Association of physical activity with loss of knee joint space width over two years: a compositional data analysis in the Osteoarthritis Initiative.

OBJECTIVE: There is continued debate as to how engaging in physical activity (PA), including moderate-to-vigorous PA (MVPA), light PA (LPA), and sedentary time (SED), affects one's risk for knee osteoarthritis (OA). Traditional regression methods do not account for the codependence of these categories of PA, whereby when one category increases, the others must decrease. Thus, we used compositional data analysis (CoDA) to examine time spent in each category of PA, or PA composition, and its association with loss of knee joint space width (JSW), a common indicator of knee OA progression. METHODS: We performed a secondary analysis of data from a subset of participants in the Osteoarthritis Initiative. These participants had minute-by-minute activity data collected over 7 days at baseline; we then categorized each minute as MVPA, LPA, or SED. Our exposure, PA composition, represented min/day spent in each category. Our outcome, medial JSW loss, was the difference in medial tibiofemoral JSW from baseline to 2 years later. We employed CoDA, using an isometric log-ratio transformation, to examine the association of PA composition with medial JSW loss over 2 years, adjusting for potential confounders. RESULTS: We included 969 participants (age: 64.5 years, 56% female, body mass index [BMI]: 28.8 kg/m2). Mean PA composition was: MVPA 9.1 min/day, LPA 278 min/day, SED 690 min/day. Per adjusted regression models, higher MVPA was not associated with greater medial JSW loss (ß = -0.0005, P = 0.97), nor was LPA (ß = 0.06, P = 0.27) or SED (ß = -0.06, P = 0.21). CONCLUSION: Using CoDA, PA composition was not associated with medial JSW loss over 2 years.

Recommendations for the delivery of therapeutic exercise for people with knee and/or hip osteoarthritis. An international consensus study from the OARSI Rehabilitation Discussion Group.

OBJECTIVE: To develop evidence-informed recommendations to support the delivery of best practice therapeutic exercise for people with knee and/or hip osteoarthritis (OA). DESIGN: A multi-stage, evidence-informed, international multi-disciplinary consensus process that included: 1) a narrative literature review to synthesise existing evidence; 2) generation of evidence-informed proposition statements about delivery of exercise for people with knee and/or hip OA by an international multi-disciplinary expert panel, with statements refined and analysed thematically; 3) an e-Delphi survey with the expert panel to gain consensus on the most important statements; 4) a final round of statement refinement and thematic analysis to group remaining statements into domains. RESULTS: The expert panel included 318 members (academics, health care professionals and exercise providers, patient representatives) from 43 countries. Final recommendations comprised 54 specific proposition statements across 11 broad domains: 1) use an evidence-based approach; 2) consider exercise in the context of living with OA and pain; 3) undertake a comprehensive baseline assessment with follow-up; 4) set goals; 5) consider the type of exercise; 6) consider the dose of exercise; 7) modify and progress exercise; 8) individualise exercise; 9) optimise the delivery of exercise; 10) focus on exercise adherence; and 11) provide education about OA and the role of exercise. CONCLUSION: The breadth of issues identified as important by the international diverse expert panel highlights that delivering therapeutic exercise for OA is multi-dimensional and complex.

Epidemiology of osteoarthritis.

OBJECTIVE: To summarize the current state of the evidence regarding osteoarthritis (OA) prevalence, incidence and risk factors at the person-level and joint-level. DESIGN: This was a narrative review that took a comprehensive approach regarding inclusion of potential risk factors. The review complements prior reviews of OA epidemiology, with a focus on new research and emerging topics since 2017, as well as seminal studies. RESULTS: Studies continue to illustrate the high prevalence of OA worldwide, with a greater burden among older individuals, women, some racial and ethnic groups, and individuals with lower socioeconomic status. Modifiable risk factors for OA with the strongest evidence are obesity and joint injury. Topics of high interest or emerging evidence for a potential association with OA risk or progression include specific vitamins and diets, high blood pressure, genetic factors, metformin use, bone mineral density, abnormal joint shape and malalignment, and lower muscle strength/quality. Studies also continue to highlight the heterogenous nature of OA, with strong interest in understanding and defining OA phenotypes. CONCLUSIONS: OA is an increasingly prevalent condition with worldwide impacts on many health outcomes. The strong evidence for obesity and joint injury as OA risk factors calls for heightened efforts to mitigate these risks at clinical and public health levels. There is also a need for continued research regarding how potential person- and joint-level risk factors may interact to influence the development and progression of OA.

The association between walking speed from short- and standard-distance tests with the risk of all-cause mortality among adults with radiographic knee osteoarthritis: data from three large United States cohort studies.

