Unfolding a transmembrane helix dimer: A FRET study in mixed micelles

The exact nature of membrane protein folding and assembly is not understood in detail yet. Addition of SDS to a membrane protein dissolved in mild, non-polar detergent results in formation of mixed micelles and in subsequent denaturation of higher ordered membrane protein structures. The exact nature of this denaturation event is, however, enigmatic, and separation of an individual helix pair in mixed micelles has also not been reported yet. Here we followed unfolding of the human glycophorin A transmembrane helix dimer in mixed micelles by fluorescence spectroscopy. Energy transfer between differently labelled glycophorin A transmembrane helices decreased with increasing SDS mole fractions albeit without modifying the helicity of the peptides. The energetics and kinetics of the dimer dissociation in mixed micelles is analyzed and discussed, and the experimental data demonstrate that mixed micelles can be used as a general method to investigate unfolding of α-helical membrane proteins.     

A 13C-methylation study of glycophorin A in intact erythrocytes by 13C-NMR spectroscopy

N-terminal $\text{N}{}^{\mathrm{\alpha }}\text{-[}{}^{13}\text{C]monomethylamino}$ derivatives for the N-terminal serine and leucine residues of glycophorins A^M and A^N, respectively, were obtained by reductively ¹³C-methylating homozygous human erythrocytes (MM, NN). The ¹³C-labeled glycophorins, A^M and A^N, were then isolated. A unique structural state was observed in solution reductively ¹³C-methylated glycophorin A^M that was not observed in glycophorin A^M derived from ¹³C-methylated erythrocytes. We attribute this state to the fact that some of the glycophorin A^M forms a head-to-head dimer when subjected to reductive ¹³C-methylation in aqueous solution. The ¹³C chemical shift data and pH titration data for the N-terminal [¹³C]dimethylamino and [¹³C]monomethylamino groups of glycophorin A^M and A^N derived from reductively ¹³C-methylated erythrocytes were in agreement with the chemical shift and titration data previously obtained for the N-terminal [¹³C]dimethylamino groups of solution reductively ¹³C-methylated glycophorins and related glycopeptides and peptides and N-terminal [¹³C]monomethylamino groups of related glycopeptides and peptides.     

Association of health behaviour with heart rate variability: a population-based study

Background

Multiple randomized controlled trials (RCTs) have examined the cardiovascular effects of omega-3 fatty acids and have provided unexplained conflicting results. A meta-analysis of these RCTs to estimate efficacy and safety and potential sources of heterogeneity may be helpful.

Methods

The Cochrane library, MEDLINE, and EMBASE were systematically searched to identify all interventional trials of omega-3 fatty acids compared to placebo or usual diet in high-risk cardiovascular patients. The primary outcome was all-cause mortality and secondary outcomes were coronary restenosis following percutaneous coronary intervention and safety. Meta-analyses were carried out using Bayesian random-effects models, and heterogeneity was examined using meta-regression.

Results

A total of 29 RCTs (n = 35,144) met our inclusion criteria, with 25 reporting mortality and 14 reporting restenosis. Omega-3 fatty acids were not associated with a statistically significant decreased mortality (relative risk [RR] = 0.88, 95% Credible Interval [CrI] = 0.64, 1.03) or with restenosis prevention (RR = 0.89, 95% CrI = 0.72, 1.06), though the probability of some benefit remains high (0.93 and 0.90, respectively). However in meta-regressions, there was a >90% probability that larger studies and those with longer follow-up were associated with smaller benefits. No serious safety issues were identified.

Conclusions

Although not reaching conventional statistical significance, the evidence to date suggests that omega-3 fatty acids may result in a modest reduction in mortality and restenosis. However, caution must be exercised in interpreting these benefits as results were attenuated in higher quality studies, suggesting that bias may be at least partially responsible. Additional high quality studies are required to clarify the role of omega-3 fatty acid supplementation for the secondary prevention of cardiovascular disease.     

