Arabidopsis transcriptome responses to low water potential using high-throughput plate assays.

Soil-free assays that induce water stress are routinely used to investigate drought responses in the plant Arabidopsis thaliana. Due to their ease of use, the research community often relies on polyethylene glycol (PEG), mannitol, and salt (NaCl) treatments to reduce the water potential of agar media, and thus induce drought conditions in the laboratory. However, while these types of stress can create phenotypes that resemble those of water deficit experienced by soil-grown plants, it remains unclear how these treatments compare at the transcriptional level. Here, we demonstrate that these different methods of lowering water potential elicit both shared and distinct transcriptional responses in Arabidopsis shoot and root tissue. When we compared these transcriptional responses to those found in Arabidopsis roots subject to vermiculite drying, we discovered many genes induced by vermiculite drying were repressed by low water potential treatments on agar plates (and vice versa). Additionally, we also tested another method for lowering water potential of agar media. By increasing the nutrient content and tensile strength of agar, we show the 'hard agar' (HA) treatment can be leveraged as a high-throughput assay to investigate natural variation in Arabidopsis growth responses to low water potential.

A stronger role for long-term moisture change than for CO2 in determining tropical woody vegetation change.

Anthropogenically elevated CO2 (eCO2) concentrations have been suggested to increase woody cover within tropical ecosystems through fertilization. The effect of eCO2 is built into Earth system models, although testing the relationship over long periods remains challenging. Here, we explore the relative importance of six drivers of vegetation change in western Africa over the past ~500,000 years (moisture availability, fire activity, mammalian herbivore density, temperature, temperature seasonality, CO2) by coupling past environmental change data from Lake Bosumtwi (Ghana) with global data. We found that moisture availability and fire activity were the most important factors in determining woody cover, whereas the effect of CO2 was small. Our findings suggest that the role of eCO2 effects on tropical vegetation in predictive models must be reconsidered.

Loss of Diacylglycerol Kinase α Enhances Macrophage Responsiveness.

The diacylglycerol kinases (DGKs) are a family of enzymes responsible for the conversion of diacylglycerol (DAG) to phosphatidic acid (PA). In addition to their primary function in lipid metabolism, DGKs have recently been identified as potential therapeutic targets in multiple cancers, including glioblastoma (GBM) and melanoma. Aside from its tumorigenic properties, DGKα is also a known promoter of T-cell anergy, supporting a role as a recently-recognized T cell checkpoint. In fact, the only significant phenotype previously observed in Dgka knockout (KO) mice is the enhancement of T-cell activity. Herein we reveal a novel, macrophage-specific, immune-regulatory function of DGKα. In bone marrow-derived macrophages (BMDMs) cultured from wild-type (WT) and KO mice, we observed increased responsiveness of KO macrophages to diverse stimuli that yield different phenotypes, including LPS, IL-4, and the chemoattractant MCP-1. Knockdown (KD) of Dgka in a murine macrophage cell line resulted in similar increased responsiveness. Demonstrating in vivo relevance, we observed significantly smaller wounds in Dgka-/- mice with full-thickness cutaneous burns, a complex wound healing process in which macrophages play a key role. The burned area also demonstrated increased numbers of macrophages. In a cortical stab wound model, Dgka-/- brains show increased Iba1+ cell numbers at the needle track versus that in WT brains. Taken together, these findings identify a novel immune-regulatory checkpoint function of DGKα in macrophages with potential implications for wound healing, cancer therapy, and other settings.

Using natural variation to understand plant responses to iron availability.

Iron bioavailability varies dramatically between soil types across the globe. This has given rise to high levels of natural variation in plant iron responses, allowing members of even a single species to thrive across a wide range of soil types. In recent years we have seen the use of genome-wide association analysis to identify natural variants underlying plant responses to changes in iron availability in both Arabidopsis and important crop species. These studies have provided insights into which genes have been important in shaping local adaptation to iron availability in different plant species and have allowed the discovery of novel regulators and mechanisms, not previously identified using mutagenesis approaches. Furthermore, these studies have allowed the identification of markers that can be used to accelerate breeding of future elite varieties with increased resilience to iron stress and improved nutritional quality. The studies highlighted here show that, in addition to studying plant responses to iron alone, it is important to consider these responses within the context of plant nutrition more broadly and to also consider iron regulation in relation to additional traits of agronomic importance such as yield and disease resistance.