OBJECTIVE: Adults with radiographic knee OA (rKOA) are at increased risk of mortality and walking difficulty may modify this relation. Little is known about specific aspects of walking difficulty that increase mortality risk. We investigated the association of walking speed (objective measure of walking difficulty) with mortality and examined the threshold that best discriminated this risk in adults with rKOA. METHODS: Participants with rKOA from the Johnston County Osteoarthritis Project (JoCoOA, longitudinal population-based cohort), Osteoarthritis Initiative and Multicenter Osteoarthritis Study (OAI and MOST, cohorts of individuals with or at high risk of knee OA) were included. Baseline speed was measured via 2.4-meter (m) walk test (short-distance) in JoCoOA and 20-m walk test (standard-distance) in OAI and MOST. To examine the association of walking speed with mortality risk over 9 years, hazard ratios (HR) and 95% confidence intervals (CI) were calculated from Cox regression models adjusted for potential confounders. A Maximal Likelihood Ratio Chi-square Approach was utilized to identify an optimal threshold of walking speed predictive of mortality. RESULTS: Deaths after 9 years of follow-up occurred in 23.3% (290/1244) of JoCoOA and 5.9% (249/4215) of OAI + MOST. Walking 0.2 m/s slower during short- and standard-distance walk tests was associated with 23% (aHR [95%CI]; 1.23 [1.10, 1.39]) and 25% (1.25 [1.09, 1.43]) higher mortality risk, respectively. Walking <0.5 m/s on short-distance and <1.2 m/s standard-distance walk tests, best discriminated those with and without mortality risk. CONCLUSION: Slower walking speed measured via short- and standard-distance walk tests was associated with increased mortality risk in adults with rKOA.

Adsorption and superficial transport of oil on biological and bionic superhydrophobic surfaces: a novel technique for oil-water separation.

Superhydrophobicity is a physical feature of surfaces occurring in many organisms and has been applied (e.g. lotus effect) in bionic technical applications. Some aquatic species are able to maintain persistent air layers under water (Salvinia effect) and thus become increasingly interesting for drag reduction and other 'bioinspired' applications. However, another feature of superhydrophobic surfaces, i.e. the adsorption (not absorption) and subsequent superficial transportation and desorption capability for oil, has been neglected. Intense research is currently being carried out on oil-absorbing bulk materials like sponges, focusing on oleophilic surfaces and meshes to build membranes for oil-water separation. This requires an active pumping of oil-water mixtures onto or through the surface. Here, we present a novel passive, self-driven technology to remove oil from water surfaces. The oil is adsorbed onto a superhydrophobic material (e.g. textiles) and transported on its surface. Vertical and horizontal transportation is possible above or below the oil-contaminated water surface. The transfer in a bioinspired novel bionic oil adsorber is described. The oil is transported into a container and thus removed from the surface. Prototypes have proven to be an efficient and environmentally friendly technology to clean oil spills from water without chemicals or external energy supply. This article is part of the theme issue 'Bioinspired materials and surfaces for green science and technology (part 3)'.

Live-cell imaging of Streptomyces conjugation.

Time-lapse imaging of conjugative plasmid transfer in Streptomyces revealed intriguing insights into the unique two-step conjugation process of this Gram+ mycelial soil bacterium. Differentially labelling of donor and recipient strains with distinct fluorescent proteins allowed the visualization of plasmid transfer in living mycelium. In nearly all observed matings, plasmid transfer occurred when donor and recipient hyphae made intimate contact at the lateral walls. Plasmid transfer does not involve a complete fusion of donor and recipient hyphae, but depends on a pore formed by the FtsK-like DNA translocase TraB. Following the initial transfer at the contact site of donor and recipient, the plasmids spread within the recipient mycelium by invading neighboring compartments, separated by cross walls. Intra-mycelial plasmid spreading depends on a septal cross wall localized multi-protein DNA translocation apparatus consisting of TraB and several Spd proteins and is abolished in a spd mutant. The ability to spread within the recipient mycelium is a crucial adaptation to the mycelial life style of Streptomyces, potentiating the efficiency of plasmid transfer.

Differential knee joint loading patterns during gait for individuals with tibiofemoral and patellofemoral articular cartilage defects in the knee.

