Influence des contraintes édaphiques sur la nutrition minérale, le développement et la production du cocotier (Cocos nucifera L.) dans des sols sulfatés acides salés ou non salés du delta du Mékong : effet améliorant d'un apport de phosphate naturel

La production d'huile végétale est un enjeu économique majeur au Viet Nam. Cependant, l'extension de la culture du cocotier à des sols sulfatés acides ou sulfatés acides salés, carencés en phosphore et en calcium, a entraîné une chute importante de la production par comparaison aux sols alluviaux. Ces carences ont été confirmées par le diagnostic foliaire mais aussi racinaire. Les potentiels hydriques élevés montrent que le cocotier ne souffre pas de stress hydrique dans le delta du Mékong même en saison sèche. Par contre, pendant cette saison, dans les zones soumises à l'influence de la marée, la salinité élevée provoque la fermeture des stomates et la baisse de l'assimilation photosynthétique. Le taux de sodium et un milieu asphyxique sont les causes d'une inhibition de la croissance des systèmes racinaire et aérien. L'augmentation excessive des teneurs en ions toxiques (Fe(3+), Al(3+), Na(+)) dans les racines par rapport aux feuilles a montré leur rôle filtrant. Un essai conduit avec des jeunes plants arrosés à l'eau salée, a permis de déterminer un niveau de salinité optimum (5 pour mille) et confirme le rôle de filtre des racines. L'apport de phosphate naturel augmente le nombre de noix et le poids de coprah par cocotier, l'effet étant relativement plus important avec les sols sulfatés acides salés. La solubilité de l'engrais phosphaté et sa teneur en calcium jouent un rôle essentiel dans l'efficacité du traitement : le calcium remonte le pH ce qui diminue l'activité des ions Al(3+) et améliore la structure du sol, le phosphore corrige sa carence et complexe une partie de Al. En se limitant aux zones où la salinité est inférieure à 10 pour mille de nouvelles plantations pourraient être développées sur plus de 100.000 ha dans le delta du Mékong. (Résumé d'auteur

Indochinese bamboos: biodiversity informatics to assist the identification of “vernacular taxa”

Bamboo (Bambusoides – Gramineae) is one of the most important natural resource in Southeast Asia. However, bamboo identification has many difficulties. In the area of SEP programme «Indochina Bamboos» (2008-2010), the final objective is to update the bamboo flora of Indochine (Vietnam, Laos, Cambodege) and to publish an e-flora including free access keys, digital images and information about the traditional and economic use of bamboos. During field trips in Vietnam, Laos and Cambodgia, samples, pictures and morphological description sheets were collected in various locations and previously assigned to the local vernacular names. We use an informatic program, Xper2, to assist the comparison and identification of “vernacular bamboo taxa” based on morphological characteristics

HIGH PERFORMANCE LIQUID CHROMATOGRAPHY ASSAY FOR DETERMINATION OF MOXIFLOXACIN IN HUMAN PLASMA

A simple reversed phase HPLC method with UV detection has been successfully developed and validated for determination of moxifloxacin in human plasma. The sample pretreatment involves only single-step protein precipitation with tricloroacetic acid. Moxifloxacin was measured in plasma using a validated HPLC method with UV detector at 295 nm, C18 column (25cm×4.5mm, 5µm), a mixture of phosphate buffer pH 4.0 and acetonitrile (70:30, v/v) as mobile phase at a flow rate of 0.8 ml/min. Retention time of moxifloxacin was found to be 7.4 min. The mean recovery for the drug was obtained 97.30%. The calibration curve was linear over the concentration range of 0.3 to 25.0 µg/mL with coefficient correlation of 0.9991. This method was successfully applied for therapeutic drug monitoring

Developing a zebrafish-based pipeline to investigate the biological properties of medicinal plant extracts from Northern Vietnam