The southern rural health and mortality penalty: A review of regional health inequities in the United States.

Rural-urban differences in morbidity and mortality across the United States have been well documented and termed the "rural mortality penalty". However, research studies frequently treat rural areas as homogeneous and often do not account for geospatial variability in rural health risks by both county, state, region, race, and sex within the United States. Additionally, people living in the rural South of the US have higher rates of morbidity and mortality compared to both their urban counterparts and other rural areas. Of those living in southern rural communities, people of color experience higher rates of death and disease compared to white populations. Although there is a wealth of research that uses individual-level behaviors to explain rural-urban health disparities, there is less focus on how community and structural factors influence these differences. This review focuses on the "southern rural health penalty", a term coined by the authors, which refers to the high rate of mortality and morbidity in southern rural areas in the USA compared to both urban areas and non-southern rural places. We use macrosocial determinants of health to explain possible reasons for the "southern rural health penalty". This review can guide future research on rural health between southern and non-southern populations in the US and examine if macrosocial determinants of health can explain health disparities within southern rural populations.

Variation in the expression of a transmembrane protein influences cell growth in Arabidopsis thaliana petals by altering auxin responses.

BACKGROUND: The same species of plant can exhibit very diverse sizes and shapes of organs that are genetically determined. Characterising genetic variation underlying this morphological diversity is an important objective in evolutionary studies and it also helps identify the functions of genes influencing plant growth and development. Extensive screens of mutagenised Arabidopsis populations have identified multiple genes and mechanisms affecting organ size and shape, but relatively few studies have exploited the rich diversity of natural populations to identify genes involved in growth control. RESULTS: We screened a relatively well characterised collection of Arabidopsis thaliana accessions for variation in petal size. Association analyses identified sequence and gene expression variation on chromosome 4 that made a substantial contribution to differences in petal area. Variation in the expression of a previously uncharacterised gene At4g16850 (named as KSK) had a substantial role on variation in organ size by influencing cell size. Over-expression of KSK led to larger petals with larger cells and promoted the formation of stamenoid features. The expression of auxin-responsive genes known to limit cell growth was reduced in response to KSK over-expression. ANT expression was also reduced in KSK over-expression lines, consistent with altered floral identities. Auxin responses were reduced in KSK over-expressing cells, consistent with changes in auxin-responsive gene expression. KSK may therefore influence auxin responses during petal development. CONCLUSIONS: Understanding how genetic variation influences plant growth is important for both evolutionary and mechanistic studies. We used natural populations of Arabidopsis thaliana to identify sequence variation in a promoter region of Arabidopsis accessions that mediated differences in the expression of a previously uncharacterised membrane protein. This variation contributed to altered auxin responses and cell size during petal growth.

Cardiac phenotype in ATP1A3-related syndromes: A multicenter cohort study.

