A ratiometric NMR pH sensing strategy based on a slow-proton-exchange (SPE) mechanism

Real time and non-invasive detection of pH in live biological systems is crucial for understanding the physiological role of acid-base homeostasis and for detecting pathological conditions associated with pH imbalance. One method to achieve in vivo pH monitoring is NMR. Conventional NMR methods, however, mainly utilize molecular sensors displaying pH-dependent chemical shift changes, which are vulnerable to multiple pH-independent factors. Here, we present a novel ratiometric strategy for sensitive and accurate pH sensing based on a small synthetic molecule, SPE1, which exhibits exceptionally slow proton exchange on the NMR time scale. Each protonation state of the sensor displays distinct NMR signals and the ratio of these signals affords precise pH values. In contrast to standard NMR methods, this ratiometric mechanism is not based on a chemical shift change, and SPE1 binds protons with high selectivity, resulting in accurate measurements. SPE1 was used to measure the pH in a single oocyte as well as in bacterial cultures, demonstrating the versatility of this method and establishing the foundation for broad biological applications.

Evaluation of a point-of-care blood test for identification of Ebola virus disease at Ebola holding units, Western Area, Sierra Leone, January to February 2015

Current Ebola virus disease (EVD) diagnosis relies on reverse transcription-PCR (RT-PCR) technology, requiring skilled laboratory personnel and technical infrastructure. Lack of laboratory diagnostic capacity has led to diagnostic delays in the current West African EVD outbreak of 2014 and 2015, compromising outbreak control. We evaluated the diagnostic accuracy of the EVD bedside rapid diagnostic antigen test (RDT) developed by the United Kingdom's Defence Science and Technology Laboratory, compared with Ebola virus RT-PCR, in an operational setting for EVD diagnosis of suspected cases admitted to Ebola holding units in the Western Area of Sierra Leone. From 22 January to 16 February 2015, 138 participants were enrolled. EVD prevalence was 11.5%. All EVD cases were identified by a positive RDT with a test line score of 6 or more, giving a sensitivity of 100% (95% confidence interval (CI): 78.2-100). The corresponding specificity was high (96.6%, 95% CI: 91.3-99.1). The positive and negative predictive values for the population prevalence were 79.0% (95% CI: 54.4-93.8) and 100% (95% CI: 96.7-100), respectively. These results, if confirmed in a larger study, suggest that this RDT could be used as a 'rule-out' screening test for EVD to improve rapid case identification and resource allocation.

Improving the use of sputum cultures in lower respiratory tract infection

BACKGROUND

The clinical value of sputum culture in suspected lower respiratory tract infection (LRTI) remains contentious. The quality of samples submitted significantly impacts their clinical usefulness.

METHODS

Using pre-defined criteria we prospectively analysed the appropriateness of sputum samples submitted from consecutive patients with suspected LRTI attending two acute hospital units over ten weeks. We then provided an education package for staff on when and how to collect appropriate sputum samples, and repeated the evaluation.

RESULTS

Our intervention reduced sample numbers from 347 to 133, simultaneously increasing the proportion of appropriately sent samples from 40.5 to 60.2% (p=0.001) and reducing cost. Appropriate sampling was associated with a higher yield of pathogens (relative risk 1.51, 95% confidence intervals 1.03-2.21, p=0.03). The rate at which sputum samples appeared to alter clinicians' management remained low and constant at 18% pre- and post-intervention.

CONCLUSION

A simple educational intervention can significantly increase appropriateness of sputum sampling, reducing workload and cost.

Different APC genotypes in proximal and distal sporadic colorectal cancers suggest distinct WNT/β-catenin signalling thresholds for tumourigenesis

