The binding and activation of the glucagon-like peptide-1 receptor by exendin-4

Background and purpose Exendin-4 (EX4) has the same physiological properties as glucagon-like peptide-1 (7-36)amide (GLP-1). EX4 has 50% identity with GLP-1, with an extra nine amino acids at its C-terminus. The two peptides mediate their functions through coupling to the glucagon like peptide-1 receptor (GLP-1R) with similar affinity and potency. Unlike N-terminally truncated GLP-1, (GLP-1(15-36)amide), the equivalently truncated EX4(9-39) binds GLP-1R without significant loss of affinity; furthermore, GLP-1(15-36) is a partial agonist while EX4(9-39) is an antagonist. Previous binding analysis of either N or C-terminally truncated EX4 at rGLP-1R suggested that the residues responsible for its extra affinity are at its C-terminus, EX4 residues 31-39. Crystal structures supported by mutagenesis showed similar interactions of both GLP-1 and EX4 at the isolated N-terminal domain of human GLP-1R (hGLP-1R-NTD) apart from a subtle hydrogen bond between Ser32 in EX4 and Glu68 in hGLP-1R-NTD. Experimental approach The affinities and activities of GLP-1, EX4 and various analogues were measured at human and rat GLP-1R (hGLP-1R and rGLP-1R, respectively) and various receptor variants. Computer models, molecular dynamics coupled with in silico mutagenesis, were used to model and interpret the data. Key results The membrane-tethered NTDs of hGLP-1R displayed similar affinity for GLP-1 and EX4 in contrast to previous studies using the soluble isolated domain. The selective high affinity at rGLP-1R and the rGLP-1R-like mutant hGLP-1R-Glu68Asp for EX4(9–39) over EX4(9–30) was due to Ser32 in the ligand. This selectivity was not observed with hGLP-1R and the hGLP-1R-like mutant rGLP-1R-Asp68Glu. Gly16-EX4(9–30) was an agonist for rGLP-1R and hGLP-1R-Glu68Asp but was an antagonist for hGLP-1R and rGLP-1R-Asp68Glu. Glu22-GLP-1(15-36) was a partial agonist for all tested receptors. Insertion of (EEEAVRL) of EX4 instead of their equivalent sequence in GLP-1(15-36) prevented its activity and did not enhance its affinity. Substitution of Ser32 in EX4 by similar hydrogen bond donor amino acids did not enhance EX4 affinity or potency. Conclusions and implications GLP-1 and EX4 bind to the NTD of hGLP-1R with similar affinity. A hydrogen bond between Ser32 of EX4 and Asp68 of rGLP-1R is responsible for the improved affinity of EX4 and can play a role in the antagonist/agonist switch of Gly16-EX4(9–30) at the rat receptor. The discovery of the novel antagonist/agonist switch suggests a new mechanism of activation by GLP-1 which does not require its extreme N-terminal residues.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

EFFECT OF OILS, SURFACTANTS AND COSURFACTANTS ON PHASE BEHAVIOR AND PHYSICOCHEMICAL PROPERTIES OF SELF-NANOEMULSIFYING DRUG DELIVERY SYSTEM (SNEDDS) FOR IRBESARTAN AND OLMESARTAN

Objective: The main purpose of this study was to optimize the different conditions for the preparation of self-nanoemulsifying drug delivery system (SNEDDS) for both Irbesartan (IRB) and Olmesartan (OLM). Methods: Based on solubility study and emulsification efficiency, Preliminary investigations of various oils, surfactants and cosurfactants were carried out for selection of the proper SNEDDS ingredients. Pseudoternary phase diagrams were then plotted using series of concentrations to obtain optimum SNEDDS components that identify the efficient self-nanoemulsifying region. Sixteen unloaded SNEEDS formulae were prepared using Capryol 90, Cremophor RH 40 and Transcutol HP as oil, surfactant and cosurfactant respectively. The prepared SNEDDS were evaluated for self-nanoemulsification time, the effect of dilution (with different volumes at different pH values), optical clarity, viscosity, droplet size analysis as well as the polydispersity index (PDI). SNEDDS formulae were also evaluated for thermodynamic stability and zeta potential to confirm the stability of the prepared SNEDDS. Results: The results showed that the mean droplet size of all reconstituted SNEDDS was found to be in the nanometric range (<100 nm) and showed optimum PDI values. All formulae also showed rapid emulsification time, good optical clarity and found to be highly stable. Formulae with the smallest particle size, lowest emulsification time, best optical clarity and robust to dilution and pH change were selected to be loaded with IRB and OLM for further study. Conclusion: It was concluded that the prepared self-emulsified prototype was ready to incorporate many poorly soluble drugs in order to improve their solubility as well as bioavailability profile. Keywords: Irbesartan, Olmesartan, Self-nanoemulsifying drug delivery system (SNEDDS), Capryol 90, Cremophor RH 40 and Transcutol HP

