Floral bagging differentially affects handling behaviours and single-visit pollen deposition by honey bees and native bees

1. Measurements of pollinator performance are crucial to pollination studies, enabling researchers to quantify the relative value of different pollinator species to plant reproduction. One of the most widely employed measures of pollinator performance is single-visit pollen deposition, the number of conspecific pollen grains deposited to a stigma after one pollinator visit. To ensure a pollen-free stigma, experimenters must first bag flowers before exposing them to a pollinator. 2. Bagging flowers, however, may unintentionally manipulate floral characteristics to which pollinators respond. In this study, we quantified the effect of bagging on nectar volume in watermelon (Citrullus lanatus) flowers, and how this affects pollinator performance and behaviour. 3. Experimental bagging resulted in roughly 30-fold increases in nectar volume relative to unmanipulated, open-pollinated field flowers after only a few hours. Honey bees, but not native bees, consistently displayed elevated handling times and single-visit pollen deposition on unmanipulated bagged flowers relative to those from which we removed nectar to mimic volumes in open-pollinated flowers. 4. Furthermore, we identify specific bee foraging behaviours during a floral visit that account for differences in pollen deposition, and how these differ between honey bees and native bees. 5. Our findings suggest that experimental bagging of flowers, without accounting for artificially accumulated nectar, can lead to biased estimates of pollinator performance in pollinator taxa that respond strongly to nectar volume. We advise that pollination studies be attentive to nectar secretion dynamics in their focal plant species to ensure unbiased estimates of pollinator performance across multiple pollinator species.     

A novel approach to investigate the effect of methionine oxidation on pharmacokinetic properties of therapeutic antibodies

Preserving the chemical and structural integrity of therapeutic antibodies during manufacturing and storage is a major challenge during pharmaceutical development. Oxidation of Fc methionines Met252 and Met428 is frequently observed, which leads to reduced affinity to FcRn and faster plasma clearance if present at high levels. Because oxidation occurs in both positions simultaneously, their individual contribution to the concomitant changes in pharmacokinetic properties has not been clearly established. A novel pH-gradient FcRn affinity chromatography method was applied to isolate three antibody oxidation variants from an oxidized IgG1 preparation based on their FcRn binding properties. Physico-chemical characterization revealed that the three oxidation variants differed predominantly in the number of oxMet252 per IgG (0, 1, or 2), but not significantly in the content of oxMet428. Corresponding to the increase in oxMet252 content, stepwise reduction of FcRn affinity in vitro, as well as faster clearance and shorter terminal half-life, in huFcRn-transgenic mice were observed. A single Met252 oxidation per antibody had no significant effect on pharmacokinetics (PK) compared with unmodified IgG. Importantly, only molecules with both heavy chains oxidized at Met252 exhibited significantly faster clearance. In contrast, Met428 oxidation had no apparent negative effect on PK and even led to somewhat improved FcRn binding and slower clearance. This minor effect, however, seemed to be abrogated by the dominant effect of Met252 oxidation. The novel approach of functional chromatographic separation of IgG oxidation variants followed by physico-chemical and biological characterization has yielded the first experimentally-backed explanation for the unaltered PK properties of antibody preparations containing relatively high Met252 and Met428 oxidation levels.     

Histone XH2AX Is Required for Xenopus Anterior Neural Development: CRITICAL ROLE OF THREONINE 16 PHOSPHORYLATION*

A role for histone H2AX, one of the variants of the nucleosome core histone H2A, has been demonstrated in DNA repair, tumor suppression, apoptosis, and cell cycle checkpoint function. However, the physiological function and post-translational modification of histone H2AX during vertebrate development have not been elucidated. Here, we provide evidence showing that Xenopus histone H2AX (XH2AX) has a role in the anterior neural plate for eye field formation during Xenopus embryogenesis. A loss-of-function study clearly demonstrated a critical role of XH2AX in anterior neural specification. Through a differentiation assay with Xenopus animal cap embryonic stem cells, we confirmed that XH2AX is required for the activin-induced anterior neural specification of the ectoderm. Furthermore, we found that Chk1 is an essential kinase to phosphorylate histone XH2AX at Thr¹⁶, which is involved in the biological function of this histone. Taken together, our findings reveal that XH2AX has a specific role in anterior neural formation of Xenopus, which is mediated through phosphorylation of XH2AX at Thr¹⁶ by Chk1.     

