Notch signaling functions in retinal pericyte survival

PURPOSE

Pericytes, the vascular cells that constitute the outer layer of capillaries, have been shown to have a crucial role in vascular development and stability. Loss of pericytes precedes endothelial cell dysfunction and vascular degeneration in small-vessel diseases, including diabetic retinopathy. Despite their clinical relevance, the cellular pathways controlling survival of retinal pericytes remain largely uncharacterized. Therefore, we investigated the role of Notch signaling, a master regulator of cell fate decisions, in retinal pericyte survival.

METHODS

A coculture system of ligand-dependent Notch signaling was developed using primary cultured retinal pericytes and a mesenchymal cell line derived from an inducible mouse model expressing the Delta-like 1 Notch ligand. This model was used to examine the effect of Notch activity on pericyte survival using quantitative PCR (qPCR) and a light-induced cell death assay. The effect of Notch gain- and loss-of-function was analyzed in monocultures of retinal pericytes using antibody arrays to interrogate the expression of apoptosis-related proteins.

RESULTS

Primary cultured retinal pericytes differentially expressed key molecules of the Notch pathway and displayed strong expression of canonical Notch/RBPJK (recombination signal-binding protein 1 for J-kappa) downstream targets. A gene expression screen using gain- and loss-of-function approaches identified genes relevant to cell survival as downstream targets of Notch activity in retinal pericytes. Ligand-mediated Notch activity protected retinal pericytes from light-induced cell death.

CONCLUSIONS

Our results have identified signature genes downstream of Notch activity in retinal pericytes and suggest that tight regulation of Notch signaling is crucial for pericyte survival.

Sequential TPF chemotherapy followed by concurrent chemoradiotherapy in locally advanced head and neck cancer--a retrospective analysis of toxicity and outcomes

BACKGROUND AND AIMS

Phase III trials have shown that the addition of a taxane to cisplatin/5FU-based induction chemotherapy (TPF) improves response rates and overall survival in unresectable stage III/IV head and neck cancer. We sought to assess the tolerability, compliance and clinical outcomes of this treatment regime.

METHODS

A retrospective study of patients treated within a single centre between September 2007 and November 2010. Toxicities were graded according to CTCAE version 3.0. Survival, distant metastasis and local control rates are expressed as percentages at two years using the Kaplan-Meier method.

RESULTS

A total of 100 patients were identified (11% stage III, 86% stage IV) and 32% of patients were admitted as an emergency after TPF. The rate of neutropenic fever was 31%, this number fell to 9% when prophylactic G-CSF was used. In addition, 89% of patients underwent radical chemoradiation. Of these, 96% completed the full radiotherapy course. However, only 64% of patients received a minimum of two cycles of concurrent platinum chemotherapy. The two-year overall survival, metastasis free survival and local control rates were 62.6%, 88.5% and 73.3%, respectively.

CONCLUSIONS

TPF chemotherapy can be delivered safely in a non-trial cohort of patients. There is, however, a significant reduction in concurrent chemotherapy dose intensity. The long-term impact of this remains unclear.

Impaired macrophage phagocytosis in non-eosinophilic asthma

BACKGROUND

Many patients with non-eosinophilic asthma have increased numbers of neutrophils in the airways. The explanation for this chronic inflammation remains unclear, but may result from an impaired ability of alveolar macrophages to phagocytose apoptotic cells (a process termed 'efferocytosis'), as we have shown in chronic obstructive pulmonary disease (COPD).

OBJECTIVES

To examine induced sputum as a non-invasive technique to characterize efferocytosis in chronic lung diseases and to compare efferocytosis in patients with non-eosinophilic asthma, eosinophilic asthma and COPD.

METHODS

Participants with stable asthma (20 with eosinophilic and 30 with non-eosinophilic) and COPD (n = 11) underwent clinical assessment including allergy skin tests, saline challenge and sputum induction. Sputum cells were dispersed using dithiothreitol and resuspended in culture medium. Efferocytosis of apoptotic bronchial epithelial cells by sputum-derived macrophages was determined using flow cytometry.