EFFECT OF ADDITIVES ON IN-VITRO RELEASE OF ORODISPERSIBLE DOSAGE FORM

Objective: The aim of this investigation was to prepare orodispersible tablets of meloxicam using various concentrations of superdisintegrants like Ac-DI-Sol, crospovidone, sodium starch glycolate by the direct compression method. Methods: Nine formulae of Meloxicam orodispersible tablets were prepared. These tablets were evaluated for their drug content, weight variation, friability, hardness, wetting time, In-vitro disintegration time and drug release.Results: All the formulation exhibited hardness between 4.21–4.55 kg/cm2. The tablets were disintegrating within 8.3 to 21.9 sec. Dissolution studies revealed that formula containing 7.5 % sodium starch glycolate showed 100% of drug release, at the end of six minutes. Among the formulated tablets, formula F9 containing 7.5 % sodium starch glycolate showed superior organoleptic properties along with excellent In-vitro disintegration time and drug release as compared to other formulae. The concentration of superdisintegrants had an effect on disintegration time and In-vitro drug dissolution whereas hardness and friability of resulting tablets were found to be independent of disintegrant concentration. It was concluded that the superdisintegrants addition technique is a useful method for preparing orodispersible tablets by the direct compression method.Â

H5N1 Clade 2.2 Polymorphism Tracing Identifies Influenza Recombination and Potential Vaccine Targets

Highly pathogenic Influenza A H5N1 was first identified in Guangdong Province in 1996, followed by human cases in Hong Kong in 1997 1. The number of confirmed human cases now exceeds 300 and the associated Case Fatality Rate exceeds 60% 2. The genetic diversity of the serotype continues to increase. Four distinct clades or sub-clades have been linked to human cases 3.4. The gradual genetic changes identified in the sub-clades have been attributed to copy errors by viral encoded polymerases that lack an editing function, thereby resulting in antigenic drift 5. We traced polymorphism acquisition in Clade 2.2 sequences. We report here the concurrent acquisition of the same polymorphism by multiple, genetically distinct, Clade 2.2 sub-clades in Egypt, Russia and Ghana. These changes are not easily explained by the current theory of “random mutation” through copy error, and are more easily explained by recombination with a common source. This conclusion is supported by additional polymorphisms shared by Clade 2.2 isolates in Egypt, Nigeria and Germany including aggregation of regional polymorphisms from each of these areas into a single Nigerian human hemagglutinin gene

Morpho-agronomical and biochemical traits screening and genetic variability in selected black cumin (Nigella sativa) mutant lines

The production of new Nigella sativa cultivars by plant breeding programs is difficult due to its narrow genetic base. A number of induced morphological traits, yield components and percent content of fatty acid methyl esters in the parent line and nine selected mutants (Mt1-Mt9) have been reported in two generations (M3 and M4) of N. sativa to determine the best genotype to release as a new cultivar. The results showed that Mt2 plants were the tallest (118.3 and 149.7 cm in M3 and M4, respectively). The highest seed yield per plant was measured for Mt5; Mt4 showed the highest per cent of palmitic and stearic acids, 11.93% and 13.70%, respectively; whereas Mt8 had the highest percent content (45.67%) of linoleic acid. Five Inter Simple Sequence Repeat (ISSR) markers were used to investigate genetic variability within mutant lines and their parent. These primers generated 71 reproducible and scorable amplification products across the genotypes tested. Fifty-eight of these fragments were highly polymorphic (81.7%). The proportion of common bands (13) was low (18.3%). All primers produced unique fragments and generated 33 specific alleles. The average number of amplification products per primer was 14.2. The size of ISSR amplified fragments varied from 1109 to 148 base pairs (bp). The similarity between each mutant and the parent line varied from 0.56% to 100%. Finally, the present investigation indicated that mutants Mt5 and Mt6 are promising high yielding genotypes which can be recommended as new cultivars, whereas Mt3 and Mt7 possess an attractive phenotype appropriate for ornamental use

Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London

Laparoscopy in management of appendicitis in high-, middle-, and low-income countries: a multicenter, prospective, cohort study.

