Measuring the permeability of thin solid layers of natural waxes.

HYPOTHESIS: Previous experimental work has shown that microcapsule walls, made by solidification of a molten wax, are unexpectedly permeable. The hypothesis was that this was due more to the structure of the wall than the material itself. EXPERIMENTS: The permeability of thin (sub and low micron thickness) natural waxes was measured where a membrane was placed between two cells and the diffusion of a dye (fluorescein) measured. A filter paper was used to support the membranes. Two methods were used to coat the filter paper; simple dipping and spin coating. The resulting surfaces were examined using SEM, XRD and contact angle. FINDINGS: Results indicate that the permeability of very thin walled capsules can be investigated by forming a layer on a porous support and measuring diffusion rates. Both the composition of the wax and the sample preparation is extremely important to the structure and resulting permeability of the membranes. Spin coating was much more effective than dip coating in reducing permeability. Carnauba wax had a much lower permeability than beeswax. A difference in levels between the two cells was observed, indicating a potential Osmotic pressure difference at play which should be further investigated.

Fatal injuries among Hispanic workers in the U.S. construction industry: Findings from FACE investigation reports.

INTRODUCTION: Identifying and understanding the characteristics of workplace accidents can provide vital information required to clarify their causes and prevent similar accidents from happening in the future. The Hispanic workforce represents a significant segment of the U.S. construction labor force that is projected to continue increasing in population. The government statistical data show higher rates of fatalities among Hispanic workers when compared to other ethnic groups. METHOD: This study aims to provide details about the trends of fatal injuries among Hispanic workers. The study examined 92 government investigation reports to reveal the general trends, then an examination of fatal fall injuries within the study sample was conducted since falling is the predominant cause of fatal injuries. RESULTS: The findings suggest differences in accident characteristics between Hispanic workers and all workers, which could indicate a need for different interventions to improve the overall site safety. The study also revealed the dire need to propose revised investigation procedures that would help identify the root causes of accidents, which in turn leads to better recommendations and interventions.

Production of Concentrated Pickering Emulsions with Narrow Size Distributions Using Stirred Cell Membrane Emulsification.

Stirred cell membrane emulsification (SCME) has been employed to prepare concentrated Pickering oil in water emulsions solely stabilized by fumed silica nanoparticles. The optimal conditions under which highly stable and low-polydispersity concentrated emulsions using the SCME approach are highlighted. Optimization of the oil flux rates and the paddle stirrer speeds are critical to achieving control over the droplet size and size distribution. Investigating the influence of oil volume fraction highlights the criticality of the initial particle loading in the continuous phase on the final droplet size and polydispersity. At a particle loading of 4 wt %, both the droplet size and polydispersity increase with increasing of the oil volume fraction above 50%. As more interfacial area is produced, the number of particles available in the continuous phase diminishes, and coincidently a reduction in the kinetics of particle adsorption to the interface resulting in larger polydisperse droplets occurs. Increasing the particle loading to 10 wt % leads to significant improvements in both size and polydispersity with oil volume fractions as high as 70% produced with coefficient of variation values as low as ∼30% compared to ∼75% using conventional homogenization techniques.

Measurements of Submicron Particle Adsorption and Particle Film Elasticity at Oil-Water Interfaces.

The influence of particle adsorption on liquid/liquid interfacial tension is not well understood, and much previous research has suggested conflicting behaviors. In this paper we investigate the surface activity and adsorption kinetics of charge stabilized and pH-responsive polymer stabilized colloids at oil/water interfaces using two tensiometry techniques: (i) pendant drop and (ii) microtensiometer. We found, using both techniques, that charge stabilized particles had little or no influence on the (dynamic) interfacial tension, although dense silica particles affected the "apparent" measured tension in the pendent drop, due to gravity driven elongation of the droplet profile. Nevertheless, this apparent change additionally allowed the study of adsorption kinetics, which was related qualitatively between particle systems by estimated diffusion coefficients. Significant and real interfacial tension responses were measured using ∼53 nm core-shell latex particles with a pH-responsive polymer stabilizer of poly(methyl methacrylate)-b-poly(2-(dimethylamino)ethyl methacrylate) (pMMA-b-pDMAEMA) diblock copolymer. At pH 2, where the polymer is strongly charged, behavior was similar to that of the bare charge-stabilized particles, showing little change in the interfacial tension. At pH 10, where the polymer is discharged and poorly soluble in water, a significant decrease in the measured interfacial tension commensurate with strong adsorption at the oil-water interface was seen, which was similar in magnitude to the surface activity of the free polymer. These results were both confirmed through droplet profile and microtensiometry experiments. Dilational elasticity measurements were also performed by oscillation of the droplet; again, changes in interfacial tension with droplet oscillation were only seen with the responsive particles at pH 10. Frequency sweeps were performed to ascertain the dilational elasticity modulus, with measured values being significantly higher than previously reported for nanoparticle and surfactant systems, and similar in magnitude to protein stabilized droplets.

