The conventional gait model, an open-source implementation that reproduces the past but prepares for the future

BACKGROUND

The Conventional Gait Model (CGM), known by a variety of different names, is widely used in clinical gait analysis. We present pyCGM2, an open-source implementation of the CGM with two versions. The first, CGM1.0, is a clone of Vicon Plug In Gait (PiG) with all its variants. CGM1.0 provides a platform to test the effect of modifications to the CGM on data collected and processed retrospectively or to provide backward compatibility. The second version, CGM1.1, offers some practical modifications and includes three well documented improvements.

RESEARCH QUESTION

How do improvements of the conventional gait model affect joint kinematics and kinetics?

METHOD

The practical modifications include the possibility to use a medial knee epicondyle marker, during static calibration only, to define the medio-lateral axis of the femur in place of the knee alignment device. The three improvements correspond to the change of pelvis angle decomposition sequence, the adoption of a single tibia coordinate system, and the default decomposition of the joint moments in the joint coordinate system. We validated the outputs of version CGM1.0 against Vicon-PiG, and estimated the effect of the modifications included in version CGM1.1 using gait data collected in 16 healthy participants.

RESULTS

Kinematics and kinetics of CGM1.0 were superimposed with that of Vicon-PiG, with root mean square differences less than 0.04° for kinematics and less than 0.05 N.m.kg-1 for kinetics.

SIGNIFICANCE

The differences between the CGM1.1 and CGM1.0 were minimal in the healthy participant cohort but we discussed the expected difference in participants with different gait pathologies. We hope that the pyCGM2 will facilitate the systematic testing and the use of improved processing methods for the conventional gait model.

An Introductory Guide to Survey Research in Anaesthesia

Surveys allow convenient and inexpensive research. Surveys include mail-out questionnaires, email questionnaires, telephone interviews, and personal interviews. Despite a widespread perception that surveys are easy to conduct, good surveys need rigorous design, implementation and analysis. This requires substantial planning, time and effort. The most important step in designing a survey is to clearly define the question (s) the survey aims to answer. The target population, measured variables and types of associations being investigated should be specific and unambiguous. Investigators should concentrate on what they ‘need to know’ rather than what would be ‘nice to know’. During development surveys should be piloted to identify problems. The main goal when implementing a survey is to maximize the response rate to avoid misleading results. Evidence-based strategies, including brief personalized surveys with stamped return envelopes, can be used to maximize the response rate. A poorly conducted survey can lead to misleading or invalid conclusions and may undermine participation in subsequent surveys by the target population.

Therapeutic glucocorticoids prevent bone loss but drive muscle wasting when administered in chronic polyarthritis

BACKGROUND

Patients with rheumatoid arthritis (RA) experience extra-articular manifestations including osteoporosis and muscle wasting, which closely associate with severity of disease. Whilst therapeutic glucocorticoids (GCs) reduce inflammation in RA, their actions on muscle and bone metabolism in the context of chronic inflammation remain unclear. We utilised the TNF-tg model of chronic polyarthritis to ascertain the impact of therapeutic GCs on bone and muscle homeostasis in the context of systemic inflammation.

METHODS

TNF-tg and wild-type (WT) animals received either vehicle or the GC corticosterone (100 μg/ml) in drinking water at onset of arthritis. Arthritis severity and clinical parameters were measured, serum collected for ELISA and muscle and bone biopsies collected for μCT, histology and mRNA analysis. In vivo findings were examined in primary cultures of osteoblasts, osteoclasts and myotubes.

RESULTS

TNF-tg mice receiving GCs showed protection from inflammatory bone loss, characterised by a reduction in serum markers of bone resorption, osteoclast numbers and osteoclast activity. In contrast, muscle wasting was markedly increased in WT and TNF-tg animals receiving GCs, independently of inflammation. This was characterised by a reduction in muscle weight and fibre size, and an induction in anti-anabolic and catabolic signalling.

CONCLUSIONS

This study demonstrates that when given in early onset chronic polyarthritis, oral GCs partially protect against inflammatory bone loss, but induce marked muscle wasting. These results suggest that in patients with inflammatory arthritis receiving GCs, the development of interventions to manage deleterious side effects in muscle should be prioritised.