peer reviewe

Belgium

peer reviewedPurpose: Traditional medicines have been used in Vietnam for thousands of years, and still play an essential role in healthcare. However, so far, there is no clear definition of circumstances in which plants can be collected, conserved, and extracted; viable models for a productive and sustainable exploitation of natural extracts are missing, sometimes leading to severe and unfavorable consequences on health. In this study, we aim to develop a cost-effective pipeline to assess the pharmaco-/toxicological properties of these medicinal materials using the zebrafish embryo as an in vivo model. Methods: Medicinal plants extracts were prepared by incorporating in the design more standardized methods as the traditional ones, using increasing polarity solvents. After that, the zebrafish has been chosen as a whole animal model to determine the core of the biological properties of a specific extract. Embryotoxicity was analyzed by exposing extracts to zebrafish embryos, which were monitored at specific times during 4 days for survival and the presence of developmental malformations. In addition, the zebrafish transgenic line Tg(fli1:EGFP) displaying fluorescent endothelial cells was used to visualize blood vessels and detect effects on angiogenesis. Proof-of-concept experiments were done by passing samples from two plants: Caesalpinia sappan L. and Glochidion eriocarpum to evaluate its efficiency. Results: Effects of C. sappan L. extract on zebrafish embryonic morphology and lethality were determined in the corresponding concentration-response curves (LC50=500 mg/L and EC50=40 mg/L). Analysis of transgenic zebrafish showed the anti-angiogenic properties in a dose dependent manner. In addition, the interaction between this plant extract and the embryo chorion was explored. On the other hand, G. eriocarpum extract exposure led to a biphasic response from the zebrafish embryos, suggesting a protective role of the embryonic chorion. Our results may contribute to the design of a rational high throughput pharmacological screening approach using the zebrafish model

Penicillium digitatum as a Model Fungus for Detecting Antifungal Activity of Botanicals: An Evaluation on Vietnamese Medicinal Plant Extracts.

peer reviewedMedicinal plants play important roles in traditional medicine, and numerous compounds among them have been recognized for their antimicrobial activity. However, little is known about the potential of Vietnamese medicinal plants for antifungal activity. In this study, we examined the antagonistic activity of twelve medicinal plant species collected in Northern Vietnam against Penicillium digitatum, Aspergillus flavus, Aspergillus fumigatus, and Candida albicans. The results showed that the antifungal activities of the crude extracts from Mahonia bealei, Ficus semicordata, and Gnetum montanum were clearly detected with the citrus postharvest pathogen P. digitatum. These extracts could fully inhibit the growth of P. digitatum on the agar medium, and on the infected citrus fruits at concentrations of 300-1000 µg/mL. Meanwhile, the other tested fungi were less sensitive to the antagonistic activity of the plant extracts. In particular, we found that the ethanolic extract of M. bealei displayed a broad-spectrum antifungal activity against all four pathogenic fungi. Analysis of this crude extract by enrichment coupled with high-performance liquid chromatography revealed that berberine and palmatine are major metabolites. Additional inspections indicated berberine as the key compound responsible for the antifungal activity of the M. bealei ethanolic extract. Our study provides a better understanding of the potential of Vietnamese medicinal plant resources for combating fungal pathogens. This work also highlights that the citrus pathogen P. digitatum can be employed as a model fungus for screening the antifungal activity of botanicals

The influence of human genetic variation on early transcriptional responses and protective immunity following immunization with Rotarix vaccine in infants in Ho Chi Minh City in Vietnam : a study protocol for an open single-arm interventional trial [awaiting peer review]

Background: Rotavirus (RoV) remains the leading cause of acute gastroenteritis in infants and children aged under five years in both high- and low-middle-income countries (LMICs). In LMICs, RoV infections are associated with substantial mortality. Two RoV vaccines (Rotarix and Rotateq) are widely available for use in infants, both of which have been shown to be highly efficacious in Europe and North America. However, for unknown reasons, these RoV vaccines have markedly lower efficacy in LMICs. We hypothesize that poor RoV vaccine efficacy across in certain regions may be associated with genetic heritability or gene expression in the human host. Methods/design: We designed an open-label single-arm interventional trial with the Rotarix RoV vaccine to identify genetic and transcriptomic markers associated with generating a protective immune response against RoV. Overall, 1,000 infants will be recruited prior to Expanded Program on Immunization (EPI) vaccinations at two months of age and vaccinated with oral Rotarix vaccine at two and three months, after which the infants will be followed-up for diarrheal disease until 18 months of age. Blood sampling for genetics, transcriptomics, and immunological analysis will be conducted before each Rotarix vaccination, 2-3 days post-vaccination, and at each follow-up visit (i.e. 6, 12 and 18 months of age). Stool samples will be collected during each diarrheal episode to identify RoV infection. The primary outcome will be Rotarix vaccine failure events (i.e. symptomatic RoV infection despite vaccination), secondary outcomes will be antibody responses and genotypic characterization of the infection virus in Rotarix failure events. Discussion: This study will be the largest and best powered study of its kind to be conducted to date in infants, and will be critical for our understanding of RoV immunity, human genetics in the Vietnam population, and mechanisms determining RoV vaccine-mediated protection. Registration: ClinicalTrials.gov, ID: NCT03587389. Registered on 16 July 2018

