Ten-Year Trends in Coronary Calcification in Individuals without Clinical Cardiovascular Disease in the Multi-Ethnic Study of Atherosclerosis

Background

Coronary heart disease (CHD) incidence has declined significantly in the US, as have levels of major coronary risk factors, including LDL-cholesterol, hypertension and smoking, but whether trends in subclinical atherosclerosis mirror these trends is not known.

Methods and Findings

To describe recent secular trends in subclinical atherosclerosis as measured by serial evaluations of coronary artery calcification (CAC) prevalence in a population over 10 years, we measured CAC using computed tomography (CT) and CHD risk factors in five serial cross-sectional samples of men and women from four race/ethnic groups, aged 55–84 and without clinical cardiovascular disease, who were members of Multi-Ethnic Study of Atherosclerosis (MESA) cohort from 2000 to 2012. Sample sizes ranged from 1062 to 4837. After adjusting for age, gender, and CT scanner, the prevalence of CAC increased across exams among African Americans, whose prevalence of CAC was 52.4% in 2000–02, 50.4% in 2003–04, 60.0% is 2005–06, 57.4% in 2007–08, and 61.3% in 2010–12 (p for trend <0.001). The trend was strongest among African Americans aged 55–64 [prevalence ratio for 2010–12 vs. 2000–02, 1.59 (95% confidence interval 1.06, 2.39); p = 0.005 for trend across exams]. There were no consistent trends in any other ethnic group. Risk factors generally improved in the cohort, and adjustment for risk factors did not change trends in CAC prevalence.

Conclusions

There was a significant secular trend towards increased prevalence of CAC over 10 years among African Americans and no change in three other ethnic groups. Trends did not reflect concurrent general improvement in risk factors. The trend towards a higher prevalence of CAC in African Americans suggests that CHD risk in this population is not improving relative to other groups.     

Three epigenetic information channels and their different roles in evolution

There is increasing evidence for epigenetically mediated transgenerational inheritance across taxa. However, the evolutionary implications of such alternative mechanisms of inheritance remain unclear. Herein, we show that epigenetic mechanisms can serve two fundamentally different functions in transgenerational inheritance: (i) selection-based effects, which carry adaptive information in virtue of selection over many generations of reliable transmission; and (ii) detection-based effects, which are a transgenerational form of adaptive phenotypic plasticity. The two functions interact differently with a third form of epigenetic information transmission, namely information about cell state transmitted for somatic cell heredity in multicellular organisms. Selection-based epigenetic information is more likely to conflict with somatic cell inheritance than is detection-based epigenetic information. Consequently, the evolutionary implications of epigenetic mechanisms are different for unicellular and multicellular organisms, which underscores the conceptual and empirical importance of distinguishing between these two different forms of transgenerational epigenetic effect.     

On the origins of the weak folding cooperativity of a designed ββα ultrafast protein FSD-1

FSD-1, a designed small ultrafast folder with a ββα fold, has been actively studied in the last few years as a model system for studying protein folding mechanisms and for testing of the accuracy of computational models. The suitability of this protein to describe the folding of naturally occurring α/β proteins has recently been challenged based on the observation that the melting transition is very broad, with ill-resolved baselines. Using molecular dynamics simulations with the AMBER protein force field (ff96) coupled with the implicit solvent model (IGB = 5), we shed new light into the nature of this transition and resolve the experimental controversies. We show that the melting transition corresponds to the melting of the protein as a whole, and not solely to the helix-coil transition. The breadth of the folding transition arises from the spread in the melting temperatures (from ∼325 K to ∼302 K) of the individual transitions: formation of the hydrophobic core, β-hairpin and tertiary fold, with the helix formed earlier. Our simulations initiated from an extended chain accurately predict the native structure, provide a reasonable estimate of the transition barrier height, and explicitly demonstrate the existence of multiple pathways and multiple transition states for folding. Our exhaustive sampling enables us to assess the quality of the Amber ff96/igb5 combination and reveals that while this force field can predict the correct native fold, it nonetheless overstabilizes the α-helix portion of the protein (Tm = ∼387K) as well as the denatured structures.     

Increased epithelial cell proliferation in very premature baboons with chronic lung disease

Coordinated proliferation of lung cells is required for normal lung growth and differentiation. Chronic injury to developing lung may disrupt normal patterns of cell proliferation. To examine patterns of cell proliferation in injured developing lungs, we investigated premature baboons delivered at 125 days gestation (approximately 67% of term) and treated with oxygen and ventilation for 6, 14, or 21 days (PRN). Each PRN treatment group contained 3 or 4 animals. During normal in utero lung development, the proportion of proliferating lung cells declined as measured by the cell-cycle marker Ki67. In the PRN group, the proportion of proliferating lung cells was 2.5-8.5-fold greater than in corresponding gestational controls. By 14 days of treatment, the proportion of cells that expressed pro-surfactant protein B (proSP-B) was ~2.5-fold greater than in gestational controls. In the PRN group, 41% of proliferating cells expressed proSP-B compared with 5.8% in the gestational controls. By 21 days of treatment, proliferation of proSP-B-expressing epithelial cells declined substantially, but the proportion of proliferating non-proSP-B-expressing cells increased approximately sevenfold. These data show that the development of chronic lung disease is associated with major alterations in normal patterns of lung-cell proliferation.     

