Investigation of the role of hydrophilic chain length in amphiphilic perfluoropolyether/poly(ethylene glycol) networks: towards high-performance antifouling coatings

The facile preparation of amphiphilic network coatings having a hydrophobic dimethacryloxy-functionalized perfluoropolyether (PFPE-DMA; M(w) = 1500 g mol(-1)) crosslinked with hydrophilic monomethacryloxy functionalized poly(ethylene glycol) macromonomers (PEG-MA; M(w) = 300, 475, 1100 g mol(-1)), intended as non-toxic high-performance marine coatings exhibiting antifouling characteristics is demonstrated. The PFPE-DMA was found to be miscible with the PEG-MA. Photo-cured blends of these materials containing 10 wt% of PEG-MA oligomers did not swell significantly in water. PFPE-DMA crosslinked with the highest molecular weight PEG oligomer (ie PEG1100) deterred settlement (attachment) of algal cells and cypris larvae of barnacles compared to a PFPE control coating. Dynamic mechanical analysis of these networks revealed a flexible material. Preferential segregation of the PEG segments at the polymer/air interface resulted in enhanced antifouling performance. The cured amphiphilic PFPE/PEG films showed decreased advancing and receding contact angles with increasing PEG chain length. In particular, the PFPE/PEG1100 network had a much lower advancing contact angle than static contact angle, suggesting that the PEG1100 segments diffuse to the polymer/water interface quickly. The preferential interfacial aggregation of the larger PEG segments enables the coating surface to have a substantially enhanced resistance to settlement of spores of the green seaweed Ulva, cells of the diatom Navicula and cypris larvae of the barnacle Balanus amphitrite as well as low adhesion of sporelings (young plants) of Ulva, adhesion being lower than to a polydimethyl elastomer, Silastic T2.     

Down-regulation of epithelial cadherin is required to initiate metastatic outgrowth of breast cancer

Reduced epithelial cadherin (E-cad) is a hallmark of invasive carcinomas that have acquired epithelial-mesenchymal transition (EMT) phenotypes. Here we show that down-regulated E-cad expression induced by transforming growth factor-β (TGF-β) and EMT preceded breast cancer outgrowth in three-dimensional (3D) organotypic assays and in the lungs of mice. Pharmacological inhibitors against focal adhesion kinase prevented metastatic outgrowth of newly seeded organoids, but not that of their fully established counterparts. Interrogating the D2-HAN (hyperplastic alveolar nodule) model of breast cancer dormancy and metastasis showed that dormant D2.OR cells produced branched organoid morphologies in 3D-cultures, and expressed robust quantities of E-cad that was uncoupled from regulation by TGF-β. In contrast, metastatic D2.A1 organoids were spherical and wholly lacked E-cad expression. Interestingly, D2.A1 cells engineered to re-express E-cad formed branched organoids, down-regulated β1 integrin expression, and failed to undergo metastatic outgrowth. The tumor-suppressing function of E-cad was inactivated by increased microenvironmental rigidity, and was not recapitulated by expression of an E-cad mutant lacking its extracellular domain. Twist expression, but not that of Snail, reinitiated metastatic outgrowth in dormant D2.OR cells. Our findings show that EMT and its down-regulated expression of E-cad circumvent breast cancer dormancy in part by facilitating β1 integrin expression necessary for metastatic outgrowth.     

Negative effects of yolk testosterone and ticks on growth in canaries

Maternal yolk hormones in bird eggs are thought to adjust the offspring to the post-hatching environment. This implies that the effects of maternal yolk hormones should vary with the post-hatching environment, but to date such context-dependency has largely been ignored. We experimentally increased yolk testosterone concentrations in canary eggs and simultaneously manipulated the post-hatching context via an experimental tick-infestation of the chicks. This allows us to evaluate the context-dependency of hormone-mediated maternal effects, as it has previously been shown that ectoparasites alter the maternal yolk androgen deposition. The experimental tick infestation reduced growth in chicks from sham-treated eggs, indicating harmful effects of this ectoparasite in canaries. Chicks from testosterone-treated eggs were not affected in their development by ticks, suggesting lower ectoparasite vulnerability. But this may also be due to the fact that experimentally elevated yolk testosterone levels impaired growth even under parasite-free conditions. This contrasts previous studies, but these studies often manipulated first laid eggs, while we used eggs of subsequent laying positions. Later laid eggs are presumably of lower quality and contain higher yolk testosterone concentrations. Thus, the effects of elevated yolk testosterone on growth may be dose-dependent or vary with the egg quality, suggesting prenatal context-dependency.     

