Seasonal variation of leaf thickness: An overlooked component of functional trait variability.

The dry and wet seasons in the Neotropics have strong effects on soil water and nutrient availability, as well as on forest dynamics. Despite these major effects on forest ecology, little is known on how leaf traits vary throughout the seasons in tropical rainforest trees. Here, we investigated the influence of seasonal variations in climate and soil characteristics on leaf trait variation in two tropical tree species. We measured two leaf traits, thickness and water mass per area, in 401 individuals of two species of Symphonia (Clusiaceae) in the Paracou research station in French Guiana tropical lowland rainforest. We found a significant effect of seasonal variation on these two leaf traits. Soil relative extractable water was a strong environmental predictor of leaf trait variation in response to seasonal variation. Reduced soil water availability during the dry season was associated with increased leaf thickness and water mass per area, possibly as a result of stomatal closure. Our findings advocate the need to account for environmental seasonality when studying leaf traits in seasonal ecosystems such as tropical forests.

[The contribution of teleconsultation and isolation of symptomatic cases in control of the COVID-19 outbreak a military base]. / Apport de la téléconsultation et de l'isolement des cas symptomatiques dans la maîtrise de l'épidémie COVID-19 au sein d'une base militaire.

BACKGROUND: The first wave of COVID-19 swept over France during the first quarter of 2020, leading to saturation of the health care system. We wished to study, in a French military medical unit assisting one of the country's largest armed forces populations, the impact of teleconsultation and the systematic isolation of all possible, probable and confirmed cases of COVID-19. METHODS: This is a retrospective study carried out from March 9 to May 31, 2020 on the basis of our activity register. The variables collected included type of medical consultation procedure, occupational status, classification of cases and date of onset of first symptoms. We have paralleled our activity with that of SOS Médecins and the emergency departments of the Île-de-France region. RESULTS/DISCUSSION: During this period, 1719 episodes of care (teleconsultations or physical consultations) were recorded, of which 91% (n=1561) were linked to COVID-19. We identified 598 "suspected" (possible and probable) and confirmed cases. "Isolated" teleconsultations (not followed by a face-to-face medical consultation, sample taking or necessitating the dispatch of prompt assistance) represented 86% of episodes of care (n=1482). Comparison of our activity and the number of new cases with the databases of SOS Médecins and the Île-de-France emergency services suggests that our isolation strategy was timely and effective. CONCLUSION: The contribution of teleconsultation was substantial and reassuring. Teleconsultation makes it possible to absorb a large volume of patients, is easy to implement, and entails no nosocomial risk. Isolation of infected patients should be a priority during an outbreak. Once it has become a priority to rapidly bring an epidemic under control, this attitude must be extended to all symptomatic patients.

Investigations of the charge transfer phenomenon at the hybrid dye/BiVO4 interface under visible radiation.

Photocatalytic hybrid systems were realized by associating bismuth vanadate (BiVO4) nanostructured thin films with anchored organic and metal-organic complex molecules. The chosen dyes are based on indoline and azo-based moieties. Optical and photoinduced charge transfer features were investigated experimentally and analysed theoretically through the electron band alignment on the organic/inorganic interface. Quantum calculations were carried out for the studied hybrid systems by using DFT and semi-empirical approaches. The calculations were performed by implementing a cluster model applied for the nanostructures and hybrid systems. The electronic density peculiarities point out efficient charge transfer for D149 based hybrids compared to azo-based systems. The electron distribution in hybrid systems inferred from the computational analysis and their experimental probing using Kelvin Force Microscopy (KFM) maps the way to understanding the photoinduced charge transfer occurring at the interfaces between organic dyes and an inorganic photocatalyst. The presented approach helps to predict suitable photoactive hybrid materials leading to efficient photocatalytic devices.

[Venous thromboembolic risk during repatriation for medical reasons]. / Risque veineux thromboembolique et sa prévention lors d'un rapatriement sanitaire.