RESULTS

There were no significant differences in efferocytosis between paired sputum and bronchoalveolar lavage macrophages from three subjects. Efferocytosis was significantly impaired in patients with non-eosinophilic asthma [mean (SD) 0.95 (0.24)] compared with eosinophilic asthma [1.17 (0.19)] and to a similar degree as patients with COPD [1.04 (0.16)]. Sputum neutrophils were significantly higher in patients with COPD and non-eosinophilic asthma compared with eosinophilic asthma.

CONCLUSION AND CLINICAL RELEVANCE

Induced sputum provides a reliable and non-invasive method for studying macrophage efferocytosis in chronic lung disease. Macrophage efferocytosis is impaired in non-eosinophilic asthma to a similar degree as that in COPD and may explain the persistent airway neutrophilia and chronic inflammation that characterizes this asthma subtype.

A phenomenological model of muscle fatigue and the power-endurance relationship

The relationship between power output and the time that it can be sustained during exercise (i.e., endurance) at high intensities is curvilinear. Although fatigue is implicit in this relationship, there is little evidence pertaining to it. To address this, we developed a phenomenological model that predicts the temporal response of muscle power during submaximal and maximal exercise and which was based on the type, contractile properties (e.g., fatiguability), and recruitment of motor units (MUs) during exercise. The model was first used to predict power outputs during all-out exercise when fatigue is clearly manifest and for several distributions of MU type. The model was then used to predict times that different submaximal power outputs could be sustained for several MU distributions, from which several power-endurance curves were obtained. The model was simultaneously fitted to two sets of human data pertaining to all-out exercise (power-time profile) and submaximal exercise (power-endurance relationship), yielding a high goodness of fit (R(2) = 0.96-0.97). This suggested that this simple model provides an accurate description of human power output during submaximal and maximal exercise and that fatigue-related processes inherent in it account for the curvilinearity of the power-endurance relationship.

Longitudinally-graded optical fibers

Optical fibers have become ubiquitous tools for the creation, propagation, manipulation, and detection of light. However, while the intensity of light propagating through the fiber can increase or decrease along the length through amplification or attenuation, respectively, the properties of the fiber itself generally do not, thus removing an opportunity to further control the behavior of light and performance of fiber-based devices. Shown here are optical fibers that exhibit significant changes in their longitudinal optical properties, specifically a tailored longitudinal numerical aperture change of about 12% over less than 20 meters of length. This is about 1900 times greater than previously reported. The Brillouin gain coefficient was found to decrease by over 6 dB relative to a standard commercial single mode fiber. Next generation analogs are expected to exhibit more than a 10 dB reduction in SBS gain using larger, yet still reasonably manufacturable gradients over practical lengths.

Corticosteroid treatment selectively decreases mast cells in the smooth muscle and epithelium of asthmatic bronchi

BACKGROUND

Mast cells are important in the pathophysiology of airway inflammation and evidence suggests their sub-localisation within the airway is altered in asthma. Little is known about the effect of corticosteroids on mast cell localisation within the bronchi.

METHODS

We therefore performed an immunohistochemical analysis of mast cell numbers within the smooth muscle, epithelium and submucosa of healthy subjects (n = 10) and well-characterised asthmatic patients, using either β(2)-agonists alone (n = 10) or β(2)-agonists and inhaled corticosteroids (n = 10).

RESULTS

Patients using inhaled corticosteroids displayed significantly lower numbers of mast cells within their epithelium and smooth muscle compared to those not treated with inhaled corticosteroids. Submucosal mast cells were not affected by corticosteroid treatment. Numbers of smooth muscle mast cells correlated with bronchial responsiveness and epithelial mast cells with exhaled NO.

CONCLUSION

We demonstrate that glucocorticosteroids differentially affect mast cell numbers within specific airway sub-locations highlighting the importance of mast cell and smooth muscle/epithelial interactions in asthma pathogenesis.

Training in Current Medical Education: Surgeons are Different from Their Medical Colleagues

Education and training in surgery have focused on an apprenticeship style of learning, particularly in the operating theatre, with little emphasis on understanding how trainees learn. This focus on one style of training may not achieve the best possible outcomes. The need to deliver training over a shorter period since the introduction of the European WorkingTime regulations makes each learning opportunity vital. Learning styles have already been suggested as an important issue in obstetrics and gynaecology.