OBJECTIVE: To define the risks and consequences of cardiac abnormalities in ATP1A3-related syndromes. METHODS: Patients meeting clinical diagnostic criteria for rapid-onset dystonia-parkinsonism (RDP), alternating hemiplegia of childhood (AHC), and cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss (CAPOS) with ATP1A3 genetic analysis and at least 1 cardiac assessment were included. We evaluated the cardiac phenotype in an Atp1a3 knock-in mouse (Mashl+/-) to determine the sequence of events in seizure-related cardiac death. RESULTS: Ninety-eight patients with AHC, 9 with RDP, and 3 with CAPOS (63 female, mean age 17 years) were included. Resting ECG abnormalities were found in 52 of 87 (60%) with AHC, 2 of 3 (67%) with CAPOS, and 6 of 9 (67%) with RDP. Serial ECGs showed dynamic changes in 10 of 18 patients with AHC. The first Holter ECG was abnormal in 24 of 65 (37%) cases with AHC and RDP with either repolarization or conduction abnormalities. Echocardiography was normal. Cardiac intervention was required in 3 of 98 (≈3%) patients with AHC. In the mouse model, resting ECGs showed intracardiac conduction delay; during induced seizures, heart block or complete sinus arrest led to death. CONCLUSIONS: We found increased prevalence of ECG dynamic abnormalities in all ATP1A3-related syndromes, with a risk of life-threatening cardiac rhythm abnormalities equivalent to that in established cardiac channelopathies (≈3%). Sudden cardiac death due to conduction abnormality emerged as a seizure-related outcome in murine Atp1a3-related disease. ATP1A3-related syndromes are cardiac diseases and neurologic diseases. We provide guidance to identify patients potentially at higher risk of sudden cardiac death who may benefit from insertion of a pacemaker or implantable cardioverter-defibrillator.

A Serum Proteomic Signature Predicting Survival in Patients with Glioblastoma.

PURPOSE: Glioblastoma (GBM) is the most common form of brain tumor and has a uniformly poor prognosis. Development of prognostic biomarkers in easily accessible serum samples have the potential to improve the outcomes of patients with GBM through personalized therapy planning. MATERIAL/METHODS: In this study pre-treatment serum samples from 30 patients newly diagnosed with GBM were evaluated using a 40-protein multiplex ELISA platform. Analysis of potentially relevant gene targets using The Cancer Genome Atlas database was done using the Glioblastoma Bio Discovery Portal (GBM-BioDP). A ten-biomarker subgroup of clinically relevant molecules was selected using a functional grouping analysis of the 40 plex genes with two genes selected from each group on the basis of degree of variance, lack of co-linearity with other biomarkers and clinical interest. A Multivariate Cox proportional hazard approach was used to analyze the relationship between overall survival (OS), gene expression, and resection status as covariates. RESULTS: Thirty of 40 of the MSD molecules mapped to known genes within TCGA and separated the patient cohort into two main clusters centered predominantly around a grouping of classical and proneural versus the mesenchymal subtype as classified by Verhaak. Using the values for the 30 proteins in a prognostic index (PI) demonstrated that patients in the entire cohort with a PI below the median lived longer than those patients with a PI above the median (HR 1.8, p=0.001) even when stratified by both age and MGMT status. This finding was also consistent within each Verhaak subclass and highly significant (range p=0.0001-0.011). Additionally, a subset of ten proteins including, CRP, SAA, VCAM1, VEGF, MDC, TNFA, IL7, IL8, IL10, IL16 were found to have prognostic value within the TCGA database and a positive correlation with overall survival in GBM patients who had received gross tumor resection followed by conventional radiation therapy and temozolomide treatment concurrent with the addition of valproic acid. CONCLUSION: These findings demonstrate that proteomic approaches to the development of prognostic assays for treatment of GBM may hold potential clinical value.

Variation in Expression of the HECT E3 Ligase UPL3 Modulates LEC2 Levels, Seed Size, and Crop Yields in Brassica napus.

Identifying genetic variation that increases crop yields is a primary objective in plant breeding. We used association analyses of oilseed rape/canola (Brassica napus) accessions to identify genetic variation that influences seed size, lipid content, and final crop yield. Variation in the promoter region of the HECT E3 ligase gene BnaUPL3 C03 made a major contribution to variation in seed weight per pod, with accessions exhibiting high seed weight per pod having lower levels of BnaUPL3 C03 expression. We defined a mechanism in which UPL3 mediated the proteasomal degradation of LEC2, a master transcriptional regulator of seed maturation. Accessions with reduced UPL3 expression had increased LEC2 protein levels, larger seeds, and prolonged expression of lipid biosynthetic genes during seed maturation. Natural variation in BnaUPL3 C03 expression appears not to have been exploited in current B napus breeding lines and could therefore be used as a new approach to maximize future yields in this important oil crop.