Impact des métaux lourds sur les interactions plante/ ver de terre/ microflore tellurique

L objectif de ce travail était d étudier les interactions entre une plante phytoremédiatrice , Lantana camara (Verbenaceae), le ver de terre, Pontoscolex corethrurus (Glossoscolecidae) et les microorganismes telluriques d un sol pollué au plomb. Dans un premier temps, il apparaît que dans les sols contaminés, la présence de ver conduit à un accroissement de la biomasse des parties aériennes et racinaires des plantes ainsi qu à une augmentation de l absorption de plomb. La caractérisation physico-chimique des agrégats racinaires a montré que l activité des vers augmente le taux de matière organique, la capacité d échange cationique ainsi que l azote total, le potassium total et disponible. De plus, la présence des vers augmente certaines activités enzymatiques de la rhizosphère. La croissance accrue de L. camara pourrait résulter de ces différentes actions. L action des vers de terre sur les plantes se ferait via les communautés microbiennes telluriques. Ainsi, la biomasse des microorganismes, bactéries et champignons, des agrégats racinaires augmente en présence de vers. La PCR-DGGE n a pas permis de mettre en évidence de modifications de la structure taxonomique des communautés bactériennes sous l influence du Pb et/ou du vers, par contre l analyse des profils physiologiques par plaques Biolog montre clairement une diversification fonctionnelle bactérienne. Les communautés fongiques voient, elles, leur diversité taxonomique, augmenter sous l action des vers. La restructuration des populations microbiennes, en présence de vers, des agrégats racinaires élaborés par les plantes en milieu pollué au plomb est l élément déterminant pour la compréhension de l impact de P. corethrurus sur la croissance et la phytoremédiation de L. camara. L association de ces deux organismes aurait donc un potentiel considérable pour le traitement de sites industriels pollués au plombThe objective of this work was to study the interactions between phytoremediating plant Lantana camara (Verbenaceae), the earthworm Pontoscolex corethrurus (Glossocolecidae) and microorganisms in soil contaminated with lead. Initially, it appears that in the contaminated soil, the presence of earthworm leads to an increase in the biomass of root and aerial parts of plants and increased absorption of lead. The physico-chemical characterization of root-aggregates showed that the activity of earthworms increases the rate of organic matter, cation exchange capacity, total nitrogen, total and available potassium. Moreover, the presence of earthworms increases certain enzymatic activities in the rhizosphere. The increased growth of L. camara could result from these different actions. The action of earthworm on plants would be through terrestrial microbial-communities. Thus, the biomass of microorganisms, bacteria and fungi, of root-aggregates increase in the presence of earthworms. By PCR-DGGE, we were unable to demonstrate differences in taxonomic diversity of the bacteria community but the analysis of physiological profiles with Biolog plates showed that the activities of earthworm enhance the functional diversity of soil bacteria. In other hand, the restructuring of fungal taxonomy has been clearly observed by the activity of earthworm. All changes observed can explain increased growth of plants and improved phytoextraction of heavy metal. Finally, the study underlines the role of the earthworms on the growth and the phytoextraction efficiency of the plants. So, the combination of earthworm P. corethrurus and plant L. camara could be considerable potential for the treatment of industrial sites polluted with leadPARIS-EST-Université (770839901) / SudocSudocFranceF

The resilience of the tourism and hospitality workforce

Resilience, which is understood as the capacity of a system to absorb disturbance and reorganise while undergoing change, has increasingly become an important topic in both professional practices and academic research. In tourism and hospitality, this is an essential ability for the destinations, the organisations, as well as the workforce to adapt and thrive during competitive and challenging times. This chapter focuses on the workforce, aiming to provide a comprehensive understanding of resilience from the organisational perspective and the individual career perspective. It provides a thorough theoretical background of organisational resilience, employee resilience, and career resilience. Additionally, empirical data from Vietnam in the context of a major health crisis, that is, the COVID-19 pandemic, will further illustrate and broaden the knowledge of these issues. Two empirical studies will be included. The first study, with a qualitative approach and from a managerial perspective, demonstrates human resource (HR) practices during the pandemic to ensure the resilience of the organisation and the workforce. A framework of HR practices to enhance resilience during a crisis is proposed. The second study, with a quantitative approach and from an employee perspective, explores the factors which influence the career resilience of the hospitality and tourism workforce, with the foundation of the protection motivation theory. The link of resilience between these two perspectives is then drawn, together with practical and theoretical implications

Characterization of hygrothermal insulating biomaterials modified by inorganic adsorbents

International audienc