Evaluation of endothelial cell culture as a model system of vascular ageing

The purpose of this study was to evaluate the relevance of long-term endothelial cell culture as a model system of vascular ageing. Micro- and macrovascular endothelial cells were serially passaged until replicative senescence and their ability to form tube-like structures when cultured on Matrigel was assessed throughout their lifespan. For both cell types low passage cultures adopted a homogeneous cobblestone morphology, while senescent cultures were extremely heterogeneous. Furthermore, both cell types showed a reduction in tube formation ability with in vitro ageing, which is in accordance with the reduction in angiogenic potential observed with ageing in vivo. Examination of senescence associated β-galactosidase activity revealed an increased activity in cells forming tubes as compared to cells cultured on plastic, which could be attributed to an increased lysosomal content of cells undergoing tube formation. As this increased senescence associated β-galactosidase activity was unrelated to the replicative age of the cells, senescence associated β-galactosidase activity may not be a relevant senescence marker for differentiating endothelial cells. The age-related reduction in tube formation ability suggested that long-term culture of endothelial cells may be a valid model system of vascular ageing, which makes it an ideal platform for high throughput screening of compounds influencing angiogenesis.     

Diversity among Tacaribe serocomplex viruses (Family Arenaviridae) associated with the southern plains woodrat (Neotoma micropus)

The southern plains woodrat (Neotoma micropus) is the principal host of Catarina virus in southern Texas and a natural host of other North American Tacaribe serocomplex viruses. The objectives of this study were to increase our knowledge of the genetic diversity among Tacaribe serocomplex viruses associated with N. micropus and to define better the natural host relationships of these viruses. Pairwise comparisons of complete glycoprotein precursor gene sequences and complete nucleocapsid protein gene sequences revealed a high level of genetic diversity among Tacaribe serocomplex viruses associated with N. micropus in western Oklahoma, southern New Mexico, and northern and southern Texas. Collectively, the results of Bayesian analyses of nucleotide sequences and pairwise comparisons of amino acid sequences confirmed that the arenaviruses associated with N. micropus in Oklahoma and New Mexico should be included in the Whitewater Arroyo species complex, and indicated that that the arenaviruses associated with N. micropus in northern Texas are strains of a novel arenaviral species – tentatively named “Middle Pease River virus”. Together, the results of assays for arenavirus and assays for anti-arenavirus antibody in 54 southern plains woodrats and 325 other rodents captured at 2 localities suggested that the southern plains woodrat is the principal host of Middle Pease River virus in northern Texas.     

Dendritic cell preactivation impairs MHC class II presentation of vaccines and endogenous viral antigens

When dendritic cells (DCs) encounter signals associated with infection or inflammation, they become activated and undergo maturation. Mature DCs are very efficient at presenting antigens captured in association with their activating signal but fail to present subsequently encountered antigens, at least in vitro. Such impairment of MHC class II (MHC II) antigen presentation has generally been thought to be a consequence of down-regulation of endocytosis, so it might be expected that antigens synthesized by the DCs themselves (for instance, viral antigens) would still be presented by mature DCs. Here, we show that DCs matured in vivo could still capture and process soluble antigens, but were unable to present peptides derived from these antigens. Furthermore, presentation of viral antigens synthesized by the DCs themselves was also severely impaired. Indeed, i.v. injection of pathogen mimics, which caused systemic DC activation in vivo, impaired the induction of CD4 T cell responses against subsequently encountered protein antigens. This immunosuppressed state could be reversed by adoptive transfer of DCs loaded exogenously with antigens, demonstrating that impairment of CD4 T cell responses was due to lack of antigen presentation rather than to overt suppression of T cell activation. The biochemical mechanism underlying this phenomenon was the down-regulation of MHC II-peptide complex formation that accompanied DC maturation. These observations have important implications for the design of prophylactic and therapeutic DC vaccines and contribute to the understanding of the mechanisms causing immunosuppression during systemic blood infections.     

The influence of nasal abnormalities in adherence to continuous positive airway pressure device therapy in obstructive sleep apnea patients

Background

The few studies that examine the effect of nasal abnormalities on continuous positive airway pressure device (CPAP) adherence are controversial. The aim of this study was to evaluate the contribution of nasal abnormalities in CPAP adherence.

Methods

We included patients with moderate to severe OSA. The patients were submitted to rhinoscopy, nasofibroscopy, nasal inspiratory peak flow, and acoustic rhinometry. The patients who used a CPAP for 4 h or more per night for at least 70 % of the nights over a 6-month period were considered to have good adherence.

Results

Thirty-four patients finished the study. Eleven (33.4 %) were female and 23 (67.6 %) were male. Sixteen (47.1 %) patients had good adherence. The body mass index (p?=?0.030), neck circumference (p?=?0.006), and apnea–hypopnea index (p?=?0.032) were higher, and the oxyhemoglobin saturation minimum was lower (p?=?0.041) in the good adherence group. Nasal parameters showed no differences between good and poor adherence groups. In Spearman’s correlation, surprisingly, there was a negative correlation between the highest number of hours of CPAP use with smaller values of nasal minimal cross-sectional areas in the supine position (r, 0.375; p?=?0.029). In the linear regression model, the nasal findings that predicted increased of the CPAP use were the following: lower scores of nasal symptoms (p?=?0.007) and lower nasal volume in supine position (p?=?0.001).

