Suppurative mediastinitis secondary to Burkholderia cepacia in a patient with cystic fibrosis

Burkholderia cepacia is an important opportunistic pathogen among patients with cystic fibrosis (CF); it is associated with deterioration of lung function, poor outcome following lung transplantation and increased mortality. Fever, an elevated white blood cell count, weight loss and an often fatal deterioration in pulmonary function characterize a particular clinical course, termed ‘Cepacia syndrome’. The present case report describes a 40-year-old man with CF who developed Cepacia syndrome complicated by suppurative mediastinitis, from which B cepacia was isolated. Despite optimal medical and surgical therapy, this patient succumbed to his illness. Those caring for patients with CF should be aware of this potentially catastrophic complication of B cepacia infection, especially in the setting of Cepacia syndrome.     

Precise evaluation of liver histology by computerized morphometry shows that steatosis influences liver stiffness measured by transient elastography in chronic hepatitis C

Background

Liver stiffness evaluation (LSE) by Fibroscan is now widely used to assess liver fibrosis in chronic hepatitis C. Liver steatosis is a common lesion in chronic hepatitis C as in other chronic liver diseases, but its influence on LSE remains unclear. We aimed to precisely determine the influence of steatosis on LSE by using quantitative and precise morphometric measurements of liver histology.

Methods

650 patients with chronic hepatitis C, liver biopsy, and LSE were included. Liver specimens were evaluated by optical analysis (Metavir F and A, steatosis grading) and by computerized morphometry to determine the area (%, reflecting quantity) and fractal dimension (FD, reflecting architecture) of liver fibrosis and steatosis.

Results

The relationships between LSE and liver histology were better described using morphometry. LSE median was independently linked to fibrosis (area or FD), steatosis (area or FD), activity (serum AST), and IQR/LSE median. Steatosis area ≥4.0 % induced a 50 % increase in LSE result in patients with fibrosis area <9 %. In patients with IQR/LSE median ≤0.30, the rate of F0/1 patients misclassified as F ≥ 2 by Fibroscan was, respectively for steatosis area <4.0 and ≥4.0 %: 12.6 vs 32.4 % (p = 0.003). Steatosis level did not influence LSE median when fibrosis area was ≥9 %, and consequently did not increase the rate of F ≤ 3 patients misclassified as cirrhotic.

Conclusion

A precise evaluation of liver histology by computerized morphometry shows that liver stiffness measured by Fibroscan is linked to liver fibrosis, activity, and also steatosis. High level of steatosis induces misevaluation of liver fibrosis by Fibroscan.     

Islet of Langerhans isolation from pediatric and juvenile donor pancreases

Islet grafts isolated from young donors allow superior functional outcomes but are often associated with poor islet isolation yields. The objective of this study was to comparatively analyze the outcomes of islet isolation between young and older donors. We retrospectively analyzed 564 pancreas isolations performed at our institution. Isolation outcomes were compared between donors aged ≤20 years (n = 42, YD) and >20 years (n = 522, OD). Isolation procedure was identical in both groups. Prepurification percentage of embedded islets was higher in YD (44.3 ± 22.7% vs. 24.9 ± 20.9%, P < 0.001). This led to a lower recovery rate in YD (48% vs. 76%, P = 0.002) and hence lower postpurification IEQ/g pancreas in YD (2 412 ± 1 789 IEQ/g vs. 3 194 ± 1 892 IEQ/g, P = 0.01). Final yield was 180 982 ± 128 073 IEQ in YD and 244 167 ± 134 137 IEQ in OD, (P = 0.006). In vitro function was markedly, albeit nonsignificantly, higher in YD (SI: 4.5 ± 5.1 vs. 3.0 ± 5.7, P = 0.350). Proportion of transplanted preparations was similar in both groups, 38% (16/42) in YD vs. 43% (224/522) in OD, P = 0.628. In spite of isolation and purification difficulties, pancreases from young donors allowed similar islet transplantation rates as older donors. Efforts should be directed at improving islet extraction in these donors to realize their full potential for islet transplantation.     

