Structure–function relationships of the peptide Paulistine: A novel toxin from the venom of the social wasp Polybia paulista

Background

The peptide Paulistine was isolated from the venom of wasp Polybia paulista. This peptide exists under a natural equilibrium between the forms: oxidised — with an intra-molecular disulphide bridge; and reduced — in which the thiol groups of the cysteine residues do not form the disulphide bridge. The biological activities of both forms of the peptide are unknown up to now.

Methods

Both forms of Paulistine were synthesised and the thiol groups of the reduced form were protected with the acetamidemethyl group [Acm-Paulistine] to prevent re-oxidation. The structure/activity relationships of the two forms were investigated, taking into account the importance of the disulphide bridge.

Results

Paulistine has a more compact structure, while Acm-Paulistine has a more expanded conformation. Bioassays reported that Paulistine caused hyperalgesia by interacting with the receptors of lipid mediators involved in the cyclooxygenase type II pathway, while Acm-Paullistine also caused hyperalgesia, but mediated by receptors involved in the participation of prostanoids in the cyclooxygenase type II pathway.

Conclusion

The acetamidemethylation of the thiol groups of cysteine residues caused small structural changes, which in turn may have affected some physicochemical properties of the Paulistine. Thus, the dissociation of the hyperalgesy from the edematogenic effect when the actions of Paulistine and Acm-Paulistine are compared to each other may be resulting from the influence of the introduction of Acm-group in the structure of Paulistine.

General significance

The peptides Paulistine and Acm-Paulistine may be used as interesting tools to investigate the mechanisms of pain and inflammation in future studies.     

Pigment Epithelium‐Derived Factor,Insulin Sensitivity,and Adiposity in Polycystic Ovary Syndrome: Impact of Exercise Training

Pigment epithelium‐derived factor (PEDF) is upregulated in obese rodents and is involved in the development of insulin resistance (IR). We aim to explore the relationships between PEDF, adiposity, insulin sensitivity, and cardiovascular risk factors in obese women with polycystic ovary syndrome (PCOS) and weight‐matched controls and to examine the impact of endurance exercise training on PEDF. This prospective cohort intervention study was based at a tertiary medical center. Twenty obese PCOS women and 14 non‐PCOS weight‐matched women were studied at baseline. PEDF, cardiometabolic markers, detailed body composition, and euglycemic—hyperinsulinemic clamps were performed and measures were repeated in 10 PCOS and 8 non‐PCOS women following 12 weeks of intensified aerobic exercise. Mean glucose infusion rate (GIR) was 31.7% lower (P = 0.02) in PCOS compared to controls (175.6 ± 96.3 and 257.2 ± 64.3 mg.m^?2.min^?1) at baseline, yet both PEDF and BMI were similar between groups. PEDF negatively correlated to GIR (r = ?0.41, P = 0.03) and high‐density lipoprotein (HDL) (r = ?0.46, P = 0.01), and positively to cardiovascular risk factors, systolic (r = 0.41, P = 0.02) and diastolic blood pressure (r = 0.47, P = 0.01) and triglycerides (r = 0.49, P = 0.004). The correlation with GIR was not significant after adjusting for fat mass (P = 0.07). Exercise training maintained BMI and increased GIR in both groups; however, plasma PEDF was unchanged. In summary, PEDF is not elevated in PCOS, is not associated with IR when adjusted for fat mass, and is not reduced by endurance exercise training despite improved insulin sensitivity. PEDF was associated with cardiovascular risk factors, suggesting PEDF may be a marker of cardiovascular risk status.     