Conclusions

The majority of the nasal parameters evaluated in this study did not influence CPAP adherence.     

Life-Space Mobility of Middle-Aged and Older Adults at Various Stages of Usage of Power Mobility Devices

Auger C, Demers L, Gélinas I, Miller WC, Jutai JW, Noreau L. Life-space mobility of middle-aged and older adults at various stages of usage of power mobility devices.

Objective

To examine whether the impact of power mobility devices (PMDs) varies as a function of stage of usage and to explore key factors associated with greater life-space mobility for middle-aged and older adults.

Design

Multicohort study with respondents grouped as a function of stage of PMD usage (reference group with mobility impairments, n=42; initial users, 1-6mo, n=35; long-term users, 12-18mo, n=39). Cohorts were compared with respect to life-space mobility in a continuum of environments ranging from home to outside town, using analysis of variance and chi-square tests. Baseline personal, assistive device, intervention, and environmental factors associated with life-space mobility were explored with age-adjusted linear regression models.

Setting

Four Canadian rehabilitation centers.

Participants

Random sample of middle-aged and older adults (N=116; 50-89y) living in the community or residential care.

Intervention

Procurement of a powered wheelchair or scooter.

Main Outcome Measure

Life-Space Assessment composite score.

Results

Cohort comparisons showed higher frequency of outings for PMD users in the neighborhood (P<.001) and around home (P<.05) and significantly greater Life-Space Assessment composite scores for initial and long-term users than for the reference group (P<.05). Factors such as sex, the nature of activities, and device type explained variances in Life-Space Assessment composite score ranging from 15.9% to 18.0% (P<.006).

Conclusions

Life-space mobility increases after PMD use and remains stable across the stages of initial and long-term use. To appreciate the impact of PMDs, clinicians should consider the environment and a combination of personal and device factors that are associated with the range of life-space mobility in the first 18 months after procurement.     

Proapoptotic Rassf1A/Mst1 signaling in cardiac fibroblasts is protective against pressure overload in mice

Mammalian sterile 20-like kinase 1 (Mst1) is a mammalian homolog of Drosophila Hippo, the master regulator of cell death, proliferation, and organ size in flies. It is the chief component of the mammalian Hippo pathway and promotes apoptosis and inhibits compensatory cardiac hypertrophy, playing a critical role in mediating heart failure. How Mst1 is regulated, however, remains unclear. Using genetically altered mice in which expression of the tumor suppressor Ras-association domain family 1 isoform A (Rassf1A) was modulated in a cell type-specific manner, we demonstrate here that Rassf1A is an endogenous activator of Mst1 in the heart. Although the Rassf1A/Mst1 pathway promoted apoptosis in cardiomyocytes, thereby playing a detrimental role, the same pathway surprisingly inhibited fibroblast proliferation and cardiac hypertrophy through both cell-autonomous and autocrine/paracrine mechanisms, playing a protective role during pressure overload. In cardiac fibroblasts, the Rassf1A/Mst1 pathway negatively regulated TNF-α, a key mediator of hypertrophy, fibrosis, and resulting cardiac dysfunction. These results suggest that the functional consequence of activating the proapoptotic Rassf1A/Mst1 pathway during pressure overload is cell type dependent in the heart and that suppressing this mechanism in cardiac fibroblasts could be detrimental.     

Loss of muscle strength, mass (sarcopenia), and quality (specific force) and its relationship with functional limitation and physical disability: the Concord Health and Ageing in Men Project

OBJECTIVES: To determine the association between loss of muscle strength, mass, and quality and functional limitation and physical disability in older men. DESIGN: Cross‐sectional study of older men participating in the Concord Health and Ageing in Men Project (CHAMP). SETTING: Elderly men living in a defined geographical region in Sydney, Australia. PARTICIPANTS: One thousand seven hundred five community‐dwelling men aged 70 and older who participated in the baseline assessments of CHAMP. MEASUREMENTS: Upper and lower extremity strength were measured using dynamometers for grip and quadriceps strength. Appendicular skeletal lean mass was assessed using dual X‐ray absorptiometry. Muscle quality was defined as the ratio of strength to mass in upper and lower extremities. For each parameter, subjects in the lowest 20% of the distribution were defined as below normal. Functional limitation was assessed according to self‐report and objective lower extremity performance measures. Physical disability was measured according to self‐report questionnaire. RESULTS: After adjusting for important confounders, the prevalence ratio (PR) for poor quadriceps strength and self‐reported functional limitation was 1.91 (95% confidence interval (CI)=1.10–2.40); for performance‐based functional limitation the PR was 1.81 (95% CI=1.45–2.24). The adjusted PR for poor grip strength and physical disability in instrumental activities of daily living (IADLs) was 1.37 (95% CI=1.20–1.56). The adjusted PR for low skeletal lean mass (adjusted for fat mass) and physical disability in basic activities of daily living was 2.08 (95% CI=1.37–3.15). For muscle quality, the PR for lower extremity specific force and functional limitation and physical disability was stronger than upper extremity specific force. CONCLUSION: Muscle strength is the single best measure of age‐related muscle change and is associated with physical disability in IADLs and functional limitation.