The proposed system for assessment of equine articular tissues provides a useful method to quantify OA change. It is believed that addition of quantitative tracing onto plastic and macroscopic measurement as recently described would be an improvement for overall assessment of articular cartilage change.

No abstract

Regional limb perfusion involves administration of an antimicrobial solution into the vasculature of a selected portion of the limb that has been isolated from the systemic circulation by controlled application of a tourniquet. The technique provides high antimicrobial concentrations in the region of interest and greatly contributes to the elimination of infection.

The interfacial sequence DKWASLWNWFNITNWL-WYIK, preceding the transmembrane anchor of gp41 glycoprotein subunit, has been shown to be essential for fusion activity and incorporation into virions. HIV c , a peptide representing this region, formed lytic pores in liposomes composed of the main lipids occurring in the human immunodeficiency virus, type 1 (HIV-1), envelope, i.e. 1-palmitoyl-2-oleoylphosphatidylcholine (POPC):sphingomyelin (SPM):cholesterol (Chol) (1:1:1 mole ratio), at low (>1:10,000) peptide-to-lipid mole ratio, and promoted the mixing of vesicular lipids at >1: 1000 peptide-to-lipid mole ratios. Inclusion of SPM or Chol in POPC membranes had different effects. Whereas SPM sustained pore formation, Chol promoted fusion activity. Even if partitioning into membranes was not affected in the absence of both SPM and Chol, HIV c had virtually no effect on POPC vesicles. Conditions described to disturb occurrence of lateral separation of phases in these systems reproduced the high peptidedose requirements for leakage as found in pure POPC vesicles and inhibited fusion. Surface aggregation assays using rhodamine-labeled peptides demonstrated that SPM and Chol promoted HIV c self-aggregation in membranes. Employing head-group fluorescent phospholipid analogs in planar supported lipid layers, we were able to discern HIV c clusters associated to ordered domains. Our results support the notion that the pretransmembrane sequence may participate in the clustering of gp41 monomers within the HIV-1 envelope, and in bilayer architecture destabilization at the loci of fusion.

Equinatoxin-II is a eukaryotic pore-forming toxin belonging to the family of actinoporins. Its interaction with model membranes is largely modulated by the presence of sphingomyelin. We have used large unilamellar vesicles and lipid monolayers to gain further information about this interaction. The coexistence of gel and liquid-crystal lipid phases in sphingomyelin/phosphatidylcholine mixtures and the coexistence of liquid-ordered and liquiddisordered lipid phases in phosphatidylcholine/cholesterol or sphingomyelin/phosphatidylcholine/cholesterol mixtures favor membrane insertion of equinatoxin-II. Phosphatidylcholine vesicles are not permeabilized by equinatoxin-II. However, the localized accumulation of phospholipase C-generated diacylglycerol creates conditions for toxin activity. By using epifluorescence microscopy of transferred monolayers, it seems that lipid packing defects arising at the interfaces between coexisting lipid phases may function as preferential binding sites for the toxin. The possible implications of such a mechanism in the assembly of a toroidal pore are discussed.Equinatoxin II (Eqt-II) 1 is a member of the actinoporins, a group of sea anemone cytolysins (1). It is a 179-amino acid residue protein with a molecular mass of 19.8 kDa and an isoelectric point of 10.5 (2). Its three-dimensional structure has been solved by x-ray crystallography and NMR (3, 4). Eqt-II forms cation-selective pores with a diameter of ϳ2 nm in cell and model membranes (5-7). The mechanism of pore formation is a multistep process consisting of (i) membrane binding of the water-soluble monomer, (ii) oligomerization on the membrane surface, and (iii) pore formation (1,(5)(6)(7)(8)(9)(10)(11). This mechanism is common to other actinoporins like sticholysin-II from Stichodactyla helianthus (12, 13). Membrane insertion of Eqt-II and sticholysins is favored by the presence of sphingomyelin within the target membrane (6, 8, 14 -16). The recent finding of a phosphocholine binding site in the three-dimensional structure of sticholysin-II (13) supports the role of sphingomyelin as a specific receptor for actinoporins, as other authors have suggested (17, 18). However, the presence of sphingomyelin is not strictly necessary for the lytic activity of these toxins, which are also active in phosphatidylcholine/cholesterol mixtures (14, 16). Therefore, other factors are likely to govern their mechanism of action.Mixtures of sphingomyelin, phosphatidylcholine, and cholesterol are characteristic of the so-called rafts, microdomains in which the concentration of membrane components (lipids or proteins) and their physicochemical properties are different from the surrounding environment. The increasing amount of information pointing to the existence of lipid domains in cell and model membranes and their implication in many crucial biological processes has been extensively reviewed (19 -26). One important characteristic of rafts is their resistance to detergent solubilization (27)(28)(29)(30). This property is associated with the fact...