Revising rapid-onset dystonia-parkinsonism: Broadening indications for ATP1A3 testing.

BACKGROUND AND OBJECTIVES: Rapid-onset dystonia-parkinsonism (RDP) is caused by mutations in the ATP1A3 gene, which codes for the α-3 subunit of the Na+ /K+ ATPase. It has been characterized by rapid-onset bulbar dysfunction, limb dystonia, bradykinesia, and a rostrocaudal spatial gradient of expression, usually after a physiologic trigger. We reexamined whether these features were in fact characteristic. METHODS: We characterized phenotypic variation within a cohort of 50 ATP1A3 mutation-positive individuals (carriers) and 44 mutation-negative family members (noncarriers). Potential participants were gathered through referral for clinical suspicion of RDP or alternating hemiplegia of childhood. Inclusion criteria were having a ATP1A3 mutation or being a family member of such an individual. RESULTS: We found RDP is underdiagnosed if only "characteristic" patients are tested. Rapid onset and bulbar predominance were not universally present in carriers. Among those with at least mild symptoms of dystonia, rostrocaudal severity gradient was rare (7%). Symptoms began focally but progressed to be generalized (51%) or multifocal (49%). Arm (41%) onset was most common. Arms and voice were typically most severely affected (48% and 44%, respectively). Triggers preceded onset in 77% of the participants. Rapid onset, dystonia, parkinsonism, bulbar symptoms, headaches, seizures, frontal impairment, and a history of mood disorder and a history of psychosis were more common in carriers. Approximately half of the proband mutations occurred de novo (56%). CONCLUSIONS: Our findings suggest that patients should not be excluded from ATP1A3 testing because of slow onset, limb onset, absent family history, or onset in middle adulthood. RDP should be strongly considered in the differential for any bulbar dystonia. © 2019 International Parkinson and Movement Disorder Society.

Effects of Social Stress on Autonomic, Behavioral, and Acoustic Parameters in Adults Who Stutter.

Purpose The purpose of this study was to assess changes in autonomic, behavioral, and acoustic measures in response to social stress in adults who stutter (AWS) compared to adults who do not stutter (ANS). Method Participants completed the State-Trait Anxiety Inventory ( Speilberger, Gorsuch, Luschene, Vagg, & Jacobs, 1983 ). In order to provoke social stress, participants were required to complete a modified version of the Trier Social Stress Test (TSST-M, Kirschbaum, Pirke, & Hellhammer, 1993 ), which included completing a nonword reading task and then preparing and delivering a speech to what was perceived as a group of professionals trained in public speaking. Autonomic nervous system changes were assessed by measuring skin conductance levels, heart rate, and respiratory sinus arrhythmia (RSA). Behavioral changes during speech production were measured in errors, percentage of syllable stuttered, percentage of other disfluencies, and speaking rate. Acoustic changes were measured using 2nd formant frequency fluctuations. In order to make comparisons of speech with and without social-cognitive stress, measurements were collected while participants completed a speaking task before and during TSST-M conditions. Results AWS showed significantly higher levels of self-reported state and trait anxiety compared to ANS. Autonomic nervous system changes revealed similar skin conductance level and heart rate across pre-TSST-M and TSST-M conditions; however, RSA levels were significantly higher in AWS compared to ANS across conditions. There were no differences found between groups for speaking rate, fundamental frequency, and percentage of other disfluencies when speaking with or without social stress. However, acoustic analysis revealed higher levels of 2nd formant frequency fluctuations in the AWS compared to the controls under pre-TSST-M conditions, followed by a decline to a level that resembled controls when speaking under the TSST-M condition. Discussion Results suggest that AWS, compared to ANS, engage higher levels of parasympathetic control (i.e., RSA) during speaking, regardless of stress level. Higher levels of self-reported state and trait anxiety support this view point and suggest that anxiety may have an indirect role on articulatory variability in AWS.

