Multimerization of the adenovirus DNA-binding protein is the driving force for ATP-independent DNA unwinding during strand displacement synthesis.

In contrast to other replication systems, adenovirus DNA replication does not require a DNA helicase to unwind the double-stranded template. Elongation is dependent on the adenovirus DNA-binding protein (DBP) which has helix-destabilizing properties. DBP binds cooperatively to single-stranded DNA (ssDNA) in a non-sequence-specific manner. The crystal structure of DBP shows that the protein has a C-terminal extension that hooks on to an adjacent monomer which results in the formation of long protein chains. We show that deletion of this C-terminal arm results in a monomeric protein. The mutant binds with a greatly reduced affinity to ssDNA. The deletion mutant still stimulates initiation of DNA replication like the intact DBP. This shows that a high affinity of DBP for ssDNA is not required for initiation. On a single-stranded template, elongation is also observed in the absence of DBP. Addition of DBP or the deletion mutant has no effect on elongation, although both proteins stimulate initiation on this template. Strand displacement synthesis on a double-stranded template is only observed in the presence of DBP. The mutant, however, does not support elongation on a double-stranded template. The unwinding activity of the mutant is highly reduced compared with intact DBP. These data suggest that protein chain formation by DBP and high affinity binding to the displaced strand drive the ATP-independent unwinding of the template during adenovirus DNA replication.     

Dietary Myoinositol Results in Lower Urine Glucose and in Lower Postprandial Plasma Glucose in Obese Insulin Resistant Rhesus Monkeys.

In a previous study, D-chiroinositol added to a meal (0.5 g/kg) resulted in significantly lower postprandial plasma glucose concentrations without an increase in insulin concentrations in obese insulin-resistant monkeys. The present report describes the effects of another isomer of inositol, myoinositol, on postprandial plasma glucose and insulin concentrations and on urine glucose concentrations in 6 similarly insulin-resistant monkeys. The three 5 day study periods included a control period (liquid diet ad libitum) and 2 experimental periods (liquid diet ad libitum with either 1.5 g/kg/day myoinositol or D-chiroinositol added). Twenty-four hour urine samples were collected during each 5 day period. On the sixth day of each period the monkeys were anesthetized 110 min after completing either the control meal (15 ml/kg) or the experimental meals (1.5 g/kg myoinositol or D-chiroinositol) and plasma samples were obtained at 120, 150,180, 210, 240, 270 and 300 min. The plasma glucose concentration was lower after the meal with myoinositol compared to the control meal at 120, 150 and 180 min (p's<0.05). The plasma insulin concentration was lower after the meal with myoinositol compared to the control meal at 150 and 180 min (p's<0.05). In addition, 24 hour urine glucose concentrations were lower during the myoinositol diet compared to the control diet (p<0.001). The plasma glucose concentration was lower after the meal with D-chiroinositol compared to the control meal at 150, 240, 270 and 300 min (p's≥0.05). In obese insulin-resistant monkeys, myoinositol added to the diet lowers urine glucose concentrations and both myoinositol and D-chiroinositol added to a meal lower postprandial plasma glucose concentrations without increasing postprandial insulin concentrations. Therefore, myoinositol, like D-chiroinositol, may be a useful agent for reducing meal-induced hyperglycemia without inducing hyperinsulinemia in insulin-resistant subjects.     

The influence of bile salts on the response of liposomes to ultrasound

Context: Triggering drug release from delivery vehicles with ultrasound has potential applications in targeted drug delivery. It was hypothesized that the addition of bile salts would increase the sensitivity of liposomes to ultrasound through creation of defects.

Objective: The aim of this study was to investigate whether incorporating bile salts into liposomes would lead to differential effects on their response to low and high frequency ultrasound.

Materials and methods: Cholate, chenodeoxycholate, ursodeoxycholate, glycocholate and taurocholate were the selected bile salts. Response to ultrasound was characterized by measuring the release of carboxyfluorescein (CF).

Results: At 30?kHz ultrasound, taurocholate containing liposomes were most responsive and released 70% (±2) CF after 30 seconds of sonication. Compared to this, liposomes that did not contain bile salts released just 7% (±2). At 1.1?MHz ultrasound, all liposome formulations were unresponsive. To increase the response of liposomes at 1.1?MHz ultrasound, a combination of membrane destabilizers were added to DSPC liposomes. DOPE, a hexagonal phase lipid was used in combination with taurocholate. Surprisingly, liposomes containing DOPE and taurocholate were more resistant to 1.1?MHz ultrasound than ones containing only DOPE.