Role for standards in assays of botulinum toxins: international collaborative study of three preparations of botulinum type A toxin

The biological activity of therapeutic preparations of botulinum type A toxin is currently expressed in units defined on the basis of the median lethal intraperitoneal dose of that preparation in mice at 72 h, the LD50 dose. In this study we describe the comparison, by ten laboratories in five countries, of three different formulations of botulinum type A toxin using the mouse lethality test, and also using the relative activities of the preparations. The results of this study show that use of a standard preparation and expression of relative potency gives substantially greater consistency between and within laboratories than when mouse LD50 unit is used to define activity of botulinum toxin.     

Investigations on the mutagenicity of 1,4-dichlorobenzene and its main metabolite 2,5-dichlorophenol in vivo and in vitro

The genotoxic potential of 1,4-dichlorobenzene (1,4-DCB) has been extensively evaluated in vitro and in vivo. The majority of the studies demonstrated the absence of a genotoxic potential for 1,4-DCB. At variance are a bone marrow micronucleus test (MNT) after intraperitoneal (i.p.) treatment of NMRI mice [Mohtashamipur et al., Mutagenesis 2 (1987) 111–113] and a gene mutation assay on mouse lymphoma cells [McGregor et al., Environ. Mol. Mutagen. 12 (1988) 85–145]. Therefore, we investigated 1,4-DCB and its main metabolite 2,5-dichlorophenol (2,5-DCP) for both endpoints. In an MNT, male and female NMRI mice were treated orally with single doses of 2500 mg/kg 1,4-DCB and 1500 mg/kg 2,5-DCP, respectively. Smears were prepared 24, 48 and 72 h thereafter. No induction of micronuclei was detected for both compounds. Also under the conditions of Mohtashamipur et al. (1987), intraperitoneal treatments of male and female mice with 2 × 177.5 and 2 × 355 mg/kg 1,4-DCB failed to induce micronuclei. In addition, CHO/HPRT-gene mutation tests with 1,4-DCB and 2,5-DCP yielded negative results for both compounds with and without metabolic activation system. Therefore, 1,4-DCB and 2,5-DCP are considered to be non-mutagenic in these test systems.     

Correlation between mRNA and protein abundance in Desulfovibrio vulgaris: a multiple regression to identify sources of variations

Parallel profiling of mRNA and protein on a global scale and integrative analysis of these two data types could provide additional insights into the metabolic mechanisms underlying complex biological systems. However, because mRNA and protein abundance are affected by many cellular and physical processes, there have been conflicting results on their correlation. Using whole-genome microarray and LC-MS/MS proteomic data collected from Desulfovibrio vulgaris grown under three different conditions, we systematically investigate the relationship between mRNA and protein abundance by a multiple regression approach, in which some of the key covariates that may affect mRNA-protein relationship were included. The results showed that mRNA abundance alone can explain only 20-28% of the total variation of protein abundance, suggesting mRNA-protein correlation can not be determined by mRNA abundance alone. Among various covariates, analytic variation of protein abundance is the major source for the variation of mRNA-protein correlation, which contributes to 34-44% of the total variation of mRNA-protein correlation. The cellular functional category of genes/proteins contributes 10-15% of the total variation of mRNA-protein correlation, with a more pronounced correlation of the two properties was observed for "central intermediary metabolism" and "energy metabolism" categories. In addition, protein stability also contributes 5% of the total variation of mRNA-protein correlation. The study presents the first quantitative analysis of the contributions of various biochemical and physical sources to the correlation of mRNA and protein abundance in D. vulgaris.     

Chemical purity and mutagenicity: Case study of a drug in development

During a routine Ames assay of a potential antipsychotic drug candidate, the compound appeared to be a frameshift mutagen in Salmonella typhimurium strains TA98 and TA1538. Additional testing indicated the mutagenic activity was due to one or more contaminants incurred during synthesis. While the compound was initially shown to be > 98% pure by high-performance liquid chromatography, the presence of small amounts (0.01 – 0.1%) of a highly mutagenic impurity produced positive mutagenicity results. The need to assess for chemical purity before discontinuing development of drug candidates found positive in the Ames assay is discussed.     

