Altered atrial restitution dynamics and refractoriness in metabolic syndrome due to up-regulation of potassium repolarizing currents increases susceptibility to atrial fibrillation

Background

Metabolic alterations, such as Metabolic Syndrome (MS), describe an association of factors including diabetes, hypertension, obesity and dyslipidemia, linked to higher risk and prevalence of overall cardiovascular disease, arrhythmogenesis and sudden cardiac death. Obese and diabetic patients have shown an increased risk for developing atrial fibrillation (AF). However, underlying mechanisms are not understood.

Purpose

To study the effects of MS and obesity remodeling in atrial restitution dynamics, frequency-dependent adaptation, refractoriness and its potential susceptibility to AF.

Methods

Electrophysiological experimental data from High-fat (HF-O, standard rabbit chow with an additional 15% fat) and Hig-fat High-Sucrose Metabolic Syndrome (HFHS-MS, 10% hydrogenated coconut oil and 5% lard, 15% high-sucrose dissolved in water) rabbit models were used to adjust computational models atrial electrophysiology remodeling under each condition. Additionally, isoproterenol and AF conditions were considered to challenge both in-silico models. Validation and sensitivity analysis were performed for each model parameters. Computational simulations in conditions of pacing at different pacing cycle lengths was assessed at 100, 125, 150, 200, 250, 350, 450, 500, 650, 750, 850, 1000 ms. Restitution dynamics were automatically determined and analyzed, as well as restitution slopes and presence of automaticity, early after-depolarizations, alternans and cardiac arrhythmia induction.

Results

Shortening of action potential duration and refractoriness in the left atrium was observed under HFHS-MS. Upstroke velocity, maximum excitability and sodium availability were altered both in HF-O and HFHS-MS. HF-O remodeling showed presence of alternans at high pacing frequencies. Repolarization restitution was shortened in conditions of ISO and MS-AF. Restitution slopes were >1 in HF-O and HFHS-MS, which was correlated to higher susceptibility to AF, and further increased in MS-AF. Under MS-AF, abbreviation in APD in both atria, resulted in increased reentrant frequencies in AF, which was exacerbated under IK1 up-regulation, increasing atrial vulnerability.

Conclusions

HFHS-MS underlies modifications in atrial electrophysiology including shorter refractoriness in HFHS-MS, as well as modifications in atrial excitability, which may be pro-arrhythmic mainly at high frequency rates. This could be explained in part by an up-regulation of outward potassium channels. These results could partially explain increased susceptibility for AF in MS.

Funding Acknowledgement

Type of funding sources: None.

Co-composting of forest and industrial wastes watered with pig manure

Co-composting of forest-derived wastes (chestnut forest burr, CST; scrubland biomass, SRB; industrial sludge, MDFS, from the Medium Density Fibreboard production process) watered with pig manure (PM) may constitute a feasible management technique for both solid and liquid streams. PM provided water and improved the carbon to nitrogen (C/N) ratio. Four piles of 1.8-2.4 m³ were conformed: A (SRB, with compaction bulk density), B (SRB, without compaction), C (SRB and MDFS at a volumetric ratio of 3:1) and D (CST). Thermophilic temperatures were maintained for 8 (B), 16 (A), 28 (C) and 40 (D) days. Stable compost was obtained after 35 (A, B, C) and 48 (D) days. Hygienization was only complete in piles C and D. N losses were higher in piles A (39.3%) and B (33.6%) in relation to C (17.0%) and D (8.9%) which could be attributed to the characteristics of MDFS and CST. Increasing the matrix size from 340 L to around 2000 L led to a higher intensity of the thermophilic phase. Besides, compaction significantly increased the temperature during composting. PM was added at ratios ranging from 1.8 to 2.5 L/kg dry matter, being favoured by pre-drying of solid wastes.

