On the effect of temperature on the insertion of zinc into hydroxyapatite.

International audienceRietveld analysis on X-ray powder diffraction patterns recorded from 28 hydroxyapatite samples containing various amount of zinc (0, 1.6, 3.2 and 6.1 wt. Zn %) and heat treated at various temperatures (between 500°C and 1100°C) have allowed to finely characterize the Zn insertion mechanism into the HAp crystal structure. The formation of Zn-doped HAp was achieved above 900°C only. Zn-doped HAp has the Ca10Znx(PO4)6(OH)2-2xO2x (0 < x ≤ 0.25) chemical composition with a constant Ca/P ratio of 1.67 due to the insertion mechanism into the hexagonal channel (partial occupancy of the 2b Wyckoff site with formation of linear OZn- O entities). Samples heat treated at 500 °C were almost single phase, HAp did not incorporate Zn and about half of the Zn atoms incorporated during the synthesis are not observable by X-ray powder diffraction (contained in an amorphous compound or physisorbed at the HAp surface). The reversible formation of Zn-doped β-TCP phase was observed at 600°C, reached its maximum content at 900°C and almost vanished at 1100°C. The results presented here strengthen the recently described mechanism of Zn insertion in the interstitial 2b Wyckoff position of the HAp structure, and explain the origin of the contradictory reports in the corresponding literature

Structural characterization of Sol-Gel derived Sr-substituted calcium phosphates with anti-osteoporotic and anti-inflammatory properties.

International audienceSol-Gel chemistry has been successfully used to prepare un-doped and Sr-doped calcium phosphate ceramics exhibiting a porous structure. The samples composition is very close to the nominal one. All samples present phase mixtures mainly Hydroxyapatite (HAp) and Tri Calcium Phosphate (Β-TCP). Doping with Sr2+ ions has a clear effect on the proportions of the different phases, increasing the amount of Β-TCP. An amorphous phase is also observed incorporating some 40 % of the total amount of strontium. Strontium ions also substitute for calcium both in HAp and Β-TCP in specific sites that have been determined from Rietveld refinement on synchrotron powder diffraction data. The soluble amorphous and TCP phases are responsible for a beneficial partial release of strontium ions in solution during interactions between the material and biological fluids. Preliminary in vitro study demonstrates anti-inflammatory effect of strontium for human monocytes cultured in contact with calcium phosphates

Preparation and characterization of functionalized hybrid hydroxyapatite from phosphorite and its potential application to Pb2+ remediation

International audienceCalcium hydroxyapatite-aspartate (CaHAp-Asp) and calcium hydroxyapatite-glutamate (CaHAp-Glu) hybrid materials were prepared by the dissolution of Tunisian Phosphate Rocks in concentrated nitric acid and re-precipitation in basic solution in the presence of aspartic and glutamic acids. Chemical analyses, X-Ray Powder Diffraction, Infrared spectroscopy, 13C MAS-NMR spectroscopy, ThermoGravimetry and Scanning Electron Microscopy were used to characterize the materials and also the organic-inorganic interfaces. All techniques converge to the formation of hybrid organic-inorganic compounds composed of hydroxyapatite solids with organic anions incorporated at the surface. XRPD and SEM observations showed that not only was the crystallinity significantly affected by the presence of organic anions, but also the structural and morphological properties. The presence of organic anions has been confirmed by IR and 13C MS-NMR spectroscopies, and their amount has been evaluated by TG and chemical analyses. The three CaHAp, CaHAp-Asp and CaHAp-Glu materials were evaluated for Pb2+ sorption from aqueous solutions. Sorption isotherms have been analyzed using Langmuir and Freundlich models showing that the Pb2+ sorption capacity is increased for CaHAp-Asp and CaHAp-Glu. The comparison of the two models indicates a single active site corresponding to a homogeneous interface between Pb2+ aqueous adsorbate and the solid adsorbent surface

Oesophagite à éosinophiles : une maladie d’actualité

L’œsophagite à éosinophiles est définie comme une maladie chronique, médiée par des réponses immunologiques à des antigènes (allergènes), caractérisée cliniquement par les symptômes liés à un dysfonctionnement œsophagien, et histologiquement par une infiltration à éosinophiles prédominante de la muqueuse (Eos> 15/ champ 400) (Liacouras, 2011). Elle constitue une entité isolée, distincte de l’oesophagite par reflux gastro-oesophagien, et non intégrable dans les affections gastro-intestinales et coliques à éosinophiles (Sherrill, 2011). Elle touche l’adulte comme l’enfant, quoique 8 fois plus fréquente en population pédiatrique où l’acmé du diagnostic se situe dans les trois premières années. On estime sa prévalence à 4 sur 10 000 dans la population pédiatrique. Est-elle en accroissement ? Oui, pour certain (Potter, 2004). Non, pour d’autres auteurs…Eosinophilic esophagitis can be defined as a chronic disease, mediated by immunological responses to antigens (allergens), clinically characterized by symptoms related to esophageal disorders, and histologically by a mucosa predominantly infiltrated by eosinophils (Eos> 15/ field 400) (Liacouras, 2011). It is an isolated entity, distinct from esophagitis by gastro esophageal reflux, and it cannot be integrated to gastrointestinal and colic eosinophilic pathologies (Sherrill, 2011).The disease occurs in adults as well as in children, although it is 8 times more frequent in a pediatric population where the peak of the diagnosis arises during the first three years. Its prevalence is estimated at 4 out of 10 000 in a pediatric population. Is it increasing? Some say yes (Potter, 2004); other authors say no