Assessment of oxidative status and genotoxicity in photocopier operators: a pilot study

Occupational exposure to photocopiers has been indicated as being responsible for a number of health complaints, particularly effects on the respiratory, immunological, and nervous systems. In this study, we investigated oxidative and genotoxic damage in photocopier operators by assessing catalase activity (CAT), reduced vs. oxidized glutathione ratio (GSH/GSSG), level of lipid peroxidation (TBARS), damage index by Comet assay (DICA), and buccal cells with micronuclei (BCMN). Our results reveal that the TBARS levels in operators were increased (27%; p<0.05) but that no significant alterations to GSH/GSSG or CAT activity were observed. The DICA and the number of BCMN were significantly increased (134% and 100%, respectively; p<0.05) in the exposed group. There was a significant association between the time in months spent at work and DNA damage in lymphocytes (r_s?=?0.720; p<0.001) and buccal cell with MN (r_s?=?0.538; p<0.001). Because laser printers and photocopiers have become increasingly used, it is important to control human exposure using reliable biomarkers.     

Visit-to-visit blood pressure variability and the risk of stroke in the Netherlands: A population-based cohort study

BackgroundApart from blood pressure level itself, variation in blood pressure has been implicated in the development of stroke in subgroups at high cardiovascular risk. We determined the association between visit-to-visit blood pressure variability and stroke risk in the general population, taking into account the size and direction of variation and several time intervals prior to stroke diagnosis.Methods and findingsFrom 1990 to 2016, we included 9,958 stroke-free participants of the population-based Rotterdam Study in the Netherlands. This is a prospective cohort study including participants aged 45 years and older. Systolic blood pressure (SBP) variability was calculated as absolute SBP difference divided by mean SBP over 2 sequential visits (median 4.6 years apart). Directional SBP variability was defined as SBP difference over 2 visits divided by mean SBP. Using time-varying Cox proportional hazards models adjusted for age, sex, mean SBP, and cardiovascular risk factors, hazard ratios (HRs) for stroke up to January 2016 were estimated per SD increase and in tertiles of variability. We also conducted analyses with 3-, 6-, and 9-year intervals between variability measurement and stroke assessment. These analyses were repeated for diastolic blood pressure (DBP). The mean age of the study population was 67.4 ± 8.2 years and 5,776 (58.0%) were women. During a median follow-up of 10.1 years, 971 (9.8%) participants had a stroke, including 641 ischemic, 89 hemorrhagic, and 241 unspecified strokes. SBP variability was associated with an increased risk of hemorrhagic stroke (HR per SD 1.27, 95% CI 1.05–1.54, p = 0.02) and unspecified stroke (HR per SD 1.21, 95% CI 1.09–1.34, p < 0.001). The associations were stronger for all stroke subtypes with longer time intervals; the HR for any stroke was 1.29 (95% CI 1.21–1.36, p < 0.001) at 3 years, 1.47 (95% CI 1.35–1.59, p < 0.001) at 6 years, and 1.38 (95%CI 1.24–1.51, p < 0.001) at 9 years. For DBP variability, we found an association with unspecified stroke risk. Both the rise and fall of SBP and the fall of DBP were associated with an increased risk for unspecified stroke. Limitations of the study include that, due to an average interval of 4 years between visits, our findings may not be generalizable to blood pressure variability over shorter periods.ConclusionsIn this population-based study, we found that visit-to-visit blood pressure variation was associated with an increased risk of unspecified and hemorrhagic stroke, independent of direction of variation or mean blood pressure.

In a population-based cohort study, Alis Heshmatollah and colleagues investigate the associations between blood pressure variability and risk of stroke among adults in the Netherlands.     

