Influence of viscosity on myocardium mechanical activity: a mathematical model

We have previously proposed and validated a mathematical model of myocardium contraction-relaxation cycle based on current knowledge of regulatory role of Ca2+ and cross-bridge kinetics in cardiac cell. That model did not include viscous elements. Here we propose a modification of the model, in which two viscous elements are added, one in parallel to the contractile element, and one more in parallel to the series elastic element. The modified model allowed us to simulate and explain some subtle experimental data on relaxation velocity in isotonic twitches and on a mismatch between the time course of sarcomere shortening/lengthening and the time course of active force generation in isometric twitches. Model results were compared with experimental data obtained from 28 rat LV papillary muscles contracting and relaxing against various loads. Additional model analysis suggested contribution of viscosity to main inotropic and lusitropic characteristics of myocardium performance.     

The poliovirus replication machinery can escape inhibition by an antiviral drug that targets a host cell protein

Viral replication depends on specific interactions with host factors. For example, poliovirus RNA replication requires association with intracellular membranes. Brefeldin A (BFA), which induces a major rearrangement of the cellular secretory apparatus, is a potent inhibitor of poliovirus RNA replication. Most aspects governing the relationship between viral replication complex and the host membranes remain poorly defined. To explore these interactions, we used a genetic approach and isolated BFA-resistant poliovirus variants. Mutations within viral proteins 2C and 3A render poliovirus resistant to BFA. In the absence of BFA, viruses containing either or both of these mutations replicated similarly to wild type. In the presence of BFA, viruses carrying a single mutation in 2C or 3A exhibited an intermediate-growth phenotype, while the double mutant was fully resistant. The viral proteins 2C and 3A have critical roles in both RNA replication and vesicle formation. The identification of BFA resistant mutants may facilitate the identification of cellular membrane-associated proteins necessary for induction of vesicle formation and RNA replication. Importantly, our data underscore the dramatic plasticity of the host-virus interactions required for successful viral replication.     

Stable benefit of embryonic stem cell therapy in myocardial infarction

Conventional therapies for myocardial infarction attenuate disease progression without contributing significantly to repair. Because of the capacity for de novo cardiogenesis, embryonic stem cells are considered a potential source for myocardial regeneration, yet limited information is available on their ultimate therapeutic value. We treated infarcted rat hearts with CGR8 embryonic stem cells preexamined for cardiogenicity, serially probed left ventricular function, and determined final pathological outcome. Stem cell delivery generated new cardiomyocytes of embryonic stem cell origin that integrated with host myocardium within infarct regions. This resulted in a functional benefit within 3 wk that remained sustained over 12 wk of continuous follow-up and included a vigorous inotropic response to beta-adrenergic challenge. Integration of stem cell-derived cardiomyocytes was associated with normalized ventricular architecture, little scar, and a decrease in signs of myocardial necrosis. In contrast, sham-treated infarcted hearts exhibited ventricular cavity dilation and aneurysm formation, poor ventricular function, and a lack of response to beta-adrenergic stimulation. No evidence of graft rejection, ectopy, sudden cardiac death, or tumor formation was observed after therapy. These findings indicate that embryonic stem cells, through differentiation within the host myocardium, can contribute to a stable beneficial outcome on contractile function and ventricular remodeling in the infarcted heart.     

The mechanism of EDHF-mediated responses in subcutaneous small arteries from healthy pregnant women

We studied the importance of endothelium-derived hyperpolarizing factor (EDHF) vs. nitric oxide (NO) and prostacyclin (PGI(2)) in bradykinin (BK)-induced relaxation in isolated small subcutaneous arteries from normal pregnant women. We also explored the contribution of cytochrome P-450 (CYP450) product of arachidonic acid (AA) metabolism, hydrogen peroxide (H(2)O(2)), and gap junctions that have been suggested to be involved in EDHF-mediated responses. Isolated arteries obtained from subcutaneous fat biopsies of normal pregnant women (n = 30) undergoing planned cesarean section were mounted in a wire-myography system. In norepinephrine-constricted vessels, incubation with N(G)-nitro-L-arginine methyl ester (L-NAME) resulted in a significant reduction in relaxation to BK. Simultaneous incubation with L-NAME and indomethacin failed to modify this response further. BK-mediated dilatation in the presence of K(+)-modified solution was decreased to similar level as obtained after incubation with L-NAME. Incubation with L-NAME abolished BK-induced responses in K(+)-modified solution. Sulfaphenazole, a specific inhibitor of CYP450 epoxygenase, and catalase (an enzyme that decomposes H(2)O(2)) did not affect the EDHF-mediated relaxation because concentration-response curves to BK were similar in arteries after incubation with L-NAME vs. L-NAME + sulfaphenazole and L-NAME + catalase. The inhibitor of gap junctions, 18 alpha-glycyrrhetinic acid, significantly reduced BK-mediated relaxation both without and with incubation with L-NAME. We found that both NO and EDHF, but not PGI(2), are involved in the endothelium-dependent dilatation to BK. BK-induced relaxation is almost equally mediated by NO and EDHF. CYP450 epoxygenase metabolites of AA or H(2)O(2) do not account for EDHF-mediated response; however, gap junctions are involved in the EDHF-mediated responses to BK in subcutaneous small arteries in normal pregnancy.     