Molybdenum threshold for ecosystem scale alternative vanadium nitrogenase activity in boreal forests

Biological nitrogen fixation (BNF) by microorganisms associated with cryptogamic covers, such as cyanolichens and bryophytes, is a primary source of fixed nitrogen in pristine, high-latitude ecosystems. On land, low molybdenum (Mo) availability has been shown to limit BNF by the most common form of nitrogenase (Nase), which requires Mo in its active site. Vanadium (V) and iron-only Nases have been suggested as viable alternatives to countering Mo limitation of BNF; however, field data supporting this long-standing hypothesis have been lacking. Here, we elucidate the contribution of vanadium nitrogenase (V-Nase) to BNF by cyanolichens across a 600-km latitudinal transect in eastern boreal forests of North America. Widespread V-Nase activity was detected (∼15–50% of total BNF rates), with most of the activity found in the northern part of the transect. We observed a 3-fold increase of V-Nase contribution during the 20-wk growing season. By including the contribution of V-Nase to BNF, estimates of new N input by cyanolichens increase by up to 30%. We find that variability in V-based BNF is strongly related to Mo availability, and we identify a Mo threshold of ∼250 ng·glichen−1 for the onset of V-based BNF. Our results provide compelling ecosystem-scale evidence for the use of the V-Nase as a surrogate enzyme that contributes to BNF when Mo is limiting. Given widespread findings of terrestrial Mo limitation, including the carbon-rich circumboreal belt where global change is most rapid, additional consideration of V-based BNF is required in experimental and modeling studies of terrestrial biogeochemistry

Refractory anaphylaxis: Data from the European Anaphylaxis Registry

Refractory anaphylaxis (unresponsive to treatment with at least two doses of minimum 300 μg adrenaline) is a rare and often fatal hypersensitivity reaction. Comprehensive data on its definition, prevalence, and risk factors are missing. Using the data from the European Anaphylaxis Registry (11,596 cases in total) we identified refractory anaphylaxis cases (n = 42) and analyzed these in comparison to a control group of severe anaphylaxis cases (n = 4,820). The data show that drugs more frequently elicited refractory anaphylaxis (50% of cases, p < 0.0001) compared to other severe anaphylaxis cases (19.7%). Cases elicited by insects (n = 8) were more often due to bees than wasps in refractory cases (62.5 vs. 19.4%, p = 0.009). The refractory cases occurred mostly in a perioperative setting (45.2 vs. 9.05, p < 0.0001). Intramuscular adrenaline (as a first line therapy) was administered in 16.7% of refractory cases, whereas in 83.3% of cases it was applied intravenously (significantly more often than in severe anaphylaxis cases: 12.3%, p < 0.0001). Second line treatment options (e.g., vasopression with dopamine, methylene blue, glucagon) were not used at all for the treatment of refractory cases. The mortality rate in refractory anaphylaxis was significantly higher (26.2%) than in severe cases (0.353%, p < 0.0001). Refractory anaphylaxis is associated with drug-induced anaphylaxis in particular if allergens are given intravenously. Although physicians frequently use adrenaline in cases of perioperative anaphylaxis, not all patients are responding to treatment. Whether a delay in recognition of anaphylaxis is responsible for the refractory case or whether these cases are due to an overflow with mast cell activating substances—requires further studies. Reasons for the low use of second-line medication (i.e., methylene blue or dopamine) in refractory cases are unknown, but their use might improve the outcome of severe refractory anaphylaxis cases

Anaphylaxis in Elderly Patients—Data From the European Anaphylaxis Registry

Background: Elicitors and symptoms of anaphylaxis are age dependent. However, little is known about typical features of anaphylaxis in patients aged 65 years or more.Methods: The data from the Network for Online Registration of Anaphylaxis (NORA) considering patients aged ≥65 (elderly) in comparison to data from adults (18–64 years) regarding elicitors, symptoms, comorbidities, and treatment measures were analyzed.Results: We identified 1,123 elderly anaphylactic patients. Insect venoms were the most frequent elicitor in this group (p &lt; 0.001), followed by drugs like analgesics and antibiotics. Food allergens elicited less frequently anaphylaxis (p &lt; 0.001). Skin symptoms occurred less frequently in elderly patients (77%, p &lt; 0.001). The clinical symptoms were more severe in the elderly (51% experiencing grade III/IV reactions), in particular when skin symptoms (p &lt; 0.001) were absent. Most strikingly, a loss of consciousness (33%, p &lt; 0.001) and preexisting cardiovascular comorbidity (59%, p &lt; 0.001) were more prevalent in the elderly. Finally, adrenaline was used in 30% of the elderly (vs. 26% in the comparator group, p &lt; 0.001) and hospitalization was more often required (60 vs. 50%, p &lt; 0.001).Discussion and Conclusion: Anaphylaxis in the elderly is often caused by insect venoms and drugs. These patients suffer more often from cardiovascular symptoms, receive more frequently adrenaline and require more often hospitalization. The data indicate that anaphylaxis in the elderly tends to be more frequently life threatening and patients require intensified medical intervention. The data support the need to recognize anaphylaxis in this patient group, which is prone to be at a higher risk for a fatal outcome