Chemical purity and mutagenicity: case study of a drug in development.

During a routine Ames assay of a potential antipsychotic drug candidate, the compound appeared to be a frameshift mutagen in Salmonella typhimurium strains TA98 and TA1538. Additional testing indicated the mutagenic activity was due to one or more contaminants incurred during synthesis. While the compound was initially shown to be greater than 98% pure by high-performance liquid chromatography, the presence of small amounts (0.01-0.1%) of a highly mutagenic impurity produced positive mutagenicity results. The need to assess for chemical purity before discontinuing development of drug candidates found positive in the Ames assay is discussed.     

Analysis of allozyme variability in three Plantago species and a comparison to morphological variability

Summary The level of electrophoretic variability in three Plantago species, P. major, P. coronopus, and P. lanceolata, was analyzed in relation to their breeding systems and compared with their morphological variability. From each species several populations were analyzed. The outcrossing P. lanceolata had the highest level of electrophoretic variability and the lowest population differentiation. The inbreeding P. major showed the opposite: a low level of electrophoretic variability and a high population differentiation. P. coronopus, with an intermediate breeding system, had an intermediate level of variability and differentiation. In comparing the species, it appeared that P. coronopus and P. major showed good concordance in the distribution of both kinds of variability, each having only a slightly higher morphological than electrophoretic differentiation between populations. P. lanceolata showed a higher morphological than electrophoretic differentiation between populations. A comparison of populations, within species, revealed good concordance of electrophoretic and morphological variability only within P. coronopus, while some populations of the other two species had relatively lower morphological variability compared with electrophoretic variability.Grassland Species Research Group Publication No. 182     

Effectiveness of seasonal malaria chemoprevention in three regions of Togo: a population-based longitudinal study from 2013 to 2020

Human landing catches (HLC) are an entomological collection technique in which humans are used as attractants to capture medically relevant host-seeking mosquitoes. The use of this method has been a topic of extensive debate for decades mainly due to ethical concerns. Many alternatives to HLC have been proposed; however, no quantitative review and meta-analysis comparing HLC to outdoor alternative trapping methods has been conducted. A total of 58 comparisons across 12 countries were identified. We conducted a meta-analysis comparing the standardized mean difference of Anopheles captured by HLC and alternative traps. To explain heterogeneity, three moderators were chosen for analysis: trap type, location of study, and species captured. A meta-regression was fit to understand how the linear combination of moderators helped in explaining heterogeneity. The possibility of biased results due to publication bias was also explored. Random-effects meta-analysis showed no statistically significant difference in the mean difference of Anopheles collected. Moderator analysis was conducted to determine the effects of trap type, geographical location of study, and the species of Anopheles captured. On average, tent-based traps captured significantly more Anopheles than outdoor HLC (95% CI: [− .9065, − 0.0544]), alternative traps in Africa captured on average more mosquitoes than outdoor HLC (95% CI: [− 2.8750, − 0.0294]), and alternative traps overall captured significantly more Anopheles gambiae s.l. than outdoor HLC (95% CI: [− 4.4613, − 0.2473]) on average. Meta-regression showed that up to 55.77% of the total heterogeneity found can be explained by a linear combination of the three moderators and the interaction between trap type and species. Subset analysis on An. gambiae s.l. showed that light traps specifically captured on average more of this species than HLC (95% CI: [− 18.3751, − 1.0629]). Publication bias likely exists. With 59.65% of studies reporting p-values less than 0.025, we believe there is an over representation in the literature of results indicating that alternative traps are superior to outdoor HLC. Currently, there is no consensus on a single “magic bullet” alternative to outdoor HLC. The diversity of many alternative trap comparisons restricts potential metrics for comparisons to outdoor HLC. Further standardization and specific question-driven trap evaluations that consider target vector species and the vector control landscape are needed to allow for robust meta-analyses with less heterogeneity and to develop data-driven decision-making tools for malaria vector surveillance and control.     

