Stability and fusion of lipid layers on polyelectrolyte multilayer supports studied by colloidal force spectroscopy.

The interaction between lipid layers supported by polyelectrolyte multilayer cushions has been studied by means of colloidal force spectroscopy. In a typical experiment, a colloidal probe engineered with a layer-by-layer film and a lipid bilayer on top is approached to a planar surface coated in a symmetrical way. Kinks of a few nanometres in width appear when lipid layers are pressed together--reflecting either fusion processes between lipid layers or membranes, or the penetration of polymer blobs into or through the lipid layers.

Trapping, pattern formation, and ordering of polyelectrolyte/single-wall carbon nanotube complexes at the air/water and air/solid interfaces.

The Langmuir and Langmuir-Blodgett (LB) techniques have been applied in a novel approach to build structurally well-ordered, oriented, and organized assemblies of water-soluble single-wall carbon nanotubes (ws-SWCNTs) at the air/water and air/solid interfaces. The SWCNTs were rendered hydrophilic by complexing them with a quenched polyelectrolyte. We observed that the ws-SWCNT concentration at the air/water interface increases with time condensing into different patterns, among which are isolated soap-froths, rings, and the aggregation of cumuli-like 2D-structures.

From hollow shells to artificial cells: biointerface engineering on polyelectrolyte capsules.

Biomimetic composites can be fabricated by coating hollow polyelectrolyte capsules with biological interfaces such as a phospholipid membrane and proteins. Polyelectrolyte capsules have been templated applying the Layer-by-Layer technique of polyelectrolyte assembled on decomposable cores, which are destroyed after the assembly of the polyelectrolyte multilayer. Phospholipid vesicles of 200-300 nm size are spreaded on the capsule wall forming a continuous lipid membrane.

Controlling ionic conductivity in lipid polyelectrolyte composite capsules by cholesterol.

The effect of cholesterol on the formation and properties of bilayer lipid membranes deposited on polyelectrolyte multilayered capsules was studied. The permeability of lipid/cholesterol coated capsules for NaCl was derived from osmotic response experiments and ranged from 1.45 x 10(-8) to 2.

Permeability and conductivity of red blood cell templated polyelectrolyte capsules coated with supplementary layers.

The permeability of ions and small polar molecules through polyelectrolyte multilayer capsules templated on red blood cells was studied by means of confocal microscopy and electrorotation. Capsules were obtained by removing the cell after polyelectrolyte multilayer formation by means of NaOCl treatment. This procedure results in cross-linking of poly(allylamine hydrochloride) (PAH) molecules and destroying poly(styrene sulfonate) (PSS) within the multilayer.

Composite lipid polyelectrolyte capsules templated on red blood cells: fabrication and structural characterisation.

Charged phospholipids and mixtures of charged phospholipids with zwitterionic lipids were adsorbed onto polyelectrolyte capsules templated on erythrocytes. The assembly was proved by means of electrophoretic mobility measurements, confocal laser scanning microscopy and flow cytometry. Freeze-fracture electron microscopy proved that the phospholipids assemble as bilayers or multilayers.

Freeze-fracture electron microscopy of lipid membranes on colloidal polyelectrolyte multilayer coated supports.

Lipid membranes were assembled on polyelectrolyte (PE)-coated colloidal particles. The assembly was studied by means of confocal microscopy, flow cytometry, scanning force microscopy, and freeze-fracture electron microscopy. A homogeneous lipid coverage was established within the limits of optical resolution.

Swelling and shrinking of polyelectrolyte microcapsules in response to changes in temperature and ionic strength.

Swelling and shrinking of polyelectrolyte microcapsules consisting of poly(styrene sulfonate, sodium salt) (PSS) and poly(diallyldimethyl ammonium) chloride (PDADMAC) multilayers have been observed in response to temperature and electrolyte exposure, respectively. Heat-induced capsule swelling and capsule wall volume reduction were observed by confocal laser scanning microscopy (CLSM) and scanning force microscopy (SFM). On the other hand, pronounced shrinking in diameter induced by exposure to an electrolyte was observed in parallel to increases in the thickness of the capsule wall.

Hollow polymer shells from biological templates: fabrication and potential applications.

Three-dimensional ultrathin polymer shells have been produced by a combination of step-by-step adsorption of polyelectrolytes on glutaraldehyde-treated human erythrocytes and subsequent solubilization of the cytoplasmatic constituents by means of a deproteinizing agent. The obtained hollow films preserve both the size and shape of the templating cells. This opens a pathway for the fabrication of polymeric capsules within a wide range of size and shape by using various biological templates.

Permeation of macromolecules into polyelectrolyte microcapsules.

Polyelectrolyte microcapsules (PEMCs) have been prepared by coating red blood cells with the polyelectrolytes poly(styrenesulfonate), poly(allylamine hydrochloride), and dextran sulfate applying the layer-by-layer technique with subsequent dissolution of the core. The capsule permeability for human serum albumin (HSA) was studied as a function of the ionic strength and pH by means of confocal microscopy. PEMCs produced with dextran sulfate and poly(allylamine hydrochloride) show a significant increase in permeability for HSA at salt concentrations over 1 mM.

Synthesis, structure, and antitumor activity of a novel tetranuclear titanium complex.

