The early evolution of land plants, from fossils to genomics: a commentary on Lang (1937) ‘On the plant-remains from the Downtonian of England and Wales'

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Fragments of the earliest land plants

The earliest fossil evidence for land plants comes from microscopic dispersed spores. These microfossils are abundant and widely distributed in sediments, and the earliest generally accepted reports are from rocks of mid-Ordovician age (Llanvirn, 475 million years ago). Although distribution, morphology and ultrastructure of the spores indicate that they are derived from terrestrial plants, possibly early relatives of the bryophytes, this interpretation remains controversial as there is little in the way of direct evidence for the parent plants. An additional complicating factor is that there is a significant hiatus between the appearance of the first dispersed spores and fossils of relatively complete land plants (megafossils): spores predate the earliest megafossils (Late Silurian, 425 million year ago) by some 50 million years. Here we report the description of spore-containing plant fragments from Ordovician rocks of Oman. These fossils provide direct evidence for the nature of the spore-producing plants. They confirm that the earliest spores developed in large numbers within sporangia, providing strong evidence that they are the fossilized remains of bona fide land plants. Furthermore, analysis of spore wall ultrastructure supports liverwort affinities

RELATING CELLULAR ASSOCIATION WITH LIPOSOME CYTOTOXICITY IN HUMAN ENDOTHELIAL CELLS

INTRODUCTION Interactions with the endothelium play a key role in the behaviour of intravenously administered nanoparticle drug carriers[1]. Hence, quantifying cellular association (membrane adhesion and cell internalization) of liposomes with endothelial cells is an effective screening method of biocompatibility and success of new drug carriers. Current methods are inaccurate as concentration does not necessarily equate to local cellular association. The focus of this experiment is to quantify the cellular association between liposomes and two types of human endothelial cells and compare the associations with cells’ cytotoxic response. Cellular association of liposomes as well as cell viability were quantified on cellular level at different concentrations of liposomes. METHODS Two different types of cells, Human Umbilical Vein Endothelial cell, which is a common cell type used in vitro studies, and Human MicroVascular Cell, which is more accurate representation of in vivo, were used[2]. HUVEC and HMVEC were cultured and passaged onto chamber slides using standard cell culture techniques. The confluent cells were exposed to fluorescent liposomes with hydrodynamic diameter of 90.4 nm at concentrations ranging from 0.08nM to 8nM for 24 hours, membrane stained with CellMask Deep Red and fixed with paraformaldehyde, following same protocols for both types of cells. Cell viability on exposure to the same concentration range of liposomes was determined using Vialight assay using manufacturer protocols. Z-stacks of the treated cells were obtained using Olympus Fluoview FV1000 confocal microscope. Region of interest, limited by cell membranes, was set using the membrane stain channel using ImageJ. The region of interest was superimposed onto the fluorescent liposome channel to determine exclusively the fluorescence of cell adhered and cell internalized liposomes RESULTS Compared to HUVECs, higher cellular association of liposomes was observed for HMVC as shown in Figure 1.While cellular association of liposomes increased with concentration, cell viability was in the range of 85 to nearly 100% for the concentration range of 0.08-4 nM with no significant difference. Only at 8 nM, cell viability decreased significantly to approximately 62 %. DISCUSSION AND CONCLUSIONS Liposome cellular association provide insight into the cytotoxicity and the endothelial cytotoxicity of the liposomes at low concentration of 8nM raises cautions on documented innocuous properties of liposomes. Cytotoxicity and cellular association upon comparison showed exponential relationship. Because the cytotoxicity and cellular association relationship is exponential, slight over-administration can cause severe toxicity. 8nM is lower than concentration of current intravenous liposome-based drug doxorubicin[3]. High toxicity and exponential relationship raise caution on the importance of proper safe dosage

