Helium ion microscopy based wall thickness and surface roughness analysis of polymer foams obtained from high internal phase emulsion

Due to their wide range of applications, porous polymers obtained from high internal phase emulsions have been widely studied using scanning electron microscopy. However, due to their lack of electrical conductivity, quantitative information of wall thicknesses and surface roughness, which are of particular interest to tissue engineering, has not been obtained. Here, Helium Ion Microscopy is used to examine uncoated polymer foams and some very strong but unexpected contrast is observed, the origin of which is established here. Based on this analysis, a method for the measurement of wall thickness variations and wall roughness measurements has been developed, based on the modeling of Helium ion transmission. The results presented here indicate that within the walls of the void structure there exist small features with height variations of ~30 nm and wall thickness variations from ~100 nm to larger 340 nm in regions surrounding interconnecting windows within the structure. The suggested imaging method is applicable to other porous carbon based structures with wall thicknesses in the range of 40-340 nm.

Smart Polymersomes: Formation, Characterisation and Applications

The term polymersome, which refers to a fully synthetic polymeric vesicle, became commonplace around the turn of the millennium. Since then these highly intriguing structures have been at the center of multi-disciplinary research, bridging the fields of nanotechnology, chemistry, physics, biology, medicine and imaging and, more recently, pioneering the field of synthetic biology. As structures they offer greater control into understanding the relationship between amphiphile properties and membrane curvature. Moreover, as delivery vectors for therapeutic and diagnostic compounds they enable greater efficiency of current therapies and targeted delivery. With the rising costs of both healthcare and drug development, polymersomes and nanomedicine are well placed to combat these modern-day problems. This chapter provides an overview of the approaches to prepare and to characterize polymersomes as well as their applications in biomedicine, highlighting recent achievements in the stimuli-responsive drug delivery field.

Thiol-Functionalized Block Copolymer Vesicles

Thiol-functionalized block copolymer vesicles are readily prepared via RAFT-mediated polymerization-induced self-assembly (PISA). More specifically, a disulfide-functionalized poly(glycerol monomethacrylate) macro-CTA is chain-extended using 2-hydroxypropyl methacrylate): the growing water-insoluble poly(2-hydroxypropyl methacrylate) chains drive in situ self-assembly to produce diblock copolymer vesicles in concentrated aqueous solution. The disulfide bonds in the poly(glycerol monomethacrylate) stabilizer chains are reductively cleaved in situ using either tributyl phosphine or tris(2-carboxyethyl)phosphine to generate thiol groups, which react immediately with either a quaternary acrylate to introduce cationic character or with rhodamine B acrylate or rhodamine B isothiocyanate to confer a convenient fluorescent tag. In addition to such facile derivatization, such thiol-functionalized vesicles may offer some potential for drug delivery applications, because enhanced muco-adhesion is anticipated for these nano-objects.

Group III and subtype 4 metabotropic glutamate receptor agonists: discovery and pathophysiological applications in Parkinson's disease

Restoring the balance between excitatory and inhibitory circuits in the basal ganglia, following the loss of dopaminergic (DA) neurons of the substantia nigra pars compacta, represents a major challenge to treat patients affected by Parkinson's disease (PD). The imbalanced situation in favor of excitation in the disease state may also accelerate excitotoxic processes, thereby representing a potential target for neuroprotective therapies. Reducing the excitatory action of glutamate, the major excitatory neurotransmitter in the basal ganglia, should lead to symptomatic improvement for PD patients and may promote the survival of DA neurons. Recent studies have focused on the modulatory action of metabotropic glutamate (mGlu) receptors on neurodegenerative diseases including PD. Group III mGlu receptors, including subtypes 4, 7 and 8, are largely expressed in the basal ganglia. Recent studies highlight the use of selective mGlu4 receptor positive allosteric modulators (PAMs) for the treatment of PD. Here we review the effects of newly-designed group-III orthosteric agonists on neuroprotection, neurorestoration and reduction of l-DOPA induced dyskinesia in animal models of PD. The combination of orthosteric mGlu4 receptor selective agonists with PAMs may open new avenues for the symptomatic treatment of PD. This article is part of a Special Issue entitled 'Metabotropic Glutamate Receptors'.

