Crop rotational diversity can mitigate climate-induced grain yield losses

Diversified crop rotations have been suggested to reduce grain yield losses from the adverse climatic conditions increasingly common under climate change. Nevertheless, the potential for climate change adaptation of different crop rotational diversity (CRD) remains undetermined. We quantified how climatic conditions affect small grain and maize yields under different CRDs in 32 long-term (10-63 years) field experiments across Europe and North America. Species-diverse and functionally rich rotations more than compensated yield losses from anomalous warm conditions, long and warm dry spells, as well as from anomalous wet (for small grains) or dry (for maize) conditions. Adding a single functional group or crop species to monocultures counteracted yield losses from substantial changes in climatic conditions. The benefits of a further increase in CRD are comparable with those of improved climatic conditions. For instance, the maize yield benefits of adding three crop species to monocultures under detrimental climatic conditions exceeded the average yield of monocultures by up to 553 kg/ha under non-detrimental climatic conditions. Increased crop functional richness improved yields under high temperature, irrespective of precipitation. Conversely, yield benefits peaked at between two and four crop species in the rotation, depending on climatic conditions and crop, and declined at higher species diversity. Thus, crop species diversity could be adjusted to maximize yield benefits. Diversifying rotations with functionally distinct crops is an adaptation of cropping systems to global warming and changes in precipitation.

Confidence does not mediate a relationship between owner experience and likelihood of using weight management approaches for native ponies

Native ponies are at increased risk of obesity and metabolic perturbations, such as insulin dysregulation (ID), a key risk factor for endocrinopathic laminitis. Management and feeding practices can be adapted to maintain healthy body condition and support metabolic health, but owners may inadvertently provide their ponies with inappropriate management leading to obesity and exacerbating risk of metabolic disease. Adoption of preventative weight management approaches (WMAs), including regular monitoring of body condition, providing appropriate preserved forage, promoting seasonal weight loss, and using exercise accordingly, are key in supporting native ponies' metabolic health. The factors influencing the adoption of WMAs, such as owners' experience and confidence, require exploration. The aim of the current study was to understand factors influencing owners' likelihood to undertake certain WMAs, to develop our understanding of suitable intervention targets. A total of 571 responses to an online cross-sectional questionnaire were analysed. Mediation analysis revealed that whilst long term (≥20 years) experience caring for native ponies was associated with owners increased, self-reported confidence in identifying disease and managing their native ponies, this did not translate to an increased likelihood of implementing WMAs. Conversely, respondents who managed ponies with dietary requirements related to obesity, laminitis, or equine metabolic syndrome were more likely to use WMAs related to feeding, seasonal weight management and exercise. Owner confidence was assessed and rejected as a mediator of the relationship between experience and WMA use. These results highlight the need for further work that elucidates the pathways leading owners to undertake action against obesity without the need for ponies to develop overt disease, as well as suggesting a need for long term managers of native ponies to update management practices with preventative care as the focus.

Supporting wild pollinators in agricultural landscapes through targeted legume mixtures

Insect-pollinated legumes are rich in plant-based proteins making them a vital constituent of sustainable healthy diets for people and livestock. Furthermore, they deliver or support a range of ecosystem services that underpin agricultural production and their prevalence in agricultural landscapes is likely to increase. Under typical implementation and management, the value of legumes to pollinators has, however, been questioned. Through exploring a range of legume crops, grown as monocultures and mixtures, this study aims to identify multifunctional legume cropping systems that optimise forage availability for a diversity of wild pollinators whilst delivering a wide range of agronomic and environmental benefits. This study innovatively explores legume mixtures concurrently with monocultures of the component species using replicated small-plot field trials established in two geographical locations. Observational plots assessed the richness and abundance of floral resources, and wild pollinators (i.e. bumblebees and hoverflies) throughout the peak flowering period. Densely flowering, highly profitable legumes (e.g. Trifolium incarnatum and Trifolium mixes) supported abundant and rich pollinator assemblages. The functional makeup of floral visitors was strongly influenced by flower structure and hoverflies, with their shorter proboscises, were largely constrained to legumes with shallower corolla and open weed species. Floral richness was not a key driver of pollinator assemblages; however, clear intra-specific differences were observed in flowering phenology. Combining functionally distinct legumes with respect to flower structure and phenology, will support a wider suite of pollinating insects and help stabilise the temporal availability of forage. For highly competitive legumes (e.g. Vicia faba and Vicia sativa), planting in discrete patches is recommended to reduce the risk of less competitive species failing in mixtures. Legumes can provide valuable forage for pollinators; however, they fail to meet all resource requirements. They should therefore be used in combination with agri-environmental measures targeted to promote early-season forage (e.g. hedgerows and farm woodlands), open flowers for hoverflies, saprophytic hoverfly larval resources (e.g. ditches and ponds) and nesting habitats (e.g. undisturbed field margins).

COVID-19 impacts equine welfare: Policy implications for laminitis and obesity

The COVID-19 pandemic continues to impact human health and welfare on a global level. In March 2020, stringent national restrictions were enforced in the UK to protect public health and slow the spread of the SARS-CoV-2 virus. Restrictions were likely to have resulted in collateral consequences for the health and welfare of horses and ponies, especially those at risk of obesity and laminitis and this issue warranted more detailed exploration. The current study utilised qualitative methodology to investigate the implications of COVID-19 related policies upon equine management and welfare with a focus on horses and ponies at risk of laminitis and obesity. Twenty-four interviews with five sub-groups of key equestrian welfare stakeholders in the UK were conducted between May and July of 2020 to understand the challenges facing equine welfare in the context of laminitis and obesity susceptible animals. Thematic analysis revealed lockdown-associated factors with the potential to compromise welfare of horses and ponies at risk of obesity and laminitis. These included: disparate information and guidance, difficulties enacting public health measures in yard environments, and horses having reduced exercise during the pandemic. Positive examples of clear and consistent information sharing by farriers were reported to have improved horse owner understanding of routine hoof care during lockdown. Analysis suggested that the recommendations for supporting the management-based needs of horses under reduced supervision were not clearly defined, or were not sufficiently disseminated, across the equine industry. These findings support the development of guidelines specific to the care of horses and ponies at risk of obesity and laminitis through collaborative input from veterinary and welfare experts, to reduce the negative impacts of future lockdown events in the UK.