In France, approximately 3000 people are repatriated every year, either in a civil situation by insurers. Repatriation also concerns French army soldiers. The literature is scarce on the topic of venous thromboembolic risk and its prevention during repatriation for medical reasons, a common situation. Most studies have focused on the association between venous thrombosis and travel, a relationship recognized more than 60 years ago but still subject to debate. Examining the degree of venous thromboembolic risk during repatriation for medical reasons must take into account several parameters, related to the patient, to comorbid conditions and to repatriation modalities. Appropriate prevention must be determined on an individual basis.

Osteonecrosis of the jaw in a male osteoporotic patient treated with denosumab.

Osteonecrosis of the jaw (ONJ) is a clinical condition associated with long-term exposure to inhibitors of bone resorption, mainly bisphosphonates. Denosumab (DMab) is a human monoclonal antibody of the receptor activator of nuclear factor kappa-B ligand. It prevents osteoclast-mediated bone resorption and is widely prescribed for the management of postmenopausal osteoporosis. Whereas ONJ has already been reported in women treated with DMab, we report for the first time the development of ONJ, following tooth extraction, in a male patient treated for idiopathic osteoporosis with DMab. Due to the constant increase in DMab prescription, for the management of osteoporosis, in both genders, physicians should be made aware of this potential risk.

Synthesis of new materials by laser pyrolysis: ZrO2, Y2O3:Ce and TiC(x)N(y) nanoparticles.

New developments concerning the synthesis of oxide and non oxide nanoparticles by laser pyrolysis are reported here. In order to be able to study the relations between the host and the guest in doped nanostructured luminescent oxide matrix, tetragonal ZrO2 nanoparticles were synthesized with sizes as low as 3 nm in weighable amounts. Y2O3 nanoparticles doped with Ce were also prepared with grains in the 10-20 nm size range. Concerning the non-oxide materials, TiC, TiN, and TiC(x)N(y) nanopowders were obtained from simple annealing treatments performed on TiO2/C nanocomposites grown by laser pyrolysis. The final crystalline phase was controlled by the initial C content and the annealing atmosphere. Once sintered, these materials will allow the study of the mechanical properties of nanostructured carbonitride ceramics.

Dynamic scaling properties of TeO2-based gels.

Homogeneous, transparent, and mechanically rigid gels have been successfully synthesized in the tellurium isopropoxide-isopropanol-citric acid and water system. The sol to gel transition and the gels microstructure have been studied by using small angle X-ray scattering (SAXS) experiments. For any value of the two key synthesis parameters, which are the citric acid ratio and the alkoxide concentration, very small Te-rich elementary particles, about 1-1.5 nm in radius, form immediately when the water is added, leading to colloidal sols. During gelation, these elementary particles stick progressively together to build up fractal aggregates by a pure hierarchical aggregation process which has been identified as a reaction-limited cluster aggregation (RLCA) mechanism. The SAXS curve analysis, based on scaling concepts, shows that the gelling network exhibits a time and length scale invariant structure factor characterized by self-similarity. This self-similarity is also displayed for a wide range of chemical compositions and the gel microstructures only differ in their fractal aggregate size according to the tellurium isopropoxide concentration as well as the citric acid ratio.

Influence of ageing, grinding and preheating on the thermal behaviour of alpha-lactose monohydrate.

It is shown that the onset temperature and the magnitude of thermal events observed during DSC analyses of alpha-lactose monohydrate can be strongly affected by various treatments such as ageing, manual grinding and preheating (cycle of preliminary dehydration and rehydration). In the case of grinding and preheating, the change of dehydration pathways was further investigated by using a suitable combination of characterization techniques, including X-ray powder diffraction (XRPD) performed with a synchrotron source (allowing an accurate Rietveld analysis), scanning electron microscopy (SEM), laser particle size measurements, FTIR spectroscopy and (1)H NMR for the determination of beta-lactose contents in samples. It appeared that the dehydration mechanism is affected not only by a smaller particle size distribution, but also by residual anisotropic lattice distortions and by the formation of surface defects or high energy surfaces. The fusion-recrystallization process occurring between anhydrous forms of alpha-lactose at ca. 170 degrees C is not significantly affected by grinding, whereas a preheating treatment induces an unexpected large increase of the enthalpy associated with this transition. Our observations and interpretations confirm the important role of water molecules in the crystal cohesion of the title compound and illustrate the necessity to consider the history of each sample for a satisfactory understanding of the physical properties and the behaviour of this important pharmaceutical excipient.