Results from an Italian multicentric registry comparing heparin-bonded ePTFE graft and autologous saphenous vein in below-knee femoro-popliteal bypasses

AIM

The aim of this study was to evaluate early and follow-up results of below-knee bypasses performed with a bioactive heparin-treated ePTFE graft in patients with peripheral arterial obstructive disease (PAOD) in a multicentric retrospective registry involving seven Italian vascular centers and to compare them with those obtained in patients operated on with autologous saphenous vein (ASV) in the same centres in the same period of time.

METHODS

Over a nine-year period, ending in 2010, a heparin bonded prosthetic graft (Propaten Gore-Tex, W.L. Gore & Associates Inc, Flagstaff, AZ, USA) was implanted in 556 patients undergoing below-knee revascularization for PAOD (HePTFE group). In the same period of time 394 below-knee bypasses with ipsilateral ASV were performed (ASV group). Data concerning these interventions were retrospectively collected in a multicenter registry with a dedicated database. Early (<30 days) results were analyzed in terms of graft patency, major amputation rates and mortality. Follow-up results were analyzed in terms of primary and secondary graft patency, limb salvage and survival.

RESULTS

Among patients of HePTFE group, 413 had critical limb ischemia (74%); the corresponding figure for ASV group was 84% (332 interventions, P<0.001). Eighty-nine patients in HePTFE group (16%) and 207 patients in ASV group (52.5%; P<0.001) had distal tibial anastomosis. Patients in HePTFE group had more frequently adjunctive procedures performed at distal anastomotic sites in order to improve run-off status. Thirty-day death rate was 1.9% in HePTFE group and 0.5% in ASV group (P=0.08). The rates of perioperative thromboses and amputations were 6% and 3.5% in HePTFE group, and 5% and 1.7% in ASV group, without significant differences between the two groups. Mean duration of follow-up was 28.5±22.1 months; 921 patients (97%) had at least one postoperative clinical and ultrasonographic control. Estimated 48-month survival rates were 81% in HePTFE group and 74% in ASV group (P=0.7, log rank 0.1). Primary patency rate at 48 months was significantly better in ASV group (61%) than in HePTFE group (44.5%; P=0.004, log rank 8.1). The rates of secondary patency at 48 months were 57% in HePTFE group and 67.5% in ASV group (P=0.1, log rank 1.9); the corresponding values in terms of limb salvage in patients with critical limb ischemia were 77% and 79.5% (P=0.3, log rank 0.9), respectively.

CONCLUSION

Data from this large, retrospective registry confirmed that the indexed heparin-bonded ePTFE graft provides satisfactory early and mid-term results in patients undergoing surgical below-knee revascularization. While autologous saphenous vein maintains its superiority in terms of primary patency, secondary patency and limb salvage rates are comparable.

Programmed cell death 4 nuclear loss and miR-21 or activated Akt overexpression in esophageal squamous cell carcinogenesis

The programmed cell death 4 (PDCD4) tumor suppressor is down-regulated in several malignancies, and the (subcellular) expression of its protein product is modulated by both oncomiR miR-21 and protein kinase B (Akt). PDCD4 and activated Akt (phosphorylated Akt [pAkt]) expression were assessed immunohistochemically in 53 tissue samples obtained from 25 endoscopic esophageal mucosal resections performed for squamous intraepithelial neoplasia (IEN) or squamous intramucosal carcinoma (IM-SSC). In total, 33 IEN (low-grade = 15; high-grade = 15) and 20 IM-SSC specimens were considered; 50 additional tissue samples of histologically proven normal esophageal mucosa were considered as normal controls. To further validate the results achieved, miR-21 expression (as assessed by quantitative real-time polymerase chain reaction and in situ hybridization) was tested in another series of 15 normal esophageal tissue samples, 15 high-grade IEN, and 15 IM-SCCs. Normal suprabasal squamous epithelial layers consistently featured strong PDCD4 nuclear immunostaining, which was significantly lower (P < 0.001) in IEN (both low-and high-grade) and in IM-SSC. Conversely, pAkt and miR-21 expression was significantly up-regulated in the whole spectrum of preneoplastic/neoplastic lesions considered. PDCD4 down-regulation, as assessed by immunohistochemistry, is a reliable biomarker of early-stage squamous cell esophageal neoplasia, providing additional information in the histological assessment of these lesions.

