ATP Hydrolysis Activity and Polymerization State of Ribulose-1,5-Bisphosphate Carboxylase Oxygenase Activase (Do the Effects of Mg2+, K+, and Activase Concentrations Indicate a Functional Similarity to Actin?)

The ATPase activity and fluoresence of ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco) activase were determined over a range of MgCl2, KCl, and activase concentrations. Both salts promoted ADP release from ATP and intrinsic fluorescence enhancement by adenosine 5[prime]-[[gamma]-thio] triphosphate, but Mg2+ was about 10 times more effective than K+. ATPase and fluorescence enhancement both increased from zero to saturation within the same Mg2+ and K+ concentration ranges. At saturating concentrations (5 mM Mg2+ and 22 mM K+), the specific activity of ATPase (turnover time, about 1 s) and specific intrinsic fluorescence enhancement were maximal and unaffected by activase concentration above 1 [mu]M activase; below 1 [mu]M activase, both decreased sharply. These responses are remarkably similar to the behavior of actin. Intrinsic fluorescence enhancement of Rubisco activase reflects the extent of polymerization, showing that the smaller oligomer or monomer present in low-salt and activase concentrations is inactive in ATP hydrolysis. However, quenching of 1-anilinonapthaline-8-sulfonate fluorescence revealed that ADP and adenosine 5[prime]-[[gamma]-thio] triphosphate bind equally well to activase at low- and high-salt concentrations. This is consistent with an actin-like mechanism requiring a dynamic equilibrium between monomer and oligomers for ATP hydrolysis. The specific activation rate of substrate-bound decarbamylated Rubisco decreased at activase concentrations below 1 [mu]M. This suggests that a large oligomeric form of activase, rather than a monomer, interacts with Rubisco when performing the release of bound ribulose-1,5-bisphosphate from the inactive enzyme.     

Does Interdisciplinary Research Lead to Higher Citation Impact? The Different Effect of Proximal and Distal Interdisciplinarity

This article analyses the effect of degree of interdisciplinarity on the citation impact of individual publications for four different scientific fields. We operationalise interdisciplinarity as disciplinary diversity in the references of a publication, and rather than treating interdisciplinarity as a monodimensional property, we investigate the separate effect of different aspects of diversity on citation impact: i.e. variety, balance and disparity. We use a Tobit regression model to examine the effect of these properties of interdisciplinarity on citation impact, controlling for a range of variables associated with the characteristics of publications. We find that variety has a positive effect on impact, whereas balance and disparity have a negative effect. Our results further qualify the separate effect of these three aspects of diversity by pointing out that all three dimensions of interdisciplinarity display a curvilinear (inverted U-shape) relationship with citation impact. These findings can be interpreted in two different ways. On the one hand, they are consistent with the view that, while combining multiple fields has a positive effect in knowledge creation, successful research is better achieved through research efforts that draw on a relatively proximal range of fields, as distal interdisciplinary research might be too risky and more likely to fail. On the other hand, these results may be interpreted as suggesting that scientific audiences are reluctant to cite heterodox papers that mix highly disparate bodies of knowledge—thus giving less credit to publications that are too groundbreaking or challenging.     

Photochemical Efficiency of PSⅡand Membrane Lipid Peroxidation in Leaves of indica and japonica Rice (Oryza sativa) Under Chilling Temperature and Strong Light Stress Conditions

Relationships between fluorescence parameters and membrane lipid peroxidation in leaves of indica and japonica rice (Oryza sativa L.) during later growth stage were studied under chilling temperature and strong light stress conditions. Results showed that D1 protein contents of PSⅡ in photosynthetic app aratus dropped, the generation of antheraxanthin (A) and zeaxanthin (Z)of xanthophyll cycle were inhibited partly, PSⅡ photochemical efficiency （Fv/Fm）and non photochemical quenching (qN) were also decreased obviously. In addition, endogenous active oxygen scavenger—superoxide dismutase (SOD) reduced, superoxide anion radical (O[SX(B-*3)-[]·[SX]]2) and malondialdehyde (MDA) accumulated, as a result, photooxidation of leaves occurred under chilling temperature and strong light stress conditions. Obvious differences in the changes of the above mentioned physiological parameters between indica and japonica rice were observed. Experiments in leaves treated with inhibitors under chilling temperature and strong light conditions showed that indica rice was more sensitive to chilling temperature with strong light and subjected to photooxidation more than japonica rice. Notable positive correlation between D1 protein contents and Fv/Fm or (A+Z)/(A+Z+V), and a marked negative correlation between Fv/Fm and MDA contents were obtained by regression analysis in indica and japonica rice during chilling temperature and strong light conditions. According to the facts mentioned above, it was inferred that PSⅡ photochemical efficiency（Fv/Fm） was the key index to forecast for the prediction of photooxidation under stress circumstances and the physiological basis were the synthetic capacity of D1 protein and the protection of xanthophyll cycle.     