Novel 11-Substituted Ellipticines as Potent Anticancer Agents with Divergent Activity against Cancer Cells.

Ellipticines have well documented anticancer activity, in particular with substitution at the 1-, 2-, 6- and 9-positions. However, due to limitations in synthesis and coherent screening methodology the full SAR profile of this anticancer class has not yet been achieved. In order to address this shortfall, we have set out to explore the anticancer activity of this potent natural product by substitution. We currently describe the synthesis of novel 11-substituted ellipticines with two specific derivatives showing potency and diverging cellular growth effects.

Limb phase flexibility in walking: a test case in the squirrel monkey (Saimiri sciureus).

BACKGROUND: Previous analyses of factors influencing footfall timings and gait selection in quadrupeds have focused on the implications for energetic cost or gait mechanics separately. Here we present a model for symmetrical walking gaits in quadrupedal mammals that combines both factors, and aims to predict the substrate contexts in which animals will select certain ranges of footfall timings that (1) minimize energetic cost, (2) minimize rolling and pitching moments, or (3) balance the two. We hypothesize that energy recovery will be a priority on all surfaces, and will be the dominant factor determining footfall timings on flat, ground-like surfaces. The ability to resist pitch and roll, however, will play a larger role in determining footfall choice on narrower and more complex branch-like substrates. As a preliminary test of the expectations of the model, we collected sample data on footfall timings in a primate with relatively high flexibility in footfall timings - the squirrel monkey (Saimiri sciureus) - walking on a flat surface, straight pole, and a pole with laterally-projecting branches to simulate simplified ground and branch substrates. We compare limb phase values on these supports to the expectations of the model. RESULTS: As predicted, walking steps on the flat surface tended towards limb phase values that promote energy exchange. Both pole substrates induced limb phase values predicted to favor reduced pitching and rolling moments. CONCLUSIONS: These data provide novel insight into the ways in which animals may choose to adjust their behavior in response to movement on flat versus complex substrates and the competing selective factors that influence footfall timing in mammals. These data further suggest a pathway for future investigations using this perspective.

Pitch control and speed limitation during overground deceleration in lemurid primates.

An animal's fitness is influenced by the ability to move safely through its environment. Recent models have shown that aspects of body geometry, for example, limb length and center of mass (COM) position, appear to set limits for pitch control in cursorial quadrupeds. Models of pitch control predict that the body shape of these and certain other primates, with short forelimbs and posteriorly positioned COM, should allow them to decelerate rapidly while minimizing the risk of pitching forward. We chose to test these models in two non-cursorial lemurs: Lemur catta, the highly terrestrial ring-tailed lemur, and Eulemur fulvus, the highly arboreal brown lemur. We modeled the effects of changes in limb length and COM position on maximum decelerative potential for both species, as well as collecting data on maximal decelerations across whole strides. In both species, maximum measured decelerations fell below the range of pitch-limited deceleration values predicted by the geometric model, with the ring-tailed lemur approaching its pitch limit more closely. Both lemurs showed decelerative potential equivalent to or higher than horses, the only comparative model currently available. These data reinforce the hypothesis that a relatively simple model of body geometry can predict aspects of maximum performance in animals. In this case, it appears that the body geometry of primates is skewed toward avoiding forward pitch in maximal decelerations.

Effective Genomic Selection in a Narrow-Genepool Crop with Low-Density Markers: Asian Rapeseed as an Example.