Discussion: This suggests that the sensitivity of liposomes towards ultrasound may not simply be defined by a single membrane component but instead depends on the interaction between constituting lipid components. Furthermore, strategies other than membrane destabilization may be required to sensitize liposomes towards high frequency ultrasound.

Conclusion: Bile salts may be used to increase or decrease the sensitivity of liposomes to low frequency ultrasound.     

Ethical challenges at the science-policy interface: an ethical risk assessment and proposition of an ethical infrastructure

Developing an interface between knowledge holders, stakeholders and decision makers on biodiversity issues, just as any science-policy interface, will face many challenges. In the crucial endeavour to tackle all those challenges, determining an ethical course of actions will be essential to the prestige and credibility of such an interface. The paper identifies and assesses potential ethical risks that may arise in interactions between science, society and policy and uses the Network of Knowledge (NoK) process as an example to show how an ethical infrastructure could be developed for minimizing the ethical risks and their potential consequences. Indeed, when various actors from different spheres (politics, academia, lobbyism, media, etc.) are called upon to interact within one process as complex as the NoK, the integrity and credibility of the latter are at high risk of being compromised if the ethical risks are not adequately addressed. In order to limit those risks, which science-policy interfaces such as IPCC and IPBES have already encountered, we propose to set up an ethical governance infrastructure that will guide (and regulate) interactions among internal actors of the NoK (knowledge coordination body, secretariat, expert working groups, etc.) as well as with external actors (requesters, stakeholders, etc.). A thorough evaluation of the interaction between the actors for every step of the process is carried out and potential ethical risks are identified. Suggestions as to how the risks can be handled and prevented are presented and integrated as part of an ethical infrastructure. The main objective of the paper is to address how a science-policy interface and the scientific community as a whole would benefit from implementing ethical measures and instruments to help prevent sensitive issues and undesired consequences undermining credibility and legitimacy.     

Diversity of Synechococcus at the Martha’s Vineyard Coastal Observatory: Insights from Culture Isolations,Clone Libraries,and Flow Cytometry

The cyanobacterium Synechococcus is a ubiquitous, important phytoplankter across the world’s oceans. A high degree of genetic diversity exists within the marine group, which likely contributes to its global success. Over 20 clades with different distribution patterns have been identified. However, we do not fully understand the environmental factors that control clade distributions. These factors are likely to change seasonally, especially in dynamic coastal systems. To investigate how coastal Synechococcus assemblages change temporally, we assessed the diversity of Synechococcus at the Martha’s Vineyard Coastal Observatory (MVCO) over three annual cycles with culture-dependent and independent approaches. We further investigated the abundance of both phycoerythrin (PE)-containing and phycocyanin (PC)-only Synechococcus with a flow cytometric setup that distinguishes PC-only Synechococcus from picoeukaryotes. We found that the Synechococcus assemblage at MVCO is diverse (13 different clades identified), but dominated by clade I representatives. Many clades were only isolated during late summer and fall, suggesting more favorable conditions for isolation at this time. PC-only strains from four different clades were isolated, but these cells were only detected by flow cytometry in a few samples over the time series, suggesting they are rare at this site. Within clade I, we identified four distinct subclades. The relative abundances of each subclade varied over the seasonal cycle, and the high Synechococcus cell concentration at MVCO may be maintained by the diversity found within this clade. This study highlights the need to understand how temporal aspects of the environment affect Synechococcus community structure and cell abundance.     

Changes in P3b Latency and Amplitude Reflect Expertise Acquisition in a Football Visuomotor Learning Task

Learning is not a unitary phenomenon. Rather, learning progresses through stages, with the stages reflecting different challenges that require the support of specific cognitive processes that reflect the functions of different brain networks. A theory of general learning proposes that learning can be divided into early and late stages controlled by corticolimbic networks located in frontal and posterior brain regions, respectively. Recent human studies using dense-array EEG (dEEG) support these results by showing progressive increases in P3b amplitude (an Event Related Potential with estimated sources in posterior cingulate cortex and hippocampus) as participants acquire a new visuomotor skill. In the present study, the P3b was used to track the learning and performance of participants as they identify defensive football formations and make an appropriate response. Participants acquired the task over three days, and P3b latency and amplitude significantly changed when participants learned the task. As participants demonstrated further proficiency with extensive training, amplitude and latency changes in the P3b continued to closely mirror performance improvements. Source localization results across all days suggest that an important source generator of the P3b is located in the posterior cingulate cortex. Results from the study support prior findings and further suggest that the careful analysis of covert learning mechanisms and their underlying electrical signatures are a robust index of task competency.