BACKGROUND: Appendicitis is the most common abdominal surgical emergency worldwide. Differences between high- and low-income settings in the availability of laparoscopic appendectomy, alternative management choices, and outcomes are poorly described. The aim was to identify variation in surgical management and outcomes of appendicitis within low-, middle-, and high-Human Development Index (HDI) countries worldwide. METHODS: This is a multicenter, international prospective cohort study. Consecutive sampling of patients undergoing emergency appendectomy over 6 months was conducted. Follow-up lasted 30 days. RESULTS: 4546 patients from 52 countries underwent appendectomy (2499 high-, 1540 middle-, and 507 low-HDI groups). Surgical site infection (SSI) rates were higher in low-HDI (OR 2.57, 95% CI 1.33-4.99, p = 0.005) but not middle-HDI countries (OR 1.38, 95% CI 0.76-2.52, p = 0.291), compared with high-HDI countries after adjustment. A laparoscopic approach was common in high-HDI countries (1693/2499, 67.7%), but infrequent in low-HDI (41/507, 8.1%) and middle-HDI (132/1540, 8.6%) groups. After accounting for case-mix, laparoscopy was still associated with fewer overall complications (OR 0.55, 95% CI 0.42-0.71, p < 0.001) and SSIs (OR 0.22, 95% CI 0.14-0.33, p < 0.001). In propensity-score matched groups within low-/middle-HDI countries, laparoscopy was still associated with fewer overall complications (OR 0.23 95% CI 0.11-0.44) and SSI (OR 0.21 95% CI 0.09-0.45). CONCLUSION: A laparoscopic approach is associated with better outcomes and availability appears to differ by country HDI. Despite the profound clinical, operational, and financial barriers to its widespread introduction, laparoscopy could significantly improve outcomes for patients in low-resource environments. TRIAL REGISTRATION: NCT02179112

Surgical site infection after gastrointestinal surgery in high-income, middle-income, and low-income countries: a prospective, international, multicentre cohort study

Background: Surgical site infection (SSI) is one of the most common infections associated with health care, but its importance as a global health priority is not fully understood. We quantified the burden of SSI after gastrointestinal surgery in countries in all parts of the world. Methods: This international, prospective, multicentre cohort study included consecutive patients undergoing elective or emergency gastrointestinal resection within 2-week time periods at any health-care facility in any country. Countries with participating centres were stratified into high-income, middle-income, and low-income groups according to the UN's Human Development Index (HDI). Data variables from the GlobalSurg 1 study and other studies that have been found to affect the likelihood of SSI were entered into risk adjustment models. The primary outcome measure was the 30-day SSI incidence (defined by US Centers for Disease Control and Prevention criteria for superficial and deep incisional SSI). Relationships with explanatory variables were examined using Bayesian multilevel logistic regression models. This trial is registered with ClinicalTrials.gov, number NCT02662231. Findings: Between Jan 4, 2016, and July 31, 2016, 13 265 records were submitted for analysis. 12 539 patients from 343 hospitals in 66 countries were included. 7339 (58·5%) patient were from high-HDI countries (193 hospitals in 30 countries), 3918 (31·2%) patients were from middle-HDI countries (82 hospitals in 18 countries), and 1282 (10·2%) patients were from low-HDI countries (68 hospitals in 18 countries). In total, 1538 (12·3%) patients had SSI within 30 days of surgery. The incidence of SSI varied between countries with high (691 [9·4%] of 7339 patients), middle (549 [14·0%] of 3918 patients), and low (298 [23·2%] of 1282) HDI (p < 0·001). The highest SSI incidence in each HDI group was after dirty surgery (102 [17·8%] of 574 patients in high-HDI countries; 74 [31·4%] of 236 patients in middle-HDI countries; 72 [39·8%] of 181 patients in low-HDI countries). Following risk factor adjustment, patients in low-HDI countries were at greatest risk of SSI (adjusted odds ratio 1·60, 95% credible interval 1·05–2·37; p=0·030). 132 (21·6%) of 610 patients with an SSI and a microbiology culture result had an infection that was resistant to the prophylactic antibiotic used. Resistant infections were detected in 49 (16·6%) of 295 patients in high-HDI countries, in 37 (19·8%) of 187 patients in middle-HDI countries, and in 46 (35·9%) of 128 patients in low-HDI countries (p < 0·001). Interpretation: Countries with a low HDI carry a disproportionately greater burden of SSI than countries with a middle or high HDI and might have higher rates of antibiotic resistance. In view of WHO recommendations on SSI prevention that highlight the absence of high-quality interventional research, urgent, pragmatic, randomised trials based in LMICs are needed to assess measures aiming to reduce this preventable complication