Photochemical Efficiency of PSⅡ and Characteristics of Photosynthetic CO2 Exchange in Indica and Japonica Subspecies of Rice and Their Reciprocal Cross F1 Hybrids Under Photoinhibitory Conditions

To elucidate photoinhibitory characteristics and their genetic background in rice (Oryza sativa L. ), PS Ⅱ electron transport activities, D1 protein contents, chlorophyll a fluorecence parameters, net photosynthetic rates (PN), photorespiratory rates (PR) and RuBPCase/Oase activities were measured, and kinetic analysis of RuBPCase was carried out in indica and japonica subspecies of rice and their reciprocal cross Fl hybrids after photoinhibitory treatment in 21% O2 and CO2-free gases under a PFD of 1 000/anol photons'm-2 · s-l for 3 h. The results are as follows: Japonica rice, keeping less net degradation of D1 protein and maintaining higher PS Ⅱ electron transport activities and photo chemical efficiency of PS Ⅱ (FV/Fm), was more tolerant to photo inhibition as compared with indica rice. However, the D1 protein contents, PS Ⅱ electron transport activities and Fv/Fm in their reciprocal cross F1 hybrids, though lying between the values of their parents, were closer to those in their maternal lines rather to their paternal lines. Characteristics of photosynthetic CO2 exchange were further observed. The Pa was relatively stable, yet the PN decreased obviously and, as a results, the PR/PN increased in all genotypes. There were more decrease in PN and more increase in PR/PN in photoinhibition-sensitive indica than in the photoinhibition-tolerant japonica. However, the PR/PN in the reciprocal cross Fl hybrids, though lying between the values of their parents, was closer to that in their maternal lines than to paternal lines. No obvious changes were observed in the activities of RuBPCase/Oase, Km (CO2) and Vmax (CO2) of RuBPCase in indica and japonica rice and their reciprocal cross F1 hybrids before and after photoinhibitory treatment. Furthermore, markedly positive correlation between D1 protein contents and Fv/Fm(r = -0.950 1), and negative correlation between D1 protein contents and PR/PN(r = 0.976 8) were demons trated. These results infer that the D1 protein encoded by the plastid gene from maternal line was the molecular basis of photoinhibitory characteristics and their physiological inheritance.     

Photosynthetic Activity in Seed Wings of Dipterocarpaceae in a Masting Year: Does Wing Photosynthesis Contribute to Reproduction?

The photosynthetic rate of seed wings developed from sepals was compared with the leaf photosynthetic rate in nine dipterocarp tree species (Dipterocarpus pachyphyllus, Dryobalanops aromatica, Dryobalanops lanceolata, Shorea beccariana, Shorea ferruginea, Shorea macroptera ssp. bailonii, Shorea macroptera ssp. macropterifolia, Shorea pilosa, and Vatica spp.). The wings showed positive photosynthetic activity, but at much lower rates than in the leaves. The daily CO₂ uptake of wings showed slightly negative values in diurnal gas exchange measurements, even in D. aromatica that showed the highest photosynthetic capacity of all nine species. This low photosynthetic rate in the wings may be the result of low nitrogen and chlorophyll contents in the wing compared with leaves. However, the wings had a higher C/N ratio than leaves, and were thicker. Hence, dipterocarp wings have physical strength and defence against herbivores as higher priorities than photosynthetic activity.     

Influence of a Thiophosphate Linkage on the Duplex Stability - Does Sp Configuration Always Lead to Higher Stability Than Rp?