5 Gene expression analysis and DNA methylation patterns of porcine somatic cell nuclear transfer blastocysts with high and low incidence of apoptosis

Somatic cell NT (SCNT) efficiency remains poor, preventing the technology from being regularly used in the agricultural industry. It is believed that faulty epigenetic reprogramming of SCNT embryos leads to the low overall success. A clear apoptotic signature is associated with inappropriate gene expression and epigenomic aberrancies in many experimental cell culture systems, and we hypothesised that an apoptosis biomarker could be used to effectively separate properly reprogrammed porcine SCNT embryos from those that are destined to fail due to incomplete reprogramming. Therefore, our objective was to evaluate global gene expression and DNA methylation patterns in high- and low-apoptosis individual embryos in an effort to characterise the extent of genomic reprogramming that had taken place. Porcine SCNT blastocysts on Day 6 of development were stained with a nontoxic, noninvasive caspase activity reporter, and the top and bottom 20% of detected caspase activity were classified as high and low apoptosis, respectively (3 replicate cloning sessions; n=13 embryos per group). Genomic DNA and total RNA were isolated from each individual blastocyst. The RNA sequencing libraries were prepared using the Ovation SoLo RNA-Seq system (NuGen, San Carlos, CA, USA). Reduced representation bisulfite sequencing libraries were prepared for DNA methylation analysis using a modification of the single-cell reduced representation bisulfite sequencing global DNA methylation analysis approach detailed by Guo et al. (2015 Nat. Protoc. 10, 645-59). The RNA sequencing analysis using EdgeR (https://bioconductor.org/packages/release/bioc/html/edgeR.html) revealed 175 total differentially expressed genes (fold change ≥1.5; false discovery rate ≤0.05) between the high- and low-apoptosis SCNT embryos. This list of differentially expressed genes was used to perform enrichment analysis to identify overrepresented Gene Ontology (GO) terms or Kyoto Encyclopedia of Genes and Genomes pathways (DAVID Ease version 6.8 (https://david.ncifcrf.gov/) against the Sus scrofa background genome). However, no significantly enriched GO terms or pathways were identified (false discovery rate P>0.05). Analysis of global DNA methylation patterns between high- and low-apoptosis SCNT embryos using MethylKit (Akalin et al. 2012Genome Biol. 13, R87) revealed 335 differentially methylated 100-bp regions with at least 25% difference in methylation (adjusted P ≤ 0.01). Gene transcription start sites associated with these regions were used for enrichment analysis; again, no significant enrichment of GO terms or Kyoto Encyclopedia of Genes and Genomes pathways was identified. Principal component analysis of CpG methylation showed the low-apoptosis embryos clustering more tightly than the high-apoptosis embryos, which were highly scattered. Ongoing comparisons of high- and low-apoptosis cloned embryos with naturally fertilized embryos produced invivo may provide more information about which embryos were properly reprogrammed. Although we are still pursuing a link between reprogramming and gene expression in high- and low-apoptosis embryos, we conclude that these data support a model of stochastic epigenetic reprogramming following SCNT and reinforce the necessity of identifying embryos most likely to be successful due to proper epigenetic reprogramming in order to increase SCNT efficiency.

Search for Subsolar-Mass Ultracompact Binaries in Advanced LIGO's First Observing Run

We present the first Advanced LIGO and Advanced Virgo search for ultracompact binary systems with component masses between 0.2  M_{⊙}-1.0  M_{⊙} using data taken between September 12, 2015 and January 19, 2016. We find no viable gravitational wave candidates. Our null result constrains the coalescence rate of monochromatic (delta function) distributions of nonspinning (0.2  M_{⊙}, 0.2  M_{⊙}) ultracompact binaries to be less than 1.0×10^{6}  Gpc^{-3}  yr^{-1} and the coalescence rate of a similar distribution of (1.0  M_{⊙}, 1.0  M_{⊙}) ultracompact binaries to be less than 1.9×10^{4}  Gpc^{-3}  yr^{-1} (at 90% confidence). Neither black holes nor neutron stars are expected to form below ∼1  M_{⊙} through conventional stellar evolution, though it has been proposed that similarly low mass black holes could be formed primordially through density fluctuations in the early Universe and contribute to the dark matter density. The interpretation of our constraints in the primordial black hole dark matter paradigm is highly model dependent; however, under a particular primordial black hole binary formation scenario we constrain monochromatic primordial black hole populations of 0.2  M_{⊙} to be less than 33% of the total dark matter density and monochromatic populations of 1.0  M_{⊙} to be less than 5% of the dark matter density. The latter strengthens the presently placed bounds from microlensing surveys of massive compact halo objects (MACHOs) provided by the MACHO and EROS Collaborations.