The effect of high fat diet and saturated fatty acids on insulin signaling in the amygdala and hypothalamus of rats.

Insulin injections into the central nucleus of the amygdala (CeA) inhibit food intake but this response is lost quickly on feeding a high fat diet. The purpose of the studies described in this manuscript was to identify the potential mechanism for the development of this insulin resistance. High fat diets (HFD) induced PKCθ activation and blocked the stimulation of Akt but not mTOR phosphorylation in the amygdala in response to CeA insulin injections. Infusions of palmitic acid onto the CeA had identical effects to HFD on PKCθ expression and insulin signaling in the amygdala. CeA insulin also induced an increase in Akt phosphorylation in the hypothalamus but had no effect on hypothalamic mTOR phosphorylation. Feeding HFD but not CeA palmitate infusions reversed the hypothalamic Akt signaling response to CeA insulin. These data, which show the independence of Akt and mTOR signaling responses to insulin in the amygdala and the effect of insulin signaling in the CeA on hypothalamic Akt signaling, suggest that the amygdala might also have a significant role in regulating hypothalamic responses to dietary fat.

PKCθ expression in the amygdala regulates insulin signaling, food intake and body weight.

OBJECTIVE: To investigate the signaling mechanisms that might underlie the loss of anorectic response to insulin injections into the central nucleus of the amygdala (CeA) within 3 days of feeding a high fat diet. DESIGN AND METHODS: Protein samples from amygdala and hypothalamus of rats fed high or low fat diets were subjected to a phosphorylation screening assay. The effects of dietary fat intake on the expression and activation of protein kinase C theta (PKCθ) in brain regions was studied. Finally, lentiviral vectors were used to overexpress rat PKCθ unilaterally or bilaterally into the CeA of rats and the effects on food intake, body weight and insulin stimulation of Akt phosphorylation were studied. RESULTS: The level of pMARCKS (Myristoylated alanine-rich C-kinase substrate), a major substrate of PKCθ, was increased 116% in amygdala of high fat diet fed rats but reduced in the hypothalamus. High fat diets increased the level of PKCθ in a region specific manner in the brain and this PKCθ was activated by membrane association. Overexpressing rat PKCθ either unilaterally or bilaterally into the CeA inhibited insulin stimulation of Akt signaling and blocked the anorectic response to insulin injected into the amygdala. Bilaterally injected PKCθ rats gained more weight and body fat and had increased food intake when fed a high fat diet compared to the control rats that received a lentiviral-Green Fluorescent Protein construct. CONCLUSION: The data suggest that insulin may have a physiological role within the amygdala to regulate energy balance.

PKCθ over expression in the central nucleus of the amygdala or hypothalamus has differential effects on energy balance and peripheral glucose homeostasis.