Do greater rates of body heat storage precede the accelerated reduction of self-paced exercise intensity in the heat?

Aim

To reevaluate the previous hypothesis that greater reductions in self-paced exercise intensity in the heat are mediated by early differences in the rate of body heat storage (S).

Methods

Eight trained volunteers cycled in 19 °C/1.8 kPa (COOL), 25 °C/1.2 kPa (NORM), and 34 °C/1.6 kPa (HOT), while maintaining an RPE of 16. Potential differences in S following the onset of exercise were assessed by comparing rates of esophageal temperature change (ΔT _es/Δt); and estimated S values using a traditional two-compartment thermometric model (S _therm) of changes in rectal (T _re) and skin (T _sk) temperature, and partitional calorimetry (S _cal).

Results

After 15 min of exercise, workload decreased more in HOT vs. COOL (P = 0.03), resulting in a shorter time (HOT: 40.7 ± 14.9 min; COOL: 53.5 ± 18.7 min; P = 0.04) to 70 % of initial workload. However, there were no preceding differences in ΔT _es/Δt between conditions (P = 0.18). S _therm values were different between HOT and COOL during the first 5 min of exercise (P < 0.05), primarily due to negative S _therm values (?32 ± 15 kJ min^?1) in COOL, which according to partitional calorimetric measurements, required improbably high (~56 kJ min^?1) rates of evaporation when no sweating on the back and thigh was observed until after 7.6 ± 1.5 min and 4.8 ± 1.7 min of exercise, respectively. S _cal values in the first 5 min of exercise confirmed S was actually positive in COOL (+21 ± 8 kJ min^?1) and not negative. Different S _therm values following the onset of exercise at different environmental temperatures are simply due to transient differences in the rate of change in T _sk.

Conclusion

Reductions in self-paced exercise intensity in the heat are not mediated by early differences in S following the onset of exercise.     

Investigating Canadian medical school attrition metrics to inform socially accountable admissions planning

Objective: Attrition from Canadian medical degree programs was never described despite differences in admissions requirements at the 17 faculties of medicine. Knowledge on attrition metrics could help the faculties evaluate new avenues for addressing the Association of Faculties of Medicine’s (AFMC) Future of Medical Education in Canada (FMEC MD) recommendation to enhance admissions practices with the goal to improve social accountability and student diversity.

Method: AFMC databases were used to track medical degree completion of all Canadian M.D. students who enrolled between 2003 and 2007. Students were followed and assigned an M.D. completion status as of by July 1, 2013. Bivariate statistics were used to evaluate if demographic, admission and degree progression variables were associated with medical school attrition.

Results: Of 11,454 students enrolled in Canadian M.D. programs from 2003 to 2007, only 197 (1.7%) did not complete. Québec had significantly higher attrition than other jurisdictions with age, educational attainment at time of enrolment, MCAT completion and struggling academically associated with attrition.

Conclusion: Attrition from Canadian MD programs is rare and associated with differences in admission requirements and possibly suggests an optimum life stage for medical studies. Improved knowledge of attrition-related factors may offer an additional level of evidence for improving the alignment between admissions policies and the social accountability objectives of medical schools.     

Rheological Behaviour of Cementitious Materials Incorporating Solid–Solid Phase Change Materials

Nowadays, thermal regulation of the indoor environment is mandatory to reduce greenhouse gas emissions. The incorporation of Phase Change Materials (PCMs) and especially solid–solid PCMs (s/s PCMs) into building materials can be a major step forward in reducing energy consumption. Such materials are used for their high latent heat to save and release heat during phase change. To integrate these products in the fabrication of cementitious materials, it is essential to predict their influence on the rheological behaviour of construction materials. In this work, rheological measurements were carried out on composite suspensions made of cement or mortar plus s/s PCMs. Results showed that the fitting of the Herschel–Bulkley model with a constant value of flow exponent was reliable. The s/s PCMs influenced the consistency and the yield strength values, with the yield strength value being only slightly affected. The adaptation of an existing viscosity model is proposed to predict the consistency value of suspensions. Finally, an innovative approach to predict the flow behaviour is proposed and we highlight the research needs to mainstream the use of s/s PCMs in construction materials.     