Abstract

ABSTRACT: In order to design an oligodeoxynucleoside phosphorothioate as an antisense molecule, it is important to establish the structure of the S-oligo with a strong affinity to the target RNA. In these molecules, internucleotide thiophosphate linkages produce diastereomers, the number of which increases in proportion to 2ⁿ (n: number of thiophosphate). To estimate the effect of this linkage on the duplex stability by UV melting curves, oligodeoxynucleotides having a single thiophosphate (referred to Soligo), dGCNsN'CG (s: thiophosphate, N, N′ = A or T), were prepared and their diastereomers isolated by HPLC. As demonstrated previously, the melting temperatures (Tm) for the Sp isomers were higher than those of the Rp when DNA was a target. On the other hand, it was found that for RNA as a target, the Rp isomers of dGCTsTCG and dGCAsTCG had higher stability than the Sp, and that the difference in the Tm values between the diastereomers was smaller than when DNA was a target. With dGCsTsACG, which has two thiophosphates, it was also found that the Tm values decreased with an increase in the number of thiophosphate linkages, and that the difference in Tm between the diastereomers was smaller when RNA was a target. Consequently, in practical clinical applications where RNA is a target, the influence of thiophosphate chirality on the duplex structure is almost negligible and Rp/Sp separation of an S-oligo may be of no major concern.     

Minimization of the Photon Energy Absorbed by ‘Closed’ Reaction Centers of Photosystem 2 as a Photoprotective Strategy in Higher Plants

Photoinactivation of photosystem 2 (PS2) results from absorption of so-called excessive photon energy. Chlorophyll a fluorescence can be applied to quantitatively estimate the portion of excessive photons by means of the parameter E = (F – F₀)/F_m, which reflects the share of the absorbed photon energy that reaches the reaction centers (RCs) of PS2 complexes with Q_A in the reduced state (closed RCs). Data obtained for cotton (Gossypium hirsutum), bean (Phaseolus vulgaris), and arabidopsis (Arabidopsis thaliana) suggest a linear relationship between the total amount of the photon energy absorbed in excess (excessive irradiation) and the decline in PS2 activity, though the slope may differ depending on the species. This relationship was sensitive not only to the leaf temperature but also to treatment with methyl viologen. Such observations imply that the intensity of the oxidative stress as well as the plant's ability to detoxify active oxygen species may interact to determine the damaging potential of the excessive photons absorbed by PS2 antennae. Energy partitioning in PS2 complexes was adjusted during adaptation to irradiation and in response to a decrease in leaf temperature to minimize the excitation energy that is trapped by closed PS2 RCs. The same amount of the excessive photons absorbed by PS2 antennae led to a greater decrease in PS2 activity at warmer temperatures, however, the delay in the development of non-photochemical and photochemical energy quenching under lower temperature resulted in faster accumulation of excessive photons during induction. Irradiance response curves of EF suggest that, at high irradiance (above 700 mol m^–2 s^–1), steady-state levels of this parameter tend to be similar regardless of the leaf temperature.     

Does Long-Term Elevation of CO2 Concentration Increase Photosynthesis in Forest Floor Vegetation? (Indiana Strawberry in a Maryland Forest)

As the partial pressure of CO2 (pCO2) in the atmosphere rises, photorespiratory loss of carbon in C3 photosynthesis will diminish and the net efficiency of light-limited photosynthetic carbon uptake should rise. We tested this expectation for Indiana strawberry (Duchesnea indica) growing on a Maryland forest floor. Open-top chambers were used to elevate the pCO2 of a forest floor habitat to 67 Pa and were paired with control chambers providing an ambient pCO2 of 38 Pa. After 3.5 years, D. indica leaves grown and measured in the elevated pCO2 showed a significantly greater maximum quantum efficiency of net photosynthesis (by 22%) and a lower light compensation point (by 42%) than leaves grown and measured in the control chambers. The quantum efficiency to minimize photorespiration, measured in 1% O2, was the same for controls and plants grown at elevated pCO2. This showed that the maximum efficiency of light-energy transduction into assimilated carbon was not altered by acclimation and that the increase in light-limited photosynthesis at elevated pCO2 was simply a function of the decrease in photorespiration. Acclimation did decrease the ribulose-1,5-bisphosphate carboxylase/oxygenase and light-harvesting chlorophyll protein content of the leaf by more than 30%. These changes were associated with a decreased capacity for light-saturated, but not light-limited, photosynthesis. Even so, leaves of D. indica grown and measured at elevated pCO2 showed greater light-saturated photosynthetic rates than leaves grown and measured at the current atmospheric pCO2. In situ measurements under natural forest floor lighting showed large increases in leaf photosynthesis at elevated pCO2, relative to controls, in both summer and fall. The increase in efficiency of light-limited photosynthesis with elevated pCO2 allowed positive net photosynthetic carbon uptake on days and at locations on the forest floor that light fluxes were insufficient for positive net photosynthesis in the current atmospheric pCO2.     