Batch‐to‐Batch Variation of Polymeric Photovoltaic Materials: its Origin and Impacts on Charge Carrier Transport and Device Performances

A detailed investigation of the impact of molecular weight distribution of a photoactive polymer, poly[N‐9′‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole)] (PCDTBT), on photovoltaic device performance and carrier transport properties is reported. It is found that different batches of as‐received polymers have substantial differences in their molecular weight distribution. As revealed by gel permeation chromatography (GPC), two peaks can generally be observed. One of the peaks corresponds to a high molecular weight component and the other peak corresponds to a low molecular weight component. Photovoltaic devices fabricated with a higher proportion of low molecular weight component have power conversion efficiencies (PCEs) reduced from 5.7% to 2.5%. The corresponding charge carrier mobility at the short‐circuit region is also significantly reduced from 2.7 × 10^?5 to 1.6 × 10^?8 cm² V^?1 s^?1. The carrier transport properties of the polymers at various temperatures are further analyzed by the Gaussian disorder model (GDM). All polymers have similar energetic disorders. However, they appear to have significant differences in carrier hopping distances. This result provides insight into the origin of the molecular weight effect on carrier transport in polymeric semiconducting materials.     

Diagnostic epitope variability within Taenia solium 8 kDa antigen family: implications for cysticercosis immunodetection

To study diagnostic epitopes within the Taenia solium 8 kDa antigen family, six overlapping synthetic peptides from an 8 kDa family member (Ts8B2) were synthesized and evaluated by ELISA and MABA with sera from patients with neurocysticercosis (NCC), from infected pigs and from rabbits immunized with recombinant Ts8B2 protein. The pre-immune rabbit sera and the Ts8B2 recombinant protein served as negative and positive controls, respectively. A similar analysis was done with the already described antigenic peptides from another member of the 8 kDa family, highly similar to Ts8B2, the CyDA antigen. Surprisingly, neither the Ts8B2 peptides nor the CyDA peptides were recognized by infected human and porcine sera. However, the entire Ts8B2 recombinant, as well as amino and carboxy-terminal halves were recognized by the positive serum samples. The observed lack of recognition of linear Ts8B2 peptides suggests that the principal serological response to the Ts8B2 family is focused on conformational epitopes in contrast to the previously observed antigenicity of the CyDA peptides. This differential antigenicity of 8 kDa family peptides could be related with parasite antigenic variability. The fact that rabbits experimentally immunized with Ts8B2 did make anti-peptide antibodies to peptides Ts8B2-6 and CyDA-6, located in the carboxy-terminal region demonstrated that the Ts8B2 peptides are not intrinsically non-immunogenic.     

Salinity tolerance of Saprolegnia parasitica coker

Experiments on two strains ofS. parasitica have shown that this species together with other species ofSaprolegnia have a high tolerance to salinity when vegetative growth alone is considered. The effect of temperature and salinity on asexual sporulation shows that at temperatures of up to 20°C good sporulation occurs in salinities of 3.5%.. At temperatures above this, sporulation is repressed and gammae tend to be formed. Temperature appears to have a marked effect on the initial germination of zoospores, but after 12 hours this effect is minimized.

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Zusammenfassung Untersuchungen an zwei Stämmen vonS. parasitica haben gezeigt, daß diese Art, zusammen mit anderen Arten vonSaprolegnia, eine hohe Toleranz gegen Salinität hat, wenn das vegetative Wachstum allein in Betracht gezogen wird. Die Wirkung von Temperatur und Salinität an asexuellen Sporulation zeigt, daß bei Temperaturen bis zu 20°C eine gute Sporulation in einer Salinität von 3.5%. vorherrscht. Bei höheren Temperaturen wird Sporulation unterdrückt und bilden sich Gammae. Temperatur scheint eine bedeutende Wirkung an der initialen Germination von Zoosporen zu haben, jedoch ist diese Wirkung nach 12 Stunden minimal.