Biallelic protein-truncating mutations in the adenomatous polyposis coli (APC) gene are prevalent in sporadic colorectal cancer (CRC). Mutations may not be fully inactivating, instead producing WNT/β-catenin signalling levels 'just-right' for tumourigenesis. However, the spectrum of optimal APC genotypes accounting for both hits, and the influence of clinicopathological features on genotype selection remain undefined. We analysed 630 sporadic CRCs for APC mutations and loss of heterozygosity (LOH) using sequencing and single-nucleotide polymorphism microarrays, respectively. Truncating APC mutations and/or LOH were detected in 75% of CRCs. Most truncating mutations occurred within a mutation cluster region (MCR; codons 1282-1581) leaving 1-3 intact 20 amino-acid repeats (20AARs) and abolishing all Ser-Ala-Met-Pro (SAMP) repeats. Cancers commonly had one MCR mutation plus either LOH or another mutation 5' to the MCR. LOH was associated with mutations leaving 1 intact 20AAR. MCR mutations leaving 1 vs 2-3 intact 20AARs were associated with 5' mutations disrupting or leaving intact the armadillo-repeat domain, respectively. Cancers with three hits had an over-representation of mutations upstream of codon 184, in the alternatively spliced region of exon 9, and 3' to the MCR. Microsatellite unstable cancers showed hyper-mutation at MCR mono- and di-nucleotide repeats, leaving 2-3 intact 20AARs. Proximal and distal cancers exhibited different preferred APC genotypes, leaving a total of 2 or 3 and 0 to 2 intact 20AARs, respectively. In conclusion, APC genotypes in sporadic CRCs demonstrate 'fine-tuned' interdependence of hits by type and location, consistent with selection for particular residual levels of WNT/β-catenin signalling, with different 'optimal' thresholds for proximal and distal cancers.

Effect of terbutaline on hyperpnoea-induced bronchoconstriction and urinary club cell protein 16 in athletes

Repeated injury of the airway epithelium caused by hyperpnoea of poorly conditioned air has been proposed as a key factor in the pathogenesis of exercise-induced bronchoconstriction (EIB) in athletes. In animals, the short-acting β2-agonist terbutaline has been shown to reduce dry airflow-induced bronchoconstriction and the associated shedding of airway epithelial cells. Our aim was to test the efficacy of inhaled terbutaline in attenuating hyperpnoea-induced bronchoconstriction and airway epithelial injury in athletes. Twenty-seven athletes with EIB participated in a randomized, double-blind, placebo-controlled, crossover study. Athletes completed an 8-min eucapnic voluntary hyperpnoea (EVH) test with dry air on two separate days 15 min after inhaling 0.5 mg terbutaline or a matching placebo. Forced expiratory volume in 1 s (FEV1) and urinary concentration of the club cell (Clara cell) protein 16 (CC16, a marker of airway epithelial perturbation) were measured before and up to 60 min after EVH. The maximum fall in FEV1 of 17 ± 8% (SD) on placebo was reduced to 8 ± 5% following terbutaline (P < 0.001). Terbutaline gave bronchoprotection (i.e., post-EVH FEV1 fall <10%) to 22 (81%) athletes. EVH caused an increase in urinary excretion of CC16 in both conditions (P < 0.001), and terbutaline significantly reduced this rise (pre- to postchallenge CC16 increase 416 ± 495 pg/μmol creatinine after placebo vs. 315 ± 523 pg/μmol creatinine after terbutaline, P = 0.016). These results suggest that the inhalation of a single therapeutic dose of terbutaline offers significant protection against hyperpnoea-induced bronchoconstriction and attenuates acute airway epithelial perturbation in athletes.

Combined dysfunctions of immune cells predict nosocomial infection in critically ill patients

BACKGROUND

Nosocomial infection occurs commonly in intensive care units (ICUs). Although critical illness is associated with immune activation, the prevalence of nosocomial infections suggests concomitant immune suppression. This study examined the temporal occurrence of immune dysfunction across three immune cell types, and their relationship with the development of nosocomial infection.

METHODS

A prospective observational cohort study was undertaken in a teaching hospital general ICU. Critically ill patients were recruited and underwent serial examination of immune status, namely percentage regulatory T-cells (Tregs), monocyte deactivation (by expression) and neutrophil dysfunction (by CD88 expression). The occurrence of nosocomial infection was determined using pre-defined, objective criteria.

RESULTS

Ninety-six patients were recruited, of whom 95 had data available for analysis. Relative to healthy controls, percentage Tregs were elevated 6-10 days after admission, while monocyte HLA-DR and neutrophil CD88 showed broader depression across time points measured. Thirty-three patients (35%) developed nosocomial infection, and patients developing nosocomial infection showed significantly greater immune dysfunction by the measures used. Tregs and neutrophil dysfunction remained significantly predictive of infection in a Cox hazards model correcting for time effects and clinical confounders {hazard ratio (HR) 2.4 [95% confidence interval (CI) 1.1-5.4] and 6.9 (95% CI 1.6-30), respectively, P=0.001}. Cumulative immune dysfunction resulted in a progressive risk of infection, rising from no cases in patients with no dysfunction to 75% of patients with dysfunction of all three cell types (P=0.0004).