Grain legume yields are as stable as other spring crops in long-term experiments across northern Europe

Grain legumes produce high-quality protein for food and feed, and potentially contribute to sustainable cropping systems, but they are grown on only 1.5% of European arable land. Low temporal yield stability is one of the reasons held responsible for the low proportion of grain legumes, without sufficient quantitative evidence. The objective of this study was to compare the yield stability of grain legumes with other crop species in a northern European context and accounting for the effects of scale in the analysis and the data. To avoid aggregation biases in the yield data, we used data from long-term field experiments. The experiments included grain legumes (lupin, field pea, and faba bean), other broad-leaved crops, spring, and winter cereals. Experiments were conducted in the UK, Sweden, and Germany. To compare yield stability between grain legumes and other crops, we used a scale-adjusted yield stability indicator that accounts for the yield differences between crops following Taylor's Power Law. Here, we show that temporal yield instability of grain legumes (30%) was higher than that of autumn-sown cereals (19%), but lower than that of other spring-sown broad-leaved crops (35%), and only slightly greater than spring-sown cereals (27%). With the scale-adjusted yield stability indicator, we estimated 21% higher yield stability for grain legumes compared to a standard stability measure. These novel findings demonstrate that grain legume yields are as reliable as those of other spring-sown crops in major production systems of northern Europe, which could influence the current negative perception on grain legume cultivation. Initiatives are still needed to improve the crops agronomy to provide higher and more stable yields in future.

Demographic quantification of carbon and nitrogen dynamics associated with root turnover in white clover

As well as capturing resources, roots lose resources during their lives. We quantified carbon (C) and nitrogen (N) losses associated with root turnover in white clover (Trifolium repens L.). We grew contrasting cultivars for 18 weeks in soil microcosms. Using repeated in situ observations, destructive sampling, and demographic analysis, we measured changes in C and N concentrations in dry matter of 1st- or 2nd-order (terminal) roots to derive C and N fluxes into and out of root cohorts. C and N fluxes from roots during turnover depended on cohort age and order. Ninety per cent of losses occurred from 2nd-order cohorts younger than 18 weeks. Losses were greater from roots of the larger, faster growing cultivar Alice than from the smaller lower yielding cultivar S184. C:N ratios of roots and lost material were similar within each order and between cultivars but smaller in 2nd- compared with 1st-order roots. C and N losses during root turnover could be equivalent to at least 6% of aboveground dry matter production in S184 and 12% in Alice at the field scale. C and N losses associated with root turnover will have potentially significant and previously unrecognized impacts on crop productivity, resource dynamics, and long-term soil fertility.

A framework of connections between soil and people can help improve sustainability of the food system and soil functions

Globally soil quality and food security continue to decrease indicating that agriculture and the food system need to adapt. Improving connection to the soil by knowledge exchange can help achieve this. We propose a framework of three types of connections that allow the targeting of appropriate messages to different groups of people. Direct connection by, for example, handling soil develops soil awareness for management that can be fostered by farmers joining groups on soil-focused farming such as organic farming or no-till. Indirect connections between soil, food and ecosystem services can inform food choices and environmental awareness in the public and can be promoted by, for example, gardening, education and art. Temporal connection revealed from past usage of soil helps to bring awareness to policy workers of the need for the long-term preservation of soil quality for environmental conservation. The understanding of indirect and temporal connections can be helped by comparing them with the operations of the networks of soil organisms and porosity that sustain soil fertility and soil functions.

A Comparative Nitrogen Balance and Productivity Analysis of Legume and Non-legume Supported Cropping Systems: The Potential Role of Biological Nitrogen Fixation

The potential of biological nitrogen fixation (BNF) to provide sufficient N for production has encouraged re-appraisal of cropping systems that deploy legumes. It has been argued that legume-derived N can maintain productivity as an alternative to the application of mineral fertilizer, although few studies have systematically evaluated the effect of optimizing the balance between legumes and non N-fixing crops to optimize production. In addition, the shortage, or even absence in some regions, of measurements of BNF in crops and forages severely limits the ability to design and evaluate new legume-based agroecosystems. To provide an indication of the magnitude of BNF in European agriculture, a soil-surface N-balance approach was applied to historical data from 8 experimental cropping systems that compared legume and non-legume crop types (e.g., grains, forages and intercrops) across pedoclimatic regions of Europe. Mean BNF for different legume types ranged from 32 to 115 kg ha^-1 annually. Output in terms of total biomass (grain, forage, etc.) was 30% greater in non-legumes, which used N to produce dry matter more efficiently than legumes, whereas output of N was greater from legumes. When examined over the crop sequence, the contribution of BNF to the N-balance increased to reach a maximum when the legume fraction was around 0.5 (legume crops were present in half the years). BNF was lower when the legume fraction increased to 0.6-0.8, not because of any feature of the legume, but because the cropping systems in this range were dominated by mixtures of legume and non-legume forages to which inorganic N as fertilizer was normally applied. Forage (e.g., grass and clover), as opposed to grain crops in this range maintained high outputs of biomass and N. In conclusion, BNF through grain and forage legumes has the potential to generate major benefit in terms of reducing or dispensing with the need for mineral N without loss of total output.