Anaphylaxis in Elderly Patients-Data From the European Anaphylaxis Registry

Background: Elicitors and symptoms of anaphylaxis are age dependent. However, little is known about typical features of anaphylaxis in patients aged 65 years or more. Methods: The data from the Network for Online Registration of Anaphylaxis (NORA) considering patients aged ≥65 (elderly) in comparison to data from adults (18–64 years) regarding elicitors, symptoms, comorbidities, and treatment measures were analyzed. Results: We identified 1,123 elderly anaphylactic patients. Insect venoms were the most frequent elicitor in this group (p < 0.001), followed by drugs like analgesics and antibiotics. Food allergens elicited less frequently anaphylaxis (p < 0.001). Skin symptoms occurred less frequently in elderly patients (77%, p < 0.001). The clinical symptoms were more severe in the elderly (51% experiencing grade III/IV reactions), in particular when skin symptoms (p < 0.001) were absent. Most strikingly, a loss of consciousness (33%, p < 0.001) and preexisting cardiovascular comorbidity (59%, p < 0.001) were more prevalent in the elderly. Finally, adrenaline was used in 30% of the elderly (vs. 26% in the comparator group, p < 0.001) and hospitalization was more often required (60 vs. 50%, p < 0.001). Discussion and Conclusion: Anaphylaxis in the elderly is often caused by insect venoms and drugs. These patients suffer more often from cardiovascular symptoms, receive more frequently adrenaline and require more often hospitalization. The data indicate that anaphylaxis in the elderly tends to be more frequently life threatening and patients require intensified medical intervention. The data support the need to recognize anaphylaxis in this patient group, which is prone to be at a higher risk for a fatal outcome

Peanut‐induced anaphylaxis in children and adolescents: Data from the European Anaphylaxis Registry

Background Peanut allergy has a rising prevalence in high-income countries, affecting 0.5%-1.4% of children. This study aimed to better understand peanut anaphylaxis in comparison to anaphylaxis to other food triggers in European children and adolescents. Methods Data was sourced from the European Anaphylaxis Registry via an online questionnaire, after in-depth review of food-induced anaphylaxis cases in a tertiary paediatric allergy centre. Results 3514 cases of food anaphylaxis were reported between July 2007 - March 2018, 56% in patients younger than 18 years. Peanut anaphylaxis was recorded in 459 children and adolescents (85% of all peanut anaphylaxis cases). Previous reactions (42% vs. 38%; p = .001), asthma comorbidity (47% vs. 35%; p < .001), relevant cofactors (29% vs. 22%; p = .004) and biphasic reactions (10% vs. 4%; p = .001) were more commonly reported in peanut anaphylaxis. Most cases were labelled as severe anaphylaxis (Ring&Messmer grade III 65% vs. 56% and grade IV 1.1% vs. 0.9%; p = .001). Self-administration of intramuscular adrenaline was low (17% vs. 15%), professional adrenaline administration was higher in non-peanut food anaphylaxis (34% vs. 26%; p = .003). Hospitalization was higher for peanut anaphylaxis (67% vs. 54%; p = .004). Conclusions The European Anaphylaxis Registry data confirmed peanut as one of the major causes of severe, potentially life-threatening allergic reactions in European children, with some characteristic features e.g., presence of asthma comorbidity and increased rate of biphasic reactions. Usage of intramuscular adrenaline as first-line treatment is low and needs to be improved. The Registry, designed as the largest database on anaphylaxis, allows continuous assessment of this condition

Secondary prevention measures in anaphylaxis patients: Data from the anaphylaxis registry

Background: Patients with a history of anaphylaxis are at risk of future anaphylactic reactions. Thus, secondary prevention measures are recommended for these patients to prevent or attenuate the next reaction. Methods: Data from the Anaphylaxis Registry were analyzed to identify secondary prevention measures offered to patients who experienced anaphylaxis. Our analysis included 7788 cases from 10 European countries and Brazil. Results:The secondary prevention measures offered varied across the elicitors. A remarkable discrepancy was observed between prevention measures offered in specialized allergy centers (84% of patients were prescribed adrenaline autoinjectors following EAACI guidelines) and outside the centers: Here, EAACI guideline adherence was only 37%. In the multivariate analysis, the elicitor of the reaction, age of the patient, mastocytosis as comorbidity, severity of the reaction, and reimbursement/availability of the autoinjector influence physician's decision to prescribe one. Conclusions: Based on the low implementation of guidelines concerning secondary prevention measures outside of specialized allergy centers, our findings highlight the importance of these specialized centers and the requirement of better education for primary healthcare and emergency physicians