Cinnabarinic acid, an endogenous metabolite of the kynurenine pathway, activates type 4 metabotropic glutamate receptors

Cinnabarinic acid is an endogenous metabolite of the kynurenine pathway that meets the structural requirements to interact with glutamate receptors. We found that cinnabarinic acid acts as a partial agonist of type 4 metabotropic glutamate (mGlu4) receptors, with no activity at other mGlu receptor subtypes. We also tested the activity of cinnabarinic acid on native mGlu4 receptors by examining 1) the inhibition of cAMP formation in cultured cerebellar granule cells; 2) protection against excitotoxic neuronal death in mixed cultures of cortical cells; and 3) protection against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine toxicity in mice after local infusion into the external globus pallidus. In all these models, cinnabarinic acid behaved similarly to conventional mGlu4 receptor agonists, and, at least in cultured neurons, the action of low concentrations of cinnabarinic acid was largely attenuated by genetic deletion of mGlu4 receptors. However, high concentrations of cinnabarinic acid were still active in the absence of mGlu4 receptors, suggesting that the compound may have off-target effects. Mutagenesis and molecular modeling experiments showed that cinnabarinic acid acts as an orthosteric agonist interacting with residues of the glutamate binding pocket of mGlu4. Accordingly, cinnabarinic acid did not activate truncated mGlu4 receptors lacking the N-terminal Venus-flytrap domain, as opposed to the mGlu4 receptor enhancer, N-phenyl-7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxamide (PHCCC). Finally, we could detect endogenous cinnabarinic acid in brain tissue and peripheral organs by high-performance liquid chromatography-tandem mass spectrometry analysis. Levels increased substantially during inflammation induced by lipopolysaccharide. We conclude that cinnabarinic acid is a novel endogenous orthosteric agonist of mGlu4 receptors endowed with neuroprotective activity.

How does cross-linking affect the stability of block copolymer vesicles in the presence of surfactant?

Block copolymer vesicles are conveniently prepared directly in water at relatively high solids by polymerization-induced self-assembly using an aqueous dispersion polymerization formulation based on 2-hydroxypropyl methacrylate. However, dynamic light scattering studies clearly demonstrate that addition of small molecule surfactants to such linear copolymer vesicles disrupts the vesicular membrane. This causes rapid vesicle dissolution in the case of ionic surfactants, with nonionic surfactants proving somewhat less destructive. To address this problem, glycidyl methacrylate can be copolymerized with 2-hydroxypropyl methacrylate and the resulting epoxy-functional block copolymer vesicles are readily cross-linked in aqueous solution using cheap commercially available polymeric diamines. Such epoxy-amine chemistry confers exceptional surfactant tolerance on the cross-linked vesicles and also leads to a distinctive change in their morphology, as judged by transmission electron microscopy. Moreover, pendent unreacted amine groups confer cationic character on these cross-linked vesicles and offer further opportunities for functionalization.

The development of anisotropic behaviours of 3T3 fibroblasts on microgrooved patterns

3T3 fibroblasts cultured on microgrooved polydimethylsiloxane (PDMS) surfaces of two different widths (25 μm and 55 μm) were individually tracked using confocal microscopy with a novel live-cell staining technique over several hours without noticeable cytotoxic effects. By quantifying the cell morphology, orientation, and migration over time, we identified the timescale (about 2-4 h after seeding) over which cell behaviours transitioned from isotropy to anisotropy, where the preference is in the direction parallel to the pattern. The development of anisotropy occurred more rapidly and distinctly when a narrower ridge width was used, suggesting that it is the ridge width that imposed a physical barrier on the cells' morphology and motility. Furthermore, while we found a weak but statistically significant correlation between cell orientation and morphology on the single-cell level, there is a lack of correlation on the same level between cell orientation and migratory direction. This suggests that while morphology and migration are affected anisotropically by topographical patterns in a similar way, the underlying processes giving rise to the anisotropy is slightly different in the two cases.

Protective role for type-1 metabotropic glutamate receptors against spike and wave discharges in the WAG/Rij rat model of absence epilepsy