Trade-Offs between Economic and Environmental Impacts of Introducing Legumes into Cropping Systems

Europe's agriculture is highly specialized, dependent on external inputs and responsible for negative environmental impacts. Legume crops are grown on less than 2% of the arable land and more than 70% of the demand for protein feed supplement is imported from overseas. The integration of legumes into cropping systems has the potential to contribute to the transition to a more resource-efficient agriculture and reduce the current protein deficit. Legume crops influence the production of other crops in the rotation making it difficult to evaluate the overall agronomic effects of legumes in cropping systems. A novel assessment framework was developed and applied in five case study regions across Europe with the objective of evaluating trade-offs between economic and environmental effects of integrating legumes into cropping systems. Legumes resulted in positive and negative impacts when integrated into various cropping systems across the case studies. On average, cropping systems with legumes reduced nitrous oxide emissions by 18 and 33% and N fertilizer use by 24 and 38% in arable and forage systems, respectively, compared to systems without legumes. Nitrate leaching was similar with and without legumes in arable systems and reduced by 22% in forage systems. However, grain legumes reduced gross margins in 3 of 5 regions. Forage legumes increased gross margins in 3 of 3 regions. Among the cropping systems with legumes, systems could be identified that had both relatively high economic returns and positive environmental impacts. Thus, increasing the cultivation of legumes could lead to economic competitive cropping systems and positive environmental impacts, but achieving this aim requires the development of novel management strategies informed by the involvement of advisors and farmers.

Improving intercropping: a synthesis of research in agronomy, plant physiology and ecology

Intercropping is a farming practice involving two or more crop species, or genotypes, growing together and coexisting for a time. On the fringes of modern intensive agriculture, intercropping is important in many subsistence or low-input/resource-limited agricultural systems. By allowing genuine yield gains without increased inputs, or greater stability of yield with decreased inputs, intercropping could be one route to delivering ‘sustainable intensification’. We discuss how recent knowledge from agronomy, plant physiology and ecology can be combined with the aim of improving intercropping systems. Recent advances in agronomy and plant physiology include better understanding of the mechanisms of interactions between crop genotypes and species – for example, enhanced resource availability through niche complementarity. Ecological advances include better understanding of the context-dependency of interactions, the mechanisms behind disease and pest avoidance, the links between above- and below-ground systems, and the role of microtopographic variation in coexistence. This improved understanding can guide approaches for improving intercropping systems, including breeding crops for intercropping. Although such advances can help to improve intercropping systems, we suggest that other topics also need addressing. These include better assessment of the wider benefits of intercropping in terms of multiple ecosystem services, collaboration with agricultural engineering, and more effective interdisciplinary research.

Improving intercropping: a synthesis of research in agronomy, plant physiology and ecology

Intercropping is a farming practice involving two or more crop species, or genotypes, growing together and coexisting for a time. On the fringes of modern intensive agriculture, intercropping is important in many subsistence or low-input/resource-limited agricultural systems. By allowing genuine yield gains without increased inputs, or greater stability of yield with decreased inputs, intercropping could be one route to delivering ‘sustainable intensification’. We discuss how recent knowledge from agronomy, plant physiology and ecology can be combined with the aim of improving intercropping systems. Recent advances in agronomy and plant physiology include better understanding of the mechanisms of interactions between crop genotypes and species – for example, enhanced resource availability through niche complementarity. Ecological advances include better understanding of the context-dependency of interactions, the mechanisms behind disease and pest avoidance, the links between above- and below-ground systems, and the role of microtopographic variation in coexistence. This improved understanding can guide approaches for improving intercropping systems, including breeding crops for intercropping. Although such advances can help to improve intercropping systems, we suggest that other topics also need addressing. These include better assessment of the wider benefits of intercropping in terms of multiple ecosystem services, collaboration with agricultural engineering, and more effective interdisciplinary research.

Coherent singlet-triplet oscillations in a silicon-based double quantum dot

Silicon is more than the dominant material in the conventional microelectronics industry: it also has potential as a host material for emerging quantum information technologies. Standard fabrication techniques already allow the isolation of single electron spins in silicon transistor-like devices. Although this is also possible in other materials, silicon-based systems have the advantage of interacting more weakly with nuclear spins. Reducing such interactions is important for the control of spin quantum bits because nuclear fluctuations limit quantum phase coherence, as seen in recent experiments in GaAs-based quantum dots. Advances in reducing nuclear decoherence effects by means of complex control still result in coherence times much shorter than those seen in experiments on large ensembles of impurity-bound electrons in bulk silicon crystals. Here we report coherent control of electron spins in two coupled quantum dots in an undoped Si/SiGe heterostructure and show that this system has a nuclei-induced dephasing time of 360 nanoseconds, which is an increase by nearly two orders of magnitude over similar measurements in GaAs-based quantum dots. The degree of phase coherence observed, combined with fast, gated electrical initialization, read-out and control, should motivate future development of silicon-based quantum information processors.

T-helper type 1 responses to the BCG vaccine component PPD in mice are unaffected by the filarial nematode immunomodulatory molecule ES-62

Helminth infections are generally characterized by dominant T-helper type 2 (Th2) immune response polarization and have been shown in some cases to modulate immune responses to vaccines, i.e., the Bacillus Calmette-Guerin (BCG) vaccine. The filarial nematode secreted product ES-62 has been shown to possess immunomodulatory activities, such as the ability to inhibit pro-inflammatory/Th1 immune responses and to have therapeutic potential against diseases associated with such responses. This study aimed to investigate the ability of ES-62 to modulate the immune response to purified protein derivative (PPD), a component of the BCG vaccine designed to provoke a Th1 response. Overall, the results show that ES-62 was not capable of modulating the Th1 immune response induced by PPD, demonstrating that the helminth product, if employed therapeutically, is unlikely to interfere with the protective effects of the vaccine.

Favorable therapeutic index of the direct factor Xa inhibitors, apixaban and rivaroxaban, compared with the thrombin inhibitor dabigatran in rabbits

BACKGROUND

Apixaban is an oral, direct factor Xa (FXa) inhibitor in late-stage clinical development. This study assessed effects of the direct FXa inhibitors, apixaban and rivaroxaban, vs. the direct thrombin inhibitor, dabigatran, on venous thrombosis (VT), bleeding time (BT) and clotting times in rabbits.