Parallel isoelectric focusing chip

Fast isoelectric focusing (IEF) is becoming a key method in modern protein analysis. We report here the theory and experimental results of new parallel isoelectric devices (PID) for fast IEF. The main separation tool of any PID is a dielectric membrane with conducting channels filled by immobiline gels of varying pH. The pH value of the surrounding aqueous solution is not equal to the pH of any of the channels. The membrane is held perpendicular to the applied electric field. Proteins are collected (trapped) in the channels whose pH values are equal to the pI of the proteins. The fast particle transport between different channels takes place due to convection in the aqueous solution. We developed a mathematical model for PID. Experiment duration is shown to be proportional to the number of different bands N (the peak capacity in standard IEF) in contrast with N(2) for usual IEF devices. This model was validated with experimental results. Parallel IEF accelerates the fractionation of proteins by their pI values (down to several minutes) allowing a more desirable collection efficiency to be achieved. The main theoretical limitation of PID resolution is the sensitivity of proteins to pH change due to the Coulomb blockade effect. The existence of a minimal pH change deltapH(min) for each type of protein is shown: deltapH(min) approximately r(-1) for globular molecules with radius r.     

Impact of type 2 diabetes mellitus on short- and long-term mortality after coronary artery bypass surgery

Background

Type 2 diabetes mellitus (DM) is a frequent co-morbidity among patients undergoing coronary artery bypass grafting (CABG) surgery. The aim of this study was to evaluate the impact of DM on the early- and long-term outcomes of patients who underwent isolated CABG.

Methods

We performed an observational cohort study in a large tertiary medical center over a period of 11 years. All data from patients who had undergone isolated CABG surgery between 2004 and 2014 were obtained from our departmental database. The study population included 2766 patients who were divided into two groups: Group I (1553 non-diabetic patients), and Group II (1213 patients suffering from type 2 DM). Group II patients were then divided into two subgroups: subgroup IIA (981 patients treated with oral antihyperglycemic medications) and subgroup IIB (232 insulin-treated patients with or without additional oral antihyperglycemic drugs). In-hospital, 1-, 3-, 5- and 10-year mortality outcome variables were evaluated. Mean follow-up was 97?±?41 months.

Results

In-hospital mortality was similar between Group I and Group II patients (1.87% vs. 2.31%, p?=?0.422) and between the subgroups IIA and IIB (2.14% vs. 3.02%, p?=?0.464). Long-term mortality (1, 3, 5 and 10 years) was higher in Group II (DM type 2) compared with Group I (non-diabetic patients) (5.3% vs. 3.6%, p?=?0.038; 9.3% vs. 5.6%, p?<?0.001; 15.3% vs. 9.3%, p?<?0.001 and 47.3% vs. 29.6% p?<?0.001). Kaplan–Meier analysis demonstrated that all-cause mortality was higher in Group II compared with Group I (p?<?0.001) and in subgroup IIB compared with subgroup IIA (p?=?0.001). Multivariable analysis showed that DM increased the mortality hazard by twofold, and among diabetic patients, insulin treatment increased the mortality hazard by twofold.

Conclusions

Diabetic and non-diabetic patients have similar in-hospital mortality rates. Survival rates of diabetic patients start to deteriorate 3 year after surgery. Type 2 DM is an independent predictor for long-term mortality after isolated CABG surgery. Mortality is even higher when the diabetes treatment strategy included insulin.

     

Ditches as species‐rich secondary habitats and refuge for meadow species in agricultural marsh grasslands

Questions

Can drainage ditches in agricultural marsh grassland provide a suitable habitat for the persistence of fen meadow species? How does the ditch margin vegetation develop as a function of regular dredging? Is ornithologically oriented management also beneficial for plant biodiversity?

