Pulmonary gas exchange is reduced by the cardiovascular diving response in resting humans

The diving response reduces the pulmonary O(2) uptake in exercising humans, but it has been debated whether this effect is present at rest. Therefore, respiratory and cardiovascular responses were recorded in 16 resting subjects, performing apnea in air and apnea with face immersion in cold water (10 degrees C). Duration of apneas were predetermined to be identical in both conditions (average: 145 s) and based on individual maximal capacity (average: 184 s). Compared to apnea in air, an augmented diving response was elicited by apnea with face immersion. The O(2) uptake from the lungs was reduced compared to the resting eupneic control (4.6 ml min(-1)kg(-1)), during apnea in air (3.6 ml min(-1)kg(-1)) and even more so during apnea with face immersion (3.4 ml min(-1)kg(-1)). We conclude that the cardiovascular adjustments of the diving response reduces pulmonary gas exchange in resting humans, allowing longer apneas by preserving the lungs' O(2) store for use by vital organs.     

Thrombospondin-1: an islet endothelial cell signal of importance for β-cell function

OBJECTIVE

Loss of thrombospondin (TSP)-1 in pancreatic islets has been shown to cause islet hyperplasia. This study tested the hypothesis that endothelial-derived TSP-1 is important for β-cell function.

RESEARCH DESIGN AND METHODS

Islet function was evaluated both in vivo and in vitro. Messenger RNA and protein expression were measured by real-time PCR and Western blot, respectively. The role of endothelial-derived TSP-1 for β-cell function was determined using a transplantation design in which recipient blood vessels either were allowed to grow or not into the transplanted islets.

RESULTS

TSP-1–deficient mice were glucose intolerant, despite having an increased β-cell mass. Moreover, their islets had decreased glucose-stimulated insulin release, (pro)insulin biosynthesis, and glucose oxidation rate, as well as increased expression of uncoupling protein-2 and lactate dehydrogenase-A when compared with control islets. Almost all TSP-1 in normal islets were found to be derived from the endothelium. Transplantation of free and encapsulated neonatal wild-type and TSP-1–deficient islets was performed in order to selectively reconstitute with TSP-1–positive or –negative blood vessels in the islets and supported that the β-cell defects occurring in TSP-1–deficient islets reflected postnatal loss of the glycoprotein in the islet endothelial cells. Treatment of neonatal TSP-1–deficient mice with the transforming growth factor (TGF)β-1–activating sequence of TSP-1 showed that reconstitution of TGFβ-1 activation prevented the development of decreased glucose tolerance in these mice. Thus, endothelial-derived TSP-1 activates islet TGFβ-1 of importance for β-cells.

CONCLUSIONS

Our study indicates a novel role for endothelial cells as functional paracrine support for pancreatic β-cells.The vasculature traditionally has been regarded mainly as a transport system that mediates metabolic exchange between tissues and blood. However, aside from its transport functions, blood-vessel cells have, in recent years, been recognized to be able to interact with and differentiate adjacent parenchymal cells through paracrine signals during development (1–3). Moreover, they seem to be able to provide mitotic signals during adulthood (4).To date, there have been few studies (5–7) on whether endothelial cells may directly affect parenchymal function. Islets of Langerhans in the adult have a uniquely dense network of capillaries maintained by constant exposure to vascular endothelial growth factor (VEGF)-A secreted from adjacent β-cells (8,9). The high number of islet capillaries results in each β-cell being located directly adjacent to at least one endothelial cell (10), thereby enabling a direct interaction with endothelium-derived factors. The importance of islet endothelial factors in the control of β-cell proliferation recently has been studied, and both endothelium-derived hepatocyte growth factor (11) and the vascular membrane component laminin (7) seem to be important in this context.In the current study, we investigated products of purified and isolated islet endothelial cells and thereby found the glycoprotein thrombospondin (TSP)-1 to be highly expressed in the endothelium of islets. TSP-1 is mainly known for its antiangiogenic properties (12) but also may alter the morphology of pancreatic islets and functions as a major activator of transforming growth factor (TGF)β-1 (13). Because TGFβ-1 is known to modulate β-cell function (14,15), we tested the hypothesis that endothelial cell–derived TSP-1 is important to maintain β-cell function postnatally.     

Identifying Unmet Rehabilitation Needs in Patients After Stroke With a Graphic Rehab-CompassTM

Background

Unmet rehabilitation needs are common among stroke survivors. We aimed to evaluate whether a comprehensive graphic “Rehab-Compass,” a novel combination of structured patient-reported outcome measures, was feasible and useful in facilitating a capture of patients' rehabilitation needs in clinical practice.

