Bumble bee (Bombus impatiens) survival, pollen usage, and reproduction are not affected by oxalate oxidase at realistic concentrations in American chestnut (Castanea dentata) pollen

Transgenic American chestnut trees expressing a wheat gene for oxalate oxidase (OxO) can tolerate chestnut blight, but as with any new restoration material, they should be carefully evaluated before being released into the environment. Native pollinators such as bumble bees are of particular interest: Bombus impatiens use pollen for both a source of nutrition and a hive building material. Bees are regular visitors to American chestnut flowers and likely contribute to their pollination, so depending on transgene expression in chestnut pollen, they could be exposed to this novel source of OxO during potential restoration efforts. To evaluate the potential risk to bees from OxO exposure, queenless microcolonies of bumble bees were supplied with American chestnut pollen containing one of two concentrations of OxO, or a no-OxO control. Bees in microcolonies exposed to a conservatively estimated field-realistic concentration of OxO in pollen performed similarly to no-OxO controls; there were no significant differences in survival, bee size, pollen use, hive construction activity, or reproduction. A ten-fold increase in OxO concentration resulted in noticeable but non-significant decreases in some measures of pollen usage and reproduction compared to the no-OxO control. These effects are similar to what is often seen when naturally produced secondary metabolites are supplied to bees at unrealistically high concentrations. Along with the presence of OxO in many other environmental sources, these data collectively suggest that oxalate oxidase at field-realistic concentrations in American chestnut pollen is unlikely to present substantial risk to bumble bees.

MO692COULD THE RESIDUAL RENAL FUNCTION REMAIN A KEY DETERMINANT OF PLASMA OXALIC ACID CONCENTRATION IN PERITONEAL DIALYSIS PATIENTS?

Background and Aims Under physiological conditions, the bulk of circulating oxalate (90% to 95%) is ultimately excreted by the kidneys. Under uremic and/or anuric conditions, dialysis is considered to be the main method of oxalate removal. Nevertheless, little evidence is available on oxalate balance in peritoneal dialysis (PD) patients. The present study aimed to evaluate the separate contribution of residual renal and peritoneal oxalate clearances to oxalate balance in PD patients. Method We performed a cross-sectional observational study involving 62 PD patients with the average age of 50.5±13.5 years and PD vintage of 37±24 months. Plasma oxalate (POx) concentration, levels of daily urinary (UOx) and peritoneal dialysis effluent oxalate (PDEOx) excretion were evaluated. POx concentration was measured spectrophotometrically using MAK315 kit (Sigma, Spain); UOx and PDEOx concentrations were determined using an oxalate oxidase/peroxidase reagent (BioSystems, Spain). In addition, oxalate transport status (4-hour D/P oxalate ratio), renal oxalate clearance (ROxCL) and peritoneal oxalate clearance (PerOxCL) were calculated. Results Among the examined PD patients were 41 (66%) patients with preserved diuresis and 21 (34%) patients with anuria. The anuric PD patients had lower PerOxCL and, accordingly, peritoneal and overall oxalate removal levels compared with the patients with preserved diuresis (Table 1). Conclusion The results of our research demonstrated an important role of the residual renal function in oxalate balance in PD patients. However, the decline in RRF could partially (but not completely) contribute to the increase in POx in PD patients. Thus, PerOxCL but not ROxCL could significantly affect oxalate balance in PD patients.

An Arabidopsis Oxalyl-CoA Decarboxylase, AtOXC, Is Important for Oxalate Catabolism in Plants

Considering the widespread occurrence of oxalate in nature and its broad impact on a host of organisms, it is surprising that so little is known about the turnover of this important acid. In plants, oxalate oxidase is the most well-studied enzyme capable of degrading oxalate, but not all plants possess this activity. Recently, acyl-activating enzyme 3 (AAE3), encoding an oxalyl-CoA synthetase, was identified in Arabidopsis. This enzyme has been proposed to catalyze the first step in an alternative pathway of oxalate degradation. Since this initial discovery, this enzyme and proposed pathway have been found to be important to other plants and yeast as well. In this study, we identify, in Arabidopsis, an oxalyl-CoA decarboxylase (AtOXC) that is capable of catalyzing the second step in this proposed pathway of oxalate catabolism. This enzyme breaks down oxalyl-CoA, the product of AtAAE3, into formyl-CoA and CO2. AtOXC:GFP localization suggested that this enzyme functions within the cytosol of the cell. An Atoxc knock-down mutant showed a reduction in the ability to degrade oxalate into CO2. This reduction in AtOXC activity resulted in an increase in the accumulation of oxalate and the enzyme substrate, oxalyl-CoA. Size exclusion studies suggest that the enzyme functions as a dimer. Computer modeling of the AtOXC enzyme structure identified amino acids of predicted importance in co-factor binding and catalysis. Overall, these results suggest that AtOXC catalyzes the second step in this alternative pathway of oxalate catabolism.

