifically assessed reasons for and effects of cannabis use. Despite the heterogeneity in the study samples and methodology, patients commonly reported that their reasons for cannabis use were enhancement of positive affect, relief of dysphoria and social enhancement. Fewer patients reported reasons related to relief of psychotic symptoms or relief of side effects of medication. Frequently reported positive effects of cannabis were positive changes in affect and relaxation. A large proportion of patients reported that cannabis negatively affected positive symptoms. CONCLUSIONS: Patients suffering from psychotic disorder report using cannabis mainly for affect regulation and socialization, despite the awareness that cannabis has a negative effect on positive symptoms. In spite of the heterogeneity of the studies, the results turned out to be broadly comparable and support the external validity of this review to a broad range of cannabis-using patients with psychotic disorder.

Inserting and manipulating DNA in a nanopore with optical tweezers.

The translocation of small molecules and polymers is an integral process for the functioning of living cells. Many of the basic physical, chemical, and biological interactions have not yet been studied because they are not directly experimentally accessible. We have shown that a combination of optical tweezers, single solid-state nanopores, and electrophysiological ionic current detection enable deeper insight into the behavior of polymers in confinement. Here we describe the experimental procedures that are necessary to manipulate single biopolymers in a single nanopore, not only by electrical fields, but also through mechanical forces using optical tweezers.

Low-frequency noise in solid-state nanopores.

Low-frequency ionic current noise in solid-state nanopores imposes a limitation on the time resolution achieved in translocation experiments. Recently, this 1/f noise was described as obeying Hooge's phenomenological relation, where the noise scales inversely with the number of charge carriers present. Here, we consider an alternative model in which the low-frequency noise originates from surface charge fluctuations. We compare the models and show that Hooge's relation gives the best description for the low-frequency noise in solid-state nanopores over the entire salt regime from 10(-3) to 1.6 M KCl.

Translocation of RecA-coated double-stranded DNA through solid-state nanopores.

We report translocation of double-stranded DNA (dsDNA) molecules that are coated with RecA protein through solid-state nanopores. Translocation measurements show current-blockade events with a wide variety in time duration (10-4-10-1 s) and conductance blockade values (3-14 nS). Large blockades (11.4+/-0.7 nS) are identified as being caused by translocations of RecA-dsDNA filaments. We confirm these results through a variety of methods, including changing molecular length and using an optical tweezer system to deliver bead-functionalized molecules to the nanopore. We further distinguish two different regimes of translocation: a low-voltage regime (<150 mV) in which the event rate increases exponentially with voltage, and a high-voltage regime in which it remains constant. Our results open possibilities for a variety of future experiments with (partly) protein-coated DNA molecules, which is interesting for both fundamental science and genomic screening applications.