A massive core for a cluster of galaxies at a redshift of 4.3

Massive galaxy clusters have been found that date to times as early as three billion years after the Big Bang, containing stars that formed at even earlier epochs^1-3. The high-redshift progenitors of these galaxy clusters-termed 'protoclusters'-can be identified in cosmological simulations that have the highest overdensities (greater-than-average densities) of dark matter^4-6. Protoclusters are expected to contain extremely massive galaxies that can be observed as luminous starbursts ⁷ . However, recent detections of possible protoclusters hosting such starbursts^8-11 do not support the kind of rapid cluster-core formation expected from simulations ¹² : the structures observed contain only a handful of starbursting galaxies spread throughout a broad region, with poor evidence for eventual collapse into a protocluster. Here we report observations of carbon monoxide and ionized carbon emission from the source SPT2349-56. We find that this source consists of at least 14 gas-rich galaxies, all lying at redshifts of 4.31. We demonstrate that each of these galaxies is forming stars between 50 and 1,000 times more quickly than our own Milky Way, and that all are located within a projected region that is only around 130 kiloparsecs in diameter. This galaxy surface density is more than ten times the average blank-field value (integrated over all redshifts), and more than 1,000 times the average field volume density. The velocity dispersion (approximately 410 kilometres per second) of these galaxies and the enormous gas and star-formation densities suggest that this system represents the core of a cluster of galaxies that was already at an advanced stage of formation when the Universe was only 1.4 billion years old. A comparison with other known protoclusters at high redshifts shows that SPT2349-56 could be building one of the most massive structures in the Universe today.

Mitochondrial population structure and post-glacial dispersal of longnose sucker Catostomus catostomus in Labrador, Canada: evidence for multiple refugial origins and limited ongoing gene flow

Two hundred and eighty-seven longnose sucker Catostomus catostomus were collected from 14 lakes in Labrador, 52 from three lakes in Ontario, 43 from two lakes in British Columbia and 32 from a lake in Yukon; a total of 414 in all. The resulting 34 haplotypes (20 in Labrador) contained moderate haplotypic diversity (h = 0·657) and relatively low nucleotide diversity (π = 3·730 × 10(-3) . Mean ϕST (0·453, P < 0·05) over all populations revealed distinct genetic structuring among C. catostomus populations across Canada, based on province, which was validated by the analysis and spatial analysis of molecular variance (c. 80% variation between provinces). These results probably reflect the historical imprint of recolonization from different refugia and possibly indicate limited ongoing gene flow within provinces. A haplotype network revealed one major and two minor clades within Labrador that were assigned to the Atlantic, Beringian and Mississippian refugia, respectively, with tests of neutrality and mismatch distribution indicative of a recent population expansion in Labrador, dated between c. 3500 and 8300 years ago.

Does low-energy sweetener consumption affect energy intake and body weight? A systematic review, including meta-analyses, of the evidence from human and animal studies

By reducing energy density, low-energy sweeteners (LES) might be expected to reduce energy intake (EI) and body weight (BW). To assess the totality of the evidence testing the null hypothesis that LES exposure (versus sugars or unsweetened alternatives) has no effect on EI or BW, we conducted a systematic review of relevant studies in animals and humans consuming LES with ad libitum access to food energy. In 62 of 90 animal studies exposure to LES did not affect or decreased BW. Of 28 reporting increased BW, 19 compared LES with glucose exposure using a specific ‘learning' paradigm. Twelve prospective cohort studies in humans reported inconsistent associations between LES use and body mass index (−0.002 kg m⁻² per year, 95% confidence interval (CI) −0.009 to 0.005). Meta-analysis of short-term randomized controlled trials (129 comparisons) showed reduced total EI for LES versus sugar-sweetened food or beverage consumption before an ad libitum meal (−94 kcal, 95% CI −122 to −66), with no difference versus water (−2 kcal, 95% CI −30 to 26). This was consistent with EI results from sustained intervention randomized controlled trials (10 comparisons). Meta-analysis of sustained intervention randomized controlled trials (4 weeks to 40 months) showed that consumption of LES versus sugar led to relatively reduced BW (nine comparisons; −1.35 kg, 95% CI –2.28 to −0.42), and a similar relative reduction in BW versus water (three comparisons; −1.24 kg, 95% CI –2.22 to −0.26). Most animal studies did not mimic LES consumption by humans, and reverse causation may influence the results of prospective cohort studies. The preponderance of evidence from all human randomized controlled trials indicates that LES do not increase EI or BW, whether compared with caloric or non-caloric (for example, water) control conditions. Overall, the balance of evidence indicates that use of LES in place of sugar, in children and adults, leads to reduced EI and BW, and possibly also when compared with water.

Alcohol Dependence, Co-occurring Conditions and Attributable Burden

AIMS

Alcohol dependence is associated with high rates of co-occurring disorders which impact health-related quality of life (HRQoL) and add to the cost-of-illness. This study investigated the burden of alcohol dependence and associated co-occurring conditions on health and productivity.

METHODS

A cross-sectional survey was conducted in eight European countries. Physicians (Psychiatrists and General Practitioners) completed patient record forms, which included assessment of co-occurring conditions, and patients completed matching self-completion forms. Drinking risk level (DRL) was calculated and the relationship between DRL, co-occurring conditions, work productivity, hospitalisations and rehabilitation stays was explored.

RESULTS

Data were collected for 2979 alcohol-dependent patients (mean age 48.8 ± 13.6 years; 70% male). In total, 77% of patients suffered from moderate-to-severe co-occurring psychiatric and/or somatic conditions. High DRL was significantly associated with depression, greater work productivity losses, increased hospitalisations and rehabilitation stays. Co-occurring conditions were significantly associated with poorer HRQoL and decreased work productivity, with a statistical trend towards an increased frequency of rehabilitation stays.

CONCLUSIONS

Alcohol-dependent patients manifest high rates of co-occurring psychiatric and somatic conditions, which are associated with impaired work productivity and HRQoL. The continued burden of illness observed in these already-diagnosed patients suggests an unmet need in both primary and secondary care.