Population genetic structure and demographic history of Spodoptera frugiperda (Lepidoptera: Noctuidae): implications for insect resistance management programs

BACKGROUND

Spodoptera frugiperda is a destructive pest that often imposes difficult management due to its high polyphagy and rapid insecticide resistance evolution. Knowledge of species diversification, population structure, and host preference can aid efforts to manage pest populations. Here, we investigated the patterns of hybridization, genetic structure, and gene flow in S. frugiperda populations, discussing how we can apply this knowledge to insect resistance management programs in South America.

RESULTS

The corn-strain CS-h2 of S. frugiperda was the most frequent haplotype in all sampled populations. Spodoptera frugiperda populations are experiencing demographic expansion, and the ecoregions partially explain the genetic structure and not strains. We did not find a correlation between gene flow and susceptibility levels to flubendiamide and lufenuron insecticides, but populations with high LC₅₀ sent a great number of migrants to all other locations, maintaining resistance alleles in the geographic range.

CONCLUSION

High levels of population admixture, including between corn- and rice-strains, were found in sampled populations. We showed that S. frugiperda immigrants will not necessarily cause an increase in LC₅₀ upon arrival in a new location but will assure the constant presence of resistance alleles in the area. Increases in LC₅₀ largely depend on the local pesticide management adopted in the areas. Our results indicate that pesticide resistance management must be adopted on a local or small regional scale. © 2019 Society of Chemical Industry.

Composting of pig manure and forest green waste amended with industrial sludge

The aim of this research was to study the composting of chestnut forest green waste (FGW) from short rotation chestnut stands amended with sludge resulting from the manufacture of Medium Density Fibreboard (MDFS) and pig manure (PM). Both FGW and MDFS presented low biodegradation potential but different characteristics in granulometry and bulk density that make its mixture of interest to achieve high composting temperatures. PM decreased the C/N ratio of the mixture and increased its moisture content (MC). Three mixtures of MDFS:FGW at volume ratios of 1:1.3 (M2), 1:2.4 (M3) and 0:1 (M4) were composted after increasing its MC to about 70% with PM. A control with food waste (OFW) and FGW (1:2.4 in volume) (M1) was run in parallel. Watering ratios reached 0.25 (M1), 1.08 (M2) 1.56 (M3) and 4.35 (M4) L PM/kg TS of added solids wastes. Treatments M2 and M3 reached a thermophilic phase shorter than M1, whilst M4 remained in the mesophilic range. After 48days of composting, temperature gradients in respect to ambient temperature were reduced, but the mineralization process continued for around 8months. Final reduction in total organic carbon reached 35-56%, depending mainly on the content in MDFS. MDFS addition to composting matrices largely reduced nitrogen losses, which range from 22% (M2) to 37% (M3) and 53% (M4). Final products had high nutrient content, low electrical conductivity and low heavy metal content which make it a valuable product for soil fertilization, right to amend in the chestnut forests and as a pillar of their sustainable management.

Cutaneous leishmaniasis in south-eastern Paraguay: a study of an endemic area at Limoy

An epidemiological study was performed on leishmaniasis in a newly established community in south-eastern Paraguay. 149 persons, of 172 inhabitants, were thoroughly examined by clinical, parasitological and immunological (leishmanin skin test) examinations. 88 of those examined (59%) were clinically positive for dermal and nasal (mucosal) lesions or dermal scars, while 74 (50%) were positive by the leishmanin test. Of the 88 persons, 66 (75%) were positive for both leishmanial (dermal and nasal) signs and skin test; these subjects were therefore considered to be leishmaniasis patients. Most of the patients (60%) had a single dermal lesion. Among the 66 leishmaniasis patients, serious mucosal (nasal septum) lesions were observed in the 41 subjects: 2 had destruction of the septum, 8 had ulceration and 31 had erythema. In this community the persons with dermal and/or nasal problems had been treated with meglumine antimonate (Glucantime), without any precise diagnosis having been made by parasitological or immunological examination. The socio-economical and socio-medical points of view aspects are discussed.