Biology subjects

Stubbs, C.

Publications and source records attributed to Stubbs, C..

4 recordsLinked to original sources

bioRxiv2024

Attaching artificial Achilles and tibialis cranialis tendons to bone using suture anchors in a rabbit model: assessment of outcomes

ObjectiveThe purpose of this study was to investigate the factors associated with outcomes of attaching artificial tendons to bone using suture anchors for replacement of biological tendons in rabbits. Study DesignMetal suture anchors with braided composite sutures of varying sizes (USP #1, #2, or #5) were used to secure artificial tendons replacing both the Achilles and tibialis cranialis tendons in 12 New Zealand White rabbits. Artificial tendons were implanted either at the time of (immediate replacement, n=8), or four weeks after (delayed replacement, n=4) resection of the biological tendon. Hindlimb radiographs of the rabbits were obtained immediately after surgery and approximately every other week until the study endpoint (16 weeks post-surgery). ResultsAll suture anchors used for the tibialis cranialis artificial tendons remained secure and did not fail during the study. The suture linkage between the Achilles artificial tendon and anchor failed in 9 of 12 rabbits. In all cases, the mode of failure was suture breakage distant from the knot. Based on radiographic analysis, the mean estimated failure timepoint was 5.3{+/-}2.3 weeks post-surgery, with a range of 2-10 weeks. Analysis of variance (ANOVA) tests revealed no significant effect of tendon implantation timing or suture size on either the timing or frequency of suture anchor failure. ConclusionBased on the mode of failure, suture mechanical properties, and suture anchor design, we suspect that the cause of failure was wear of the suture against the edges of the eyelet in the suture anchor post, which reduced the suture strength below in vivo loads. Suture anchor designs differed for the tibialis cranialis and did not fail during the period of study. Future studies are needed to optimize suture anchor mechanical performance under different loading conditions and suture anchor design features.

bioengineering↗

bioRxiv2024

Development of D-box peptides to inhibit the Anaphase Promoting Complex/Cyclosome

E3 ubiquitin ligases engage their substrates via degrons - short linear motifs typically located within intrinsically disordered regions of substrates. As these enzymes are large, multi-subunit complexes that generally lack natural small-molecule ligands and are hard to drug via conventional means, alternative strategies are needed to target them in diseases, and peptide-based inhibitors derived from degrons represent a promising approach. Here we explore peptide inhibitors of Cdc20, a substrate-recognition subunit and activator of the E3 ubiquitin ligase the anaphase promoting complex/cyclosome (APC/C) that is essential in mitosis and consequently of interest as an anti-cancer target. APC/C engages substrates via degrons that include the Destruction box (D-box) motif. We used a rational design approach to construct binders containing unnatural amino acids aimed at better filling a hydrophobic pocket on the surface of Cdc20. We confirmed binding by thermal-shift assays and surface plasmon resonance and determined the structures of a number of the Cdc20- peptide complexes. Using a cellular thermal shift assay, we confirmed that the D-box peptides also bind to and stabilise Cdc20 in the cell. We found that the D-box peptides inhibit ubiquitination activity of APC/CCdc20 and are more potent than the small molecule inhibitor Apcin. Lastly, these peptides function as portable degrons capable of driving the degradation of a fused fluorescent protein. Interestingly, we find that although inhibitory activity of the peptides correlates with Cdc20-binding affinity, degradation efficacy does not, which may be due to the complex nature of APC/C regulation and effects of degron binding of subunit recruitment and conformational changes. Our study lays the groundwork for the further development of these peptides as molecular therapeutics for blocking APC/C as well as potentially also for harnessing APC/C for targeted protein degradation.

biochemistry↗

bioRxiv2022

Rabbit hindlimb kinematics and ground contact pressure during the stance phase of hopping gait

Though the rabbit is a common animal model in musculoskeletal research, there is very limited data reported on healthy rabbit biomechanics. Our objective was to quantify the normative hindlimb biomechanics of six New Zealand White rabbits (3 male, 3 female) during the stance phase of hopping gait. We measured biomechanics by synchronously recording sagittal plane motion and ground contact pressure using a video camera and pressure mat, respectively. Both foot angle (i.e., angle between foot and ground) and ankle angle curves were unimodal. The peak ankle dorsiflexion angle was 65.9{degrees}{+/-}12.7{degrees} and occurred at 39% stance, while the peak ankle plantarflexion angle was 136.9{degrees}{+/-}7.8{degrees} at toe-off. Minimum and maximum foot angles were 16.6{degrees}{+/-}6.4{degrees} at 12% stance and 125.4{degrees}{+/-}4.0{degrees} at toe-off, respectively. During stance, the knee joint center gradually progressed 4.7 cm downward and 18.1 cm forward, on average. The maximum vertical ground reaction force and contact area, both averaged across rabbits, were 42.5 {+/-} 11.4 %BW and 7.5 {+/-} 1.8 cm2, respectively. Our study confirmed that rabbits exhibit a plantigrade gait pattern, similar to humans. Future studies can reference our data to quantify the extent to which orthopedic interventions affect rabbit biomechanics.

systems biology↗

bioRxiv2022

GAIT BIOMECHANICS OF RABBITS WITH EITHER ACHILLES OR TIBIALIS CRANIALIS ARTIFICIAL TENDONS

Artificial tendons have been developed as a replacement for biological tendons with irreparable pathologies and defects. Previous studies reported the mechanical strength and tissue integration of a polyester suture-based artificial tendon, but not its effect on locomotor function. The objective of this study was to quantify the hindlimb biomechanics during hopping gait of New Zealand White rabbits with surgical replacement of either the Achilles (n=2) or tibialis cranialis (TC, n=2) biological tendons with artificial tendons. Once pre-surgery and for five consecutive weeks post-surgery (starting at about two weeks post-surgery), we measured hindlimb kinematics and ground contact pressures with a video camera and pressure mat, respectively. Promisingly, post-surgical locomotor function was either consistent or improved over time in both tendon replacement groups. However, Achilles rabbits exhibited greater immediate post-surgery functional decline and less post-surgical functional recovery than TC rabbits. Compared to healthy rabbits, at the study endpoint, (1) TC rabbits had a 17.3-degree higher (i.e., more plantarflexed) ankle angle at foot strike; and (2) Achilles rabbits had a 39.2-degree lower (i.e., more dorsiflexed) ankle angle at toe off. These functional deficits suggest that the muscles attached to the artificial tendons had lower force-generating capacity. Future studies of artificial tendons are needed to quantify long-term function, determine the effectiveness of structured rehabilitation exercises, and refine surgical implementation.

bioengineering↗