Being Barbie: The Size of One’s Own Body Determines the Perceived Size of the World

A classical question in philosophy and psychology is if the sense of one's body influences how one visually perceives the world. Several theoreticians have suggested that our own body serves as a fundamental reference in visual perception of sizes and distances, although compelling experimental evidence for this hypothesis is lacking. In contrast, modern textbooks typically explain the perception of object size and distance by the combination of information from different visual cues. Here, we describe full body illusions in which subjects experience the ownership of a doll's body (80 cm or 30 cm) and a giant's body (400 cm) and use these as tools to demonstrate that the size of one's sensed own body directly influences the perception of object size and distance. These effects were quantified in ten separate experiments with complementary verbal, questionnaire, manual, walking, and physiological measures. When participants experienced the tiny body as their own, they perceived objects to be larger and farther away, and when they experienced the large-body illusion, they perceived objects to be smaller and nearer. Importantly, despite identical retinal input, this “body size effect” was greater when the participants experienced a sense of ownership of the artificial bodies compared to a control condition in which ownership was disrupted. These findings are fundamentally important as they suggest a causal relationship between the representations of body space and external space. Thus, our own body size affects how we perceive the world

Fabrication of crosslinked carboxymethylchitosan microspheres and their incorporation into composite scaffolds for enhanced bone regeneration

Carboxymethylchitosan (CMCS) microspheres were prepared by the carboxymethylation of chitosan (CS) beads using monochloroacetic acid. The CMCS microspheres were crosslinked using two different methods: the amine-amine crosslinker genipin and carbodiimide chemistry, yielding Gen-X CMCS and X-CMCS beads, respectively. The Gen-X CMCS beads were found to have poor degradation and drug release profiles. The X-CMCS microspheres displayed good potential for use in tissue engineering applications in which degradation and local drug delivery are desired. The X-CMCS beads displayed enzymatic degradation of 82.7 ± 1.2% in 100 lg/mL lysozyme after 1 month. An extended release of rhBMP-2 for at least 45 days was also observed with the X-CMCS microspheres. Scaffolds were formed by fusing beads together, and the X-CMCS beads were successfully incorporated into composite X-CMCS/CS scaffolds. The composite scaffolds had increased degradation of 14.5 ± 6.6% compared to 0.5 ± 0.4% for CS-only scaffolds, and the X-CMCS/CS scaffolds released more rhBMP-2 at all timepoints. The composite scaffolds also supported the attachment and proliferation of SAOS-2 cells. The addition of X-CMCS beads resulted in fabrication of scaffolds with improved properties for use in bone tissue engineering. © 2012 Wiley Periodicals, Inc

Ceramic composites for bone graft applications

Collagraft bone graft substitute was an early bone graft composite of collagen and hydroxyapatite developed and commercialized by Zimmer and Collagen Corporation. Collagraft was developed to partially simulate the major components in bone: collagen and hydroxyapatite. Collagraft received approval to market in 1993 by the U.S. Food and Drug Administration (FDA) through a Premarket Approval application. 2,3 Collagraft bone substitute is a composite of type 1 bovine dermal fibular collagen and a biphasic calcium phosphate ceramic, with each individual granule containing separate microdomains of hydroxyapatite (HA) and tricalcium phosphate (TCP) phases of a calcium phosphate ceramic. Collagraft created a combination of materials that were similar to bone and could have cells or other osteogenic materials/agents added to this synthetic graft.4 The combination of collagen with fast and slow degrading bioceramics presents a bone graft scaffold that allows for new bone formation.1 Multiple preclinical and clinical studies for bone graft repair reported the successful use of this bone graft composite with various biological agents and/or materials.4-6 Collagraft was the initial approved composite bone graft substitute and thus laid a developmental outline for subsequent bone graft substitute composites. It was the first composite bone grafting material containing both a calcium phosphate ceramic and a collagen binder. Previous bone-grafting products were just loose ceramic granules while Collagraft’s formulation provides a stable matrix for cells to attach to and deposit new bone within. Collagraft is no longer marketed/distributed through Zimmer; it is currently marketed/distributed through NeuColl, Inc. (Campbell, CA)

Cis-2-decenoic acid inhibits S. aureus growth and biofilm in vitro: A pilot study basic research

Background: Cis-2 decenoic acid (C2DA) disperses biofilm in many strains of microorganisms. However, whether C2DA inhibits bacterial growth or has potential to boost the actions of antibiotics is unknown. Questions/purposes: We asked whether (1) C2DA inhibited MRSA growth and biofilm, (2) antibiotics increased inhibitory effects, (3) inhibitory concentrations of C2DA were cytotoxic to human cells, and (4) effective concentrations could be delivered from a chitosan sponge drug delivery device. Methods: Broth containing seven concentrations of C2DA and six concentrations of either daptomycin, vancomycin, or linezolid was inoculated with a clinical isolate of MRSA and added to a total of 504 coated microtiter plate wells in triplicate (n = 3) for turbidity bacterial growth and crystal violet biofilm mass quantification. We used fibroblast cell viability assays of six C2DA concentrations (n = 4) to evaluate preliminary biocompatibility. We measured the elution of C2DA from a chitosan sponge drug delivery device with two representative loading concentrations (n = 3). Results: C2DA at concentrations of 500 μg/mL and above inhibited growth, while 125 μg/mL C2DA inhibited biofilm. Combination with antibiotics increased these effects. At concentrations up to 500 μg/mL, there were no cytotoxic effects on fibroblasts. Chitosan sponges loaded with 100 mg of C2DA eluted concentrations at or above biofilm-inhibitory concentrations for 5 days. Conclusions: C2DA inhibited biofilm formation by MRSA at biocompatible concentrations, with increasing biofilm reduction with added antibiotics. Elution of C2DA from a chitosan sponge can be modified through adjusting loading concentration. Clinical Relevance: By inhibiting biofilm formation on implant surfaces, C2DA may reduce the number of infections in musculoskeletal trauma. © 2012 The Association of Bone and Joint Surgeons®