Progression of late postoperative atrial fibrillation in patients with tetralogy of Fallot

1 Introduction

ToF patients are at risk for ventricular deterioration at a relatively young age, which can be aggravated by AF development. Therefore, knowledge on AF development and its timespan of progression is essential to guide treatment strategies for AF.

2 Objective

We examined late postoperative AF onset and progression in ToF patients during long‐term follow‐up after ToF correction. In addition, coexistence of AF with regular supraventricular tachyarrhythmias (SVT) and ventricular tachyarrhythmias (VTA) was analyzed.

3 Methods and results

ToF patients (N  =  29) with AF after ToF correction referred to the electrophysiology department between 2000 and 2015 were included. All available rhythm registrations were reviewed for AF, regular SVT, and VTA. AF progression was defined as transition from paroxysmal AF to (longstanding) persistent/permanent AF or from (longstanding) persistent AF to permanent AF. At the age of 44 ± 12 years, ToF patients presented with paroxysmal (N  =  14, 48%), persistent (N  =  13, 45%) or permanent AF (N  =  2, 7%). Age of AF development was similar among patients who either underwent initial shunt creation (N  =  15, 45 ± 11 [25–57] years) or primary total ToF correction (N  =  14, 43 ± 13 [26–66] years) (P  =  0.785). AF coexisted with regular SVT (N  =  18, 62%) and VTA (N  =  13, 45%). Progression of AF occurred in 11 patients (38%) within 5 ± 5 years after AF onset despite antiarrhythmic drug class II (AAD, P  =  0.052) or III (P  =  0.587) usage.

4 Conclusions

AF in our ToF population developed at a young age and showed rapid progression. Rhythm control by pharmacological therapy was ineffective in preventing AF progression.     

Prophylactic incisional negative pressure wound therapy shows promising results in prevention of wound complications following inguinal lymph node dissection for Melanoma: A retrospective case-control series

BackgroundInguinal lymphadenectomy (ILND) for melanoma is associated with a number of complications including seroma, surgical site infection (SSI), and lymphedema. Incisional negative pressure wound therapy (iNPWT) has shown promising results in preventing postoperative morbidity across a wide variety of surgical procedures, but these results are yet to be investigated in patients undergoing ILND for melanoma.MethodsIn this study, we reviewed the data of 55 melanoma patients treated with ILND between January 2015 and January 2017 at Odense University Hospital. Patients were followed up until April 2018 for the occurrence of seroma, SSI, and lymphedema. We used prophylactic iNPWT after ILND in 14 patients and compared their morbidity outcomes with the 41 patients receiving standard postoperative wound care in the same period.ResultsThe iNPWT intervention significantly reduced seroma compared to the control group (28.6% vs. 90.3%, p < 0.001) and had a trending impact on wound infection (42.9% vs. 65.9%, p = 0.13). The effect was not significant for the prevention of lymphedema (35.7% vs. 51.2%, p = 0.33). Because the iNPWT group had relatively fewer incidences of seroma, SSI, and lymphedema, the iNPWT intervention was more cost-effective than conventional wound care (US$911.2 vs. US$2542.7, p < 0.05).ConclusionThe use of prophylactic iNPWT significantly reduced seroma formation following ILND. These promising results, however, need to be confirmed in a future prospective randomized trial.     

Towards optimization in digital chest radiography using Monte Carlo modelling

A Monte Carlo based computer model of the x-ray imaging system was used to investigate how various image quality parameters of interest in chest PA radiography and the effective dose E vary with tube voltage (90-150 kV), additional copper filtration (0-0.5 mm), anti-scatter method (grid ratios 8-16 and air gap lengths 20-40 cm) and patient thickness (20-28 cm) in a computed radiography (CR) system. Calculated quantities were normalized to a fixed value of air kerma (5.0 microGy) at the automatic exposure control chambers. Soft-tissue nodules were positioned at different locations in the anatomy and calcifications in the apical region. The signal-to-noise ratio, SNR, of the nodules and the nodule contrast relative to the contrast of bone (C/C(B)) as well as relative to the dynamic range in the image (C(rel)) were used as image quality measures. In all anatomical regions, except in the densest regions in the thickest patients, the air gap technique provides higher SNR and contrast ratios than the grid technique and at a lower effective dose E. Choice of tube voltage depends on whether quantum noise (SNR) or the contrast ratios are most relevant for the diagnostic task. SNR increases with decreasing tube voltage while C/C(B) increases with increasing tube voltage.