Enhanced pelvic responses to stressors in female CRF-overexpressing mice.

Acute stress affects gut functions through the activation of corticotropin-releasing factor (CRF) receptors. The impact of acute stress on pelvic viscera in the context of chronic stress is not well characterized. We investigated the colonic, urinary, and locomotor responses monitored as fecal pellet output (FPO), urine voiding, and ambulatory activity, respectively, in female and male CRF-overexpressing (CRF-OE) mice, a chronic stress model, and their wild-type littermates (WTL). Female CRF-OE mice, compared with WTL, had enhanced FPO to 2-min handling (150%) and 60-min novel environment (155%) but displayed a similar response to a 60-min partial restraint stress. Female CRF-OE mice, compared with WTL, also had a significantly increased number of urine spots (7.3 +/- 1.4 vs. 1.3 +/- 0.8 spots/h) and lower locomotor activity (246.8 +/- 47.8 vs. 388.2 +/- 31.9 entries/h) to a novel environment. Male CRF-OE mice and WTL both responded to a novel environment but failed to show differences between them in colonic and locomotor responses. Male WTL, compared with female WTL, had higher FPO (113%). In female CRF-OE mice, the CRF(1)/CRF(2) receptor antagonist astressin B and the selective CRF(2) receptor agonist mouse urocortin 2 (injected peripherally) prevented the enhanced defecation without affecting urine or locomotor responses to novel environment. RT-PCR showed that CRF(1) and CRF(2) receptors are expressed in the mouse colonic tissues. The data show that chronic stress, due to continuous central CRF overdrive, renders female CRF-OE mice to have enhanced pelvic and altered behavioral responses to superimposed mild stressors and that CRF(1)-initiated colonic response is counteracted by selective activation of CRF(2) receptor.

Corticotropin-releasing factor receptor type 2-deficient mice display impaired coping behaviors during stress.

Two cognate receptors (CRF(1) and CRF(2)) mediate the actions of the stress-regulatory corticotropin-releasing factor (CRF) family of peptides. Defining the respective roles of these receptors in the central nervous system is critical in understanding stress neural circuitry and the development of psychiatric disorders. Here, we examined the role of CRF(2) in several paradigms that assess coping responses to stress. We report that CRF(2) knockout mice responded to a novel setting with increased aggressive behavior toward a bulbectomized conspecific male and show increased immobility during acute swim stress compared with wild-type mice. In addition, CRF(2)-deficient mice exhibited impaired adaptation to isolation stress as evinced by prolonged hypophagia and associated weight loss. Collectively, these results point toward a role for CRF(2) pathways in neural circuits that subserve stress-coping behaviors.

Temporopolar changes in temporal lobe epilepsy: a quantitative MRI-based study.

OBJECTIVES: To quantify the morphologic changes of temporopolar structures to better understand the pathophysiology of anterior temporal white matter increased T2 signal observed in temporal lobe epilepsy (TLE). METHODS: MRI was performed in 30 patients with TLE and in 30 normal control subjects and independently assessed by visual analysis and quantitative measurements. Specifically, the temporal pole (TP) volume, as well as its gray and white matter components, was measured using three-dimensional T1 MR images and a semiautomatic protocol. The authors tested whether the presence of an increased T2-weighted signal in the anterior temporal white matter was associated with significant TP atrophy. The associations between the TP volume and MRI signs of hippocampal sclerosis, age at onset, seizure frequency, duration of illness, and a history of febrile convulsions were also studied. RESULTS: Both right and left TLE populations demonstrated a reduction of the temporopolar white and gray matter volumes ipsilateral to seizure onset (p < 0.02 in right TLE; p < 0.0001 in left TLE). Twenty-two patients (72%) exhibited significantly abnormal TP volume measurements, which correctly lateralized the epileptogenic zone in all cases. The presence of an increased T2-weighted signal in the anterior temporal white matter (ISWM), but not that of hippocampal sclerosis, was associated with a greater TP volume asymmetry index (p < 0.05). CONCLUSIONS: The temporal pole is frequently atrophic ipsilateral to seizure onset in refractory TLE. The association between TP atrophy and ISWM suggests that both abnormalities might derive from a common pathologic process.

