On the radiation chemistry of thymine in aqueous solution

The reactions of thymine in aqueous solution with radiation-induced radicals OH, H, and e-aq were studied under various conditions. Competition studies using scavengers of OH radicals (methanol, ethanol, iodide) or of e-aq and/or H atoms (N2O, H+, O2) led to the conclusion that OH and H radicals destroy the chromophoric group of thymine, but e-aq does not. A trace of O2 proved to be necessary to obtain maximal destruction. Removal of the last traces of O2 resulted in a decrease of the destruction yield, possibly through restitution reactions. It was found that (1) alcohol radicals destroy thymine, even in the presence of O2; (2) the rate constant, k(OH + thymine) = 4.3 X 10(9) M(-1) sec(-1) (from competition with iodide); and (3) k(H + thymine) = 8 X 10(8) M(-1) sec(-1) (from competition with O2 in acid solution).     

Moose (<Emphasis Type="Italic">Alces alces</Emphasis>) hunters subsidize the scavenger community in Alaska

In many temperate ecosystems animal carcasses resultant from wildlife harvest can provide a high-quality food source for myriad facultative scavengers. We investigated scavenger use of human-provisioned ungulate carrion from a fall moose (Alces alces) hunt during 2010 and 2011 on the Gustavus Forelands, Alaska, USA. Using data from remote cameras, we (1) identified the scavenger species that used these resources and (2) evaluated their spatial and temporal responses to this seasonal resource event by indexing their activity patterns and relative order of arrival at carrion sites. We also quantified the length of time carrion persisted and estimated the amount of moose biomass provisioned to vertebrate scavengers by human hunters. Our results indicated that 11 vertebrate species (five birds and six mammals) scavenged moose carrion. We found that the common raven was the only species documented at all carrion sites and the most abundant species at moose carrion sites. As a species group, corvids [black-billed magpie (Pica hudsonia), common raven (Corvus corax); 0.1 ± 2.3 days] were the first to arrive at human-provisioned moose carrion sites, whereas ursids [brown bear (Ursus arctos), black bear (U. americanus); 1.3 ± 1.0 days] arrived after corvids but sooner than expected and canids [gray wolf (Canis lupus), coyote (C. latrans); 3.9 ± 3.0] arrived later than expected compared to our null model. On average, carrion persisted >20 days and hunters provided scavengers with a minimum of 2720 kg (82.7 kg/km²) and 1815 kg (64.8 kg/km²) of moose carrion during 2010 and 2011, respectively. Understanding how scavengers, particularly large carnivores, interact with human-provisioned moose carrion at the rural–wildland interface is essential for mitigating potential human–wildlife conflicts associated with humans subsidizing predators with a high-quality food resource.     

Molecular and genomic investigation of an urban outbreak of dengue virus serotype 2 in Angola, 2017–2019

BackgroundThe transmission patterns and genetic diversity of dengue virus (DENV) circulating in Africa remain poorly understood. Circulation of the DENV serotype 1 (DENV1) in Angola was detected in 2013, while DENV serotype 2 (DENV2) was detected in 2018. Here, we report results from molecular and genomic investigations conducted at the Ministry of Health national reference laboratory (INIS) in Angola on suspected dengue cases detected between January 2017 and February 2019.MethodsA total of 401 serum samples from dengue suspected cases were collected in 13 of the 18 provinces in Angola. Of those, 351 samples had complete data for demographic and epidemiological analysis, including age, gender, province, type of residence, clinical symptoms, as well as dates of onset of symptoms and sample collection. RNA was extracted from residual samples and tested for DENV-RNA using two distinct real time RT-PCR protocols. On-site whole genome nanopore sequencing was performed on RT-PCR+ samples. Bayesian coalescent models were used to estimate date and origin of outbreak emergence, as well as population growth rates.ResultsMolecular screening showed that 66 out of 351 (19%) suspected cases were DENV-RNA positive across 5 provinces in Angola. DENV RT-PCR+ cases were detected more frequently in urban sites compared to rural sites. Of the DENV RT-PCR+ cases most were collected within 6 days of symptom onset. 93% of infections were confirmed by serotype-specific RT-PCR as DENV2 and 1 case (1.4%) was confirmed as DENV1. Six CHIKV RT-PCR+ cases were also detected during the study period, including 1 co-infection of CHIKV with DENV1. Most cases (87%) were detected in Luanda during the rainy season between April and October. Symptoms associated with severe dengue were observed in 11 patients, including 2 with a fatal outcome. On-site nanopore genome sequencing followed by genetic analysis revealed an introduction of DENV2 Cosmopolitan genotype (also known as DENV2-II genotype) possibly from India in or around October 2015, at least 1 year before its detection in the country. Coalescent models suggest relatively moderately rapid epidemic growth rates and doubling times, and a moderate expansion of DENV2 in Angola during the studied period.ConclusionThis study describes genomic, epidemiological and demographic characteristic of predominately urban transmission of DENV2 in Angola. We also find co-circulation of DENV2 with DENV1 and CHIKV and report several RT-PCR confirmed severe dengue cases in the country. Increasing dengue awareness in healthcare professional, expanding the monitorization of arboviral epidemics across the country, identifying most common mosquito breeding sites in urban settings, implementing innovative vector control interventions and dengue vaccination campaigns could help to reduce vector presence and DENV transmission in Angola.     