Cardioprotection by aldosterone receptor antagonism in heart failure. Part I. The role of aldosterone in heart failure

In recent years understanding of the role of aldosterone has expanded beyond the known classic effects of promoting renal sodium retention and potassium and magnesium loss. It is now well documented that aldosterone causes myocardial and perivascular fibrosis, blocks the myocardial uptake of norepinephrine, and increases plasminogen activator inhibitor levels. In conjunction with angiotensin II, aldosterone causes vascular damage, endothelial dysfunction, and decreased vascular compliance. Therefore, the renin-angiotensin-aldosterone system (RAAS) plays a major role in the development of both hypertension and heart failure and is therefore, a key target for therapeutic interventions. Commonly prescribed medications for control of hypertension and congestive heart failure are inhibitors of the RAAS, including angiotensin converting enzyme inhibitors (ACE-I) and Angiotensin II (A-II) receptor antagonists. There is a well-documented increase in aldosterone levels that occurs over several months during chronic treatment with an ACE-I or A-II receptor antagonist. Such suppression of circulating aldosterone however, is transient, as exemplified by the term "escape" used to describe the phenomenon. This rebound of aldosterone even occurs when patients receive both an ACE-I and A-II receptor antagonist. In addition, ACE-I and A-II receptor antagonists are less effective in controlling BP in the estimated 60% of hypertensive patients who are salt (volume) sensitive and more prone to hypertension-associated morbidity such as black patients and type 2 diabetics. Thus chronic and complete blockade of aldosterone action requires an aldosterone receptor antagonist. The "Randomized Aldactone Evaluation Study" (RALES) trial results in patients with severe heart failure NYHA class III or IV and a left ventricular ejection fraction of no more than 35 percent showed that administration of a sub-hemodynamic dose of spironolactone (25 mg a day) as an add on therapy to ACE-I plus standard treatment resulted in a significant mortality reduction due both to decreased death from progressive heart failure and sudden cardiac death. These findings support the pivotal role of aldosterone in the pathophysiology of progressive heart failure. Although it is an effective antialdosterone agent, widespread use of spironolactone in humans is limited by its tendency to produce undesirable sexual side effects. At standard doses, impotence and gynaecomastia can be induced in men, whereas pre-menopausal women may experience menstrual disturbances. Data on a selective aldosterone receptor antagonist, eplerenone, appear promising for the effective blockade of aldosterone and its harmful effects without the sexual disturbances of spironolactone. Recently Eplerenone was successfully introduced for the treatment of hypertension and heart failure. Growing number of experimental studies are finding a broader role for Aldosterone in driving the pathophysiology of both heart failure and hypertension. When added to conventional therapy aldosterone receptor blockers show benefits which are in addition to those conferred by ACE-I and/or AII receptor blockers.     

Hybrid xerogel films as novel coatings for antifouling and fouling release

Hybrid sol-gel-derived xerogel films prepared from 45/55 (mol ratio) n-propyltrimethoxysilane (C3-TMOS)/tetramethylorthosilane (TMOS), 2/98 (mol ratio) bis[3-(trimethoxysilyl)propyl]-ethylenediamine (enTMOS)/tetraethylorthosilane (TEOS), 50/50 (mol ratio) n-octyltriethoxysilane (C8-TEOS)/TMOS, and 50/50 (mol ratio) 3,3,3-trifluoropropyltrimethoxysilane (TFP-TMOS)/TMOS were found to inhibit settlement of zoospores of the marine fouling alga Ulva (syn. Enteromorpha) relative to settlement on acid-washed glass and give greater release of settled zoospores relative to glass upon exposure to pressure from a water jet. The more hydrophobic 50/50 C8-TEOS/TMOS xerogel films had the lowest critical surface tension by comprehensive contact angle analysis and gave significantly greater release of 8-day Ulva sporeling biomass after exposure to turbulent flow generated by a flow channel than the other xerogel surfaces or glass. The 50/50 C8-TEOS/TMOS xerogel was also a fouling release surface for juveniles of the tropical barnacle Balanus amphitrite. X-ray photon electron data indicated that the alkylsilyl residues of the C3-TMOS-, C8-TEOS-, and TFP-TMOS-containing xerogels were located on the surface of the xerogel films (in a vacuum), which contributes to the film hydrophobicity. Similarly, the amine-containing silyl residues of the enTMOS/TEOS films were located at the surface of the xerogel films, which contributes to the more hydrophilic character and increased critical surface tension of these films.     