Does soil CO2 efflux acclimatize to elevated temperature and CO2 during long-term treatment of Douglas-fir seedlings?

We investigated the effects of elevated soil temperature and atmospheric CO2 on soil CO2 efflux (SCE) during the third and fourth years of study. We hypothesized that elevated temperature would stimulate SCE, and elevated CO2 would also stimulate SCE with the stimulation being greater at higher temperatures. The study was conducted in sun-lit controlled-environment chambers using Douglas-fir (Pseudotsuga menziesii) seedlings grown in reconstructed litter-soil systems. We used a randomized design with two soil temperature and two atmospheric CO2 treatments. The SCE was measured every 4 wk for 18 months. Neither elevated temperature nor CO2 stimulated SCE. Elevated CO2 increased the temperature sensitivity of SCE. During the winter, the relationship between SCE and soil moisture was negative but it was positive during the summer. The seasonal patterns in SCE were associated with seasonal changes in photosynthesis and above-ground plant growth. SCE acclimatized in the high-temperature treatment, probably because of a loss of labile soil carbon. Elevated CO2 treatment increased the temperature sensitivity of SCE, probably through an increase in substrate availability.     

Does Leaf Position within a Canopy Affect Acclimation of Photosynthesis to Elevated CO2? : Analysis of a Wheat Crop under Free-Air CO2 Enrichment

Previous studies of photosynthetic acclimation to elevated CO₂ have focused on the most recently expanded, sunlit leaves in the canopy. We examined acclimation in a vertical profile of leaves through a canopy of wheat (Triticum aestivum L.). The crop was grown at an elevated CO₂ partial pressure of 55 Pa within a replicated field experiment using free-air CO₂ enrichment. Gas exchange was used to estimate in vivo carboxylation capacity and the maximum rate of ribulose-1,5-bisphosphate-limited photosynthesis. Net photosynthetic CO₂ uptake was measured for leaves in situ within the canopy. Leaf contents of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), light-harvesting-complex (LHC) proteins, and total N were determined. Elevated CO₂ did not affect carboxylation capacity in the most recently expanded leaves but led to a decrease in lower, shaded leaves during grain development. Despite this acclimation, in situ photosynthetic CO₂ uptake remained higher under elevated CO₂. Acclimation at elevated CO₂ was accompanied by decreases in both Rubisco and total leaf N contents and an increase in LHC content. Elevated CO₂ led to a larger increase in LHC/Rubisco in lower canopy leaves than in the uppermost leaf. Acclimation of leaf photosynthesis to elevated CO₂ therefore depended on both vertical position within the canopy and the developmental stage.     

Does down‐regulation of photosynthetic capacity by elevated CO2 depend on N supply in Dactylis glomerata?

Dactylis glomerata was grown hydroponically in a controlled environment at ambient (360 μl l⁻¹) or elevated (680 μl l⁻¹) CO₂ and four concentrations of nitrogen (0.15, 0.6, 1.5 and 6.0 m M NO₃⁻), to test the hypothesis that reduction of photosynthetic capacity at elevated [CO₂] is dependent on N availability and mediated by a build-up of non-structural carbohydrates. Photosynthetic capacity of the youngest fully expanded leaf (leaf 5, 2 days after full expansion) was reduced in CO₂-enriched plants at low, but not high N supply and so the stimulation of net photosynthesis by CO₂ enhancement was less at low than at high N supply. CO₂ enrichment resulted in a decrease in ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) content on a leaf area basis at 0.6 and 1.5 m M NO₃⁻, but not at 0.15 and 6.0 m M NO₃⁻, and had no effect on the total N content of the leaf on an area basis. However, decreases in Rubisco content could be primarily accounted for by a decrease in total N content of leaves, independent of [CO₂]. A doubling of the Rubisco content by increasing the N supply beyond 0.6 m M had only a marginal effect on the maximum carboxylation velocity in vivo, suggesting that the fraction of inactive Rubisco increased with increasing N supply. Although CO₂-enriched plants accumulated more non-structural carbohydrates in the leaf, the reduction of photosynthetic capacity at low N supply was not mediated simply by a build-up of carbohydrates. In D . glomerata , the photosynthetic capacity was mainly determined by the total N content of the leaf.     