Effect of self-association on the structural organization of partially folded proteins: inactivated actin

The propensity to associate or aggregate is one of the characteristic properties of many nonnative proteins. The aggregation of proteins is responsible for a number of human diseases and is a significant problem in biotechnology. Despite this, little is currently known about the effect of self-association on the structural properties and conformational stability of partially folded protein molecules. G-actin is shown to form equilibrium unfolding intermediate in the vicinity of 1.5 M guanidinium chloride (GdmCl). Refolding from the GdmCl unfolded state is terminated at the stage of formation of the same intermediate state. An analogous form, known as inactivated actin, can be obtained by heat treatment, or at moderate urea concentration, or by the release of Ca(2+). In all cases actin forms specific associates comprising partially folded protein molecules. The structural properties and conformational stability of inactivated actin were studied over a wide range of protein concentrations, and it was established that the process of self-association is rather specific. We have also shown that inactivated actin, being denatured, is characterized by a relatively rigid microenvironment of aromatic residues and exhibits a considerable limitation in the internal mobility of tryptophans. This means that specific self-association can play an important structure-forming role for the partially folded protein molecules.     

Real-time digital pathogen surveillance — the time is now

It is time to shake up public health surveillance. New technologies for sequencing, aided by friction-free approaches to data sharing, could have an impact on public health efforts.     

Genome sequences of three Acinetobacter baumannii strains assigned to the multilocus sequence typing genotypes ST2, ST25, and ST78

Acinetobacter baumannii is an emerging opportunistic gram-negative pathogen responsible for hospital-acquired infections. A. baumannii epidemics described in Europe and worldwide were caused by a limited number of genotypic clusters of multidrug-resistant strains. Here, we report the availability of draft genome sequences for three multidrug-resistant A. baumannii strains assigned to multilocus sequence typing genotypes ST2, ST25, and ST78 that were more frequently isolated during outbreaks occurred in Greece, Italy, Lebanon, and Turkey.     

Liver attenuation, pericardial adipose tissue, obesity, and insulin resistance: the Multi-Ethnic Study of Atherosclerosis (MESA)

Insulin resistance is linked to general and abdominal obesity, but its relation to hepatic lipid content and pericardial adipose tissue is less clear. The purpose of this study was to examine cross‐sectional associations of liver attenuation, pericardial adipose tissue, BMI, and waist circumference with insulin resistance. We measured liver attenuation and pericardial adipose tissue using the existing cardiac computed tomography scans in 5,291 individuals free of clinical cardiovascular disease and diabetes in the Multi‐Ethnic Study of Atherosclerosis (MESA) during the study's baseline visit (2000–2002). Low liver attenuation was defined as the lowest quartile and high pericardial adipose tissue as the upper quartile of volume (cm³). We used standard clinical definitions for obesity and abdominal obesity. Insulin resistance was assessed by the homeostasis model assessment of insulin resistance (HOMA_IR) index. In multivariate linear regression with all adiposity measures in the model simultaneously, all adiposity measures were significantly (P < 0.0001) associated with insulin resistance: regression coefficients (±s.e.) were 0.31 (±0.02) for low liver attenuation, 0.27 (±0.02) for high pericardial adipose tissue, 0.27 (±0.02) for obesity, and 0.32 (±0.02) for abdominal obesity. We found significant differences (P = 0.003) between standardized liver attenuation and insulin resistance by ethnicity: regression coefficients per 1 s.d. increment were 0.10 ± 0.01 for whites, 0.11 ± 0.02 for Chinese, 0.08 ± 0.2 for blacks, and 0.14 ± 0.01 for Hispanics. Liver attenuation and pericardial adipose tissue were associated with insulin resistance, independent of BMI and waist circumference.     

Primary and secondary phenology. Does it pay a frog to spawn early?

This study examines the consequences of variation in the laying and hatching date for the time of metamorphosis in the common frog Rana temporaria . Field data are presented showing that eggs laid early tend to take longer to develop. Thus, the time advantage for early eggs is reduced at the time of hatching. There was an among-year variation in this phenomenon; it was not manifest in a phenologically late year. Also, field data revealed that mortality due to pond freezing is a real risk for early laid eggs. Finally, two experiments in tanks analyse the effects of hatching date variation for the time of metamorphosis. (1) When hatching was experimentally delayed by 7 or 11 days, this resulted in later metamorphosis, however, by only 2 and 5 days, respectively. (2a) When tadpoles from the same pond that naturally hatched at different times were compared, it was found that a hatching time difference of 6 days resulted in later metamorphosis by 2 days only. (2b) A comparison of tadpoles from two different ponds that hatched 11 days apart also resulted in only 2 days' difference in metamorphosis. In this case, the later but faster developing tadpoles metamorphosed at a smaller size. I suggest that eggs from these two ponds differed genetically in the growth and development strategy. Despite the obvious risks, and the moderate gain in terms of early metamorphosis, frogs breed dangerously early in spring. Possible reasons for this are discussed. These include external selective forces that promote early metamorphosis (also at a high cost), within-pond competition among tadpoles with an advantage for early and large tadpoles and finally factors relating to mate choice at the breeding site.