Location

Riparian marshes, Eider‐Treene‐Sorge lowland, Schleswig‐Holstein, Germany.

Methods

We performed vegetation surveys of drainage ditches along with their water body, slope and margin structures annually for 3 years. The data were analysed with respect to date and means of ditch dredging. In addition, we recorded vegetation of the surrounding agricultural grassland, measured nutrient status of the soil and the water body and sampled seed bank of the ditch slopes. We used ANOVA and multivariate methods to describe the development of the ditch vegetation and the persistence of target meadow species.

Results

Vegetation re‐development of ditch margins proceeds quite rapidly after disturbance from dredging. Dominance of mudbank species was observed only in the first year, followed by an increase of reed species and reduction of phytodiversity. Target species of wet meadow communities reach highest abundance in the second and third year and build a significant seed bank before being suppressed by reeds.

Conclusions

In heavily eutrophicated, intensively used marsh grassland, regularly disturbed ditch margins are important secondary habitats for pioneer and subdominant wetland species, which have nearly disappeared in a larger area. Current management cycles of ditch dredging every 3–4 years comply with the successional development, allowing the mudbank and wet meadow species to persist in the vegetation and seed bank. In contrast to the frequency, the form of dredging (ditch profile), which is crucial for bird protection, plays a minor role for plants. We recommend moderate disturbance (mowing of ditch margins) to suppress strong competitors in the years between dredging for additional support to target plant species.     

Coding Variants at Hexa-allelic Amino Acid 13 of HLA-DRB1 Explain Independent SNP Associations with Follicular Lymphoma Risk

Non-Hodgkin lymphoma represents a diverse group of blood malignancies, of which follicular lymphoma (FL) is a common subtype. Previous genome-wide association studies (GWASs) have identified in the human leukocyte antigen (HLA) class II region multiple independent SNPs that are significantly associated with FL risk. To dissect these signals and determine whether coding variants in HLA genes are responsible for the associations, we conducted imputation, HLA typing, and sequencing in three independent populations for a total of 689 cases and 2,446 controls. We identified a hexa-allelic amino acid polymorphism at position 13 of the HLA-DR beta chain that showed the strongest association with FL within the major histocompatibility complex (MHC) region (multiallelic p = 2.3 × 10⁻¹⁵). Out of six possible amino acids that occurred at that position within the population, we classified two as high risk (Tyr and Phe), two as low risk (Ser and Arg), and two as moderate risk (His and Gly). There was a 4.2-fold difference in risk (95% confidence interval = 2.9–6.1) between subjects carrying two alleles encoding high-risk amino acids and those carrying two alleles encoding low-risk amino acids (p = 1.01 × 10⁻¹⁴). This coding variant might explain the complex SNP associations identified by GWASs and suggests a common HLA-DR antigen-driven mechanism for the pathogenesis of FL and rheumatoid arthritis.     

Mechanistic Study of Broadly Neutralizing Human Monoclonal Antibodies against Dengue Virus That Target the Fusion Loop

There are no available vaccines for dengue, the most important mosquito-transmitted viral disease. Mechanistic studies with anti-dengue virus (DENV) human monoclonal antibodies (hMAbs) provide a rational approach to identify and characterize neutralizing epitopes on DENV structural proteins that can serve to inform vaccine strategies. Here, we report a class of hMAbs that is likely to be an important determinant in the human humoral response to DENV infection. In this study, we identified and characterized three broadly neutralizing anti-DENV hMAbs: 4.8A, D11C, and 1.6D. These antibodies were isolated from three different convalescent patients with distinct histories of DENV infection yet demonstrated remarkable similarities. All three hMAbs recognized the E glycoprotein with high affinity, neutralized all four serotypes of DENV, and mediated antibody-dependent enhancement of infection in Fc receptor-bearing cells at subneutralizing concentrations. The neutralization activities of these hMAbs correlated with a strong inhibition of virus-liposome and intracellular fusion, not virus-cell binding. We mapped epitopes of these antibodies to the highly conserved fusion loop region of E domain II. Mutations at fusion loop residues W101, L107, and/or G109 significantly reduced the binding of the hMAbs to E protein. The results show that hMAbs directed against the highly conserved E protein fusion loop block viral entry downstream of virus-cell binding by inhibiting E protein-mediated fusion. Characterization of hMAbs targeting this region may provide new insights into DENV vaccine and therapeutic strategies.