The increase in PKCθ expression in the amygdala of rats fed high fat diet (HFD) has been related to the loss of the anorectic response to insulin injections into the central nucleus of the amygdala (CeA) in these animals. PKCθ overexpression in the CeA increases food intake, body weight and body fat and inhibits insulin stimulation of Akt signaling. To study the effects of bilateral overexpression of PKCθ in the CeA of rats on peripheral metabolism, rats were injected into the CeA or 3rd ventricle with a lentiviral (LV)-PKCθ construct or LV-Green fluorescent protein (GFP) construct as a control and fed either LFD or HFD. Insulin and glucose tolerance tests were undertaken and hepatic AMPK activation, Pepck, Srebp1c gene expression and lipid levels assayed. CeA LV-PKCθ injected rats increased food intake, body weight and body fat and increased hepatic, but not serum, triglyceride levels compared to control rats that received a CeA-LV-GFP construct. Hepatic AMP-kinase activity was reduced but expression of Pepck increased while serum insulin decreased, glucose tolerance improved and the hypoglycemic response to insulin was enhanced in CeA LV-PKCθ injected rats. In contrast, rats that received LV-PKCθ injections into the 3rd Ventricle did not show any changes in food intake or body weight although serum, but not hepatic, triglyceride levels were increased and glucose tolerance was impaired. The data suggest that activation of PKCθ in the CeA and hypothalamus have different effects on energy balance and peripheral metabolism and that insulin signaling in the amygdala regulates peripheral metabolism.

Cage food location alters energy balance and endoplasmic reticulum stress in the brain of mice.

We have previously shown that voluntary wheel running activity in mice is associated with an increase in the Endoplasmic Reticulum (ER) Unfolded Protein stress response in multiple regions of the brain. Mice that are given access to running wheels show large variations in individual running activity. In contrast, when food is placed on the lid of their cages, rather than within the cage, all mice must undertake significant physical activity in order to gain access to their food. Hence we investigated the effects of food location on food intake and growth of C57BL/6 mice and on the activity of the ER stress system in the brain as reflected in the expression of two marker genes, Xbp1 and Atf6. Mice that had food in cups within their cages and allowed access to running wheels showed the anticipated changes in food intake, body weight and ER stress in the hippocampus compared to mice with no access to running wheels. Locating the food on the lid had no effect on food intake but reduced weight gain significantly. Likewise, locating food on the lid increased the expression of both Xbp1 and Atf6 in the hippocampi in the absence of any running wheel activity. Voluntary wheel running activity was reduced in mice whose food was located on the cage lid and this running actually reduced the expression of the two marker ER stress genes. We conclude that the usual practice of providing food for mice on their cage lids provides a significant level of physical activity that alters the metabolic status and increases ER stress. As such, this may not be the optimal model for the majority of mouse studies that are reported in the literature and it may significantly alter the interpretation of the effect of wheel running activity on ER stress. The differential effects of food location on hippocampal Bdnf gene expression also suggest that BDNF does not directly regulate UPR activity but may be coordinately regulated in response to running activity.

Determination of the shell permeability of microcapsules with a core of oil-based active ingredient.

An experimental and theoretical methodology is proposed to calculate the permeability of microcapsules that contain a core of oil-based active ingredient. Theoretical analysis is performed considering the polydispersity of the measurable capsule size, which allows the estimation of the permeability polydispersity via three different methods. The models proposed were applied in order to determine the permeability of melamine-formaldehyde microcapsules with hexyl salicylate as core oil. Release experiments were performed with four different co-solvents (ethanol, propan-1-ol, propan-2-ol and 1,3-butanediol) of different concentration. Permeability values were found to be constant, despite a two order magnitude of difference in the solubility concentrations.

Clay-based colloidosomes.

Poly(ethylene imine) (PEI) has been adsorbed onto the surface of Laponite clay nanoparticles from aqueous solution at pH 9 in order to produce an efficient hybrid Pickering emulsifier. This facile protocol allows formation of stable sunflower oil-in-water Pickering emulsions via homogenization at 12,000 rpm for 2 min at 20 °C. The effect of varying the extent of PEI adsorption on the Pickering emulsifier performance of the surface-modified Laponite is investigated for five oils of varying polarity using aqueous electrophoresis, thermogravimetric analysis, and laser diffraction studies. A minimum volume-average emulsion droplet diameter of around 60 µm was achieved at a Laponite concentration of 0.50% by mass when utilizing a PEI/Laponite mass ratio of 0.50. Such emulsions proved to be very stable toward droplet coalescence over time scales of months, although creaming is observed on standing within days due to the relatively large droplet size. These conditions correspond to submonolayer coverage of the Laponite particles by the PEI, which ensures that there is little or no excess PEI remaining in the aqueous continuous phase. This situation is confirmed by visual inspection of the underlying aqueous phase of the creamed emulsion when using fluorescently labeled PEI. These Pickering emulsions are readily converted into novel clay-based colloidosomes via reaction of the primary and/or secondary amine groups on the PEI chains adsorbed at the Laponite surface with either oil-soluble poly(propylene glycol) diglycidyl ether or water-soluble poly(ethylene glycol) diglycidyl ether cross-linkers. These colloidosomes were sufficiently robust to survive the removal of the internal oil phase after washing with excess alcohol, as judged by both optical and fluorescence microscopy. However, dye release studies conducted with clay-based colloidosomes suggest that these microcapsules are highly permeable and hence do not provide an effective barrier for retarding the release of small molecules.

