A Blog Around The Clock

New and Exciting in PLoS this week

Tuesday – when four out of seven PLoS journals publish new articles. As always, you should rate the articles, post notes and comments and send trackbacks when you blog about the papers. You can now also easily place articles on various social services (CiteULike, Mendeley, Connotea, Stumbleupon, Facebook and Digg) with just one click. Here are my own picks for the week – you go and look for your own favourites:

Coordinated and Cohesive Movement of Two Small Conspecific Fish Induced by Eliciting a Simultaneous Optomotor Response:

In animal groups such as herds, schools, and flocks, a certain distance is maintained between adjacent individuals, allowing them to move as a cohesive unit. Proximate causations of the cohesive and coordinated movement under dynamic conditions, however, have been poorly understood. We established a novel and simple behavioral assay using pairs of small fish (medaka and dwarf pufferfish) by eliciting a simultaneous optomotor response (OMR). We demonstrated that two homospecific fish began to move cohesively and maintained a distance of 2 to 4 cm between them when an OMR was elicited simultaneously in the fish. The coordinated and cohesive movement was not exhibited under a static condition. During the cohesive movement, the relative position of the two fish was not stable. Furthermore, adult medaka exhibited the cohesive movement but larvae did not, despite the fact that an OMR could be elicited in larvae, indicating that this ability to coordinate movement develops during maturation. The cohesive movement was detected in homospecific pairs irrespective of body-color, sex, or albino mutation, but was not detected between heterospecific pairs, suggesting that coordinated movement is based on a conspecific interaction. Our findings demonstrate that coordinated behavior between a pair of animals was elicited by a simultaneous OMR in two small fish. This is the first report to demonstrate induction of a schooling-like movement in a pair of fish by an OMR and to investigate the effect of age, sex, body color, and species on coordination between animals under a dynamic condition.

MicroRNA-122 Modulates the Rhythmic Expression Profile of the Circadian Deadenylase Nocturnin in Mouse Liver:

Nocturnin is a circadian clock-regulated deadenylase thought to control mRNA expression post-transcriptionally through poly(A) tail removal. The expression of Nocturnin is robustly rhythmic in liver at both the mRNA and protein levels, and mice lacking Nocturnin are resistant to diet-induced obesity and hepatic steatosis. Here we report that Nocturnin expression is regulated by microRNA-122 (miR-122), a liver specific miRNA. We found that the 3′-untranslated region (3′-UTR) of Nocturnin mRNA harbors one putative recognition site for miR-122, and this site is conserved among mammals. Using a luciferase reporter construct with wild-type or mutant Nocturnin 3′-UTR sequence, we demonstrated that overexpression of miR-122 can down-regulate luciferase activity levels and that this effect is dependent on the presence of the putative miR-122 recognition site. Additionally, the use of an antisense oligonucleotide to knock down miR-122 in vivo resulted in significant up-regulation of both Nocturnin mRNA and protein expression in mouse liver during the night, resulting in Nocturnin rhythms with increased amplitude. Together, these data demonstrate that the normal rhythmic profile of Nocturnin expression in liver is shaped in part by miR-122. Previous studies have implicated Nocturnin and miR-122 as important post-transcriptional regulators of both lipid metabolism and circadian clock controlled gene expression in the liver. Therefore, the demonstration that miR-122 plays a role in regulating Nocturnin expression suggests that this may be an important intersection between hepatic metabolic and circadian control.

Hippocampal Neurons Keep Track of Two Things–One Moving, One Not–Simultaneously:

Animals move, and because they do, they must be masters of multiple frames of reference. As the monkey vaults himself through the air, his eye must be on the stationary branch looming into view; as the child circles on the merry-go-round, her eye must track the brass ring just around the curve.

Each frame provides its own stream of spatial information–the moving limb, the fixed target–and processing both streams, while keeping the two separate, is the key to successful behavior in a complex world. This ability, called cognitive control, is clearly essential, but the neural mechanisms underlying it are not well understood. One tool used in cognitive control is believed to be “dynamic grouping,” in which a single set of neurons fires in different patterns, each representing a different information stream, and each pattern alternates in quick succession to allow the brain to process each stream without mashing up the information each contains.

While some studies have suggested the hippocampus–a center not only of memory creation but also of spatial positioning–engages in dynamic grouping, the evidence has been conflicting. In a study in this issue, Eduard Kelemen and André Fenton show that the hippocampus does indeed use dynamic grouping to process dual (and dueling) spatial information streams.

Sub-Saharan Africa’s Mothers, Newborns, and Children: Where and Why Do They Die?:

Nearly 4.7 million mothers, newborns, and children die each year in sub-Saharan Africa: 265,000 mothers die due to complications of pregnancy and childbirth [1]; 1,208,000 babies die before they reach one month of age [2]; and 3,192,000 children, who survived their first month of life, die before their fifth birthday [1]. This toll of more than 13,000 deaths per day accounts for half of the world’s maternal and child deaths. In addition, an estimated 880,000 babies are stillborn in sub-Saharan Africa and remain invisible on the policy agenda [3].

Sub-Saharan Africa’s Mothers, Newborns, and Children: How Many Lives Could Be Saved with Targeted Health Interventions?:

Over 13,000 mothers, newborns, and children die every day in sub-Saharan Africa–almost nine deaths every minute [1],[2]. Despite being home to just 11% of the world’s population, sub-Saharan Africa accounts for half of the global burden of maternal, newborn, and child deaths, two-thirds of global HIV/AIDS deaths, and 90% of global malaria deaths. There are some encouraging signs for maternal, newborn, and child health (MNCH) in Africa with six countries (Botswana, Cape Verde, Eritrea, Malawi, Mauritius, and Seychelles) now on track to achieve Millennium Development Goal (MDG) 4. Attention to and investment in MNCH are increasing [3],[4]. It is critical that this investment is based on priorities that maximize returns, especially given the short time remaining to reach the MDG targets in 2015.

Maternal Health: Time to Deliver:

A shocking number of women die or are disabled each year trying to give birth–more than 10 million women, according to the WHO, 99% of whom are in developing countries [1]. The maternal health Millennium Development Goals (MDGs)–to reduce maternal mortality by three-quarters and to provide universal access to reproductive health by 2015–are long considered the most underachieving of the MDGs and have been chronically low on political priority lists. Recent international attention to maternal health, including its prominence at upcoming G8, Pacific Health, African Union, and UN General Assembly Summits, is therefore a welcome development and comes at a time when critical new data are available to guide action.

Alcoholism and Strongyloides stercoralis: Daily Ethanol Ingestion Has a Positive Correlation with the Frequency of Strongyloides Larvae in the Stools:

It has been reported that Strongyloides stercoralis infection is more prevalent in chronic alcoholic patients than in non alcoholics living in the same country. In a retrospective study on the prevalence of S. stercoralis infection in a large sample of alcoholic patients, we demonstrate that this prevalence is significantly higher than in non-alcoholic patients admitted at the same hospital. Moreover, the frequency of the parasite was in close relationship with the daily amount of ingested ethanol, even in the absence of liver cirrhosis, reinforcing the idea that chronic alcoholism is associated with increased susceptibility to Strongyloides infection. Beside the bad hygiene profile of alcoholic patients, which explains high risk for acquisition of the parasite, the high prevalence of S. stercoralis in alcoholics may be in relationship with other effects of ethanol on the intestinal motility, steroid metabolism and immune system, which could enhance the chance of autoinfection and the survival and fecundity of females in duodenum. In this way, the number of larvae in the stools is higher in alcoholic patients, increasing the chance of a positive result in a stool examination by sedimentation method.