CD169+ macrophages in lymph node and spleen critically depend on dual RANK and LTbetaR signaling

CD169⁺ macrophages reside in lymph node (LN) and spleen and play an important role in the immune defense against pathogens. As resident macrophages, they are responsive to environmental cues to shape their tissue-specific identity. We have previously shown that LN CD169⁺ macrophages require RANKL for formation of their niche and their differentiation. Here, we demonstrate that they are also dependent on direct lymphotoxin beta (LTβ) receptor (R) signaling. In the absence or the reduced expression of either RANK or LTβR, their differentiation is perturbed, generating myeloid cells expressing SIGN-R1 in LNs. Conditions of combined haploinsufficiencies of RANK and LTβR revealed that both receptors contribute equally to LN CD169⁺ macrophage differentiation. In the spleen, the Cd169-directed ablation of either receptor results in a selective loss of marginal metallophilic macrophages (MMMs). Using a RANKL reporter mouse, we identify splenic marginal zone stromal cells as a source of RANKL and demonstrate that it participates in MMM differentiation. The loss of MMMs had no effect on the splenic B cell compartments but compromised viral capture and the expansion of virus-specific CD8⁺ T cells. Taken together, the data provide evidence that CD169⁺ macrophage differentiation in LN and spleen requires dual signals from LTβR and RANK with implications for the immune response.

CD169⁺ macrophages are strategically localized at the lymphatic sinuses of lymph nodes (LNs) and the marginal zone of the spleen, where they capture lymph- and blood-borne antigens, respectively (1). These macrophages reside close to B cells and mesenchymal stromal cells. B cells are a constitutive source of lymphotoxin (LT) α and LTβ that bind to the LTβ receptor (R) as LTα₁β₂ heterotrimer (2). Lack of B cells and unconditional or B cell–specific ablation of LTα or LTβ lead to loss of CD169⁺ macrophages in LNs and the spleen (3–6). Conversely, B cell–specific overexpression of LTαβ results in an increase of their numbers (7). Furthermore, administration of the decoy fusion protein LTβR-Fc or LTβR inactivation negatively affects their presence in both organs (3, 8, 9). However, although the myeloid cell lineage has been shown to express LTβR (10–12), it remains unclear whether the dependency on LTβR signaling is direct or implies an intermediate cell partner such as the adjacent stromal cells (9, 13, 14).We have recently shown that receptor activator of NF-κB ligand (RANKL) from marginal zone reticular cells (MRCs) regulates the differentiation of CD169⁺ macrophages in the LN (15). Like LTα and LTβ, RANKL is a member of the TNF superfamily and binds to the signaling receptor RANK (16). Stromal RANKL activates the lymphatic endothelial cells to form a cellular niche for macrophages and directly stimulates their differentiation into the CD169⁺ macrophages of the subcapsular sinus (subcapsular sinus macrophages, SSMs). However, a role of stromal RANKL for the splenic CD169⁺ macrophages has not been addressed. LTαβ and RANKL share many similarities in their biological functions. They are both indispensable for the organogenesis of secondary lymphoid organs (17, 18), are involved in the organogenesis of the thymus (19), and contribute to the formation of the intestinal microfold cells (20). However, RANKL stands out for its role in osteoclastogenesis (16), while LTαβ regulates the production of homeostatic chemokines and the differentiation of follicular dendritic cells (2).In the context of partially overlapping functions, we scrutinized the implication of the RANK–RANKL and LTβR–LTαβ axes in the differentiation of LN and splenic CD169⁺ macrophages. Using Cd169-directed conditional deficiency of RANK or LTβR, we report that direct RANK and LTβR signals are required for their differentiation in the LN and the spleen. In the absence of the receptors, LN CD169⁺ macrophages were replaced by myeloid cells phenotypically similar to the SIGN-R1⁺ medullary sinus macrophages. Deficiency of one copy of either Rank or Ltbr alleles sufficed for a prominent decrease in macrophage numbers, but the heterozygous deletion of both genes had a compound effect. Altered macrophage differentiation had a negative impact on lymph-borne antigen transport to B cells. In the spleen, Cd169-directed RANK or LTβR deficiency elicited a selective loss of the CD169⁺ MMMs. By the use of a RANKL reporter mouse together with RT-qPCR of sorted splenic stromal subsets, we identified CCL19⁺ splenic MRCs as a source of RANKL and demonstrated in Ccl19-cre RANKL-deficient mice that stromal RANKL participates in MMM differentiation. Their specific loss had no effect on the marginal zone B cell compartment but compromised viral capture and the formation of the virus-specific CD8⁺ T cell response. Taken together, the data provide evidence that CD169⁺ macrophage differentiation is dependent on the dual signals emanating from LTβR and RANK, with implications for the immune response to lymph- and blood-borne pathogens.     