Eight-month old WAG/Rij rats, which developed spontaneous occurring absence seizures, showed a reduced function of mGlu1 metabotropic glutamate receptors in the thalamus, as assessed by in vivo measurements of DHPG-stimulated polyphosphoinositide hydrolysis, in the presence of the mGlu5 antagonist MPEP as compared to age-matched non-epileptic control rats. These symptomatic 8-month old WAG/Rij rats also showed lower levels of thalamic mGlu1α receptors than age-matched controls and 2-month old (pre-symptomatic) WAG/Rij rats, as detected by immunoblotting. Immunohistochemical and in situ hybridization analysis indicated that the reduced expression of mGlu1 receptors found in symptomatic WAG/Rij rats was confined to an area of the thalamus that excluded the ventroposterolateral nucleus. No mGlu1 receptor mRNA was detected in the reticular thalamic nucleus. Pharmacological manipulation of mGlu1 receptors had a strong impact on absence seizures in WAG/Rij rats. Systemic treatment with the mGlu1 receptor enhancer SYN119, corresponding to compound RO0711401, reduced spontaneous spike and wave discharges spike-wave discharges (SWDs) in epileptic rats. Subcutaneous doses of 10 mg/kg of SYN119 only reduced the incidence of SWDs, whereas higher doses (30 mg/kg) also reduced the mean duration of SWDs. In contrast, treatment with the non-competitive mGlu1 receptor antagonist, JNJ16259685 (2.5 and 5 mg/kg, i.p.) increased the incidence of SWDs. These data suggest that absence epilepsy might be associated with a reduction of mGlu1 receptors in the thalamus, and that compounds that amplify the activity of mGlu1 receptors might be developed as novel anti-absence drugs. This article is part of a Special Issue entitled 'Trends in neuropharmacology: in memory of Erminio Costa'.

Activation of the JAK-STAT pathway by olanzapine is necessary for desensitization of serotonin2A receptor-stimulated phospholipase C signaling in rat frontal cortex but not serotonin2A receptor-stimulated hormone release

Chronic treatment with olanzapine causes desensitization of serotonin 2A receptor signaling. The purpose of the current study was to further understand the mechanisms underlying this desensitization response of serotonin 2A receptor signaling in vivo. We report that desensitization of serotonin 2A receptor stimulated-phospholipase C activity in rat frontal cortex induced by olanzapine is dependent on the activation of the JAK-STAT pathway. Olanzapine treatment for 7 days significantly increased the levels of the regulator of G protein signaling (RGS7) protein, RGS7 mRNA levels, and activation of JAK2 in rat frontal cortex. Pre-treatment with a JAK2 inhibitor AG490, significantly attenuated the olanzapine-induced reductions in serotonin 2A receptor-stimulated phospholipase C activity and prevented the olanzapine-induced increases in RGS7 mRNA and protein levels. In contrast, inhibition of the JAK-STAT pathway with AG490 did not reverse the olanzapine-induced desensitization of the serotonin 2A receptor pathway in the hypothalamic paraventricular nucleus mediating increases in plasma hormone levels. AG490 dose-dependently inhibited serotonin 2A receptor-stimulated oxytocin and corticosterone release. These results suggest that the olanzapine-induced increase in RGS7 expression is mediated by the activation of JAK-STAT and is necessary for olanzapine-induced desensitization of serotonin 2A receptor-stimulated phospholipase C activity in the frontal cortex but not serotonin 2A receptor-stimulated hormone release.

The effects of indoor cycling training in sedentary overweight women

AIM

The aim of this study was to evaluate the body composition and physiological effects in young sedentary overweight women after an indoor cycle training period.

METHODS

Fourteen subjects (22.6+/-2.1 yrs; 25-29.9 BMI) were trained for 12 weeks in a specific indoor cycling protocol (ICP) consisting of three sessions/week carried out in a fitness room. Body composition and physiological parameters were taken before the beginning of the study and after 12, 24 and 36 sessions.

RESULTS

We observed a reduction of 2.6% and 3.2% in body weight and of 4.3% and 5% in fat mass after 24 and 36 sessions respectively (P<0.05). Lean mass increased by 2.3% and 2.6% respectively after 24 and 36 sessions. Body circumferences diminished in response to ICP. Resting heart rate decreased by 6.5% and 9% respectively after 24 and 36 sessions. After the tenth week, we found a reduction of 11 beats.min-1 in average training heart rate, an increase of 0.5 mL/kg-1.min-1 in average training oxygen uptake and an increase of 8.6 Watts in average power output. Moreover, an increase in cardio-respiratory fitness was observed (37.1+/-4.3 vs. 40.2+/-4.6 mL/kg-1.min-1) after 36 sessions.

CONCLUSION

The decrease in body weight, without any restriction on food consumption, and the improvement in cardio-respiratory fitness suggests that ICP may be efficient for losing weight and preventing the increased risk of cardiovascular disease in young overweight women. Indoor cycling can be performed by young sedentary overweight women; however, it is fundamental to formulate training protocols which are intensity and length specific to the fitness level of the participants.