Global economic burden of unmet surgical need for appendicitis

Background: There is a substantial gap in provision of adequate surgical care in many low-and middle-income countries. This study aimed to identify the economic burden of unmet surgical need for the common condition of appendicitis. Methods: Data on the incidence of appendicitis from 170 countries and two different approaches were used to estimate numbers of patients who do not receive surgery: as a fixed proportion of the total unmet surgical need per country (approach 1); and based on country income status (approach 2). Indirect costs with current levels of access and local quality, and those if quality were at the standards of high-income countries, were estimated. A human capital approach was applied, focusing on the economic burden resulting from premature death and absenteeism. Results: Excess mortality was 4185 per 100 000 cases of appendicitis using approach 1 and 3448 per 100 000 using approach 2. The economic burden of continuing current levels of access and local quality was US $92 492 million using approach 1 and$73 141 million using approach 2. The economic burden of not providing surgical care to the standards of high-income countries was $95 004 million using approach 1 and$75 666 million using approach 2. The largest share of these costs resulted from premature death (97.7 per cent) and lack of access (97.0 per cent) in contrast to lack of quality. Conclusion: For a comparatively non-complex emergency condition such as appendicitis, increasing access to care should be prioritized. Although improving quality of care should not be neglected, increasing provision of care at current standards could reduce societal costs substantially

Pooled analysis of WHO Surgical Safety Checklist use and mortality after emergency laparotomy

Background The World Health Organization (WHO) Surgical Safety Checklist has fostered safe practice for 10 years, yet its place in emergency surgery has not been assessed on a global scale. The aim of this study was to evaluate reported checklist use in emergency settings and examine the relationship with perioperative mortality in patients who had emergency laparotomy. Methods In two multinational cohort studies, adults undergoing emergency laparotomy were compared with those having elective gastrointestinal surgery. Relationships between reported checklist use and mortality were determined using multivariable logistic regression and bootstrapped simulation. Results Of 12 296 patients included from 76 countries, 4843 underwent emergency laparotomy. After adjusting for patient and disease factors, checklist use before emergency laparotomy was more common in countries with a high Human Development Index (HDI) (2455 of 2741, 89.6 per cent) compared with that in countries with a middle (753 of 1242, 60.6 per cent; odds ratio (OR) 0.17, 95 per cent c.i. 0.14 to 0.21, P <0001) or low (363 of 860, 422 per cent; OR 008, 007 to 010, P <0.001) HDI. Checklist use was less common in elective surgery than for emergency laparotomy in high-HDI countries (risk difference -94 (95 per cent c.i. -11.9 to -6.9) per cent; P <0001), but the relationship was reversed in low-HDI countries (+121 (+7.0 to +173) per cent; P <0001). In multivariable models, checklist use was associated with a lower 30-day perioperative mortality (OR 0.60, 0.50 to 073; P <0.001). The greatest absolute benefit was seen for emergency surgery in low- and middle-HDI countries. Conclusion Checklist use in emergency laparotomy was associated with a significantly lower perioperative mortality rate. Checklist use in low-HDI countries was half that in high-HDI countries.Peer reviewe