CONCLUSIONS

Dysfunctions of T-cells, monocytes, and neutrophils predict acquisition of nosocomial infection, and combine additively to stratify risk of nosocomial infection in the critically ill.

Recombinant (F1+V) vaccine protects cynomolgus macaques against pneumonic plague

Cynomolgus macaques, immunised at the 80 μg dose level with an rF1+rV vaccine (two doses, three weeks apart), were fully protected against pneumonic plague following inhalational exposure to a clinical isolate of Yersinia pestis (strain CO92) at week 8 of the schedule. At this time, all the immunised animals had developed specific IgG titres to rF1 and rV with geometric mean titres of 96.83±20.93 μg/ml and 78.59±12.07 μg/ml, respectively, for the 40 μg dose group; by comparison, the 80 μg dose group had developed titres of 114.4±22.1 and 90.8±15.8 μg/ml to rF1 and rV, respectively, by week 8. For all the immunised animals, sera drawn at week 8 competed with the neutralising and protective Mab7.3 for binding to rV antigen in a competitive ELISA, indicating that a functional antibody response to rV had been induced. All but one of the group immunised at the lower 40 μg dose-level were protected against infection; the single animal which succumbed had significantly reduced antibody responses to both the rF1 and rV antigens. Although a functional titre to rV antigen was detected for this animal, this was insufficient for protection, indicating that there may have been a deficiency in the functional titre to rF1 and underlining the need for immunity to both vaccine antigens to achieve protective efficacy against plague. This candidate vaccine, which has been evaluated as safe and immunogenic in clinical studies, has now been demonstrated to protect cynomolgus macaques, immunised in the clinical regimen, against pneumonic plague.

Definition of the gene content of the human genome: the need for deep experimental verification

Based on the analysis of the drafts of the human genome sequence, it is being speculated that our species may possess an unexpectedly low number of genes. The quality of the drafts, the impossibility of accurate gene prediction and the lack of sufficient transcript sequence data, however, render such speculations very premature. The complexity of human gene structure requires additional and extensive experimental verification of transcripts that may result in major revisions of these early estimates of the number of human genes.

Idiopathic venous thromboembolic disease is associated with a poorer prognosis from subsequent malignancy

Methods:

We carried out a retrospective study of prognosis in Scottish patients diagnosed with cancer within 5 years after a venous thromboembolism (VTE).

Results and conclusions:

Prognosis was significantly poorer if a VTE occurred up to 2 years before cancer diagnosis, most notably if the cancer was diagnosed in the 6 months after a VTE.

Clinically suspected acute pulmonary embolism: a comparison of presentation, radiological features and outcome in patients with and without PE

BACKGROUND

Relatively little is known about prognosis in patients for whom suspected pulmonary embolism (PE) is refuted by imaging.

AIM

This prospective study of suspected PE therefore compared clinico-radiological features and outcome in patients with and without PE.

DESIGN AND METHODS

Computed tomographic pulmonary angiography (CTPA) confirmed or refuted PE in consecutive patients. Clinical, laboratory and radiological features were recorded at baseline, and mortality at 1 year determined. Univariate and multivariate analyses identified variables associated with PE.

RESULTS

PE was diagnosed in 45 patients and refuted in 141. The PE and 'non-PE' groups were similar with regard to extravascular radiology (though consolidation was significantly more common in the PE group [present in 24 (53%) of the PE group and 42 (30%) of the non-PE group, P < 0.01)], comorbidities (no significant differences), and baseline characteristics (only serum D-dimer concentrations were independently associated with PE by multivariate analysis, P = 0.001). Right ventricular dimensions were significantly higher in the PE group, [right ventricular to left ventricular ratio was 0.98 (range 0.64-2.48) in the PE group and 0.92 (range 0.66-1.95) in the non-PE group, P < 0.05]. In the PE group, right ventricular dimensions rose sharply when 10 or more segmental pulmonary arteries were occluded. One year all-cause mortality was 6.7% in the PE group and 13.5% in the non-PE group (no significant difference, P = 0.218).

CONCLUSION

Among a cohort of patients presenting with clinically suspected PE, clinical characteristics, co-morbidities and radiological features were similar when comparing groups with CTPA-proven or CTPA-refuted PE. However RV dimensions, radiological consolidation on imaging and D-dimer levels were significantly higher in the PE group. Patients with suspected PE have a poor prognosis irrespective of whether PE is confirmed. This appears accentuated in patients without PE, a finding possibly under-recognized in clinical practice.