Antiurolithiatic Evaluation of α- Mangostin Fraction Isolated from Garcinia mangostana Pericarp through Computational, in vitro and in vivo Approach

Background: The aqueous crude extract of Garcinia mangostana fruit pericarp was already proven to contain antiurolithiatic property. Based on this previous study the current study was focused on analysing the anti-urolithiatic property of α- mangostin, a xanthone polyphenol isolated from the fruit pericarp of G. manostana, which has not been tested for its anti-urolithiatic property till now. Objective: The aim of this present study is to evaluate the anti-urolithiatic property of the isolated α- mangostin from G. mangostana fruit pericarp using in silico, in vitro and in vivo analysis. Study Design: Antiurolithiatic activity of α- mangostin through Molecular docking study à In vitro S.S.M model study à Animal studies. Place and Duration: Department of Biotechnology, Sri Venkateswara College of Engineering, Post Bag No.1, Pennalur, Sriperumbudur Tk, Kancheepuram Dt, TN-602117, India. Materials and Methods: In silico Molecular docking of α- mangostin with Kidney stone forming proteins- Xanthine dehydrogenase (Xdh), Oxalate oxidase and Tamm-Horesefall Protein (THP) were performed using AutoDock 4.0 and was visualised in Discovery studio software. In vitro Simultaneous Static flow Model (S.S.M) was performed to investigate its Antiurolithiatic property against Calcium Oxalate (CaOx) and Calcium Phosphate (CaP) crystals. Based on the in silico and in vitro analysis, the study was extrapolated to Ethylene Glycol (EG) induced urolithiasis rat models. The animal study was performed with 36 Albino Wistar rats which were divided into 6 groups. All group except group I received EG (0.75% in drinking water) for the induction of Urolithiasis for 28 days under curative regimen. Group III was administered orally with Cystone (750 mg/kg) from 15th to 28thday. Group IV to VI was administered orally with GMPE (300 mg/kg, 500 mg/kg and 750 mg/kg) from 15thto 28th day. Results: Molecular Docking studies showed an inhibitory interaction of α- mangostin with oxalate oxidase, Xdh and THP with binding affinity of -4.47, -4.00 and -3.41 Kcal/mol respectively. S.S.M showed 54.71% inhibition for CaOx crystals and 62.21% inhibition of CaP crystals. The animal studies showed significant results in reduction of serum calcium (P<0.01), serum phosphate (P<0.01), urine calcium(P<0.001) and urine phosphate(P<0.01). Conclusion: Thus, α- mangostin proved to be potent Anti-urolithiatic agent by reducing and disintegrating the urinary crystals.

Decomposition of Calcium Oxalate Crystals in Colobanthus quitensis under CO2 Limiting Conditions

Calcium oxalate (CaOx) crystals are widespread among plant species. Their functions are not yet completely understood; however, they can provide tolerance against multiple environmental stress factors. Recent evidence suggested that CaOx crystals function as carbon reservoirs since its decomposition provides CO2 that may be used as carbon source for photosynthesis. This might be advantageous in plants with reduced mesophyll conductance, such as the Antarctic plant Colobanthus quitensis, which have shown CO2 diffusion limitations. In this study, we evaluate the effect of two CO2 concentrations in the CaOx crystals decomposition and chlorophyll fluorescence of C. quitensis. Plants were exposed to airflows with 400 ppm and 11.5 ppm CO2 and the number and relative size of crystals, electron transport rate (ETR), and oxalate oxidase (OxO) activity were monitored along time (10 h). Here we showed that leaf crystal area decreases over time in plants with 11.5 ppm CO2, which was accompanied by increased OxO activity and only a slight decrease in the ETR. These results suggested a relation between CO2 limiting conditions and the CaOx crystals decomposition in C. quitensis. Hence, crystal decomposition could be a complementary endogenous mechanism for CO2 supply in plants facing the Antarctic stressful habitat.