Molecular mechanisms for activation of the agouti-related protein and stimulation of appetite.

OBJECTIVE: The agouti-related protein (Agrp) is a powerful orexigenic peptide, but little is known about its transcriptional regulation. The objective of this study was to determine molecular mechanisms for the activation of hypothalamic Agrp and identify compounds that stimulate appetite. RESEARCH DESIGN AND METHODS: We used promoter analyses methods, hypothalamic cell culture and transfection, immunohistochemistry, luciferase-expressing transgenic mice, in vivo bioluminescence, anitisense RNA, mouse feeding studies, indirect calorimetry, real-time PCR, and Western blots. RESULTS: We found that the Krüppel-like factor 4 (Klf4) is a potent activator of Agrp by binding to a specific CACCC-box in its minimal promoter. We also found that an extract of tarragon, termed PMI-5011, activated hypothalamic Klf4 and Agrp. In vivo, PMI-5011 increased Agrp promoter activity in luciferase-expressing transgenic mice, increased hypothalamic Klf4 and Agrp expression, increased hypothalamic Orexin and melanin-concentrating hormone, increased food intake, reduced circulating insulin and leptin levels, attenuated energy expenditure, and enhanced body weight but only when using a high-fat diet. CONCLUSIONS: These data show that Klf4 augmented hypothalamic Agrp by binding to a specific CACCC-box onto its minimal promoter. In addition, the tarragon extract PMI-5011 activated Klf4 and orexigenic neuropeptides and reduced peripheral insulin and leptin levels leading to positive energy balance.

Adsorption kinetics of laponite and ludox silica nanoparticles onto a deposited poly(diallyldimethylammonium chloride) layer measured by a quartz crystal microbalance and optical reflectometry.

A quartz crystal microbalance with dissipation (QCM-D) and an optical reflectometer (OR) have been used to investigate the adsorption behavior of Laponite and Ludox silica nanoparticles at the solid-liquid interface. The adsorption of both Laponite and Ludox silica onto poly(diallyldimethylammonium chloride) (PDADMAC)-coated surfaces over the first few seconds were studied by OR. Both types of nanoparticles adsorbed rapidly and obtained a stable adsorbed amount after only a few minutes. The rate of adsorption for both nanoparticle types was concentration dependent. The maximum adsorption rate of Ludox nanoparticles was found to be approximately five times faster than that for Laponite nanoparticles. The QCM data for the Laponite remained stable after the initial adsorption period at each concentration tested. The observed plateau values for the frequency shifts increased with increasing Laponite particle concentration. The QCM data for the Ludox nanoparticles had a more complex long-time behavior. In particular, the dissipation data at 3 ppm and 10 ppm Ludox increased slowly with time, never obtaining a stable value within the duration of the experiment. We postulate here that this is caused by slow structural rearrangements of the particles and the PDADMAC within the surface adsorbed layer. Furthermore, the QCM dissipation values were significantly smaller for Laponite when compared with those for Ludox for all nanoparticle concentrations, suggesting that the Laponite adsorbed layer is more compact and more rigidly bound than the Ludox adsorbed layer.

Multi-layer films of block copolymer micelles adsorbed to colloidal templates.