OBJECTIVE: To determine compartment-specific loading patterns during gait, quantified as joint reaction forces (JRF), of individuals with knee articular cartilage defects (ACD) compared to healthy controls (HC). METHODS: Individuals with ACDs and HC participated. Individuals with ACDs were divided into groups according to ACD location: PF (only a patellofemoral ACD), TF (only a tibiofemoral ACD), and MIX (both PF and TF ACDs). Participants underwent three-dimensional gait analysis at self-selected speed. TF joint reaction force (TF-JRF) was calculated using inverse dynamics. PF joint reaction force (PF-JRF) was derived from estimated quadriceps force (FQUAD) and knee flexion angle. Primary variables of interest were the PF- and TF-JRF peaks (body weight [×BW]). Related secondary variables (gait speed, quadriceps strength, knee function, activity level) were evaluated as covariates. RESULTS: First peak PF-JRF and TF-JRF were similar in the TF and MIX groups (0.75-1.0 ×BW, P = 0.6-0.9). Both peaks were also similar in the PF and HC groups (1.1-1.3 ×BW, P = 0.7-0.8), and higher than the TF and MIX groups (P = 0.004-0.02). For the second peak PF-JRF, only the HC group was higher than the TF group (P = 0.02). The PF group walked at a similar speed as the HC group; both groups walked faster than the TF and MIX groups (P < 0.001). With gait speed and quadriceps strength as covariates, no differences were observed in JRF peaks. CONCLUSIONS: The results suggest the presence of a TF ACD (TF and MIX groups), but not a PF ACD (PF group), may affect joint loading patterns during walking. Walking slower may be a protective gait modification to reduce load.

Conjugative DNA-transfer in Streptomyces, a mycelial organism.

Conjugative DNA-transfer in the Gram-positive mycelial soil bacterium Streptomyces, well known for the production of numerous antibiotics, is a unique process involving the transfer of a double-stranded DNA molecule. Apparently it does not depend on a type IV secretion system but resembles the segregation of chromosomes during bacterial cell division. A single plasmid-encoded protein, TraB, directs the transfer from the plasmid-carrying donor to the recipient. TraB is a FtsK-like DNA-translocase, which recognizes a specific plasmid sequence, clt, via interaction with specific 8-bp repeats. Chromosomal markers are mobilized by the recognition of clt-like sequences randomly distributed all over the Streptomyces chromosomes. Fluorescence microcopy with conjugative reporter plasmids and differentially labelled recipient strains revealed conjugative plasmid transfer at the lateral walls of the hyphae, when getting in contact. Subsequently, the newly transferred plasmids cross septal cross walls, which occur at irregular distances in the mycelium and invade the neighboring compartments, thus efficiently colonizing the recipient mycelium. This intramycelial plasmid spreading requires the DNA-translocase TraB and a complex of several Spd proteins. Inactivation of a single spd gene interferes with intramycelial plasmid spreading. The molecular function of the Spd proteins is widely unknown. Spd proteins of different plasmids are highly diverse, none showing sequence similarity to a functionally characterized protein. The integral membrane protein SpdB2 binds DNA, peptidoglycan and forms membrane pores in vivo and in vitro. Intramycelial plasmid spreading is an adaptation to the mycelial growth characteristics of Streptomyces and ensures the rapid dissemination of the plasmid within the recipient colony before the onset of sporulation.

Rapid phytochrome-mediated changes in the uptake by bean roots of sodium acetate [1-(14)C] and their modification by cholinergic drugs.

4 min of red light increases the uptake of sodium acetate[1-(14)C] by excised, etiolated secondary roots of Phaseolus aureus Roxb. 4 min of far-red light reveres this effect. AMO-1618, which inhibits acetylcholinesterase activity, enhances the red-light effect, while d-tubocurarine, which blocks the animal acetylcholine receptor, inhibits it. Red light also increases basipetal translocation of the label. When the metabolic fate of the label was determined in dark-held roots, 36% of the label remained as acetate, 48% evolved as [(14)C]CO2, 3% partitioned with acetylcholine, and 3% effluxed from the roots. The rest of the label was associated with the coarse residue left after extraction. The major effect of red light was to increase the uptake of the label in the acetate fraction.We interpret these observations to mean that the phytochrome mechanism immediately causes an increase in uptake of the label during brief irradiation with red light. Because of our previous demonstration that both red light and acetylcholine increase respiration, it is probable that the increased absorption of the label is a process requiring respiratory energy. These data support the concept of phytochrome as a membrane-bound functional system that in bean roots is mediated by the acetylcholine mechanism.

Physiological effects of human/companion animal bonding.

Blood pressure, heart rate, and respiratory rate were recorded in 24 subjects during 3 9-minute measurement sessions in which they petted an unknown dog, petted a dog with whom a companion bond had been established, or read quietly. Based on the findings of this study, several conclusions were drawn: (1) There is a significant difference in changes over time in both systolic and diastolic blood pressure between petting a dog with whom a companion bond has been established and petting a dog with whom no bond exists; (2) the decreases in both systolic and diastolic blood pressure that occur during petting a dog with whom a companion bond has been established parallel the relaxation effect of quiet reading; and (3) there is a " greeting response" to the entry of a dog with whom a companion bond has been established, which results in significantly higher systolic and diastolic pressures than the response either to an unknown dog or to reading.