Modelling the role of surface stress on the kinetics of tissue growth in confined geometries

In a previous paper we presented a theoretical framework to describe tissue growth in confined geometries based on the work of Ambrosi and Guillou [Ambrosi D, Guillou A. Growth and dissipation in biological tissues. Cont Mech Thermodyn 2007;19:245–51]. A thermodynamically consistent eigenstrain rate for growth was derived using the concept of configurational forces and used to investigate growth in holes of cylindrical geometries. Tissue growing from concave surfaces can be described by a model based on this theory. However, an apparently asymmetric behaviour between growth from convex and concave surfaces has been observed experimentally, but is not predicted by this model. This contradiction is likely to be due to the presence of contractile tensile stresses produced by cells near the tissue surface. In this contribution we extend the model in order to couple tissue growth to the presence of a surface stress. This refined growth model is solved for two geometries, within a cylindrical hole and on the outer surface of a cylinder, thus demonstrating how surface stress may indeed inhibit growth on convex substrates.     

The development and validation of the hypertension evaluation of lifestyle and management knowledge scale

Hypertension knowledge is an integral component of the chronic care model. A valid scale to assess hypertension knowledge and self-management skills is needed. The hypertension evaluation of lifestyle and management (HELM) scale was developed as part of a community-based study designed to improve self-management of hypertension. Participants included 404 veterans with hypertension. Literature review and an expert panel were used to identify required skills. Items were generated and pilot tested in the target population. Validity was assessed through comparisons of performance with education, health numeracy, print numeracy, patient activation and self-efficacy, and hypertension control. The HELM knowledge scale had 14 items across 3 domains: general hypertension knowledge, lifestyle and medication management, and measurement and treatment goals. Scores were positively associated with education (0.28, P<.0001), print health literacy (0.21, P<.001), health numeracy (0.17, P<.001), and patient activation (0.12, P=.015) but no association was found with diastolic or systolic blood pressure. The HELM knowledge scores increased following the educational intervention from baseline (mean, 8.7; standard deviation, 2.2) to 12-month follow-up (mean, 9.2, standard deviation, 2.2; P<.001). We conclude that the HELM provides a valid measure of the knowledge required for patients to take an active role in the chronic disease management of hypertension.     

Evidence of low vitamin D intakes in the Australian population points to a need for data-driven nutrition policy for improving population vitamin D status

Background

Nearly one in four Australian adults is vitamin D deficient (serum 25-hydroxyvitamin D concentrations [25(OH)D] < 50 nmol L^–1) and current vitamin D intakes in the Australian population are unknown. Internationally, vitamin D intakes are commonly below recommendations, although estimates generally rely on food composition data that do not include 25(OH)D. We aimed to estimate usual vitamin D intakes in the Australian population.

Methods

Nationally representative food consumption data were collected for Australians aged ≥ 2 years (n = 12,153) as part of the cross-sectional 2011–2013 Australian Health Survey (AHS). New analytical vitamin D food composition data for vitamin D₃, 25(OH)D₃, vitamin D₂ and 25(OH)D₂ were mapped to foods and beverages that were commonly consumed by AHS participants. Usual vitamin D intakes (µg day^–1) by sex and age group were estimated using the National Cancer Institute method.

Results

Assuming a 25(OH)D bioactivity factor of 1, mean daily intakes of vitamin D ranged between 1.84 and 3.25 µg day^–1. Compared to the estimated average requirement of 10 µg day^–1 recommended by the Institute of Medicine, more than 95% of people had inadequate vitamin D intakes. We estimated that no participant exceeded the Institute of Medicine's Upper Level of Intake (63–100 µg day^–1, depending on age group).

Conclusions

Usual vitamin D intakes in Australia are low. This evidence, paired with the high prevalence of vitamin D deficiency in Australia, suggests that data-driven nutrition policy is required to safely increase dietary intakes of vitamin D and improve vitamin D status at the population level.     