Evaluation of the effect of diagnostic methodology on the reported incidence of ventilator-associated pneumonia

BACKGROUND

The optimal method for diagnosing ventilator-associated pneumonia (VAP) is controversial and its effect on reported incidence uncertain. This study aimed to model the impact of using either endotracheal aspirate or bronchoalveolar lavage on the reported incidence of pneumonia and then to test effects suggested from theoretical modelling in clinical practice.

METHODS

A three-part single-centre study was undertaken. First, diagnostic performance of aspirate and lavage were compared using paired samples from 53 patients with suspected VAP. Secondly, infection surveillance data were used to model the potential effect on pneumonia incidence and antibiotic use of using exclusively aspirate or lavage to investigate suspected pneumonia (643 patients; 110 clinically suspected pneumonia episodes). Thirdly, a practice change initiative was undertaken to increase lavage use; pneumonia incidence and antibiotic use were compared for the 12 months before and after the change.

RESULTS

Aspirate overdiagnosed VAP compared with lavage (89% vs 21% of clinically suspected cases, p<0.0001). Modelling suggested that changing from exclusive aspirate to lavage diagnosis would decrease reported pneumonia incidence by 76% (95% CI 67% to 87%) and antibiotic use by 30% (95% CI 20% to 42%). After the practice change initiative, lavage use increased from 37% to 58%. Although clinically suspected pneumonia incidence was unchanged, microbiologically confirmed VAP decreased from 18 to 9 cases per 1000 ventilator days (p = 0.001; relative risk reduction 0.61 (95% CI 0.46 to 0.82)), and mean antibiotic use fell from 9.1 to 7.2 antibiotic days (21% decrease, p = 0.08).

CONCLUSIONS

Diagnostic technique impacts significantly on reported VAP incidence and potentially on antibiotic use.

A profile of lower-limb deep-vein thrombosis: the hidden menace of below-knee DVT

AIMS

To describe the anatomical site and laterality of deep-vein thrombosis (DVT) in symptomatic patients using contrast venography (CV), and to assess age, sex distribution, and accuracy of pre-test clinical suspicion of DVT.

METHODS

One thousand, five hundred and seventy-two patients undergoing CV because of a clinical suspicion of DVT at a large teaching hospital from October 1995 to March 2003 were prospectively studied.

RESULTS

Thrombi were demonstrated in 511 (32.5%) of all CV studies. Isolated, below-knee thrombi were identified in 29.4% of positive studies. There was a left-sided predominance of DVT (ratio 1.24:1) that was most evident in the elderly and in more proximal veins.

CONCLUSION

Almost a third of positive cases were shown to be isolated, below-knee thrombi. These are thrombi that are more difficult to detect by non-invasive means. A left-sided predominance of DVT is evident.

The relationship between perceived stigma, disclosure patterns, support and distress in new attendees at an infertility clinic

BACKGROUND

A model suggesting that high perception of stigma is associated with reduced disclosure to others, leading to lower social support and higher distress in new attendees at an infertility clinic is tested.

METHODS

Questionnaires measuring stigmatization (Stigma consciousness questionnaire), disclosure of fertility difficulties (Disclosure questionnaire), social support (Duke-UNC Functional Social Support Questionnaire) and fertility-related [Fertility Problem Inventory (FPI)] and generic distress [Hospital Anxiety and Depression Scale (HADS)] were completed by 87 women and 64 men. Data were analysed by gender comparisons, correlations and path analysis.

RESULTS

Women reported higher stigma and disclosure than men. For women, stigma and disclosure were unrelated but in men higher stigma was associated with lower disclosure. Perceptions of stigma were related to low social support for both genders. Social support was negatively related to anxiety, depression and overall infertility distress and showed greater predictive capacity than satisfaction with partner relationship. Testing the model showed that, for men, stigma was linked to lower disclosure and support and higher fertility-related and generic distress. Disclosure itself did not link to support. For women, greater disclosure linked only to higher generic distress. Stigma was directly linked to fertility-related distress and to low perceived support which mediated a relationship with generic distress.

CONCLUSIONS

Stigma and the wider social context should be considered when supporting people with fertility problems. Greater disclosure may be associated with higher distress in women.