A diterpenoid derivate compound targets selenocysteine of thioredoxin reductases and induces Bax/Bak-independent apoptosis

We have previously shown that the natural diterpenoid derivative S3 induced Bim upregulation and apoptosis in a Bax/Bak-independent manner. However, the exact molecular target(s) of S3 and the mechanism controlling Bim upregulation are still not clear. Here, we identify that S3 targets the selenoproteins TrxR1 and TrxR2 at the selenocysteine residue of the reactive center of the enzymes and inhibits their antioxidant activities. Consequently, cellular ROS is elevated, leading to the activation of FOXO3a, which contributes to Bim upregulation in Bax/Bak-deficient cells. Moreover, S3 retards tumor growth in subcutaneous xenograft tumors by inhibiting TrxR activity in vivo. Our studies delineate the signaling pathway controlling Bim upregulation, which results in Bax/Bak-independent apoptosis and provide evidence that the compounds can act as anticancer agents based on mammalian TrxRs inhibition.     

On the Sampling Method for Grand Canonical Monte Carlo Simulations

Abstract

A bulk Lennard-Jones fluid was simulated using the grand canonical Monte Carlo method. Three different sampling methods were used in the transition matrix, namely the Metropolis, Barker and a third novel method. While it can be shown that the Metropolis method will give the most accurate ensemble averages in the limit of an infinitely long run, the new method termed “Modified Barker Sampling” (MBS), is shown to be superior for the runs of practical length for the particular system studied.     

Plant Life History and Residue Chemistry Influences Emissions of CO2 and N2O From Soil – Perspectives for Genetically Modified Cell Wall Mutants

Vascular plants have lignified tissues that transport water, minerals, and photosynthetic products throughout the plant. They are the dominant primary producers in terrestrial ecosystems and capture significant quantities of atmospheric carbon dioxide (CO₂) through photosynthesis. Some of the fixed CO₂ is respired by the plant directly, with additional CO₂ lost from rhizodeposits metabolized by root-associated soil microorganisms. Microbially-mediated mineralization of organic nitrogen (N) from plant byproducts (rhizodeposits, dead plant residues) followed by nitrification generates another greenhouse gas, nitrous oxide (N₂O). In anaerobic soils, reduction of nitrate by microbial denitrifiers also produces N₂O. The plant-microbial interactions that result in CO₂ and N₂O emissions from soil could be affected by genetic modification. Down-regulation of genes controlling lignin biosynthesis to achieve lower lignin concentration or a lower guaiacyl:syringyl (G:S) ratio in above-ground biomass is anticipated to produce forage crops with greater digestibility, improve short rotation woody crops for the wood-pulping industry and create second generation biofuel crops with low ligno-cellulosic content, but unharvested residues from such crops are expected to decompose quickly, potentially increasing CO₂ and N₂O emissions from soil. The objective of this review are the following: 1) to describe how plants influence CO₂ and N₂O emissions from soil during their life cycle; 2) to explain how plant residue chemistry affects its mineralization, contributing to CO₂ and N₂O emissions from soil; and 3) to show how modification of plant lignin biosynthesis could influence CO₂ and N₂O emissions from soil, based on experimental data from genetically modified cell wall mutants of Arabidopsis thaliana. Conceptual models of plants with modified lignin biosynthesis show how changes in phenology, morphology and biomass production alter the allocation of photosynthetic products and carbon (C) losses through rhizodeposition and respiration during their life cycle, and the chemical composition of plant residues. Feedbacks on the soil environment (mineral N concentration, soil moisture, microbial communities, aggregation) affecting CO₂ and N₂O emissions are described. Down-regulation of the Cinnamoyl CoA Reductase 1 (CCR1) gene is an excellent target for highly digestable forages and biofuel crops, but A. thaliana with this mutation has lower plant biomass and fertility, prolonged vegetative growth and plant residues that are more susceptible to biodegradation, leading to greater CO₂ and N₂O emissions from soil in the short term. The challenge in future crop breeding efforts will be to select tissue-specific genes for lignin biosynthesis that meet commercial demands without compromising soil CO₂ and N₂O emission goals.     

NOTES ON THE BREEDING OF THE BOKMAKIRI

Counting Saddle-billed Storks in a study area the size of the Kruger National Park, at 2.2 million ha, is difficult because the birds are long-lived, sparse in the landscape and have large home ranges. Aerial surveys conducted to date provide an estimate with no measure of data dispersion, thence precision. The aim of this study was to estimate the population size within associated confidence limits using a modified mark–recapture field method. The vehicle survey, conducted shortly after rainfall in the area, did not produce results with known precision under these conditions. A repeat of this census in spring, after the peak breeding season and when surface water is confined to the larger rivers and dams, should yield different results. A photographic census technique yielded sufficient information to construct a population registration database. Individual identification profiles indicate that there are at least 40 adult Saddle-billed Storks in the southern part of the Kruger National Park. This is considered the minimum number of known-to-be-alive individuals in this area. In this paper, the Cormack–Jolly–Seber mark– recapture model was used to return an estimate of the population size for each capture occasion.     