     

Echinostome infection in green frogs (Rana clamitans) is stage and age dependent

The increasing threat of emerging infectious diseases in both wildlife and humans has spurred interest in the causes of disease emergence, including the role of anthropogenic change. A prior field study of infection patterns in amphibians suggests that echinostome infection may be an emerging disease of green frogs Rana clamitans living in urbanized environments. We examined the impact of echinostome infection on green frog tadpoles at a wide range of developmental stages (Gosner stage 25–39). Echinostome infection was associated with green frog mortality rates of up to 40% in an early developmental stage, and none in later developmental stages. Tadpoles exposed to higher echinostome doses exhibited higher edema rates, a potential sign of compromised renal function. Histopathological analysis further supported the hypothesis that echinostome-induced tadpole mortality resulted from compromised renal function. Given that the timing of highest cercarial shedding can coincide with the most vulnerable stages of green frog tadpole development, echinostomes could significantly impact green frog survival in nature.     

A chimeric protein of simian immunodeficiency virus envelope glycoprotein gp140 and Escherichia coli aspartate transcarbamoylase

The envelope glycoproteins of the human immunodeficiency virus and the related simian immunodeficiency virus (SIV) mediate viral entry into host cells by fusing viral and target cell membranes. We have reported expression, purification, and characterization of gp140 (also called gp160e), the soluble, trimeric ectodomain of the SIV envelope glycoprotein, gp160 (B. Chen et al., J. Biol. Chem. 275:34946-34953, 2000). We have now expressed and purified chimeric proteins of SIV gp140 and its variants with the catalytic subunit (C) of Escherichia coli aspartate transcarbamoylase (ATCase). The fusion proteins (SIV gp140-ATC) bind viral receptor CD4 and a number of monoclonal antibodies specific for SIV gp140. The chimeric molecule also has ATCase activity, which requires trimerization of the ATCase C chains. Thus, the fusion protein is trimeric. When ATCase regulatory subunit dimers (R(2)) are added, the fusion protein assembles into dimers of trimers as expected from the structure of C(6)R(6) ATCase. Negative-stain electron microscopy reveals spikey features of both SIV gp140 and SIV gp140-ATC. The production of the fusion proteins may enhance the possibilities for structure determination of the envelope glycoprotein either by electron cryomicroscopy or X-ray crystallography.     

Characterization and functional activity of murine monoclonal antibodies specific for α1,6-glucan chain of Helicobacter pylori lipopolysaccharide

Background: The outer core region of H. pylori lipopolysaccharide (LPS) contains α1,6‐glucan previously shown to contribute to colonizing efficiency of a mouse stomach. The aim of the present study was to generate monoclonal antibodies (mAbs) specific for α1,6‐glucan and characterize their binding properties and functional activity. Materials and Methods: BALB/c mice were injected intraperitoneally with 10⁸ formalin‐fixed H. pylori O:3 0826::Kan cells 3× over 56 days to achieve significant titer. Anti‐α1,6‐glucan‐producing hybridomas were screened by indirect ELISA using purified H. pylori O:3 0826::Kan LPS. One clone, 1C4F9, was selected for further characterization. The specificities of mAbs were determined by indirect and inhibition ELISA using structurally defined H. pylori LPS and synthetic oligosaccharides, and whole‐cell indirect ELISA (WCE) of clinical isolates. They were further characterized by indirect immunofluorescent (IF) microscopy and their functional activity in vitro determined by serum bactericidal assays against wild‐type and mutant strains of H. pylori. Results: The generated anti‐α1,6‐glucan IgM, 1C4F9, has demonstrated an excellent specificity for the glucan chain containing 5 to 6 α1,6‐linked glucose residues and showed surface accessibility by IF microscopy with H. pylori cells adherent to gastric adenocarcinoma cells monolayers. Of 38 isolates from Chile, 17 strains reacted with antiglucan mAbs in WCE (OD₄₅₀ ≥ 0.2). Bactericidal activity was observed against selective wild‐type and mutant H. pylori strains exhibiting OD₄₅₀ values of ≥0.45 in WCE. Conclusions: Anti‐α1,6‐glucan mAbs could have potential application in typing and surveillance of H. pylori isolates as well as offer insights into structural requirements for the development of LPS‐based vaccine against H. pylori infections.