METHODS

We induced the formation of non-occlusive thrombus in VT models by placing threads in the vena cava, and induced bleeding by the incision of cuticles in anesthetized rabbits. Apixaban, rivaroxaban and dabigatran were infused IV to achieve a stable plasma level. Clotting times, including the activated partial thromboplastin time (aPTT), prothrombin time (PT), modified PT (mPT) and thrombin time (TT), were measured.

RESULTS

Apixaban, rivaroxaban and dabigatran exhibited dose-related efficacy in preventing VT with EC(50) of 65, 33 and 194 nm, respectively. At doses for 80% reduction of control thrombus, apixaban, rivaroxaban and dabigatran prolonged BT by 1.13 +/- 0.02-, 1.9 +/- 0.1-* and 4.4 +/- 0.4-fold*, respectively (*P < 0.05, vs. apixaban). In the treatment model, these inhibitors equally prevented growth of a preformed thrombus. Antithrombotic doses of apixaban and rivaroxaban prolonged aPTT and PT by <3-fold with no effect on TT. Dabigatran was > or = 50-fold more potent in prolonging TT than aPTT and PT. Of the clotting assays studied, apixaban, rivaroxaban and dabigatran responded the best to mPT.

CONCLUSION

Comparable antithrombotic efficacy was observed between apixaban, rivaroxaban and dabigatran in the prevention and treatment of VT in rabbits. Apixaban and rivaroxaban exhibited lower BT compared with dabigatran at equivalent antithrombotic doses. The clinical significance of these findings remains to be determined.

Arterial antithrombotic and bleeding time effects of apixaban, a direct factor Xa inhibitor, in combination with antiplatelet therapy in rabbits

BACKGROUND

Optimal treatment of arterial thrombosis may include a combination of antiplatelet and anticoagulant drugs. We evaluated apixaban, a direct and highly selective factor Xa inhibitor, in combination with clinically relevant doses of aspirin and/or clopidogrel for prevention of arterial thrombosis in rabbits.

METHODS

Studies were conducted in rabbit models of electrically induced carotid artery thrombosis and cuticle bleeding time (BT). Apixaban 0.04 and 0.3 mg kg(-1) h(-1) or aspirin 1 mg kg(-1) h(-1) was infused intravenous (i.v.) continuously from 1 h before artery injury or cuticle bleed until the end of the experiment. Clopidogrel at 3 mg kg(-1) was dosed orally once daily for three days, with the last dose given 2 h before injury.

RESULTS

Control thrombus weight and BT averaged 8.6 +/- 0.9 mg and 181 +/- 12 s, respectively (n = 6 per group). Effective doses of apixaban that reduced thrombus weight by 20 and 50% (ED(20) and ED(50)) were 0.04 and 0.3 mg kg(-1) h(-1) i.v., respectively. Addition of aspirin to apixaban ED(20) and ED(50) significantly reduced the thrombus weight from 7.4 +/- 0.5 to 5.3 +/- 0.3 and 3.6 +/- 0.3 mg, respectively, with no significant increases in BT (190 +/- 7 s vs.181 +/- 9 and 225 +/- 11 s, respectively). Addition of aspirin and apixaban (ED(20) dose) to clopidogrel produced a further significant reduction in thrombus weight from 5.3 +/- 0.3 to 0.7 +/- 0.1 mg. This combination of clopidogrel and aspirin with apixaban (ED(20) dose) produced a significant but moderate BT increase of 2.1 times control.

CONCLUSIONS

The combination of apixaban and aspirin or apixaban, aspirin and clopidogrel can reduce formation of occlusive arterial thrombosis without excessive increases in BT in rabbits.

A Brown Dwarf Mass Donor in an Accreting Binary

A long-standing and unverified prediction of binary star evolution theory is the existence of a population of white dwarfs accreting from substellar donor stars. Such systems ought to be common, but the difficulty of finding them, combined with the challenge of detecting the donor against the light from accretion, means that no donor star to date has a measured mass below the hydrogen burning limit. We applied a technique that allowed us to reliably measure the mass of the unseen donor star in eclipsing systems. We were able to identify a brown dwarf donor star, with a mass of 0.052 +/- 0.002 solar mass. The relatively high mass of the donor star for its orbital period suggests that current evolutionary models may underestimate the radii of brown dwarfs.

Functional aspects of root architecture and mycorrhizal inoculation with respect to nutrient uptake capacity

The aim of this research was to investigate the effect of arbuscular mycorrhizal (AM) colonisation on root morphology and nitrogen uptake capacity of carob (Ceratonia siliquaL.) under high and low nutrient conditions. The experimental design was a factorial arrangement of presence/absence of mycorrhizal fungus inoculation (Glomus intraradices) and high/low nutrient status. Percent AM colonisation, nitrate and ammonium uptake capacity, and nitrogen and phosphorus contents were determined in 3-month-old seedlings. Grayscale and colour images were used to study root morphology and topology, and to assess the relation between root pigmentation and physiological activities. AM colonisation lead to a higher allocation of biomass to white and yellow parts of the root. Inorganic nitrogen uptake capacity per unit root length and nitrogen content were greatest in AM colonised plants grown under low nutrient conditions. A better match was found between plant nitrogen content and biomass accumulation, than between plant phosphorus content and biomass accumulation. It is suggested that the increase in nutrient uptake capacity of AM colonised roots is dependent both on changes in root morphology and physiological uptake potential. This study contributes to an understanding of the role of AM fungi and root morphology in plant nutrient uptake and shows that AM colonisation improves the nitrogen nutrition of plants, mainly when growing at low levels of nutrients.

Crop protection--what will shape the future picture?

The drivers which influence the types of crop protection most needed by agriculture are changing. A polarisation of approaches has resulted in the needs of organic agriculture and biotechnological agriculture, which can be identified as the current extremes of the spectrum, becoming very different. The main requirements of these two sectors are identified here and used as the basis for questioning future EU research requirements in crop protection. Factors affecting/influencing organic farming and the use of genetically modified crops are discussed in some detail.