The coordination complex cyclo-tetrakis[bis(1-phenyl-3-methyl-4-benzoylpyrazolon-5-ato++ +)mu-o xotitanium(IV)] has been synthesized and characterized with IR and NMR spectroscopies and X-ray diffraction. The core of this species consists of an eight-membered Ti-mu-oxo ring with alternate short-long Ti-O bond lengths. Besides these two O ligands, each metal is bound octahedrally to four O atoms from two chelating 1-phenyl-3-methyl-4-benzoylpyrazolon-5-ato anions.

Microencapsulation by means of step-wise adsorption of polyelectrolytes.

Step-wise adsorption of polyelectrolytes is used for the fabrication of micro- and nanocapsules with determined size, capsule wall composition and thickness. The capsule walls made of polyelectrolyte multilayers exclude high molecular weight compounds. Assembling of lipid layers onto these polyelectrolyte capsules prevents the permeation of small dyes.

Microencapsulation of Organic Solvents in Polyelectrolyte Multilayer Micrometer-Sized Shells.

Hollow-shell micrometer-sized particles were fabricated in aqueous media by stepwise deposition of oppositely charged polyelectrolytes onto melamine latex particles and biological cells with a dissolution of the core afterward. It is demonstrated that these shells can be suspended in various organic media, such as methanol, ethanol, pentanol, hexanol, octanol, octane, and decane, by a gradual solvent exchange. At this stage of the procedure the shells contain the respective organic solvent.

Interleukin-1-induced sickness behavior depends on behavioral lateralization in mice.

Inter-individual differences in brain-immune interactions have been demonstrated previously in mice using lateralization as a behavioral trait of population heterogeneity. Lipopolysaccharide (LPS), which is known to induce neurochemical, neuroendocrine, and immune responses depending on lateralization, is also able to induce sickness behavior, via the production of interleukin-1 (IL-1). The objective of this study was to determine whether lateralization can influence the behavioral response to LPS and to IL-1.

In the mouse, the corticoid stress response depends on lateralization.

The influence of brain/behavioral lateralization on the neuroendocrine stress response was studied in the mouse. Using a paw preference test in a food reaching task, mice were classified as left-pawed, ambidextrous or right-pawed. Plasma levels of corticosterone (CS) were measured in basal conditions, 4 h after an intraperitoneal injection of lipopolysaccharide (LPS) or after a short period of restraint.

The novel use of Rh(I) complexes with naphthyridine ligands and poly(oxyethylene) as antitumorals.

Rh(I) complexes adsorbed on polymers, as a way to improve their transport and solubility properties, were studied as antitumor agents. The binding constants of the complexes to the polymer were evaluated in order to determine the conditions for maximum association to the vehicle. The toxicity of the pure complexes and those bound were determined in vivo using female mice.

Energetic consequences of mild Giardia intestinalis infestation in Mexican children.

This study explored the effects of mild infestation with Giardia on energy intake and expenditure at rest and in activity in an urban Mexican population. Ten boys aged 6-10 y living in low-income sectors in northwest Mexico who had Giardia infestation were recruited. Energy intake, basal metabolic rate (BMR), and total free-living expenditure (TEE) measured by the doubly labeled water method were determined for 7 d during both infestation and after treatment.

Basal metabolic rate and body fatness of adult men in northern Mexico.

To investigate the possibility that overprediction of basal metabolic rate (BMR) of tropical populations is related to differences in fatness between tropical and temperate populations, 32 Mexican men aged 18-40 years underwent measurements of BMR and body fat content. The men were divided into four body mass index (BMI) groups (< 20, 20-25, 25-30 and 30-40). The mean weight was 78 (range 52-119) kg and the mean height was 1.

[Effect of ripening and drying on pro-vitamin A carotenoid content in pepper (Capsicum annuum var. Anaheim)].

The content of the principal carotenes with biological activity (alpha-, beta, gamma-carotene and beta-criptoxantine) in green pepper (Capsicum annuum var. Anaheim) was determined in order to investigate the vitamin A content during the traditional process of ripening and drying. The analytical technique used was high pressure liquid chromatography (HPLC) with a Novapack C18 column and acetonitrile/methanol/tetrahydrofuran (58V:35V:7V) as a mobile phase.

Hormonal regulation of rat testicular gamma-glutamyl-transpeptidase "in vivo" and "in vitro".

The hormonal regulation of gamma-glutamyl transpeptidase (gamma-GTP), an enzyme marker of Sertoli cells, was studied in immature rats that received 50 micrograms/day of testosterone propionate (TP) during 6 days to suppress pituitary LH and FSH. Suppression of LH was monitored indirectly by the determination of intratesticular levels of testosterone and suppression of FSH by radioimmunoassay of serum FSH. Enzyme activity in the testis decreased in parallel to intratesticular testosterone suppression, and it did recover up to control values when animals received 500 micrograms/day of TP, a dose that was able to maintain intratesticular testosterone at normal levels.

Relative cellular distribution of particulate androgen binding between Sertoli and germ cells in rat testis.

An androgen binding activity with characteristics similar to ABP is present in a particulate fraction (105,000 g pellet) obtained by differential centrifugation of seminiferous tubules, impure Sertoli cells and impure germ cells homogenates. Purification of germ cells through albumin gradients, results in almost a complete loss of androgen binding activity in the purified germ cell suspensions. Furthermore, Sertoli cell enriched testes from 22-, 32- and 40-day old rats showed increases in particulate androgen binding, when compared to matched controls, parallel to increments in the activity of a Sertoli cell marker enzyme (beta-glucuronidase).