Genomic selection (GS) has revolutionized breeding for quantitative traits in plants, offering potential to optimize resource allocation in breeding programs and increase genetic gain per unit of time. Modern high-density single nucleotide polymorphism (SNP) arrays comprising up to several hundred thousand markers provide a user-friendly technology to characterize the genetic constitution of whole populations and for implementing GS in breeding programs. However, GS does not build upon detailed genotype profiling facilitated by maximum marker density. With extensive genome-wide linkage disequilibrium (LD) being a common characteristic of breeding pools, fewer representative markers from available high-density genotyping platforms could be sufficient to capture the association between a genomic region and a phenotypic trait. To examine the effects of reduced marker density on genomic prediction accuracy, we collected data on three traits across 2 yr in a panel of 203 homozygous Chinese semiwinter rapeseed ( L.) inbred lines, broadly encompassing allelic variability in the Asian genepool. We investigated two approaches to selecting subsets of markers: a trait-dependent strategy based on genome-wide association study (GWAS) significance thresholds and a trait-independent method to detect representative tag SNPs. Prediction accuracies were evaluated using cross-validation with ridge-regression best linear unbiased predictions (rrBLUP). With semiwinter rapeseed as a model species, we demonstrate that low-density marker sets comprising a few hundred to a few thousand markers enable high prediction accuracies in breeding populations with strong LD comparable to those achieved with high-density arrays. Our results are valuable for facilitating routine application of cost-efficient GS in breeding programs.

Dissecting the complex regulation of lodging resistance in Brassica napus.

Lodging continues to be a major cause of yield loss in important crop species such as Brassica napus. Understanding the genetic regulation of lodging resistance is therefore of key interest to breeders worldwide. Current strategies aimed at minimising lodging risk involve the incorporation of dwarfing genes or the application of plant growth regulators. However, despite these efforts, lodging continues to be a persistent problem and it is therefore of high interest that novel, complimentary strategies for lodging control are implemented. One approach would be to focus on understanding the genetic properties underlying stem mechanical strength. With this in mind, we screened a training genetic diversity panel of B. napus accession for variation in stem mechanical strength and related traits. Using Associative Transcriptomics, we identified molecular markers for a suite of valuable traits. Using an independent test genetic diversity panel, we show that the methods employed are robust for identification of predictive markers. Furthermore, based on conserved synteny with Arabidopsis thaliana, we are able to provide a biological context to the marker associations detected and provide evidence for a role in pectin methylesterification in contributing to stem mechanical strength in Brassicaceae.

Resistance and tolerance: The role of nutrients on pathogen dynamics and infection outcomes in an insect host.

Tolerance and resistance are the two ways in which hosts can lessen the effects of infection. Tolerance aims to minimize the fitness effects resulting from incumbent pathogen populations, whereas resistance aims to reduce the pathogen population size within the host. While environmental impacts on resistance have been extensively, recorded their impacts on variation in tolerance are virtually unexplored. Here, we ask how the environment, namely the host diet, influences the capacity of an organism to tolerate and resist infection, using a model host-parasite system, the burying beetle, Nicrophorus vespilloides and the entomopathogenic bacteria, Photorhabdus luminescens. We first considered dose-responses and pathogen dynamics within the host, and compared our findings to responses known from other host species. We then investigated how investment in tolerance and resistance changed under different nutritional regimes. Beetles were maintained on one of five diets that varied in their ratio of protein to fat for 48 hr and then injected with P. luminescens. Survival was monitored and the phenoloxidase (PO) response and bacterial load at 24-hr postinfection were ascertained. The dose required to kill 50% of individuals in this species was several magnitudes higher than in other species and the bacteria were shown to display massive decreases in population size, in contrast to patterns of proliferation found in other host species. Diet strongly modified host survival after infection, with those on the high fat/low protein diet showing 30% survival at 8 days, vs. almost 0% survival on the low-fat/high-protein diet. However, this was independent of bacterial load or variation in PO, providing evidence for diet-mediated tolerance mechanisms rather than immune-driven resistance. Evolutionary ecology has long focussed on immune resistance when investigating how organisms avoid succumbing to infection. Tolerance of infection has recently become a much more prominent concept and is suggested to be influential in disease dynamics. This is one of the first studies to find diet-mediated tolerance.

Astronomical age constraints and extinction mechanisms of the Late Triassic Carnian crisis.