Observation of Traditional Caregiver-Infant Feeding Behaviours and Porridge and Energy Intakes during One Meal to Define Key Messages for Promoting Responsive Feeding in the Amparafaravola District,Rural Madagascar

Undernutrition is highly prevalent in young children in Madagascar and insufficient intake per meal could be one of the main causes. A cross-sectional survey of infant feeding practices including video-recorded meal observations was carried out with 101 caregiver–infant pairs in the Amparafaravola district, Northeast Madagascar. The objective was to quantify the porridge/energy intake of 9–11-month-old children and assess its association with the caregiver–infant feeding behaviours. Then, key messages for promoting responsive feeding (RF) were developed and tested through focus group discussions. The mean porridge intake was 12.8 ± 7.5 g/kg body weight (BW)/meal, corresponding to hardly one-third of the 300 kcal recommended from complementary foods for 9–11-month-old children. Analysis of meal videos suggested that mothers practiced the five positive feeding behaviours (self-feeding, responsive, active, social, and distraction), and rarely the negative ones. Only 6.9% of mothers used positive RF “very frequently”, although it was associated with higher intakes (p < 0.05), with mean intake reaching 21 g/kg BW. In focus groups, caregivers approved the six RF messages and related counselling cards. They suggested some modifications to improve their understanding, and counselling cards were revised accordingly. The long-term impact of RF-promoting card use on the meal intakes and the nutritional status of young children must now be assessed.     

Dynamic porous organic polymers with tuneable crosslinking degree and porosity

Porous organic polymers (POPs) show enormous potential for applications in separation, organic electronics, and biomedicine due to the combination of high porosity, high stability, and ease of functionalisation. However, POPs are usually insoluble and amorphous materials making it very challenging to obtain structural information. Additionally, important parameters such as the exact molecular structure or the crosslinking degree are largely unknown, despite their importance for the final properties of the system. In this work, we introduced the reversible multi-fold nitroxide exchange reaction to the synthesis of POPs to tune and at the same time follow the crosslinking degree in porous polymer materials. We synthesised three different POPs based on the combination of linear, trigonal, and tetrahedral alkoxyamines with a tetrahedral nitroxide. We could show that modulating the equilibrium in the nitroxide exchange reaction, by adding or removing one nitroxide species, leads to changes in the crosslinking degree. Being able to modulate the crosslinking degree in POPs allowed us to investigate both the influence of the crosslinking degree and the structure of the molecular components on the porosity. The crosslinking degree of the frameworks was characterised using EPR spectroscopy and the porosity was determined using argon gas adsorption measurements. To guide the design of POPs for desired applications, our study reveals that multiple factors need to be considered such as the structure of the molecular building blocks, the synthetic conditions, and the crosslinking degree.

We synthesised three different POPs via a nitroxide exchange reaction and modulated their crosslinking degree. That allowed us to investigate the influence of the crosslinking degree and the structure of the molecular components on the porosity.