RELATING QUANTUM DOT ASSOCIATION WITH HUMAN ENDOTHELIAL CELLS WITH THEIR CYTOTOXIC EFFECTS

INTRODUCTION Advances in the field of nanotechnology have enabled researchers to pursue biomedical applications of nanoparticles. Quantum dots are commonly used fluorescent probes because they are brighter and less prone to photobleaching than other fluorophores [1]. However, despite the advantages, potential for toxicity must be acknowledged. Quantum dots are commonly made with toxic metal elements, which can cause oxidative stress [2]. Cadmium ions have been shown to disrupt mitochondria activity, leading to cell death [2]. Quantum dots have been shown to attach to the cell membrane as well as be internalized through endocytic mechanisms [3]. In this study, we aim to quantify quantum dot association and compare results from cytotoxicity assays for identical conditions, relating cellular association with cytotoxicity. METHODS Human Umbilical Vein Endothelial Cells (HUVECs) and Human Micro-vascular Endothelial Cells (HMVECs) were cultured in static conditions in 8-well chamber slides then exposed to amino-PEG quantum dots at a concentration of 0.2nM to 200nM. After exposure for 24 hours, the cells were washed, fixed, and stained. Z-stacks were obtained using an Olympus Fluoview FV1000 confocal microscope. Images were analyzed using ImageJ software to quantify mean fluorescence intensity within the defined region of interest, selected from the boundaries of stained cell membranes. Statistical analysis using one-way Analysis of Variance (ANOVA) and post-hoc Tukey HSD test was performed. Finally, Vialight assay was used to test cell viability after exposure to quantum dots under the same experimental conditions used for association experiments. RESULTS Exposure to different concentrations of quantum dots results in significant changes in the observed fluorescence intensity per area. Non-linear dependence of cellular association of quantum dots on exposure concentration was observed. A representative example of mean fluorescence intensity of quantum dots associated with HUVECs is shown in Figure 1.A significant decrease in the viability of HUVECs was observed on exposure to quantum dots (30-50% cell viability relative to 100% for non-exposed cells). However, no significant difference in cell viability was observed between 0.2nM to 200nM concentrations. DISCUSSION AND CONCLUSIONS Nanoparticle association studies play a vital role in predicting cell viability in nanoparticle cytotoxicity studies. The non-linear trend observed suggests that for the range of concentrations examined, cellular association does not increase linearly with exposure concentration, and that cytotoxicity can be related to association, rather than just to exposure concentration. This experiment provides an approach to advance future studies relating cellular association to cytotoxicity

Following in the Wake of Anger: When Not Discriminating Is Discriminating

Does seeing a scowling face change your impression of the next person you see? Does this depend on the race of the two people? Across four studies, White participants evaluated neutrally expressive White males as less threatening when they followed angry (relative to neutral) White faces; Black males were not judged as less threatening following angry Black faces. This lack of threat-anchored contrast for Black male faces is not attributable to a general tendency for White targets to homogenize Black males—neutral Black targets following smiling Black faces were contrasted away from them and seen as less friendly—and emerged only for perceivers low in motivation to respond without prejudice (i.e., for those relatively comfortable responding prejudicially). This research provides novel evidence for the overperception of threat in Black males

Childhood IQ and marriage by mid-life: the Scottish Mental Survey 1932 and the Midspan Studies

The study examined the influence of IQ at age 11 years on marital status by mid-adulthood. The combined databases of the Scottish Mental Survey 1932 and the Midspan studies provided data from 883 subjects. With regard to IQ at age 11, there was an interaction between sex and marital status by mid-adulthood (p = 0.0001). Women who had ever-married achieved mean lower childhood IQ scores than women who had never-married (p < 0.001). Conversely, there was a trend for men who had ever-married to achieve higher childhood IQ scores than men who had never-married (p = 0.07). In men, the odds ratio of ever marrying was 1.35 (95% CI 0.98–1.86&#59; p = 0.07) for each standard deviation increase in childhood IQ. Among women, the odds ratio of ever marrying by mid-life was 0.42 (95% CI 0.27–0.64; p = 0.0001) for each standard deviation increase in childhood IQ. Mid-life social class had a similar association with marriage, with women in more professional jobs and men in more manual jobs being less likely to have ever-married by mid-life. Adjustment for the effects of mid-life social class and height on the association between childhood IQ and later marriage, and vice versa, attenuated the effects somewhat, but suggested that IQ, height and social class acted partly independently

I only have eyes for you: Ovulation redirects attention (but not memory) to attractive men

A number of studies have found a disjunction between women’s attention to, and memory for, handsome men. Although women pay initial attention to handsome men, they do not remember those men later. The present study examines how ovulation might differentially affect these attentional and memory processes. We found that women near ovulation increased their visual attention to attractive men. However, this increased visual attention did not translate into better memory. Discussion focuses on possible explanations, in the context of an emerging body of findings on disjunctions between attention to, and memory for, other people.National Institute of Mental Health (U.S.) (R01MH064734

Evolution of leaf-form in land plants linked to atmospheric CO2 decline in the Late Palaeozoic era

The widespread appearance of megaphyll leaves, with their branched veins and planate form, did not occur until the close of the Devonian period at about 360 Myr ago. This happened about 40 Myr after simple leafless vascular plants first colonized the land in the Late Silurian/Early Devonian, but the reason for the slow emergence of this common feature of present-day plants is presently unresolved. Here we show, in a series of quantitative analyses using fossil leaf characters and biophysical principles, that the delay was causally linked with a 90% drop in atmospheric pCO2 during the Late Palaeozoic era. In contrast to simulations for a typical Early Devonian land plant, possessing few stomata on leafless stems, those for a planate leaf with the same stomatal characteristics indicate that it would have suffered lethal overheating, because of greater interception of solar energy and low transpiration. When planate leaves first appeared in the Late Devonian and subsequently diversified in the Carboniferous period, they possessed substantially higher stomatal densities. This observation is consistent with the effects of the pCO2 on stomatal development and suggests that the evolution of planate leaves could only have occurred after an increase in stomatal density, allowing higher transpiration rates that were sufficient to maintain cool and viable leaf temperatures

PERSONALITY AND SOCIAL PSYCHOLOGY BULLETIN Becker et al. / MEMORY FOR ATTRACTIVENESS Concentrating on Beauty: Sexual Selection and Sociospatial Memory

In three experiments, location memory for faces was examine