Are amoxycillin and folate inhibitors as effective as other antibiotics for acute sinusitis? A meta-analysis

Objectives: To examine whether antibiotics are indicated in treating uncomplicated acute sinusitis and, if so, whether newer and more expensive antibiotics with broad spectra of antimicrobial activity are more effective than amoxycillin or folate inhibitors. Design: Meta-analysis of randomised trials. Setting: Outpatient clinics. Subjects: 2717 patients with acute sinusitis or acute exacerbation of chronic sinusitis from 27 trials. Interventions: Any antibiotic versus placebo; amoxycillin or folate inhibitors versus newer, more expensive antibiotics. Main outcome measurements: Clinical failures and cures. Results: Compared with placebo, antibiotics decreased the incidence of clinical failures by half (risk ratio 0.54 (95% confidence interval 0.37 to 0.79)). Risk of clinical failure among 1553 randomised patients was not meaningfully decreased with more expensive antibiotics as compared with amoxycillin (risk ratio 0.86 (0.62 to 1.19); risk difference 0.9 fewer failures per 100 patients (1.4 more failures to 3.1 fewer failures per 100 patients)). The results were similar for other antibiotics versus folate inhibitors (risk ratio 1.01 (0.52 to 1.97)), but data were sparse (n=410) and of low quality. Conclusions: Amoxycillin and folate inhibitors are essentially as effective as more expensive antibiotics for the initial treatment of uncomplicated acute sinusitis. Small differences in efficacy may exist, but are unlikely to be clinically important.

Key messages

• A major question in managing acute sinusitis is whether antibiotics should be used, and if so which drugs should be chosen
• In a comprehensive meta-analysis we evaluated evidence from randomised controlled trials comparing, firstly, antibiotics against placebo and, secondly, amoxycillin and folate inhibitors against newer, more expensive antibiotics
• Antibiotics were significantly more efficacious than placebo in achieving cure of clinical symptoms, but over two thirds of placebo patients showed spontaneous resolution or improvement of symptoms
• Amoxycillin and folate inhibitors had overall similar efficacy compared with newer antibiotics
• The current evidence does not justify the use of expensive, broad spectrum antibiotics in the community for treating uncomplicated acute sinusitis

     

Drought and air pollution affect nitrogen cycling and free radical scavenging in Pinus halepensis (Mill.)

Fumigation of Aleppo pines with episodes of O₃ (up to 110 nll^–) causes immediate depressions of in vivo nitrate reductase(NaR) activities, slightly delayed reductions in the rates ofethene emissions (typical of O₃ plants), steady accumulationsof total polyamines (although putrescine declines), and increasesin pool sizes of reduced glutathione (GSH) and ascorbate incurrent year needles. Severe droughting produces smaller plantswith reduced stomatal conductance and CO₂ assimilation ratesas well as lower protein contents. Their roots have low ratesof nitrate uptake but virtually no root NaR activities, whilelevels of shoot activities and NaR-associated proteins are unaffectedalthough they have no substrate. Less severe droughting allowsa restricted uptake of nitrate which is still reflected in reducedNaR activities, protein and total N contents, but the additionalpresence of O₃ (up to 120 nl l^–1) has no interactive effecton N cycling. Drought and O₃ together, however, depress CO₂assimilation still further, which can not be accounted for byadditional stomatal closure, but the interactive effects ofdrought and air pollution reduce levels of total phenols, GSHand ascorbate which, combined with a 12-fold reduction in glutathionereductase-(GR)-associated proteins, point to an increased susceptibilityof Aleppo pines to photoinhibition as a reason for their currentdecline in Mediterranean areas. Key words: Aleppo pine, ascorbate, ELISA, ethene, glutathione reductase, nitrate reductase     

Determination of pramipexole (U-98,528) in human plasma and urine by high-performance liquid chromatography with electrochemical and ultraviolet detection

A sensitive and selective high-performance liquid chromatographic (HPLC) method was developed for the determination of pramipexole in human plasma and urine. Plasma/urine is made alkaline before pramipexole and BHT-920 (internal standard) are extracted by ethyl ether and back-extracted with a solution that contains heptanesulfonic acid. Separation is achieved by ion-pair chromatography on a Zorbax Rx C₈ column with electrochemical detection at 0.6 V for plasma and ultraviolet detection at 286 nm for urine. The retention times of pramipexole and internal standard are approximately 14.4 and 10.7 min, respectively. The assay is linear in concentration ranges of 50 to 15 000 pg/ml (plasma) and 10 to 10 000 ng/ml (urine). The correlation coefficients are greater than 0.9992 for all curves. For the plasma method, the analysis of pooled quality controls (300, 3000, and 10 000 pg/ml) demonstrates excellent precision with relative standard deviations (R.S.D.) (n=18) of 1.1%, 2.3%, and 6.8%, respectively. For the urine method, quality control pools prepared at 30, 300, and 3000 ng/ml had R.S.D. values (n=18) of 2.9%, 1.7%, and 3.0%, respectively. The plasma and urine controls were stable for more than nine and three months, respectively. The mean recoveries for pramipexole and internal standard from plasma were 97.7% and 98.2%, respectively. The mean recoveries for pramipexole and internal standard from urine were 89.8% and 95.1%, respectively. The method is accurate with all intra-day (n=6) and overall (n=18) mean values for the quality control samples being less than 6.4 and 5.8% from theoretical for plasma and urine, respectively.