Postfledging parental care and unexpected foraging behaviour of juvenile Sooty Terns Onychoprion fuscata in the southern Mozambique Channel

The Berlese funnel method, and its variations, is commonly used for the extraction of arthropods from various substrates such as nest material. However, little is known about its effectivity in extracting ectoparasites from penguin nests. This study aimed to assess the efficacy of a modified Berlese funnel method in extracting ectoparasites from African Penguin Spheniscus demersus nests and to determine differences in extraction capacity across parasite taxa and life stages. African Penguin nests (n = 278) were sampled at five penguin colonies along the south-west coast of South Africa in 2017. Nest samples were subjected to a modified Berlese funnel method with naphthalene as a repellent. Thereafter, all remaining ectoparasites were removed by hand sorting. Ectoparasite abundance was positively correlated between the two extraction methods (Spearman’s r = 0.73–0.89). Compared to total counts, flea (combined life stages and larvae) and total ectoparasite abundance and prevalence were significantly lower with the modified Berlese funnel method. In addition, adult flea and tick prevalence (but not abundance) was significantly lower with the modified Berlese funnel method compared with total counts. The modified Berlese funnel method fails as a quantitative method and can only provide a crude indication of the incidence of ectoparasites in penguin nests.     

Ultrasonication of insulin-loaded microgel particles produced by internal gelation: Impact on particle's size and insulin bioactivity

Alginate-dextran sulfate (ADS) microgel has been used to protect insulin from gastrointestinal attack and as a carrier to promote insulin permeation through intestinal epithelium. The throughput of ADS submicron particles generation by emulsification/internal gelation is limited by its wide size distribution.     

Comparison of a modified shell vial culture procedure with conventional mouse inoculation for rabies virus isolation

Rabies is a neurotropic disease that is often lethal. The early diagnosis of rabies infection is important and requires methods that allow for the isolation of the virus from animals and humans. The present study compared a modified shell vial (MSV) procedure using 24-well tissue culture plates with the mouse inoculation test (MIT), which is considered the gold standard for rabies virus isolation. Thirty brain samples (25 positive and 5 negative by the fluorescent antibody test) obtained from different animal species at the National Institute of Hygiene Rafael Rangel in Caracas, Venezuela, were studied by the MIT and MSV assays. Nine samples (36%) were positive at 24 h, 10 (40%) were positive at 48 h and six (24%) were positive at 72 h by the MSV assay. With the MIT assay, 76% were positive at six days post inoculation and 12% were positive at 12 and 18 days post inoculation. One sample that was negative according to the MSV assay was positive with MIT on the 12th day. The MSV procedure exhibited a sensitivity of 96.2%, a specificity of 100%, a positive predictive value of 100% and a negative predictive value 80%. This procedure allowed for rapid rabies virus detection. MIT can be employed as an alternative method in laboratories without tissue culture facilities.     

Does the magnetic field of a magnetic stirrer in an optical aggregometer affect concurrent platelet aggregation?

Platelets are subjected to extremely low frequency electromagnetic fields during standard aggregometry measurements owing to the use of a magnetic stir bar in the instrument. This study evaluates the effects of this magnetic field exposure on platelet aggregation by comparing the results obtained in a modified aggregometer. Blood samples from healthy volunteers were anticoagulated using citrate or heparin. Platelet‐rich plasma (PRP) samples were prepared. A mechanical stirring device was attached to the aggregometer instead of the magnetic stir bar system. The PRP samples were stirred using a stirring rod tip that did not produce any magnetic fields in one channel of the aggregometer; in the other channel, a stirring rod carrying a small magnet at its tip was used. As a result, a magnetic field in the extremely low frequency range and in the amplitude range of 1.9–65 mT was applied to the platelets assigned to the channel where the magnetic stirring rod tip was used. Aggregation was induced using adenosine diphosphate (ADP), collagen, or epinephrine. The slopes, maximum aggregation values, and areas under the aggregation curves were compared between the magnetic and neutral stirring rod tip groups. For samples stirred with the magnetic stirring rod tip, a significant decrease was observed in 12 of the 14 parameters evaluated for aggregations induced with ADP or collagen compared to the neutral stirring rod tip, regardless of the method used for anticoagulation. This observation indicates that the magnetic stir bars used in standard aggregometry may significantly alter aggregation parameters and platelets may be possible targets of electromagnetic fields. Bioelectromagnetics 34:349–357, 2013. © 2012 Wiley Periodicals, Inc.     

(−)-Reboxetine inhibits muscle nicotinic acetylcholine receptors by interacting with luminal and non-luminal sites

The interaction of (−)-reboxetine, a non-tricyclic norepinephrine selective reuptake inhibitor, with muscle-type nicotinic acetylcholine receptors (AChRs) in different conformational states was studied by functional and structural approaches. The results established that (−)-reboxetine: (a) inhibits (±)-epibatidine-induced Ca²⁺ influx in human (h) muscle embryonic (hα1β1γδ) and adult (hα1β1εδ) AChRs in a non-competitive manner and with potencies IC₅₀ = 3.86 ± 0.49 and 1.92 ± 0.48 μM, respectively, (b) binds to the [³H]TCP site with ∼13-fold higher affinity when the Torpedo AChR is in the desensitized state compared to the resting state, (c) enhances [³H]cytisine binding to the resting but activatableTorpedo AChR but not to the desensitized AChR, suggesting desensitizing properties, (d) overlaps the PCP luminal site located between rings 6′ and 13′ in the Torpedo but not human muscle AChRs. In silico mutation results indicate that ring 9′ is the minimum structural component for (−)-reboxetine binding, and (e) interacts to non-luminal sites located within the transmembrane segments from the Torpedo AChR γ subunit, and at the α1/ε transmembrane interface from the adult muscle AChR. In conclusion, (−)-reboxetine non-competitively inhibits muscle AChRs by binding to the TCP luminal site and by inducing receptor desensitization (maybe by interacting with non-luminal sites), a mechanism that is shared by tricyclic antidepressants.