Floral scent in food-deceptive orchids: species specificity and sources of variability

One third of all orchid species are deceptive and do not reward their pollinators. Such deceptive orchids are often characterised by unusually high variation in floral signals such as colour and scent. In this study, we investigated the scent composition of two Mediterranean food-deceptive orchids Orchis mascula, Orchis pauciflora, and their hybrid, O. x colemanii. Scent was collected IN SITU by headspace sorption and was subsequently analysed with gas chromatography and gas chromatography-mass spectrometry. We compared variation of odour compounds within and between populations as well as species. We identified 35 floral scent compounds, mainly monoterpenes, which were shared by both species. Both quantitative and qualitative variability within and among populations was high. Many individuals within species could be classified to different "odour-types". In spite of high qualitative and quantitative intra- and inter-population variability, the species were clearly differentiated in their scent bouquets, whereas most hybrid individuals emitted an intermediate scent.     

The evolving epidemiology of invasive meningococcal disease: a two-year prospective,population-based study in children in the area of Athens

In response to an increase in the incidence in invasive meningococcal disease (IMD) due to Neisseria meningitidis, a system of hospital- and laboratory-based surveillance was used in a prospective epidemiological and clinical assessment of IMD in children 0-13 years of age hospitalized in the Athens area between 1 January 1999 and 31 December 2000. The annual incidence of laboratory-confirmed disease was 10.2/100,000. Serogroup B strains were predominant. There was a sharp decrease in serogroup C from 19% of cases in 1999 to 3% in 2000 (P=0.013). Of note was the emergence of serogroup A responsible for 7% of the cases. The overall case fatality rate was 4.5%, but 2.8% for microbiologically confirmed cases. A remarkable decrease in disease severity assessed by admissions to intensive care units was noted during the second study year. Polymerase chain reaction-based methods for detection of meningococcal DNA were the sole positive laboratory test in 45% of the cases and the only test on which serogroup determination was based in 52% of groupable cases. The epidemiological and clinical profile of meningococcal disease appears to be rapidly evolving and close monitoring is required particularly for input into decisions regarding use of meningococcal vaccines.     

Retinal vessel diameters and obesity: a population-based study in older persons

Objective: Obesity is linked with large vessel atherosclerosis and diabetes. Its association with microvascular changes is less clear. We investigated the associations among retinal vessel diameters, vessel wall signs, and BMI in an older population. Research Methods and Procedures: Retinal photographs were taken on 3654 persons aged 49+ years at baseline of the Blue Mountains Eye Study in Australia. Arteriolar and venular diameters were measured from digitized retinal photographs of the right eyes. BMI was calculated as weight (kilograms)/height (meters²). Incident obesity was defined in persons with BMI ≤ 30 at baseline but >30 after 5 years. A significant weight gain was defined as an increase in BMI of 2+ SDs (4 or more units) over the 5‐year period. Results: At baseline, mean BMI was 26.1 (±4.6) in this population. At 5‐year examinations, 177 (10.0% of 1773 at risk) developed incident obesity, and 136 (6.4% of 2143 at risk) had significant weight gain. After adjusting for age, sex, smoking, triglyceride levels, and mean arterial blood pressure, persons with wider retinal venular diameters had a higher risk of incident obesity (odds ratio, 1.8; 95% confidence interval, 1.0 to 3.1, comparing the highest with lowest venular diameter quintiles) and significant weight gain (odds ratio, 1.7; 95% confidence interval, 0.9 to 3.2). These associations were attenuated with further adjustment for baseline BMI. Arteriolar diameter was unrelated with baseline or change in BMI. Discussion: Wider retinal venular diameter is associated with risk of obesity, independent of hypertension, diabetes, lipids, and cigarette smoking. These data may support a role for impaired microvascular function in the course of weight gain.