GW170817: Measurements of Neutron Star Radii and Equation of State

On 17 August 2017, the LIGO and Virgo observatories made the first direct detection of gravitational waves from the coalescence of a neutron star binary system. The detection of this gravitational-wave signal, GW170817, offers a novel opportunity to directly probe the properties of matter at the extreme conditions found in the interior of these stars. The initial, minimal-assumption analysis of the LIGO and Virgo data placed constraints on the tidal effects of the coalescing bodies, which were then translated to constraints on neutron star radii. Here, we expand upon previous analyses by working under the hypothesis that both bodies were neutron stars that are described by the same equation of state and have spins within the range observed in Galactic binary neutron stars. Our analysis employs two methods: the use of equation-of-state-insensitive relations between various macroscopic properties of the neutron stars and the use of an efficient parametrization of the defining function p(ρ) of the equation of state itself. From the LIGO and Virgo data alone and the first method, we measure the two neutron star radii as R_{1}=10.8_{-1.7}^{+2.0}  km for the heavier star and R_{2}=10.7_{-1.5}^{+2.1}  km for the lighter star at the 90% credible level. If we additionally require that the equation of state supports neutron stars with masses larger than 1.97  M_{⊙} as required from electromagnetic observations and employ the equation-of-state parametrization, we further constrain R_{1}=11.9_{-1.4}^{+1.4}  km and R_{2}=11.9_{-1.4}^{+1.4}  km at the 90% credible level. Finally, we obtain constraints on p(ρ) at supranuclear densities, with pressure at twice nuclear saturation density measured at 3.5_{-1.7}^{+2.7}×10^{34}  dyn cm^{-2} at the 90% level.

Vistusertib (dual m-TORC1/2 inhibitor) in combination with paclitaxel in patients with high-grade serous ovarian and squamous non-small-cell lung cancer

Background

We have previously shown that raised p-S6K levels correlate with resistance to chemotherapy in ovarian cancer. We hypothesised that inhibiting p-S6K signalling with the dual m-TORC1/2 inhibitor in patients receiving weekly paclitaxel could improve outcomes in such patients.

Patients and methods

In dose escalation, weekly paclitaxel (80 mg/m2) was given 6/7 weeks in combination with two intermittent schedules of vistusertib (dosing starting on the day of paclitaxel): schedule A, vistusertib dosed bd for 3 consecutive days per week (3/7 days) and schedule B, vistusertib dosed bd for 2 consecutive days per week (2/7 days). After establishing a recommended phase II dose (RP2D), expansion cohorts in high-grade serous ovarian cancer (HGSOC) and squamous non-small-cell lung cancer (sqNSCLC) were explored in 25 and 40 patients, respectively.

Results

The dose-escalation arms comprised 22 patients with advanced solid tumours. The dose-limiting toxicities were fatigue and mucositis in schedule A and rash in schedule B. On the basis of toxicity and pharmacokinetic (PK) and pharmacodynamic (PD) evaluations, the RP2D was established as 80 mg/m2 paclitaxel with 50 mg vistusertib bd 3/7 days for 6/7 weeks. In the HGSOC expansion, RECIST and GCIG CA125 response rates were 13/25 (52%) and 16/25 (64%), respectively, with median progression-free survival (mPFS) of 5.8 months (95% CI: 3.28-18.54). The RP2D was not well tolerated in the SqNSCLC expansion, but toxicities were manageable after the daily vistusertib dose was reduced to 25 mg bd for the following 23 patients. The RECIST response rate in this group was 8/23 (35%), and the mPFS was 5.8 months (95% CI: 2.76-21.25).

Discussion

In this phase I trial, we report a highly active and well-tolerated combination of vistusertib, administered as an intermittent schedule with weekly paclitaxel, in patients with HGSOC and SqNSCLC.

Clinical trial registration

ClinicialTrials.gov identifier: CNCT02193633.

Meta-analysis of prognostic factors for overall survival in patients with resected hilar cholangiocarcinoma

BACKGROUND

Hilar cholangiocarcinoma is staged using the AJCC staging system. Numerous other prognostically important histopathological and demographic characteristics have been reported. The objective of this meta-analysis was to assess statistically the effect of postresectional tumour characteristics on overall survival of patients undergoing attempted radical curative resection for hilar cholangiocarcinoma.

METHODS

Relevant studies were identified by searching the Ovid MEDLINE and PubMed databases. The search was limited to studies published between 2009 and 2017. Papers referring to intrahepatic or distal cholangiocarcinoma were excluded from review. Data extraction used standard Parmar modifications to determine pooled univariable hazard ratios (HRs).

RESULTS

Twenty-four articles, containing 4599 patients, were assessed quantitatively. In pooled analyses, age (HR 1·16, 95 per cent c.i. 1·04 to 1·28), T category (HR 1·49, 1·30 to 1·70), lymph node involvement (HR 1·78, 1·65 to 1·93), microvascular invasion (HR 1·49, 1·34 to 1·68), perineural invasion (HR 1·54, 1·40 to 1·68) and tumour differentiation (HR 1·54, 1·38 to 1·72) were significant prognostic factors, with low heterogeneity. Portal vein resection (HR 1·54, 1·15 to 1·70) and resection margin status (HR 1·77, 1·57 to 1·99) had significant effects, but with high heterogeneity. Sex, tumour size and preoperative carbohydrate antigen 19-9 levels did not have a statistically significant effect on postoperative prognosis.

CONCLUSION

Several tumour biological variables not included in the seventh edition of the AJCC classification affect overall survival. These require incorporation into prognostic models to ensure a personalized approach to prognostication and treatment.