Experimental studies of phospholipid self assembly in hydrocarbon liquids: reverse vesicles as possible compartmentalisation strategies for hydrocarbon-base life on Titan

The goal of this thesis was to determine the nature of phosphatidylcholine self assembly within hydrocarbon liquids. This study was enacted in order to investigate the potential use of amphiphiles in compartmentalisation strategies for putative organisms inhabiting the hydrocarbon lakes of Titan (the largest moon of Saturn). The backbone of terrestrial cell membranes are vesicular structures composed of a phospholipid bilayer, with the hydrophilic head groups arranged around the periphery, and simple lipid vesicles are thought to be akin to the first terrestrial protocells. It may be possible that reverse vesicles, surrounding a nonpolar core and composed of a bilayer with the hydrophilic head groups arranged internally, may be ideal model cell membranes for putative hydrocarbon-based biota inhabiting Titan‟s hydrocarbon lakes. Compounds that are shown to form reverse vesicles in conditions comparable to those of Titan„s lakes could be potential „biomarkers‟ and searched for in future missions to Titan. In order to discover whether certain phosphatidylcholines can exhibit vesicular behaviour within hydrocarbon liquids, and to analyse their structure, I have carried out experimental studies using environmental conditions that are increasing comparable to those found on the surface of Titan. Studies of macroscopic and microscopic phase behaviours were used to determine the presence of self assembled particles, including reverse vesicles. These studies included the use of microscopy, confocal laser scanning fluorescence microscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS), small-angle neutron scattering (SANS) and small-angle x-ray scattering (SAXS). The systems studied included: the hydrocarbon solvents cyclohexane, octane, heptane, hexane, pentane and butane; various amphiphilic ratios of PC4:0, PC18:2 and lysoPC18 at dilute, ≤30 mM, concentrations; inclusion or exclusion of NaCl as a stabiliser; methanol or direct preparation methods; variation of sonication intensities and times; and a variety of temperatures. Results of this research demonstrate that unilamellar, multilamellar and multi-chambered reverse vesicles can form in a wide range of phosphatidylcholine-hydrocarbon systems. Small concentrations of NaCl and lyso-phosphatidylcholines were found to facilitate reverse vesicle formation. A reduction in temperature (down to the freezing point of the solvent) did not change the structural phase behaviour of most systems, but often increased the size of reverse vesicles. Decreasing the molecular weight of the alkanes was found to effect which amphiphilic ratios formed reverse vesicles; pentane solvent molecules were particularly effective at bilayer penetration. These results support the feasibility of further cryogenic self assembly experiments as analogues to the hydrocarbon environments found on Titan

Late-stage diagnosis of HIV infection in Brazilian children: evidence from two national cohort studies

This study analyzed data from two consecutive retrospective cohort samples (1983 to 1998 and 1999 to 2002) of Brazilian children with AIDS (N = 1,758) through mother-to-child-transmission. Late-stage diagnosis (CDC category C) was investigated in relation to the following variables: year of birth, year of HIV diagnosis, and time periods related to changes in government treatment guidelines. Late-stage diagnosis occurred in 731 (41.6%) of cases and was more prevalent in infants under 12 months of age. The rate of late-stage diagnosis decreased from 48% to 36% between the two periods studied. We also observed a reduction in the proportion of late-stage diagnoses and the time lapse between HIV diagnosis and ART initiation. A significant association was found between timely diagnosis and having been born in recent years (OR = 0.62; p = 0.009) and year of HIV diagnosis (OR = 0.72; p = 0.002/OR = 0.62; p < 0.001). Infants under the age of 12 months were more likely to be diagnosed at a late stage than older children (OR = 1.70; p = 0.004). Despite advances, there is a need to improve the effectiveness of policies and programs focused on improving early diagnosis and management of HIV/AIDS

Detection and quantitation of synthetic cannabinoid receptor agonists in infused papers from prisons in a constantly evolving illicit market

© 2020 John Wiley & Sons, Ltd. Drug misuse in prisons contributes to increased disruption and violence and negatively impacts prisoner safety, rehabilitation, and recovery. Synthetic cannabinoid receptor agonists (SCRAs), colloquially known as “spice”, are infused into papers and are of particular concern in a prison setting where they are commonly vaped. Methods for the qualitative and quantitative analysis of SCRA infused papers, including impurity profiling, were developed using gas chromatography–mass spectrometry (GC–MS) with qualitative confirmation by ultra high pressure liquid chromatography with photodiode array and quadrupole time of flight mass spectrometry detection (UPLC-PDA-QToF-MS) and applied to 354 individual seized paper samples originating from 168 seizures from three Scottish prisons. Of these samples, 41% (146 samples from 101 seizures) contained at least one SCRA and multiple SCRAs were detected on 23% of these papers. Concentrations ranged from < 0.05–1.17 mg/cm2 paper, representing the first reported quantitative data for SCRA infused papers. An evolution in the SCRAs detected was demonstrated; 5F-MDMB-PINACA (5F-ADB) predominated until late 2018, after which time 5F-MDMB-PICA and 4F-MDMB-BINACA became increasingly more prevalent, followed by the arrival of MDMB-4en-PINACA in June 2019. Concentration mapping data from two seized paper samples demonstrated that SCRA concentrations across larger papers were highly variable (0.47–2.38 mg/cm2 paper) making consistent dosing by users, and representative sampling by laboratory analysts, difficult. Near real-time qualitative and quantitative information on SCRAs circulating in prisons acts as an early warning system for SCRAs emerging on the wider illicit market, inform the methods used to detect them and limit supply, and provide information to support harm reduction measures

Opportunistic illnesses in Brazilian children with AIDS: results from two national cohort studies, 1983-2007

