The sag response in human muscle contraction.

PURPOSE: We examined how muscle length and time between stimuli (inter-pulse interval, IPI) influence declines in force (sag) seen during unfused tetani in the human adductor pollicis muscle. METHODS: A series of 16-pulse contractions were evoked with IPIs between 1 × and 5 × the twitch time to peak tension (TPT) at large (long muscle length) and small (short muscle length) thumb adduction angles. Unfused tetani were mathematically deconstructed into a series of overlapping twitch contractions to examine why sag exhibits length- and IPI-dependencies. RESULTS: Across all IPIs tested, sag was 62% greater at short than long muscle length, and sag increased as IPI was increased at both muscle lengths. Force attributable to the second stimulus increased as IPI was decreased. Twitch force declined from maximal values across all IPI tested, with the greatest reductions seen at short muscle length and long IPI. At IPI below 2 × TPT, the twitch with highest force occurred earlier than the peak force of the corresponding unfused tetani. Contraction-induced declines in twitch duration (TPT + half relaxation time) were only observed at IPI longer than 1.75 × TPT, and were unaffected by muscle length. CONCLUSIONS: Sag is an intrinsic feature of healthy human adductor pollicis muscle. The length-dependence of sag is related to greater diminution of twitch force at short relative to long muscle length. The dependence of sag on IPI is related to IPI-dependent changes in twitch duration and twitch force, and the timing of peak twitch force relative to the peak force of the associated unfused tetanus.

Family Physician Prescribing Practices and Perspectives on Shared Decision-Making Regarding the Use of Oral Anticoagulants for Stroke Prevention in Patients 75 Years or Older With Atrial Fibrillation.

INTRODUCTION: Atrial Fibrillation (AF) is common in older adults, yet guideline-recommended oral anti-coagulants (OACs) for stroke prevention are underused in this population. With a growing population of older adults at risk of AF seeking primary care, the objective of the study was to determine the management practices and perspectives of family physicians on the initiation of OACs for stroke prevention in AF patients 75 years or older, including their engagement of patients in shared decision-making. METHODS: This was an online survey of family physicians affiliated with a Primary Care Network in Alberta, Canada. RESULTS: Patient's risk (of falls, bleeding, or stroke) was the most common factor (17/20, 85%) physicians considered when deciding to initiate OAC in older adult patients with AF. Physicians used the CHADS2VASC (13/14, 93%) and HASBLED (11/15, 73%) tools to determine stroke and bleeding risks, respectively. Majority (11/15, 73%) of the physicians agreed that they feel confident initiating OAC for AF patients ≥75, while 20% (3/15) were neutral. All physicians agreed that their patients participated in shared decision-making to initiate OAC for stroke prevention. CONCLUSION: Family physicians strongly consider patient risks and utilize risk-assessment tools when initiating OAC in older adults with AF. Despite all physicians reporting the use of shared decision-making and that their patients were educated on the indications for OAC, confidence in initiating treatment was variable. Further exploration into factors impacting physician confidence is needed.

p21-/- Mice Exhibit Spontaneous Articular Cartilage Regeneration Post-Injury.

OBJECTIVE: Recent studies have implicated the cyclin dependent kinase inhibitor, p21, in enhanced tissue regeneration observed in MRL/MpJ "super-healer" mice. Specifically, p21 is downregulated in MRL cells and similar ear hole closure to MRL mice has been observed in p21-/- mice. However, the direct implications of p21 deletion in endogenous articular cartilage regeneration remain unknown. In this study, we investigated the role of p21 deletion in the ability of mice to heal full-thickness cartilage defects (FTCDs). DESIGN: C57BL/6 and p21-/- (Cdkn1atm1Tyj) mice were subjected to FTCD and assessment of cartilage healing was performed at 1 hour, 3 days, 1 week, 2 weeks, and 4 weeks post-FTCD using a 14-point histological scoring system. X-ray microscopy was used to quantify cartilage healing parameters (e.g., cartilage thickness, surface area/volume) between C57BL/6 and p21-/- mice. RESULTS: Absence of p21 resulted in increased spontaneous articular cartilage regeneration by 3 days post-FTCD. Furthermore, p21-/- mice presented with increased cartilage thickness at 1 and 2 weeks post-FTCD compared with uninjured controls, returning to baseline by 4 weeks post-FTCD. CONCLUSIONS: We report that p21-/- mice display enhanced articular cartilage regeneration post-FTCD compared with C57BL/6 mice. Furthermore, cartilage thickness was increased in p21-/- mice at 1 week post-FTCD compared with uninjured p21-/- mice and C57BL/6 mice.

Preparing residents to deal with human trafficking.

BACKGROUND: Victims of human trafficking (HT) are predisposed to numerous health concerns. Many encounter health care practitioners during captivity, but awareness and knowledge among front-line physicians is low. Limited data exist on attempts to address this within residency training programmes. Formal curriculum time in residency is limited and online modules may be a useful educational option. METHODS: Residents in family medicine, emergency medicine and general paediatrics at the University of Alberta were invited to participate. They completed short surveys to assess knowledge both before and after completing an online learning module either individually (n = 15) or in a facilitated session (n = 17). Baseline and post-intervention changes in self-reported and tested knowledge were assessed. RESULTS: Thirty-two residents completed the pre-intervention survey: only 6% self-identified as somewhat knowledgeable on HT and 16% knew the red flags used to identify victims. Eighty-one percent wanted this topic incorporated into residency training, but only 6% and 25% had received education previously in residency or medical school, respectively. Thirteen percent were comfortable supporting victims, and 6% reported knowing how to provide support. Twenty residents completed the post-intervention survey, with improvements in both self-reported (p < 0.001) and tested (p = 0.005) knowledge of HT. Residents also reported being more prepared to identify victims (p < 0.001), more comfortable supporting victims (p < 0.001) and more confident in knowing how to support victims (p < 0.001). DISCUSSION: Baseline HT knowledge in residents providing first-contact care appears limited. Residency programmes should consider providing more HT education in order to improve competency in care. Although an online module was shown to be effective, protected time might be necessary for the widespread adoption of online education delivery.