The potential role of arbuscular mycorrhizal (AM) fungi in the bioprotection of plants against soil-borne pathogens in organic and/or other sustainable farming systems

Sustainable farming systems strive to minimise the use of synthetic pesticides and to optimise the use of alternative management strategies to control soil-borne pathogens. Arbuscular mycorrhizal (AM) fungi are ubiquitous in nature and constitute an integral component of terrestrial ecosystems, forming symbiotic associations with plant root systems of over 80% of all terrestrial plant species, including many agronomically important species. AM fungi are particularly important in organic and/or sustainable farming systems that rely on biological processes rather than agrochemicals to control plant diseases. Of particular importance is the bioprotection conferred to plants against many soil-borne pathogens such as species of Aphanomyces, Cylindrocladium, Fusarium, Macrophomina, Phytophthora, Pythium, Rhizoctonia, Sclerotinium, Verticillium and Thielaviopsis and various nematodes by AM fungal colonisation of the plant root. However, the exact mechanisms by which AM fungal colonisation confers the protective effect are not completely understood, but a greater understanding of these beneficial interactions is necessary for the exploitation of AM fungi within organic and/or sustainable farming systems. In this review, we aim to discuss the potential mechanisms by which AM fungi may contribute to bioprotection against plant soil-borne pathogens. Bioprotection within AM fungal-colonised plants is the outcome of complex interactions between plants, pathogens and AM fungi. The use of molecular tools in the study of these multifaceted interactions may aid the optimisation of the bioprotective responses and their utility within sustainable farming systems.

Modulation of calmodulin by UV and X-rays in primary human endothelial cell cultures

PURPOSE

Previous studies by the present authors and others have shown that the expression of many genes is modulated by radiation. The purpose of this study is to identify additional genes that are affected by UV and X-radiation. Identification of specific genes affected by radiation may allow the determination of pathways important in radiation responses as well as an examination of transcriptional elements that are involved in the process.

MATERIALS AND METHODS

A modified differential display approach coupled with sequencing was used to identify genes that are modulated in response to UV and ionizing radiation, and Northern blot analysis was used to confirm specific gene modulation.

RESULTS

Treatment of human primary umbilical vein endothelial cells with UV radiation resulted in the differential expression of several genes. Sequencing of the bands revealed that one of these was calmodulin. There was a 30% reduction in accumulation of calmodulin-specific mRNA 1 h post UV exposure, and a 50% decrease 3 h after treatment. X-rays also repressed accumulation of calmodulin mRNA. Radiation exposure of HeLa cells also resulted in a decrease in expression of this gene.

CONCLUSIONS

UV and ionizing radiations cause a decrease in accumulation of calmodulin transcripts in the first 1-3 h following exposure. Repression of calmodium mRNA levels may be one mechanism of stress-induced intracellular Ca2+ modulation.

Nonpeptide factor Xa inhibitors II. Antithrombotic evaluation in a rabbit model of electrically induced carotid artery thrombosis

SK549 (mol. wt. 546 Da) is a synthetic, selective inhibitor of human coagulation factor Xa (fXa) (K(i) = 0.52 nM). This study compared the antithrombotic effects of SK549 and a series of benzamidine isoxazoline fXa inhibitors with aspirin, DuP 714 (a direct thrombin inhibitor), recombinant tick anticoagulant peptide, or heparin in a rabbit model of electrically induced carotid arterial thrombosis. Compounds were infused i.v. continuously from 60 min before electrical stimulation to the end of the experiment. Values of ED(50) (dose that increases the carotid blood flow to 50% of the control) were 0.12 micromol/kg/h for SK549, 0.56 micromol/kg/h for aspirin, 0.14 micromol/kg/h for DuP 714, 0.06 micromol/kg/h for recombinant tick anticoagulant peptide, and >100 U/kg/h for heparin. The EC(50) (plasma concentration that increased blood flow to 50% of the control) for SK549 was 97 nM. Unlike aspirin and heparin, SK549 was efficacious and, at 1.5 micromol/kg/h i.v. (n = 9), maintained carotid blood flow at 87 +/- 6% of control level for greater than 90 min. Unlike heparin, SK549 inhibited ex vivo fXa activity but not ex vivo thrombin activity. There was a highly significant correlation between K(i) (fXa) and ED(50) of a series of fXa inhibitors (r = 0. 85, P <.001). Therefore, these results suggest that SK549 is a novel, potent, and effective antithrombotic agent in a rabbit model of arterial thrombosis. It is likely that SK549 exerts its antithrombotic effect through selective inhibition of fXa. Furthermore, SK549 may be clinically useful for the prevention of arterial thrombosis.

Nonpeptide factor Xa inhibitors: I. Studies with SF303 and SK549, a new class of potent antithrombotics

A series of benzamidine isoxazoline derivatives was evaluated for their inhibitory potency against purified human factor Xa (fXa) and in a rabbit model of arteriovenous shunt thrombosis for their antithrombotic activities, expressed as K(I) and IC(50), respectively. A highly significant correlation was found between K(I) and IC(50) (r = 0.93, P <.0001). The antithrombotic effects of SF303 [mol. wt. 536; K(I): fXa, 6.3 nM; thrombin, 3,100 nM; trypsin, 110 nM; tissue plasminogen activator >20,000 nM; plasmin, 2,500 nM] and SK549 [mol. wt. 546; K(I): fXa, 0.52 nM; thrombin, 400 nM; trypsin, 45 nM; tissue plasminogen activator >33,000 nM; plasmin, 890 nM] were compared with recombinant tick anticoagulant peptide [K(I)(fXa) = 0.5 nM], DX-9065a [K(I)(fXa) = 30 nM], and heparin or low molecular weight heparin (dalteparin) in a rabbit model of arteriovenous shunt thrombosis. ID(50) values for preventing arteriovenous shunt-induced thrombosis were 0.6 micromol/kg/h for SF303, 0.035 micromol/kg/h for SK549, 0.01 micromol/kg/h for recombinant tick anticoagulant peptide, 0.4 micromol/kg/h for DX-9065a, 21 U/kg/h for heparin, and 23 U/kg/h for low molecular weight heparin. SK549 produced a concentration-dependent antithrombotic effect with an IC(50) of 0.062 microM. To evaluate its potential oral efficacy, SK549 was given intraduodenally at a dose of 5 mg/kg; it produced a peak antithrombotic effect of 59 +/- 4% with a duration of action greater than 6.7 h. Therefore, our study suggests that SF303, SK549, and their analogs represent a new class of synthetic fXa inhibitors that may be clinically useful as antithrombotic agents.

