Morphological variability (needles, galbulus) among seven populations of the Juniperus oxycedrus L. species-complex in Algeria

L’étude comparative du polymorphisme des végétaux par le biais des caractères taxinomiques d’un végétal est insuffisamment prise en compte en Algérie, surtout pour les espèces du genre Juniperus L. Le présent travail a été réalisé afin de rechercher l’existence d’une variabilité phénotypique dans sept populations naturelles de Juniperus oxycedrus L. à l’aide d’une analyse descriptive et comparative des aiguilles, des galbules et des stomates. Les surfaces épidermiques ont été également examinées dans le but de mieux caractériser cette essence. Un total de vingt-trois caractères morphologiques, quantitatifs et qualitatifs, a été étudié. L’observation et l’évaluation des caractères macro- et micro-morphologiques ont été réalisées sous loupe binoculaire, au microscope optique et au microscope électronique à balayage. L’analyse de la variance montre que les sept populations étudiées présentent une diversité morphologique considérable aux niveaux intra- et inter-populationnels pour les variables aiguilles, galbules et stomates, tandis que l’analyse multivariée a permis de séparer l’ensemble des populations étudiées en groupes bien distincts selon leurs caractères phénotypiques en mettant en évidence des corrélations entre les variables morphologiques et les caractéristiques environnementales. Par ailleurs, des variations micro-morphologiques ont été observées pour les surfaces épidermiques, incluant une variation dans la densité stomatique, la taille des stomates, l’occurrence de cire épicuticulaire, et des modifications dans la structure de l’épiderme.The comparative study of plant polymorphism using plant taxonomic characters is underrated in Algeria, especially for species of the genus Juniperus L. The present work has been realized in order to look out for the existence of phenotypic variability among seven natural populations of Juniperus oxycedrus L. through a descriptive and comparative analysis of the needles, galbulus and stomata. The epidermal surfaces have also been investigated in order to better characterize this species. Twenty-three quantitative and qualitative morphological characters have been studied. The observation and evaluation of macro and micro-morphological characters have been realized with binocular optical and scanning electronic microscopes. The variance analysis showed that the seven studied populations present a considerable morphological diversity at both intra- and inter-population levels for the variables needles, galbulus and stomata, while the multivariate analysis allowed to separate all the studied populations into distinct groups according to their phenotypic characters, highlighting correlations between the morphological variables and the environmental characteristics. Otherwise, micro-morphological variations have been observed for the epidermal surfaces including a variation in the stomatal density, the size of stomata, the occurrence of epicuticular wax and changes in the epidermal structure

New fossil genus and new extant species of diatoms (Stephanodiscaceae, Bacillariophyceae) from Pleistocene sediments in the Neotropics (Guatemala, Central America): adaptation to a changing environment?

International audienceSeveral taxa of Stephanodiscaceae were found in the upper section of Pleistocene sediments from Lake Petén-Itzá (Guatemala). A new fossil genus Cyclocostis gen. nov. and new extant Discostella gabinii sp. nov. are described. Cyclocostis is characterized by a strongly tangentially undulated valve surface, coarse unequal striation reaching a central punctum in the valve center, an absence of central lamina and domed criba, widely open alveoli with one median recessed costa bearing marginal fultoportulae and a single rimoportula all within a ring. A single valve face fultoportula is present on the raised part of the valve opposite the rimoportula. Differences relative to similar genera and the delimitation of a new genus are discussed. Discostella gabinii sp. nov. is distinguished by circular and flat valves, a small central area bearing 5 to >30 scattered large areolae giving a colliculate appearance, medium sized alveoli, marginal fultoportulae on every 4-5th costa, a single rimoportula and internal smooth valve centre. Differences to similar taxa in the genus Discostella are discussed. The succession of Cyclotella, Discostella and Cyclocostis species in our record could represent eco-phenotypic responses to particular environmental stress/change

Self-assembled liquid crystalline nanoparticles as an ophthalmic drug delivery system. Part II: optimization of formulation variables using experimental design

International audienceIn the field of keratoconus treatment, a lipid-based liquid crystal nanoparticles system has been developed to improve the preocular retention and ocular bioavailability of riboflavin, a water-soluble drug. The formulation of this ophthalmic drug delivery system was optimized by a simplex lattice experimental design. The delivery system is composed of three main components that are mono acyl glycerol (monoolein), poloxamer 407 and water and two secondary components that are riboflavin and glycerol (added to adjust the osmotic pressure). The amounts of these three main components were selected as the factors to systematically optimize the dependent variables that are the encapsulation efficiency and the particle size. In this way, 12 formulas describing experimental domain of interest were prepared. Results obtained using small angle X-rays scattering (SAXS) and cryo-transmission electron microscopy (cryo-TEM) evidenced the presence of nano-objects with either sponge or hexagonal inverted structure. In the zone of interest, the percentage of each component was determined to obtain both high encapsulation efficiency and small size of particles. Two optimized formulations were found: F7 and F1. They are very close in the ternary phase diagram as they contain 6.83% of poloxamer 407; 44.18% and 42.03% of monoolein; 46.29% and 48.44% of water for F7 and F11, respectively. These formulations displayed a good compromise between inputs and outputs investigated

Cyclotella petenensis and Cyclotella cassandrae, two new fossil diatoms from Pleistocene sediments of Lake Petén-Itzá, Guatemala, Central America

International audienceWhile analyzing the fossil diatom flora in one of the longest paleolimnological records (core PI-6) from Lake Petén-Itzá, lowland Guatemala, we encountered Aulacoseira Thwaites, Cyclotella (Kützing) and Discostella (Cleve & Grunow) Houk & Klee species appearing successively in the record. Among them, two new species that are assigned to the genus Cyclotella are described herein. Cyclotella petenensis sp. nov. is characterised by a coarse striation marked by a shadow line and a tangentially undulate central area with an arc of central fultoportulae. Cyclotella cassandrae sp. nov. has an elliptically shaped valve, coarse striae and a scattered ring of central fultoportulae in the central area. Classification and differences to similar taxa in the genus Cyclotella are discussed

Vestibular Nuclei: A New Neural Stem Cell Niche?