Site‐Dependent Reference Point Microindentation Complements Clinical Measures for Improved Fracture Risk Assessment at the Human Femoral Neck

In contrast to traditional approaches to fracture risk assessment using clinical risk factors and bone mineral density (BMD), a new technique, reference point microindentation (RPI), permits direct assessment of bone quality; in vivo tibial RPI measurements appear to discriminate patients with a fragility fracture from controls. However, it is unclear how this relates to the site of the most clinically devastating fracture, the femoral neck, and whether RPI provides information complementary to that from existing assessments. Femoral neck samples were collected at surgery after low‐trauma hip fracture (n = 46; 17 male; aged 83 [interquartile range 77–87] years) and compared, using RPI (Biodent Hfc), with 16 cadaveric control samples, free from bone disease (7 male; aged 65 [IQR 61–74] years). A subset of fracture patients returned for dual‐energy X‐ray absorptiometry (DXA) assessment (Hologic Discovery) and, for the controls, a micro‐computed tomography setup (HMX, Nikon) was used to replicate DXA scans. The indentation depth was greater in femoral neck samples from osteoporotic fracture patients than controls (p < 0.001), which persisted with adjustment for age, sex, body mass index (BMI), and height (p < 0.001) but was site‐dependent, being less pronounced in the inferomedial region. RPI demonstrated good discrimination between fracture and controls using receiver‐operating characteristic (ROC) analyses (area under the curve [AUC] = 0.79 to 0.89), and a model combining RPI to clinical risk factors or BMD performed better than the individual components (AUC = 0.88 to 0.99). In conclusion, RPI at the femoral neck discriminated fracture cases from controls independent of BMD and traditional risk factors but dependent on location. The clinical RPI device may, therefore, supplement risk assessment and requires testing in prospective cohorts and comparison between the clinically accessible tibia and the femoral neck. © 2015 American Society for Bone and Mineral Research.     

Impacts of the Affordable Care Act's Medicaid Expansion on Women of Reproductive Age: Differences by Parental Status and State Policies

Introduction

We use data from the Behavioral Risk Factor Surveillance System (BRFSS) from 2012 to 2015 to estimate the effects of the Affordable Care Act's (ACA) Medicaid expansions on insurance coverage and access to care for low-income women of reproductive age (19–44).

Recombinant human Fab fragments neutralize human type 1 immunodeficiency virus in vitro.

A panel of 20 recombinant Fab fragments reactive with the surface glycoprotein gp120 of human type 1 immunodeficiency virus (HIV-1) were examined for their ability to neutralize MN and IIIB strains of the virus. Neutralization was determined as the ability of the Fab fragments to inhibit infection as measured in both a p24 ELISA and a syncytium-formation assay. One group of closely sequence-related Fab fragments was found to neutralize virus in both assays with a 50% neutralization titer at approximately 1 micrograms/ml. Another Fab neutralized in the p24 ELISA but not in the syncytium assay. The other Fab fragments showed weak or no neutralizing ability. The results imply that virion aggregation or crosslinking of gp120 molecules on the virion surface is not an absolute requirement for HIV-1 neutralization. Further, all of the Fab fragments were shown to be competitive with soluble CD4 for binding to gp120 and yet few neutralized the virus effectively, implying that the mechanism of neutralization in this case may not involve receptor blocking. The observation of a preponderance of high-affinity Fab fragments with poor or no neutralizing ability could have implications for vaccine strategies.     

REVIEW OF NUTRITIONAL SUPPLEMENTS FOR THE TREATMENT OF BIPOLAR DEPRESSION

Many patients view psychotropics with skepticism and fear and view nutritional supplements as more consistent with their values and beliefs. The purpose of this review was to critically evaluate the evidence base for nutritional supplements in the treatment of bipolar depression (BD). A literature search for all randomized, controlled clinical trials using nutritional supplements in the treatment of BD was conducted via PubMed and Ovid MEDLINE computerized database. The studies were organized into essential nutrients/minerals, nonessential nutrients, and combinations of nutritional products. Among essential nutrients/minerals, omega‐3‐fatty acids (O3FAs) have the strongest evidence of efficacy for bipolar depression, although some studies failed to find positive effects from O3FAs. Weak evidence supports efficacy of vitamin C whereas no data support the usefulness of folic acid and choline. Among nonessential nutrients, cytidine is the least supported treatment. Studies of N‐acetylcysteine have not resolved its efficacy in treating acute depressive episodes relative to placebo. However, one study demonstrates its potential to improve depressive symptoms over time and the other, though nonsignificant, suggests it has a prophylactic effect. Studies of inositol have been mostly negative, except for 1 study. Those that were negative were underpowered but demonstrated numerically positive effects for inositol. There is no evidence that citicholine is efficacious for uncomplicated BD depression, though it may have value for comorbid substance abuse among BD patients. Finally, combination O3FA‐cytidine lacks evidence of efficacy. The findings of this review do not support the routine use of nutritional supplements in the treatment or prophylaxis of BD depression. Studies with more rigorous designs are required before definitive conclusions can be made. Despite the inadequacy of the existing data, clinicians should remain open to the value of nutritional supplements: after all, lithium is a mineral too.