Does protein kinase R mediate TNF-alpha- and ceramide-induced increases in expression and activation of matrix metalloproteinases in articular cartilage by a novel mechanism?

We investigated the role of the proinflammatory cytokine TNF-alpha, the second messenger C2-ceramide, and protein kinase R (PKR) in bovine articular cartilage degradation. Bovine articular cartilage explants were stimulated with C2-ceramide or TNF-alpha for 24 hours. To inhibit the activation of PKR, 2-aminopurine was added to duplicate cultures. Matrix metalloproteinase (MMP) expression and activation in the medium were analysed by gelatin zymography, proteoglycan release by the dimethylmethylene blue assay, and cell viability by the Cytotox 96(R) assay. C2-ceramide treatment of cartilage explants resulted in a significant release of both pro- and active MMP-2 into the medium. Small increases were also seen with TNF-alpha treatment. Incubation of explants with 2-aminopurine before TNF-alpha or C2-ceramide treatment resulted in a marked reduction in expression and activation of both MMP-2 and MMP-9. TNF-alpha and C2-ceramide significantly increased proteoglycan release into the medium, which was also inhibited by cotreatment with 2-aminopurine. A loss of cell viability was observed when explants were treated with TNF-alpha and C2-ceramide, which was found to be regulated by PKR. We have shown that C2-ceramide and TNF-alpha treatment of articular cartilage result in the increased synthesis and activation of MMPs, increased release of proteoglycan, and increased cell death. These effects are abrogated by treatment with the PKR inhibitor 2-aminopurine. Collectively, these results suggest a novel role for PKR in the synthesis and activation of MMPs and support our hypothesis that PKR and its activator, PACT, are implicated in the cartilage degradation that occurs in arthritic disease.     

Regulation of Stomatal Tropism and Infection by Light in Cercospora zeae-maydis: Evidence for Coordinated Host/Pathogen Responses to Photoperiod?

Cercospora zeae-maydis causes gray leaf spot of maize, which has become one of the most widespread and destructive diseases of maize in the world. C. zeae-maydis infects leaves through stomata, which is predicated on the ability of the pathogen to perceive stomata and reorient growth accordingly. In this study, the discovery that light was required for C. zeae-maydis to perceive stomata and infect leaves led to the identification of CRP1, a gene encoding a putative blue-light photoreceptor homologous to White Collar-1 (WC-1) of Neurospora crassa. Disrupting CRP1 via homologous recombination revealed roles in multiple aspects of pathogenesis, including tropism of hyphae to stomata, the formation of appressoria, conidiation, and the biosynthesis of cercosporin. CRP1 was also required for photoreactivation after lethal doses of UV exposure. Intriguingly, putative orthologs of CRP1 are central regulators of circadian clocks in other filamentous fungi, raising the possibility that C. zeae-maydis uses light as a key environmental input to coordinate pathogenesis with maize photoperiodic responses. This study identified a novel molecular mechanism underlying stomatal tropism in a foliar fungal pathogen, provides specific insight into how light regulates pathogenesis in C. zeae-maydis, and establishes a genetic framework for the molecular dissection of infection via stomata and the integration of host and pathogen responses to photoperiod.     

Evidence That p-Cresol and IL-6 Are Adsorbed by the HFR Cartridge: Towards a New Strategy to Decrease Systemic Inflammation in Dialyzed Patients?