Alternating layers of cationic and anionic block copolymer micelles have been deposited onto colloidal silica particles using a layer-by-layer approach. The resulting films have been investigated using a number of characterization techniques including zeta potential measurements, dynamic light scattering, thermo-gravimetric analysis and microscopy. The micelles used here demonstrate pH-responsive behaviour both in solution and when adsorbed at interfaces. It has been shown that block copolymer micelles can selectively encapsulate and release hydrophobic materials; therefore, the incorporation of such responsive species within films has the potential to offer increased functionality. The formation of films onto colloidal particles is of great interest as it can provide pathways to direct encapsulation of materials along with surface modification. This study aims to provide new insights into the nature and properties of responsive films. Such studies will allow for the future development of novel delivery systems that have potential application within a number of industrial sectors including personal care products, pharmaceuticals and agro-chemicals.

Effects of dietary fat and enterostatin on dopamine and 5-hydroxytrytamine release from rat striatal slices.

Studies have demonstrated defects of DA and 5HT neurotransmission in dietary fat induced obese animals. In the present study, we used a perfusion system to assay the release of DA and 5HT from striatal slices preloaded with [(3)H]-DA or [(3)H]-5HT. The release of both DA and 5HT from striatal slices of rats fed a high fat diet for 10 days, but not 3 days, was reduced when compared to striatal slices taken from rats fed a low fat diet. Enterostatin, an endogenous pentapeptide inhibits dietary fat intake when administered peripherally and centrally in animals. The central mechanism for the action of enterostatin is not yet determined even though several mechanisms have been suggested. We have shown that enterostatin enhanced [(3)H]-DA release, but not [(3)H]-5HT release from striatal slices of rats that had been adapted to high fat diet for 10 days. The enterostatin-induced increase in [(3)H]-DA release was blocked by nomifensine. Enterostatin did not alter [(3)H]-DA or [(3)H]-5HT release from striatal slices of rats adapted to high fat or low fat diet feeding for 3 days. These findings suggest that enterostatin may inhibit dietary fat intake by blocking dopamine reuptake transport to increase central striatal DA release from rats that have acquired diminished dopamine signal after an adaptive period of fat consumption.

A QCM study on the adsorption of colloidal laponite at the solid/liquid interface.

The adsorption of colloidal laponite at the solid/liquid interface on various substrates and over a range of laponite concentrations (10-1000 ppm) has been investigated. Although a wide range of surfaces were studied, only on a positively charged poly(diallyldimethylammonium chloride) (PDADMAC) surface was any adsorption of the laponite observed. This shows that when fully wetted, laponite adsorption depends primarily on the surface charge rather than the degree of hydrophobicity of the surface. The adsorption of spherical Ludox silica nanoparticles on PDADMAC surfaces was also examined for comparison with the disklike laponite. The QCM data for both laponite and Ludox show strong adsorption on PDADMAC surfaces; however, larger frequency shifts were seen for Ludox than laponite at all concentrations tested. Within the concentration range examined in this work, the dissipation data from the QCM suggested a simple monolayer formation for Ludox but a monolayer to multilayer transition for laponite as the concentration increases.

Organic-inorganic double shell composite microcapsules.

Here we present novel double shell composite microcapsules (melamine formaldehyde (MF) polymer inner shell and ripened CaCO(3) nanoparticle outer shell) prepared using a method based on in situ polymerisation to form a MF polymer shell inside the ripened CaCO(3) nanoparticulate microcapsules wall.

Polymeric microcapsules assembled from a cationic/zwitterionic pair of responsive block copolymer micelles.