Antithrombotic actions of selective inhibitors of blood coagulation factor Xa in rat models of thrombosis

The antithrombotic actions of selective factor Xa (FXa) inhibitors, recombinant tick anticoagulant peptide (rTAP) and DX-9065a, were evaluated in experimental thrombosis models in anesthetized rats. In the first model, thrombosis was induced by exposing flowing blood to a silk thread anchored in an arteriovenous (AV) shunt. rTAP, DX-9065a and heparin, given as an iv infusion 1 hr before blood was circulated in the AV shunt, had ID50s of 0.007, 0.6 mumol/kg/hr and 16 U/kg/hr, respectively. In the model of venous thrombosis which was induced by hypotonic saline (0.225%) followed by 15-min stasis of abdominal vena cava, rTAP and heparin had ID50s of 0.007 mumol/kg/hr and 3.5 U/kg/hr, respectively. In both models, full inhibition of thrombus formation was achieved with FXa inhibition at doses which only modestly increased ex vivo plasma clotting time APTT (1.26 to 1.82 over the baseline). By contrast, the maximum antithrombotic effect of heparin was associated with high and significant APTT prolongation (> 5 fold over the baseline). Therefore, our study suggests that FXa inhibitors are effective agents in preventing thrombosis in both rat thrombosis models and may have therapeutic antithrombotic potential.

Effects of 17beta-estradiol on cytokine-induced endothelial cell adhesion molecule expression

One of the earliest events in atherosclerosis is interaction of circulating mononuclear leukocytes and the endothelium. Endothelial cell (EC) activation by cytokines results in expression of adhesion molecules and production of chemotactic factors, augmenting leukocyte adhesion and recruitment, respectively. The incidence of atherosclerosis in premenopausal women is significantly less than that observed in age-matched males with similar risk profiles. Because estrogen has gene regulatory effects, we investigated whether 17beta-estradiol (E2) can inhibit cytokine-mediated EC adhesion molecule transcriptional activation. Cultured human umbilical vein EC (estrogen receptor-positive) were propagated in gonadal hormone-free medium and were E2-pretreated for 48 h before IL-1 activation. Detected by FACS analysis, E2 strongly (60-80%) inhibited IL-1-mediated membrane E-selectin and vascular cell adhesion molecule-1 induction, and intercellular adhesion molecule-1 hyperinduction. 17alpha-estradiol (an inactive E2 stereoisomer) had no effect. This inhibition correlated with similar reductions in steady state-induced E-selectin mRNA levels, and was abrogated by the E2 antagonist ICI 164,384, demonstrating a specific, estrogen receptor-mediated effect. Nuclear run-offs confirmed suppression at the transcriptional level. The implications of these results for the cardiovascular protective role of estrogen are discussed.

Nonpeptide angiotensin II receptor antagonists: in vivo inhibition of [125I-Sar1,Ile8]angiotensin II binding by losartan, EXP597 and L-159,282 in rats

Effects of losartan, L-159,282 and EXP597 on the in vivo binding of [125I-Sar1,Ile8]angiotensin II to kidney cortex and adrenal were examined in rats. Losartan, an AT1 receptor antagonist, completely blocked [125I-Sar1,Ile8]angiotensin II binding to the kidney cortex which contains only AT1 binding sites with an ID50 of 0.06 mg/kg. Losartan partially inhibited [125I-Sar1,Ile8]angiotensin II binding to the adrenal which contains equal amounts of AT1 and AT2 binding sites. Blockade by the AT1 receptor antagonist L-159,282 sufficiently increased the plasma levels of angiotensin II to block the AT2 receptor. EXP597 inhibited [125I-Sar1,Ile8]angiotensin II binding to the kidney cortex and adrenal almost totally with ID50s of 0.05 and 0.06 mg/kg, respectively. This result suggests that EXP597 exhibits almost equal binding affinity for AT1 and AT2 binding sites in vivo in rats.

Pharmacology of XR510, a potent orally active nonpeptide angiotensin II AT1 receptor antagonist with high affinity for the AT2 receptor subtype

The angiotensin II (Ang II) type 1 receptor (AT1) mediates all known physiological effects of ANG II, whereas functions of the type 2 (AT2) receptor are not clear. Should undesirable AT2 effects be identified, it may be advantageous to combine antagonism of AT1 and AT2 receptors. XR510 was shown to inhibit the specific binding of [125I]Sar1,Ile8-Ang II for AT1 and AT2 subtype binding sites in rat adrenal membranes with IC50 of 0.26 and 0.28 nM, respectively, and in human tissues with subnanomolar binding affinity. In isolated rabbit aorta, XR510 exerted insurmountable Ang II antagonism with a Kb value of 4 nM. In conscious renal hypertensive rats, XR510 decreased blood pressure (BP) with intravenous (i.v.) and oral (p.o.) ED30 of 0.08 and 0.27 mg/kg, respectively. In spontaneously hypertensive rats (SHR), repeated daily oral dosing of XR510, losartan, and enalapril at 30 mg/kg/day decreased BP similarly. In conscious furosemide-treated dogs, XR510, given either intravenously or orally, decreased BP. These results suggest that XR510 is an orally active and selective Ang II receptor antagonist with equal binding affinities for AT1 and AT2 receptor binding sites.