The transmembrane helix of the Escherichia coli division protein FtsI localizes to the septal ring

FtsI (also called PBP3) of Escherichia coli is a transpeptidase required for synthesis of peptidoglycan in the division septum and is one of about a dozen division proteins that localize to the septal ring. FtsI comprises a short amino-terminal cytoplasmic domain, a single transmembrane helix (TMH), and a large periplasmic domain that encodes the catalytic (transpeptidase) activity. We show here that a 26-amino-acid fragment of FtsI is sufficient to direct green fluorescent protein to the septal ring in cells depleted of wild-type FtsI. This fragment extends from W22 to V47 and corresponds to the TMH. This is a remarkable finding because it is unusual [corrected] for a TMH to target a protein to a site more specific than the membrane. Alanine-scanning mutagenesis of the TMH identified several residues important for septal localization. These residues cluster on one side of an alpha-helix, which we propose interacts directly with another division protein to recruit FtsI to the septal ring.     

Using latent effects to determine the ecological importance of dissolved organic matter to marine invertebrates

The uptake and utilization of dissolved organic matter (DOM)by marine invertebrates is a field that has received significantattention over the past 100 years. Although it is well establishedthat DOM is taken up by marine invertebrates, the extent towhich it contributes to an animal's survival, growth, and reproduction(that is, the ecological benefits) remains largely unknown.Previous work seeking to demonstrate the putative ecologicalbenefits of DOM uptake have examined them within a single lifestage of an animal. Moreover, most of the benefits are demonstratedthrough indirect approaches by examining (1) mass balance, or(2) making comparisons of oxyenthalpic conversions of transportrates to metabolic rate as judged by oxygen consumption. Wesuggest that directly examining delayed metamorphosis or thelatent effects associated with nutritional stress of larvaeis a better model for investigating the ecological importanceof DOM to marine invertebrates. We also provide direct evidencethat availability of DOM enhances survival and growth of thebryozoan Bugula neritina. That DOM offsets latent effects inB. neritina suggests that the underlying mechanisms are at leastin part energetic.     

Influence of Heparin Mimetics on Assembly of the FGF·FGFR4 Signaling Complex

Fibroblast growth factor (FGF) signaling regulates mammalian development and metabolism, and its dysregulation is implicated in many inherited and acquired diseases, including cancer. Heparan sulfate glycosaminoglycans (HSGAGs) are essential for FGF signaling as they promote FGF·FGF receptor (FGFR) binding and dimerization. Using novel organic synthesis protocols to prepare homogeneously sulfated heparin mimetics (HM), including hexasaccharide (HM₆), octasaccharide (HM₈), and decasaccharide (HM₁₀), we tested the ability of these HM to support FGF1 and FGF2 signaling through FGFR4. Biological assays show that both HM₈ and HM₁₀ are significantly more potent than HM₆ in promoting FGF2-mediated FGFR4 signaling. In contrast, all three HM have comparable activity in promoting FGF1·FGFR4 signaling. To understand the molecular basis for these differential activities in FGF1/2·FGFR4 signaling, we used NMR spectroscopy, isothermal titration calorimetry, and size-exclusion chromatography to characterize binding interactions of FGF1/2 with the isolated Ig-domain 2 (D2) of FGFR4 in the presence of HM, and binary interactions of FGFs and D2 with HM. Our data confirm the existence of both a secondary FGF1·FGFR4 interaction site and a direct FGFR4·FGFR4 interaction site thus supporting the formation of the symmetric mode of FGF·FGFR dimerization in solution. Moreover, our results show that the observed higher activity of HM₈ relative to HM₆ in stimulating FGF2·FGFR4 signaling correlates with the higher affinity of HM₈ to bind and dimerize FGF2. Notably FGF2·HM₈ exhibits pronounced positive binding cooperativity. Based on our findings we propose a refined symmetric FGF·FGFR dimerization model, which incorporates the differential ability of HM to dimerize FGFs.