Facial Expressions of Horses Using Weighted Multivariate Statistics for Assessment of Subtle Local Pain Induced by Polylactide-Based Polymers Implanted Subcutaneously.

Facial-expression-based analysis has been widely applied as a pain coding system in horses. Herein, we aimed to identify pain in horses undergoing subcutaneously polylactide-based polymer implantation. The sham group was submitted only to surgical incision. The horses were filmed before and 24 and 48 h after implantation. Five statistical methods for evaluating their facial expressions (FEs) were tested. Primarily, three levels of scores (0, 1, and 2) were applied to the seven FEs (ear movements, eyebrow tension, orbicularis tension, dilated nostrils, eye opening, muzzle tension, and masticatory muscles tension). Subsequently, the scores of the seven FEs were added (SUM). Afterwards, principal component analysis (PCoA) was performed using the scores of the seven FEs obtained using the first method. Subsequently, weights were created for each FE, based on each variable's contribution variability obtained from the PCoA (SUM.W). Lastly, we applied a general score (GFS) to the animal's face (0 = without pain; 1 = moderate pain; 2 = severe pain). The mechanical nociceptive threshold (MNT) and cutaneous temperature (CT) values were collected at the same moments. The results show no intra- or intergroup differences, when evaluating each FE separately or in the GFS. In the intragroup comparison and 48 h after implantation, the control group showed higher values for SUM, PCoA, and SUM.W, although the horses implanted with polymers displayed more obvious alterations in the CT and MNT. Our findings show that the five statistical strategies used to analyze the faces of the horses were not able to detect low-grade inflammatory pain.

Immiscible poly(lactic acid)/poly(ε-caprolactone) for temporary implants: Compatibility and cytotoxicity.

This manuscript focuses on the effect of the addition of a low molecular weight triblock copolymer derived from ε-caprolactone and tetrahydrofuran (CT) on the compatibility and cytotoxicity of immiscible poly(lactic acid) (PLA) and poly(ε-caprolactone) (PCL) blends. Binary and tertiary PLA/PCL blends were prepared by melt mixing in a twin-screw extruder and their morphological, mechanical and thermal behaviors were investigated by scanning electron microscopy (SEM), tensile and Izod impact test, dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). SEM micrographs showed the CT copolymer suppressed the coalescence phenomena and maintained the size of dispersed PCL domains at approximately 0.35µm. Bioresorbable PLA/PCL blends containing 5wt% of CT copolymer exhibited a remarkable increase in ductility and improved toughness at room temperature. Although the CT copolymer increased the interfacial adhesion, the DMA results suggest it also acts as a plasticizer exclusively for the PCL phase. The cell viability evaluated by the XTT assay confirmed PLA/PCL blends compatibilized by CT copolymer exerted no cytotoxic effect.