[Acute polyradiculoneuropathy after Chlamydia pneumoniae infection]. / Polyradiculonévrite aiguë secondaire à une infection à Chlamydia pneumoniae.

A 36-year-old woman presented acute polyradiculoneuropathy following Chlamydia pneumoniae infection. Although electrophysiologic studies were normal, clinical features were typical of Guillain-Barré syndrome (GBS). Anti-ganglioside GM1 antibodies were positive. Two other cases of GBS following Chlamydia pneumoniae infection have been reported, but no specific feature emerges. Outcome was good in our patient after intravenous globulin then antibiotic therapy. Our case supports the notion that Chlamydia pneumoniae infection can induce GBS. The association is probably underestimated.

IL-1alpha and TNFalpha down-regulate CRH receptor-2 mRNA expression in the mouse heart.

Two receptors (CRH receptor type 1 and CRH receptor type 2) have been identified for the stress-induced neuropeptide, CRH and related peptides, urocortin, and urocortin II. We previously found marked down-regulation of cardiac CRH receptor type 2 expression following administration of bacterial endotoxin, lipopolysaccharide, a model of systemic immune activation, and inflammation. We postulated that inflammatory cytokines may regulate CRH receptor type 2. We show that systemic IL-1alpha administration significantly down-regulates CRH receptor type 2 mRNA in mouse heart. In addition, TNFalpha treatment also reduces CRH receptor type 2 mRNA expression, although the effect was not as marked as with IL-1alpha. However, CRH receptor type 2 mRNA expression is not altered in adult mouse ventricular cardiomyocytes stimulated in vitro with TNFalpha or IL-1alpha. Thus, cytokine regulation may be indirect. Exogenous administration of corticosterone in vivo or acute restraint stress also reduces cardiac CRH receptor type 2 mRNA expression, but like cytokines, in vitro corticosterone treatment does not modulate expression in cardiomyocytes. Interestingly, treatment with urocortin significantly decreases CRH receptor type 2 mRNA in cultured cardiomyocytes. We speculate that in vivo, inflammatory mediators such as lipopolysaccharide and/or cytokines may increase urocortin, which in turn down-regulates CRH receptor type 2 expression in the heart. Because CRH and urocortin increase cardiac contractility and coronary blood flow, impaired CRH receptor type 2 function during systemic inflammation may ultimately diminish the adaptive cardiac response to adverse conditions.

Animal models of CRH excess and CRH receptor deficiency display altered adaptations to stress.

This review highlights new information gained from studies using recently developed animal models that harbor specific alterations in corticotropin-releasing hormone (CRH) pathways. We discuss features of a transgenic mouse model of chronic CRH overexpression and two mouse models that lack either CRH receptor type 1 (CRH-R1) or type 2 (CRH-R2). Together these models provide new insights into the role of CRH pathways in promoting stability through adaptive changes, a process known as allostasis.

[Radicular pain revealing Hodgkin's disease]. / Sciatalgie révélatrice d'une maladie de Hodgkin.

We report on a case of Hodgkin's disease, revealed in a 52 year-old woman by isolated neurological signs. Sciatica is an uncommon pattern of discovery that is particularly misleading. It may lead to a delayed diagnosis all the more prejudicial since it discloses an advanced stage of the disease. The neurological involvement is always associated with a bone lesion. This latter can be discovered at an early stage through magnetic resonance imaging.

Abnormal adaptations to stress and impaired cardiovascular function in mice lacking corticotropin-releasing hormone receptor-2.