Introduction

Hemodialysis (HD) and hemodiafiltration clear only with a low efficiency the plasma from interleukin-6 and p-cresol, two protein-bound uremic toxins associated with high cardiovascular risk in end stage renal disease. HFR Supra is a double-chamber hemodiafiltration system in which the ultrafiltrate returns to the patient after its regeneration through a resin cartridge that binds hydrophobic and protein-bound solutes. In the present study, we evaluated whether the HFR cartridge can also bind total p-cresol and IL-6 and remove them from the ultrafiltrate.

Methods

We compared the levels of IL-6 and p-cresol in ultrafiltrate samples collected at the inlet (UF_in) and at the outlet (UF_out) of the cartridge at the start or at the end of a 240 min HFR session in 12 inflamed chronic HD patients. The pro-inflammatory activity of the ultrafiltrate samples was also determined by evaluating the changes that they induced in IL-6 mRNA expression and protein release in peripheral blood mononuclear cells from 12 healthy volunteers. IL-6 and p-cresol circulating levels were also assessed in peripheral plasma blood samples collected before and after HFR and, for comparison, a control HD.

Results

p-Cresol and IL-6 were lower in UF_out than in UF_in both at the start and at the end of the HFR session, suggesting that they were retained by the cartridge. IL-6 mRNA expression and release were lower in PBMC incubated with UF_out collected at the end than with UF_in collected at the start of HFR, suggesting that passage through the cartridge reduced UF pro-inflammatory activity. Plasma total p-cresol decreased by about 53% after HFR, and 37% after HD. IL-6 circulating values were unmodified by either these dialysis procedures.

Conclusions

This study shows that the HFR-Supra cartridge retains total p-cresol and IL-6 in the ultrafiltrate and lowers plasma total p cresol but not IL-6 levels.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT01865773","term_id":"NCT01865773"}}NCT01865773     

Does triacylglycerol (TAG) serve a photoprotective function in plant leaves? An examination of leaf lipids under shading and drought

Plant survival in many ecosystems requires tolerance of large radiation loads, unreliable water supply and suboptimal soil fertility. We hypothesized that increased production of neutral lipids (triacylglycerols, TAGs) in plant leaves is a mechanism for dissipating excess radiation energy. In a greenhouse experiment, we combined drought and shade treatments and examined responses among four species differing in life form, habitat, and drought‐ and shade‐tolerance. We also present a lipid extraction protocol suitable for sclerophyllous leaves of native Australian trees (e.g. Acacia, Eucalyptus). Fluorescence measurements indicated that plants exposed to full sunlight experienced mild photoinhibition during our experiment. Accumulation of TAGs did not follow photosynthetic capacity, but instead, TAG concentration increased with non‐photochemical quenching. This suggests that plants under oxidative stress may increase biosynthesis of TAGs. Moderate drought stress resulted in a 60% reduction in TAG concentration in wheat (Triticum aestivum). Shading had no effect on TAGs, but increased concentrations of polar lipids in leaves; for example, acclimation to shade in Austrodanthonia spp., a native Australian grass, resulted in a 60% increase in associated polar lipids and higher foliar chlorophyll concentrations. Shading also reduced the digalactosyldiacylglycerol:monogalactosyldiacylglycerol (DGDG:MGDG) ratio in leaves, with a corresponding increase in the degree of unsaturation and thus fluidity of thylakoid membranes of chloroplasts. Our results suggest that prevention of photodamage may be coordinated with accumulation of TAGs, although further research is required to determine if TAGs serve a photoprotective function in plant leaves.     

Does rapid oligomerization of hepatitis B envelope proteins play a role in resistance to proteasome degradation and enhance chronicity?

This review discusses the nature of hepatitis B and C chronicity from a virological perspective. Work described in the literature and our in vitro studies of HBV polypeptide morphogenesis lead us to speculate about a role for HBsAg complex formation in immune evasion that may be especially important during the initial period of infection. Briefly, although viral structural proteins do eventually provide epitopes recognized by the host, we suggest that these HBs Ag complexes, which may themselves be refractory to proteasomal degradation, are an important way by which the virus shields its epitopes and evades early recognition by the cellular immune system. This suggests a central strategy by which the virus has evolved, structurally, to enable the establishment of persistent infection of its host. The concept offers an explanation for the nearly unidirectional and rapid kinetics whereby HBV proteins form multimers and generate a surplus of viral structures that have not been thought to serve any useful structural purpose.     