Contact-dependent endothelial class II HLA gene activation induced by NK cells is mediated by IFN-gamma-dependent and -independent mechanisms

NK lymphocytes adhere avidly to allogeneic endothelial cells (ECs) and induce their membrane expression of MHC class II Ags in vitro. Endothelial class II expression augments EC-driven CD4+ T cell proliferation in vitro, and may amplify T cell recruitment and clonal expansion in vivo. Using an ex vivo lymphocyte-skin organ coculture model, NK cells could be found lining and inducing class II HLA on microvessel endothelium. Using neutralizing anti-IFN-gamma and anti-IFN-gamma receptor Abs, a spectrum of IFN-gamma dependence was observed for NK-mediated EC HLA-DR induction at the membrane and transcriptional levels, from negligible to moderate. Trans-well experiments displayed that direct NK-EC contact is required, and Ab inhibition studies indicated that the beta 2 integrin-ICAM-1 pathway(s) is critical in the generation of these responses. The use of HLA-DR alpha promoter constructs in transient transfection assays demonstrated that the highly conserved X and S transcription boxes are required in both IFN-gamma- and NK-mediated gene activation. As expected, because of the receptor species specificity, human IFN-gamma did not induce HLA-DR alpha promoter constructs transfected in Chinese hamster ovary cells, whereas NK cells did. Taken together, these results indicate that human allogeneic NK lymphocytes induce EC class II HLA gene activation and membrane expression in an adhesion-dependent, IFN-gamma-independent fashion and suggest that, in concert with any IFN-gamma-dependent component, this induction could represent an efficient mode of endothelial activation and immune amplification in vivo.

IL-8 and angiogenesis: evidence that human endothelial cells lack receptors and do not respond to IL-8 in vitro

It has been established that IL-8 triggers angiogenesis in vivo, but this effect may be mediated either by IL-8-recruited leukocytes or by direct actions of IL-8 upon endothelial cells (EC). We have approached this question by examining interactions of recombinant human IL-8 with cultured large vessel and microvascular human EC. We are unable to detect specific IL-8 binding to cultured human umbilical vein endothelial cells (HUVEC) or leukocyte-like IL-8 receptor mRNA expression by either cultured HUVEC or human dermal microvascular endothelial cells (DMEC). We find no alteration of cytoplasmic calcium concentration ([Ca2+]i) in either cell type in response to IL-8 treatment. Finally, we find no IL-8-induced change in EC proliferative rates in the presence or absence of endothelial cell growth factor. Our data favour an indirect action for IL-8 as an angiogenic factor.

Contact-dependent endothelial class II HLA gene activation induced by NK cells is mediated by IFN-gamma-dependent and -independent mechanisms

NK lymphocytes adhere avidly to allogeneic endothelial cells (ECs) and induce their membrane expression of MHC class II Ags in vitro. Endothelial class II expression augments EC-driven CD4+ T cell proliferation in vitro, and may amplify T cell recruitment and clonal expansion in vivo. Using an ex vivo lymphocyte-skin organ coculture model, NK cells could be found lining and inducing class II HLA on microvessel endothelium. Using neutralizing anti-IFN-gamma and anti-IFN-gamma receptor Abs, a spectrum of IFN-gamma dependence was observed for NK-mediated EC HLA-DR induction at the membrane and transcriptional levels, from negligible to moderate. Trans-well experiments displayed that direct NK-EC contact is required, and Ab inhibition studies indicated that the beta 2 integrin-ICAM-1 pathway(s) is critical in the generation of these responses. The use of HLA-DR alpha promoter constructs in transient transfection assays demonstrated that the highly conserved X and S transcription boxes are required in both IFN-gamma- and NK-mediated gene activation. As expected, because of the receptor species specificity, human IFN-gamma did not induce HLA-DR alpha promoter constructs transfected in Chinese hamster ovary cells, whereas NK cells did. Taken together, these results indicate that human allogeneic NK lymphocytes induce EC class II HLA gene activation and membrane expression in an adhesion-dependent, IFN-gamma-independent fashion and suggest that, in concert with any IFN-gamma-dependent component, this induction could represent an efficient mode of endothelial activation and immune amplification in vivo.

Regulation of nitric oxide synthesis by proinflammatory cytokines in human umbilical vein endothelial cells. Elevations in tetrahydrobiopterin levels enhance endothelial nitric oxide synthase specific activity

We have examined cytokine regulation of nitric oxide synthase (NOS) in human umbilical vein endothelial cells (HUVEC). 24-h treatment with IFN-gamma (200 U/ml) plus TNF (200 U/ml) or IL-1 beta (5 U/ml) increased NOS activity in HUVEC lysates, measured as conversion of [14C]L-arginine to [14C]L-citrulline. Essentially, all NOS activity in these cells was calcium dependent and membrane associated. Histamine-induced nitric oxide release, measured by chemiluminescence, was greater in cytokine-treated cells than in control cells. Paradoxically, steady-state mRNA levels of endothelial NOS fell by 94 +/- 2.0% after cytokine treatment. Supplementation of HUVEC lysates with exogenous tetrahydrobiopterin (3 microM) greatly increased total NOS activity, and under these assay conditions, cytokine treatment decreased maximal NOS activity. IFN-gamma plus TNF or IL-1 beta increased endogenous tetrahydrobiopterin levels and GTP cyclohydrolase I activity, the rate-limiting enzyme of tetrahydrobiopterin synthesis. Intracellular tetrahydrobiopterin levels were higher in freshly isolated HUVEC than in cultured cells, but were still limiting. We conclude that inflammatory cytokines increase NOS activity in cultured human endothelial cells by increasing tetrahydrobiopterin levels in the face of falling total enzyme; similar regulation appears possible in vivo.