Interaction of Nuclease Colicins with Membranes: Insertion Depth Correlates with Bilayer Perturbation

Background

Protein transport across cellular membranes is an important aspect of toxin biology. Escherichia coli cell killing by nuclease colicins occurs through DNA (DNases) or RNA (RNases) hydrolysis and to this end their cytotoxic domains require transportation across two sets of membranes. In order to begin to unravel the molecular mechanisms underlying the membrane translocation of colicin nuclease domains, we have analysed the membrane association of four DNase domains (E9, a charge reduction E9 mutant, E8, and E7) and one ribosomal RNase domain (E3) using a biomembrane model system.

Principal Results

We demonstrate, through the use of large unilamellar vesicles composed of synthetic and E. coli lipids and a membrane surface potential sensor, that the colicin nuclease domains bind anionic membranes only, with micromolar affinity and via a cooperative binding mechanism. The evaluation of the nuclease bilayer insertion depth, through a fluorescence quenching analysis using brominated lipids, indicates that the nucleases locate to differential regions in the bilayer. Colicin DNases target the interfacial region of the lipid bilayer, with the DNase E7 showing the deepest insertion, whereas the ribosomal RNase E3 penetrates into the hydrophobic core region of the bilayer. Furthermore, the membrane association of the DNase E7 and the ribosomal RNase E3 induces vesicle aggregation, lipid mixing and content leakage to a much larger extent than that of the other DNases analysed.

Conclusions/Significance

Our results show, for the first time, that after the initial electrostatically driven membrane association, the pleiotropic membrane effects induced by colicin nuclease domains relate to their bilayer insertion depth and may be linked to their in vivo membrane translocation.     

A convenient assay for mephenytoin 4-hydroxylase activity of human liver microsomal cytochrome P-450

A simple and rapid method for the determination of (S)-mephenytoin 4-hydroxylase activity by human liver microsomal cytochrome P-450 has been developed. [Methyl-14C] mephenytoin was synthesized by alkylation of S-nirvanol with 14CH3I and used as a substrate. After incubation of [methyl-14C]mephenytoin with human liver microsomes or a reconstituted monooxygenase system containing partially purified human liver cytochrome P-450, the 4-hydroxylated metabolite of mephenytoin was separated by thin-layer chromatography and quantified. The formation of the metabolite depended on the incubation time, substrate concentration, and cytochrome P-450 concentration and was found to be optimal at pH 7.4. The Km and Vmax rates obtained with a human liver microsomal preparation were 0.1 mM and 0.23 nmol 4-hydroxymephenytoin formed/min/nmol cytochrome P-450, respectively. The hydroxylation activity showed absolute requirements for cytochrome P-450, NADPH-cytochrome P-450 reductase, and NADPH in a reconstituted monooxygenase system. Activities varied from 5.6 to 156 pmol 4-hydroxymephenytoin formed/min/nmol cytochrome P-450 in 11 human liver microsomal preparations. The basic system utilized for the analysis of mephenytoin 4-hydroxylation can also be applied to the estimation of other enzyme activities in which phenol formation occurs.     

Effects of Elevated Temperatures on Mengovirus Ribonucleic Acid Synthesis and Virus Production in Novikoff Rat Hepatoma Cells

The production of mengovirus in Novikoff rat hepatoma cells is progressively reduced with an increase in incubation temperature of the cells from 34 to 40 C, in spite of the fact that about the same amounts of single-stranded and double-stranded viral ribonucleic acid (RNA) are synthesized at 34, 37, and 40 C; the rate of overall protein synthesis is as high at 40 C as at 37 C. At 40 C, progeny viral RNA accumulates in an undegraded form without being incorporated into virus particles. The results suggest that virus maturation is preferentially inhibited at supraoptimal temperatures. At 42 C, on the other hand, no viral RNA is produced and no viral RNA polymerase activity is detectable in cell lysates. Failure of infected cells to form viral RNA polymerase at 42 C is probably due to an impairment of protein synthesis since most of the polyribosomes are rapidly lost during incubation at 42 C and the rate of amino acid incorporation into protein is 70% lower at 42 C than at 37 C. When infected cells are shifted from 37 to 42 C during the period of active viral RNA synthesis, viral RNA polymerase activity is rapidly lost from the cells, and viral RNA synthesis ceases within 45 min. In contrast, the RNA polymerase is as active in vitro at 42 C as at 37 C, and the activity is relatively stable at 42 C.     

Point Me in the Right Direction: Same and Cross Category Visual Aftereffects to Directional Cues

Of the many hand gestures that we use in communication pointing is one of the most common and powerful in its role as a visual referent that directs joint attention. While numerous studies have examined the developmental trajectory of pointing production and comprehension, very little consideration has been given to adult visual perception of hand pointing gestures. Across two studies, we use a visual adaptation paradigm to explore the mechanisms underlying the perception of proto-declarative hand pointing. Twenty eight participants judged whether 3D modeled hands pointed, in depth, at or to the left or right of a target (test angles of 0°, 0.75° and 1.5° left and right) before and after adapting to either hands or arrows which pointed 10° to the right or left of the target. After adaptation, the perception of the pointing direction of the test hands shifted with respect to the adapted direction, revealing separate mechanisms for coding right and leftward pointing directions. While there were subtle yet significant differences in the strength of adaptation to hands and arrows, both cues gave rise to a similar pattern of aftereffects. The considerable cross category adaptation found when arrows were used as adapting stimuli and the asymmetry in aftereffects to left and right hands suggests that the adaptation aftereffects are likely driven by simple orientation cues, inherent in the morphological structure of the hand, and not dependent on the biological status of the hand pointing cue. This finding provides evidence in support of a common neural mechanism that processes these directional social cues, a mechanism that may be blind to the biological status of the stimulus category.