The geological record contains evidence for numerous pronounced perturbations in the global carbon cycle, some of which are associated with mass extinction. In the Carnian (Late Triassic), evidence from sedimentology and fossil pollen points to a significant change in climate, resulting in biotic turnover, during a time termed the 'Carnian Pluvial Episode' (CPE). Evidence from the marine realm suggests a causal relationship between the CPE, a global 'wet' period, and the injection of light carbon into the atmosphere. Here we provide the first evidence from a terrestrial stratigraphic succession of at least five significant negative C-isotope excursions (CIE)'s through the CPE recorded in both bulk organic carbon and compound specific plant leaf waxes. Furthermore, construction of a floating astronomical timescale for 1.09 Ma of the Late Triassic, based on the recognition of 405 ka eccentricity cycles in elemental abundance and gamma ray (GR) data, allows for the estimation of a duration for the isotope excursion(s). Source mixing calculations reveal that the observed substantial shift(s) in δ13C was most likely caused by a combination of volcanic emissions, subsequent warming and the dissociation of methane clathrates.

Oxidation of sitosterol and transport of its 7-oxygenated products from different tissues in humans and ApoE knockout mice.

The most common phytosterols in the human diet are sitosterol and campesterol, which originate exclusively from plant derived food. These phytosterols are taken up by NPC1L1 transport from the intestine into the enterocytes together with cholesterol and other xenosterols. Phytosterols are selectively pumped back from the enterocytes into the intestinal lumen and on the liver site from hepatocytes into bile by heterodimeric ABCG5/G8 transporters. Like cholesterol, both phytosterols are prone to ring and side chain oxidation. It could be shown that oxyphytosterols, found in atherosclerotic tissue, are most likely of in situ oxidation (Schött et al.; Biochem. Biophys. Res. Commun. 2014 Apr 11;446(3):805-10). However, up to now, the entire mechanism of phytosterol oxidation is not clearly understood. Here, we provide further information about the oxidation of sitosterol and the transport of its oxidation products out of tissue. Our survey includes data of 104 severe aortic stenosis patients that underwent an elective aortic valve cusp replacement. We studied their phytosterol concentrations, as well as absolute and substrate corrected oxyphytosterol levels in plasma and valve cusp tissue. In addition, we also examined phytosterol and oxyphytosterol concentrations in plasma and tissues (from brain and liver) of 10 male ApoE knockout mice. The ratio of 7-oxygenated-sitosterol-to-sitosterol exceeds the ratio for 7-oxygenated-campesterol-to-campesterol in plasma and tissue of both humans and mice. This finding indicates that sitosterol is oxidized to a higher amount than campesterol and that a selective oxidative mechanism might exist which can differentiate between certain phytosterols. Secondly, the concentrations of oxyphytosterols found in plasma and tissue support the idea that oxysitosterols are preferably transported out of individual tissues. Selective oxidation of sitosterol and preferred transport of sitosterol oxidation products out of tissue seem to be a metabolic pathway of forced sitosterol clearance from tissue compartments.

Pollen and spores as biological recorders of past ultraviolet irradiance.

Solar ultraviolet (UV) irradiance is a key driver of climatic and biotic change. Ultraviolet irradiance modulates stratospheric warming and ozone production, and influences the biosphere from ecosystem-level processes through to the largest scale patterns of diversification and extinction. Yet our understanding of ultraviolet irradiance is limited because no method has been validated to reconstruct its flux over timescales relevant to climatic or biotic processes. Here, we show that a recently developed proxy for ultraviolet irradiance based on spore and pollen chemistry can be used over long (105 years) timescales. Firstly we demonstrate that spatial variations in spore and pollen chemistry correlate with known latitudinal solar irradiance gradients. Using this relationship we provide a reconstruction of past changes in solar irradiance based on the pollen record from Lake Bosumtwi in Ghana. As anticipated, variations in the chemistry of grass pollen from the Lake Bosumtwi record show a link to multiple orbital precessional cycles (19-21 thousand years). By providing a unique, local proxy for broad spectrum solar irradiance, the chemical analysis of spores and pollen offers unprecedented opportunities to decouple solar variability, climate and vegetation change through geologic time and a new proxy with which to probe the Earth system.