The actions of corticotropin-releasing hormone (Crh), a mediator of endocrine and behavioural responses to stress, and the related hormone urocortin (Ucn) are coordinated by two receptors, Crhr1 (encoded by Crhr) and Crhr2. These receptors may exhibit distinct functions due to unique tissue distribution and pharmacology. Crhr-null mice have defined central functions for Crhr1 in anxiety and neuroendocrine stress responses. Here we generate Crhr2-/- mice and show that Crhr2 supplies regulatory features to the hypothalamic-pituitary-adrenal axis (HPA) stress response. Although initiation of the stress response appears to be normal, Crhr2-/- mice show early termination of adrenocorticotropic hormone (Acth) release, suggesting that Crhr2 is involved in maintaining HPA drive. Crhr2 also appears to modify the recovery phase of the HPA response, as corticosterone levels remain elevated 90 minutes after stress in Crhr2-/- mice. In addition, stress-coping behaviours associated with dearousal are reduced in Crhr2-/- mice. We also demonstrate that Crhr2 is essential for sustained feeding suppression (hypophagia) induced by Ucn. Feeding is initially suppressed in Crhr2-/- mice following Ucn, but Crhr2-/- mice recover more rapidly and completely than do wild-type mice. In addition to central nervous system effects, we found that, in contrast to wild-type mice, Crhr2-/- mice fail to show the enhanced cardiac performance or reduced blood pressure associated with systemic Ucn, suggesting that Crhr2 mediates these peripheral haemodynamic effects. Moreover, Crhr2-/- mice have elevated basal blood pressure, demonstrating that Crhr2 participates in cardiovascular homeostasis. Our results identify specific responses in the brain and periphery that involve Crhr2.

Captopril and stress-induced hypertension in the borderline hypertensive rat.

OBJECTIVE: Daily exposure to air-jet stress (AJS) causes sustained elevations of blood pressure in borderline hypertensive rats (BHR). It is known that the renin-angiotensin system is activated during episodes of behavioral stress, and the purpose of this study was to assess the involvement of renin-angiotensin system in the development of stress-induced hypertension in the BHR. DESIGN: Four groups of 8- and 9-week-old rats were studied: they received, respectively, oral captopril and AJS; oral captopril without AJS; AJS without captopril; and neither AJS nor captopril. METHODS: After 10 days of AJS and captopril conditions, femoral and jugular catheters were implanted for the measurement of mean arterial pressure and pressor responses to norepinephrine and tyramine. Blood samples were collected for the measurement of norepinephrine and plasma renin activity. RESULTS: Ten days of AJS caused a significant elevation of blood pressure in BHR exposed to AJS without receiving captopril but not in those animals given captopril concurrently with AJS. Circulating norepinephrine and blood pressure responses to exogenous norepinephrine and tyramine were similar across the four groups. Plasma renin activity was highest in BHR given captopril, and was significantly elevated during an acute episode of AJS. CONCLUSIONS: The renin-angiotensin system may be important in the development of stress-induced hypertension in the BHR.

Stress-induced hypertension in the borderline hypertensive rat: stimulus duration.

Blood pressure and circulating catecholamines were evaluated in borderline hypertensive rats (BHR) that were exposed to daily sessions of either short (20 min) or long (120 min) duration air-jet stimulation. Indirect measures of systolic blood pressure indicated that within 2 weeks both experimental groups developed stress-induced hypertension in comparison to home cage controls. Animals exposed to 120 min stress sessions had significantly higher systolic blood pressure relative to the 20 min group. However, direct measures of blood pressure taken after 5 weeks of daily stress did not reveal any differences between the stress groups. Daily measurements indicated that acute changes in blood pressure during stress were modest and transient, suggesting little contribution to the chronic elevation in blood pressure observed as a consequence of stress. Circulating catecholamines were significantly increased by the stressor. Epinephrine returned to baseline within 60 min, although norepinephrine remained elevated throughout the 120 min session. The results indicate that increasing the duration of daily air jet stimulation did not impact the development of stress-induced hypertension over the 5-week measurement period.