Metal-on-Metal BearingsA Clinical Practicum /

X, 200 p. 46 illus., 26 illus. in color.online re

Emerging antibacterial biomaterial strategies for the prevention of peri-implant inflammatory diseases

Purpose: Peri-implantitis is an inflammatory disease due to bacteria and plaque formation on implant surfaces which can lead to bone resorption and loss of osseointegration. Biomaterial strategies to prevent or eliminate initial bacterial attachment, in favor of host tissue attachment may have a positive effect on decreasing peri-implantitis, particularly for at risk patient goups. This study provides a brief overview of some of the experimental biomaterial strategies aimed at suppressing or inhibiting bacterial colonization of implant surfaces in favor or host cells and tissues. Materials and Methods: These biomaterial strategies have different mechanisms of action from interfering with bacterial adhesion by modifying surface energies, immobilizing antimicrobials on implant surfaces, creating photocatalytic surfaces, as well as modifying surfaces to deliver antimicrobial agents either prophylactically or in response to bacterial challenge. This is not a comprehensive review, rather a review of studies that serve to illustrate many of the different approaches being investigated. Results: While many of these strategies have demonstrated the potential to significantly reduce bacterial attachment on implant surfaces in vitro, it is unclear if these same reductions will be adequate clinically since even a few adhering bacteria may over time develop into inflammatory inducing biofilms or plaque. Also, data on the ability of the antibacterial modified biomaterials to support osseointegration and permuosal seal formation is still needed. Conclusion: Given the complex and multivariate causes of peri-implant disease, it is likely that combinations of these strategies (eg, antimicrobial surfaces and or delivery mechanisms coupled with methods to favor stable osseointegration and permucosal seal) will be most effective in developing implants resistant to peri-implant disease. © 2011 by Quintessence Publishing Co Inc

Deacetylation of chitosan: Material characterization and in vitro evaluation via albumin adsorption and pre-osteoblastic cell cultures

Degree of deacetylation (DDA) and molecular weight (MW) of chitosans are important to their physical and biological properties. In this study, two chitosans, HS (DDA = 73.3%) and AT (DDA = 76.8%), were deacetylated with 45% sodium hydroxide under nitrogen atmosphere at 80°C or 90°C for up to 120 min, to obtain two series of chitosans. The polymers produced were characterized for MW by gel permeation chromatography, DDA by titration and UV-vis methods, and crystallinity, hydrophilicity and thermal stability by X-ray diffraction, water contact angle and differential scanning calorimetry respectively. Films, made by solution casting in dilute acetic acid at ambient conditions, were evaluated for biological activity by albumin adsorption and the attachment and growth of a pre-osteoblast cell line. Chitosans with between 80-93% DDA\u27s (based on titration) were reproducibly obtained. Even though deacetylation under nitrogen was supposed to limit chain degradation during decetylation, MW decreased (by maximum of 37.4% of HS and 63.0% for AT) with increasing deacetylation reaction time and temperature. Crystallinity and decomposition temperature increased and water contact angles decreased with processing to increase DDA. Significantly less albumin was absorbed on films made with 93% DDA chitosans as compared with the original materials and the AT chitosans absorbed less than the HS chitosans. The cells on higher DDA chitosan films grew faster than those on lower DDA films. In conclusion, processing conditions increased DDA and influenced physicochemical and biological properties. However, additional studies are needed to unambiguously determine the influence of DDA or MW on in vitro and in vivo performance of chitosan materials for bone/implant applications. © 2011 by the authors

Chitosan sponges to locally deliver amikacin and vancomycin: A pilot in vitro evaluation

Background: Open orthopaedic wounds are ideal sites for infection. Preventing infection in these wounds is critical for reducing patient morbidity and mortality, controlling antimicrobial resistance and lowering the cost of treatment. Localized drug delivery has the potential to overcome the challenges associated with traditional systemic dosing. A degradable, biocompatible polymer sponge (chitosan) that can be loaded with clinician-selected antibiotics at the point of care would provide the patient and clinician with a desirable, adjunctive preventive modality. Questions/purposes: We asked (1) if an adaptable, porous chitosan matrix could absorb and elute antibiotics for 72 hours for potential use as an adjunctive therapy to débridement and lavage; and (2) if the sponges could elute levels of antibiotic that would inhibit growth of Staphylococcus aureus and Pseudomonas aeruginosa? Methods: We fabricated a degradable chitosan sponge that can be loaded with antibiotics during a 60-second hydration in drug-containing solution. In vitro evaluation determined amikacin and vancomycin release from chitosan sponges at six time points. Activity tests were used to assess the release of inhibitory levels of amikacin and vancomycin. Results: Amikacin concentration was 881.5 μg/mL after 1 hour with a gradual decline to 13.9 μg/mL after 72 hours. Vancomycin concentration was 1007.4 μg/mL after 1 hour with a decrease to 48.1 μg/mL after 72 hours. Zone of inhibition tests were used to verify inhibitory levels of drug release from chitosan sponges. A turbidity assay testing activity of released amikacin and vancomycin indicated inhibitory levels of elution from the chitosan sponge. Clinical Relevance: Chitosan sponges may provide a potential local drug delivery device for preventing musculoskeletal infections. © 2010 The Association of Bone and Joint Surgeons®