Using a layer-by-layer (LbL) approach, this work presents the preparation of hollow microcapsules with a membrane constructed entirely from a cationic/zwitterionic pair of pH-responsive block copolymer micelles. Our previous work with such systems highlighted that, in order to retain the responsive nature of the individual micelles contained within the multilayer membranes, it is important to optimize the conditions required for the selective dissolution of the sacrificial particulate templates. Consequently, here, calcium carbonate particles have been employed as colloidal templates as they can be easily dissolved in aqueous environments with the addition of chelating agents such as ethylenediaminetetraacetic acid (EDTA). Furthermore, the dissolution can be carried out in solutions buffered to a desirable pH so not to adversely affect the pH sensitive micelles forming the capsule membranes. First, we have deposited alternating layers of anionic poly[2-(dimethylamino)ethyl methacrylate-block-poly(2-(diethylamino)ethyl methacrylate)] (PDMA-PDEA) and cationic poly(2-(diethylamino)ethyl)methacrylate-block-poly(methacrylic acid) (PDEA-PMAA) copolymer micelles onto calcium carbonate colloidal templates. After deposition of five micelle bilayers, addition of dilute EDTA solution resulted in dissolution of the calcium carbonate and formation of hollow polymer capsules. The capsules were imaged using atomic force microscopy (AFM) and scanning electron microscopy (SEM), which shows that the micelle/micelle membrane is sufficiently robust to withstand dissolution of the supporting template. Quartz crystal microbalance studies were conducted and provide good evidence that the micelle multilayer structure is retained after EDTA treatment. In addition, a hydrophobic dye was incorporated into the micelle cores prior to adsorption. After dissolution of the particle template, the resulting hollow capsules retained a high concentration of dye, suggesting that the core/shell structure of the micelles remains intact. Finally, thermogravimetric analysis (TGA) of dried capsules confirmed complete removal of the sacrificial inorganic template. As far as we are aware, this is the first demonstration of LbL assembled capsules composed entirely from responsive block copolymer micelles. The results presented here when combined with our previous findings demonstrate that such systems have potential application in the encapsulation and triggered release of actives.

Three weeks voluntary running wheel exercise increases endoplasmic reticulum stress in the brain of mice.

The unfolded protein response (UPR) is a dynamic cellular mechanism for reducing endoplasmic reticulum (ER) stress. ER stress occurs from a variety of causes such as nutritional deprivation or over-nutrition, expression of misfolded or mutant proteins and increased synthesis of secretory protein. Obesity induced by over-nutrition has been associated with ER stress. Although exercise has a beneficial effect in opposing the development of obesity and neurodegenerative diseases, there have been no studies on the effect of exercise on ER stress in the brain induced by over-nutrition. We have taken advantage of the substantial individual differences in voluntary running activity among inbred C57BL/6 mice to investigate the relation between ER stress within regions of the brain and voluntary running activity in mice fed on either a low fat or high fat diet while maintained individually in cages with running wheels. Mice were divided into three groups depending on their voluntary running level and compared with a sedentary group. ER stress was assayed by real-time PCR and Western blots of the UPR pathway markers Xbp1, PERK, eIF2alpha, Hspa5 and ATF6. Three weeks of HFD had little effect on ER stress in the brain of the sedentary group compared to animals fed the LFD. Higher voluntary running activity was associated with increased ER stress in the hypothalamus, hippocampus and cortex. The responses were largest in the hypothalamus. The increase in the UPR response in response to exercise did not induce apoptotic signals and may thus contribute to the protective effect of exercise in preventing neurodegenerative disease.

Melanocortin activity in the amygdala controls appetite for dietary fat.

The amygdala is rich in melanocortin 4 receptors. Because the reduction in dietary fat intake after enterostatin is injected in the central nucleus of the amygdala (CeA) is blocked by a melanocortin 4 receptor antagonist, we investigated the role of melanocortin activity in the CeA in regulating food intake and macronutrient choice. Sprague-Dawley rats, fitted with CeA cannulas, were fed either chow, a high-fat (HF) diet, or adapted to a two-choice HF or low-fat (LF) diet. Injections of the MC4R agonist melanotan II (MTII) in the CeA had a dose-dependent inhibitory effect on food intake that lasted for at least 24 h. This response was greater in rats fed a HF diet. The inverse agonist agouti-related protein (AgRP) and antagonist SHU-9119 increased food intake in a dose-dependent manner, with the hyperphagia lasting for 60 h. In rats adapted to a two-choice HF/LF diet, MTII decreased HF consumption but had no effect on LF consumption, resulting in a long-lasting decrease in total calorie intake (-35.5% after 24 h, P < 0.05). Total calorie intake increased in both AgRP- and SHU-9119-treated rats (32 and 109% after 24 h, respectively) as the result of increased intake of HF diet. There was no modification of LF consumption with AgRP treatment and a transient nonsignificant decrease with SHU-9119 treatment. Amygdala brain-derived neurotrophic factor expression was increased by AgRP in fed rats. These results identify the amygdala as a site of action for the melanocortin system to control food intake and dietary preferences.