Various approaches to synthesise porous organic polymers (POPs)^1–3 and conjugated microporous polymers (CMPs)^4,5 have been developed to form extremely stable but at the same time highly porous solids based on simple organic building blocks.^6,7 The organic nature allows for functionalisation of the materials using organic chemistry, while the high porosity makes the active components accessible throughout the entire material.⁸ The combination of high porosity, high stability, and ease of functionalisation results in the enormous potential of POPs for applications in separation, organic electronics, and biomedicine.^2,9–14 However, unlike the related covalent organic frameworks (COFs),^15–20 metal–organic frameworks (MOFs)^21,22 or porous coordination polymers (PCPs),²³ the synthesis of POPs and CMPs is based on irreversible reactions, which leads to insoluble and amorphous materials and makes it very challenging to obtain structural information. Additionally, important parameters such as the exact molecular structure or the crosslinking degree are largely unknown, despite their unarguably large influence on the final properties of the system.^24,25To investigate the molecular structure of the organic linkers between the centres of two similar CMP materials, the group of Bunz and co-workers introduced molecular building blocks that were modified with digestible groups or cores, by substituting carbon with tin as the central atom.²⁴ This tin centre can be digested, resulting in molecular fragments of the frameworks, which were analysed using nuclear magnetic resonance (NMR) spectroscopy. The obtained fragments show a surprisingly varied chemical composition of these networks.²⁴ In a previous study, we could show that the introduction of digestible germanium nodes in one of the building blocks of POPs can also be used for partial disruption of the framework and therefore causing a decrease or allow tuning of the porosity.²⁵ In another approach, we introduced a poly(disulfide) hyper-crosslinked polymer, which can be surface modified using unreacted thiol functions on the surface of the material.²⁶ Digestion of the samples helped to quantify the functionalisation. Employing digestible crosslinker or nodes is an attractive approach to gain insight into the structure or functionalisation of the frameworks. However, it requires the destruction of the sample and does not allow to modulate or tune the crosslinking degree reversibly in one particular system.In order to tune and at the same time follow the crosslinking degree in porous polymer materials, we introduce the reversible multi-fold nitroxide exchange reaction to the synthesis of POPs. The nitroxide exchange reaction has been used in material science for self-assembly of polymer materials²⁷ or micron-sized crystals,²⁸ for surface functionalisation,²⁹ or introducing self-healing properties to materials.³⁰ In addition, the combination of light-sensitive alkoxyamines was employed in surface coating³¹ or the creation of systems out of their equilibrium.³² The radical nature of the involved nitroxide species allows to follow the progress of the reaction and to directly determine the crosslinking degree of the final material using fluorescence spectroscopy^33,34 and electron paramagnetic resonance (EPR) spectroscopy.^35,36 The dynamic nature of the nitroxide exchange reaction allowed us to tune the crosslinking degree of the materials by varying the ratio of the two nitroxide species involved in the reaction and thereby modulating the equilibrium conditions (see Fig. 1).Open in a separate windowFig. 1Dynamic equilibrium in the nitroxide exchange reaction using two different nitroxide species, TEMPO (red) and isoindoline (green). The free nitroxide radical species are electron paramagnetic resonance (EPR) active, while the bound species are EPR silent.Next to the crosslinking degree, also the structure, rigidity, and the intrinsic free volume of the molecular components of POPs or CMPs play an important role to obtain porosity in the final material.⁶ Cooper and co-workers showed the importance of monomer design for the pore size and surface area of CMPs by systematically varying the strut length in a series of molecular building blocks.³⁷In order to study the influence of both the molecular structure and the crosslinking degree on the porosity of the final material, we produced three different POPs based on the combination of linear, trigonal, and tetrahedral alkoxyamines with tetrahedral nitroxides. We characterised the frameworks using EPR spectroscopy and argon gas adsorption measurements to determine the crosslinking degree and porosity. Furthermore, we could show that modulating the equilibrium in the nitroxide exchange reaction, by adding or removing one nitroxide species, leads to changes in the crosslinking degree and investigated this influence on the porosity of the frameworks.