<p>Abstract</p> <p>Background</p> <p>HAART has significantly reduced AIDS-related morbidity in children. However, limited evidence is available from developing countries regarding patterns of opportunistic illnesses. We describe these events and their associated factors in children with AIDS in Brazil.</p> <p>Methods</p> <p>This study is based on two representative retrospective multi-center cohorts including a total 1,859 children with AIDS, infected via mother-to-child transmission (MTCT), between 1983-2002. Opportunistic illnesses were described and analyzed over time. The association of demographic, clinical and operational data with the occurrence of opportunistic diseases was assessed.</p> <p>Results</p> <p>In total, 1,218 (65.5%) had at least one event of an opportunistic disease. Variables significantly associated with occurrence of these events included: region of residence (OR 2.68-11.33, as compared to the Northern region), age < 1 year at diagnosis (OR 2.56, 95% CI 1.81-3.61, p < 0.001), and non-performance of MTCT prevention measures (OR 1.58, 95% CI 1.21-2.07, p < 0.001). Protective factors included year of HIV diagnosis in the HAART era (OR 0.34, 95% CI 0.15-0.76, p = 0.009) and ART use (OR 0.58, 95% CI 0.44-0.77, p < 0.001). In both periods bacterial infections represented the most common opportunistic events (58.6 vs. 34.7%; p < 0.001), followed by <it>Pneumocystis jirovecii </it>pneumonia (21.9 vs. 13.2%; p < 0.001), and bacterial meningitis/sepsis (16.8 vs. 7.4%; p < 0.001).</p> <p>Conclusions</p> <p>Despite the significant reduction in recent years, opportunistic illnesses are still common in Brazilian children with AIDS in the HAART era, especially bacterial diseases. The data reinforce the need for scaling up prevention of MTCT, early diagnosis of infection, and improvement of comprehensive pediatric care.</p

Preoperative computed tomography staging of nonmetastatic colon cancer predicts outcome: implications for clinical trials

Colon cancer patients routinely undergo preoperative computed tomography (CT) scanning, but local staging is thought to be inaccurate. We aimed to determine if clinical outcome could be predicted from radiological features of the primary tumour. Consecutive patients at one hospital undergoing primary resection for colon cancer during 2000–2004 were included. Patients with visible metastases were excluded. Preoperative CT scans were reviewed independently by two radiologists blinded to histological stage and outcome. Images of the primary tumour were evaluated according to conventional TNM criteria and patients were stratified into ‘good' or ‘poor' prognosis groups. Comparison was made between prognostic group and actual clinical outcome. Hundred and twenty-six preoperative CT scans were reviewed. T-stage and nodal status was correctly predicted in only 60 and 62%, respectively. However, inter-observer agreement for prognostic group was 79% (κ=0.59) and 3-year relapse-free survival was 71 and 43% for the CT-predicted ‘good' and ‘poor' groups, respectively (P<0.0066). This compared favourably with 75 vs 43% for histology-predicted prognostic groups. Computed tomography is a robust method for stratifying patients preoperatively, with similar accuracy to histopathology for predicting outcome. Recognition of poor prognosis tumours preoperatively may permit investigation into the future use of neo-adjuvant therapy in colon cancer

Design and Synthesis of a Quintessential Self-Transmissible IncX1 Plasmid, pX1.0

DNA exchange in bacteria via conjugative plasmids is believed to be among the most important contributing factors to the rapid evolution- and diversification rates observed in bacterial species. The IncX1 plasmids are particularly interesting in relation to enteric bacteria, and typically carry genetic loads like antibiotic resistance genes and virulence factors. So far, however, a “pure” version of these molecular parasites, without genetic loads, has yet to be isolated from the environment. Here we report the construction of pX1.0, a fully synthesized IncX1 plasmid capable of horizontal transfer between different enteric bacteria. The designed pX1.0 sequence was derived from the consensus gene content of five IncX1 plasmids and three other, more divergent, members of the same phylogenetic group. The pX1.0 plasmid was shown to replicate stably in E. coli with a plasmid DNA per total DNA ratio corresponding to approximately 3–9 plasmids per chromosome depending on the growth phase of the host. Through conjugation, pX1.0 was able to self-transfer horizontally into an isogenic strain of E. coli as well as into two additional species belonging to the family Enterobacteriaceae. Our results demonstrate the immediate applicability of recent advances made within the field of synthetic biology for designing and constructing DNA systems, previously existing only in silica

Student responses to the introduction of case-based learning and practical activities into a theoretical obstetrics and gynaecology teaching programme

BACKGROUND: The fourth-year Obstetrics and Gynaecology course at our institution had previously been taught using theory classes alone. A new teaching model was introduced to provide a better link with professional practice. We wished to evaluate the impact of the introduction of case discussions and other practical activities upon students' perceptions of the learning process. METHODS: Small-group discussions of cases and practical activities were introduced for the teaching of a fourth-year class in 2003 (Group II; 113 students). Comparisons were made with the fourth-year class of 2002 (Group I; 108 students), from before the new programme was introduced. Students were asked to rate their satisfaction with various elements of the teaching programme. Statistical differences in their ratings were analysed using the chi-square and Bonferroni tests. RESULTS: Group II gave higher ratings to the clarity of theory classes and lecturers' teaching abilities (p < 0.05) and lecturers' punctuality (p < 0.001) than did Group I. Group II had greater belief that the knowledge assessment tests were useful (p < 0.001) and that their understanding of the subject was good (p < 0.001) than did Group I. Group II gave a higher overall rating to the course (p < 0.05) than did Group I. However, there was no difference in the groups' assessments of the use made of the timetabled hours available for the subject or lecturers' concern for students' learning. CONCLUSIONS: Students were very receptive to the new teaching model

Eustachian tube dysfunction: consensus statement on definition, types, clinical presentation and diagnosis

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