Structure-activity relationships of dihydrofolate reductase inhibitors

Structure-activity relationships of antibacterial dihydrofolate reductase inhibitors are reviewed. A short introduction is followed by a more detailed review of developments since 1980. The design of site directed inhibitors based on data from X-ray crystallographic, NMR spectroscopy and molecular graphic studies is discussed. The development of quantitative structure-activity relations is surveyed from a historical point of view and these are contrasted with more recent alternative approaches. Conclusions are reached regarding possible future developments.

Safety behavior among Iowa junior high and high school students

The goal of this study was to determine demographic factors associated with reported safety behavior by studying 2250 Iowa junior high and high school students via a self-administered questionnaire. Students attending rural schools used front seat belts and helmets less frequently than urban students. Seat belt and helmet use and swim safety decreased dramatically with age. Occurrences of driving or riding while drunk or high increased with age. Boys were less likely than girls to wear back seat belts and moped helmets and to check water depth before diving. Possession of a driver's license was not independently associated with any of the safety behaviors.

Actin is a major structural and functional element of the egg cortex of giant silkmoths during oogenesis

The cortex and subcortical regions of the developing follicles and eggs of silkmoths are rich in cytoskeletal elements, particularly actin. In situ analysis using [3H]-polyuridylic acid and biotinylated oligo d(T) reveals a pattern of changes in poly(A)+ RNA distribution during oogenesis. The developing pattern of distribution of actin filaments in the ooplasm closely resembles that of poly(A)+ RNA. RNA polymerase II is also associated with the cortical cytoskeleton. Destruction of the actin filaments in the developing oocytes by cytochalasin D randomizes the distribution of mRNA and causes the displacement of RNA polymerase II from the cortex. Rhodamine-conjugated phalloidin and a monoclonal antibody against cytoskeletal actin were used in combination with laser scanning confocal microscopy to examine the details of actin distribution in the oocytes. RNA polymerase II was located in developing oocytes using both anti-Drosophila RNA polymerase II antibody and fluorescein-conjugated amanitin.

Infra-additivity of combined treatments with selective D1 and D2 receptor antagonists for inhibiting sucrose reinforcement

Selective antagonists of either the D1 receptor (SCH 23390) or of the D2 receptor (raclopride) produce a dose-related inhibition of sucrose sham feeding in the rat. We investigated the effect of combined treatments with these antagonists on sucrose sham feeding and observed infra-additivity of inhibition across a range of doses. On the basis of this observed occlusive relationship, we conclude that the relevant D1 and D2 receptor mechanisms mediating sweet taste reward do not function independently.

Similar effect of raclopride and reduced sucrose concentration on the microstructure of sucrose sham feeding

Raclopride, a dopamine D2 antagonist, decreases the intake of sucrose solutions during sham feeding tests and of water during sham drinking tests in rats. To determine whether the reduced intake of sucrose by raclopride was due to a decrease in the positive reinforcing effect of sucrose or to an impairment in licking movements, we compared the rate, efficiency and pattern of licking after two procedures each of which decreased sucrose sham intake about 50%; these were (a) pretreatment with raclopride (ID50), and (b) dilution of the sucrose concentration sham fed from 10 to 5%. Microstructural analysis failed to reveal significant differences in the rate, efficiency (licks/ml) or patterns of licking between these two procedures. When raclopride inhibited the sham drinking of water, the rate and efficiency of licking were normal, but the patterns of licking were qualitatively different from those observed when raclopride inhibited the sham feeding of sucrose. We conclude that raclopride decreases intake of 10% sucrose during sham feeding and intake of water during sham drinking by decreasing the positive reinforcing potency of the orosensory effect(s) of the two liquids on licking rather than by decreasing the ability to lick. These results provide strong evidence that interaction of dopamine at D2 receptors is necessary for the normal sensory and/or hedonic processing of the orosensory stimuli produced by sucrose during sham feeding and by water during sham drinking.

Maternal messenger RNA distribution in silkmoth eggs. I. Clone Ec4B is associated with the cortical cytoskeleton

We have constructed a cDNA library from mature egg RNA of the silkmoth, Hyalophora cecropia. Differential screening of the library using cDNA made against mRNAs from the yolky cytoplasm (soluble fraction) and the cortical cytoplasm (cytoskeletal-associated or cortical fraction) resulted in several clones that hybridized to a higher degree to the cDNA from the cytoskeletal-associated fraction. We selected and analyzed the clone giving the strongest signal (designated Ec4b) for its distribution in situ and found that it bound to mRNAs in the nurse cell cytoplasm, in the cortex and in the follicle cells of oocytes. Hybridization of the insert from Ec4b to both detergent-soluble and -insoluble (cortical) RNA on dot blots further supported the observation that the mRNA corresponding to Ec4b was enriched in this cytoskeletal fraction. The mRNA for Ec4b was approximately 500 bases long and the gene seems to be a member of a large multigene family in the H. cecropia genome. Analyses of the nucleotide and amino acid sequences reveal similarity to lepidopteran chorion genes and a lesser but convincing similarity to vertebrate cytokeratins. The filter and in situ hybridization data point to the association of specific messenger RNAs with the cortical cytoskeleton of silkmoth oocytes. Aspects of the structure of the protein encoded by this mRNA suggest that it is a structural component necessary for formation of the cellular blastoderm of the embryo. The association of this maternal mRNA with the cortical cytoskeleton presents the interesting possibility that mRNA bound to the cytoskeleton may be capable of participating in the synthesis of new cytoskeleton or related structures during blastoderm formation.(ABSTRACT TRUNCATED AT 250 WORDS)

Natural infection with an attaching and effacing Escherichia coli in the small and large intestines of a calf with diarrhoea

Attaching and effacing Escherichia coli were identified in the small and large intestine of a calf with naturally occurring diarrhoea. The organisms were associated with intestinal lesions and were identified by immunoperoxidase staining and transmission and scanning electron microscopy, but they did not produce Shiga-like toxin (verotoxin).