Does Stigmatized Social Risk Lead to Denialism? Results from a Survey Experiment on Race,Risk Perception,and Health Policy in the United States

In this article, we report findings from an original survey experiment investigating the effects of different framings of disease threats on individual risk perceptions and policy priorities. We analyze responses from 1,946 white and African-American participants in a self-administered, web-based survey in the United States. We sought to investigate the effects of: 1) frames emphasizing disparities in the racial prevalence of disease and 2) frames emphasizing non-normative (blameworthy or stigmatized) behavioral risk factors. We find some evidence that when treated with the first frame, African-Americans are more likely to report higher risk of infection (compared to an African-American control group and to whites receiving the same treatment); and that whites are more likely to report trust in government data (compared to a White control group and to African-Americans receiving the same treatment). Notwithstanding, we find no support for our hypotheses concerning the interactive effects of providing both frames, which was a central motivation for our study. We argue that this may be due to very large differences in risk perception at baseline (which generate limits on possible treatment effects) and the fact that in the context of American race relations, it may not be possible to fully differentiate racialized and stigmatized frames.     

Does the response to cocaine differ as a function of sex or hormonal status in human and non-human primates?

Stimulant abuse continues to be a growing problem among women. Over the last 10-15 years, an increasing number of studies have focused on factors that may be implicated in stimulant abuse in women as compared to men, including the role of hormonal fluctuations across the menstrual cycle. Numerous preclinical studies have documented that female rodents are more sensitive than male rodents to the behavioral effects of stimulant administration and the hormone estradiol is involved in the enhanced response to stimulants observed in females. In contrast, fewer studies have been conducted in humans and non-human primates addressing the role of sex and gonadal hormones on the effects of cocaine. This review paper presents a recent update on data collected in our Human Cocaine Challenge Laboratory and our Non-human Primate Laboratory, including analysis of cocaine pharmacokinetics, sex differences, the menstrual cycle, and the role of progesterone in modulating the response to cocaine. Our studies indicate that there is minimal evidence that the response to intranasal cocaine varies across the menstrual cycle or between men and women. In contrast, the response to smoked cocaine is greater in the follicular phase than the luteal phase and differences between men and women generally only emerge when men are compared to women in the luteal phase. In terms of potential hormonal mechanisms for these differences, the hormone progesterone attenuates the subjective response to cocaine. With respect to cocaine self-administration, there are minimal changes across the menstrual cycle in both humans and non-human primates. Thus, there is converging evidence across a range of species that the behavioral effects of cocaine (1) differ between males and females, (2) differ in relation to hormonal fluctuations, (3) can be attenuated by progesterone (at least in females), and (4) do not appear to be related to differences in cocaine pharmacokinetics.     

Does Skipping a Meal Matter to a Butterfly's Appearance? Effects of Larval Food Stress on Wing Morphology and Color in Monarch Butterflies

In animals with complex life cycles, all resources needed to form adult tissues are procured at the larval stage. For butterflies, the proper development of wings involves synthesizing tissue during metamorphosis based on the raw materials obtained by larvae. Similarly, manufacture of pigment for wing scales also requires resources acquired by larvae. We conducted an experiment to test the effects of food deprivation in the larval stage on multiple measures of adult wing morphology and coloration of monarch butterflies (Danaus plexippus), a species in which long-distance migration makes flight efficiency critical. In a captive setting, we restricted food (milkweed) from late-stage larvae for either 24 hrs or 48 hrs, then after metamorphosis we used image analysis methods to measure forewing surface area and elongation (length/width), which are both important for migration. We also measured the brightness of orange pigment and the intensity of black on the wing. There were correlations between several wing features, including an unexpected association between wing elongation and melanism, which will require further study to fully understand. The clearest effect of food restriction was a reduction in adult wing size in the high stress group (by approximately 2%). Patterns observed for other wing traits were ambiguous: monarchs in the low stress group (but not the high) had less elongated and paler orange pigmentation. There was no effect on wing melanism. Although some patterns obtained in this study were unclear, our results concerning wing size have direct bearing on the monarch migration. We show that if milkweed is limited for monarch larvae, their wings become stunted, which could ultimately result in lower migration success.