We previously reported adult reactive neurogliogenesis in the deafferented vestibular nuclei following unilateral vestibular neurectomy (UVN) in the feline and the rodent model. Recently, we demonstrated that UVN induced a significant increase in a population of cells colocalizing the transcription factor sex determining region Y-box 2 (SOX2) and the glial fibrillary acidic protein (GFAP) three days after the lesion in the deafferented medial vestibular nucleus. These two markers expressed on the same cell population could indicate the presence of lesion-reactive multipotent neural stem cells in the vestibular nuclei. The aim of our study was to provide insight into the potential neurogenic niche status of the vestibular nuclei in physiological conditions by using specific markers of stem cells (Nestin, SOX2, GFAP), cell proliferation (BrdU) and neuronal differentiation (NeuN). The present study confirmed the presence of quiescent and activated adult neural stem cells generating some new neurons in the vestibular nuclei of control rats. These unique features provide evidence that the vestibular nuclei represent a novel NSC site for the generation of neurons and/or glia in the adult rodent under physiological conditions

COMPOSITION CHIMIQUE ET LA MORPHOLOGIE DE LA CIRE CHEZ QUATRE ESPECES DU GENRE PISTACIA EN ALGERIE

Leaf samples of Pistacia atlantica, P. lentiscus, P. terebinthus and P. vera from different sites, in Algeria, were characterized according to their picuticular wax chemical composition and morphology. The cuticular waxes were observed under scanning electron microscope and analyzed by gas chromatography coupled to mass spectrometry after cyclohexane extraction. Wax morphology revealed a glossy aspect with a smooth wax layer in P. lentiscus leaves while a thin structure is observed in P. atlantica. The qualitative composition of the waxes, were different for the four species. The principal components were aliphatics, phenols and terpenes. There were, as well, quantitative differences between the taxa, concerning phenol and aliphatic compounds. P. vera show the highest phenol content, while P. atlantica and P. terebinthus have the highest aliphatic contents. Regarding the infraspecific variation, P. atlantica from semi-arid-fresh site exhibit more aliphatic and terpene. For P. lentiscus, sub-humid-mild site exhibited more aliphatic compounds while the semi-arid-cold site had the highest terpenes amount

COMPOSITION CHIMIQUE ET LA MORPHOLOGIE DE LA CIRE CHEZ QUATRE ESPECES DU GENRE PISTACIA EN ALGERIE

International audienceLeaf samples of Pistacia atlantica, P. lentiscus, P. terebinthus and P. vera from different sites, in Algeria, were characterized according to their picuticular wax chemical composition and morphology. The cuticular waxes were observed under scanning electron microscope and analyzed by gas chromatography coupled to mass spectrometry after cyclohexane extraction. Wax morphology revealed a glossy aspect with a smooth wax layer in P. lentiscus leaves while a thin structure is observed in P. atlantica. The qualitative composition of the waxes, were different for the four species. The principal components were aliphatics, phenols and terpenes. There were, as well, quantitative differences between the taxa, concerning phenol and aliphatic compounds. P. vera show the highest phenol content, while P. atlantica and P. terebinthus have the highest aliphatic contents. Regarding the infraspecific variation, P. atlantica from semi-arid-fresh site exhibit more aliphatic and terpene. For P. lentiscus, sub-humid-mild site exhibited more aliphatic compounds while the semi-arid-cold site had the highest terpenes amount

Étude de la variabilité morphologique (aiguilles, galbules) du complexe spécifique Juniperus oxycedrus L., le Genévrier oxycèdre, au sein de sept populations d’Algérie

International audienceThe comparative study of plant polymorphism using plant taxonomic characters is underrated in Algeria, especially for species of the genus Juniperus L. The present work has been realized in order to look out for the existence of phenotypic variability among seven natural populations of Juniperus oxycedrus L. through a descriptive and comparative analysis of the needles, galbulus and stomata. The epidermal surfaces have also been investigated in order to better characterize this species. Twenty-three quantitative and qualitative morphological characters have been studied. The observation and evaluation of macro and micromorphological characters have been realized with binocular optical and scanning electronic microscopes. The variance analysis showed that the seven studied populations present a considerable morphological diversity at both intra- nd inter-population levels for the variables needles, galbulus and stomata, while the multivariate analysis allowed to separate all the studied populations into distinct groups according to their phenotypic characters, highlighting correlations between the morphological variables and the environmental characteristics. Otherwise, micro-morphological variations have been observed for the epidermal surfaces including a variation in the stomatal density, the size of stomata, the occurrence of epicuticular wax and changes in the epidermal structure.L'étude comparative du polymorphisme des végétaux par le biais des caractères taxinomiques d'un végétal est insuffisamment prise en compte en Algérie, surtout pour les espèces du genre Juniperus L. Le présent travail a été réalisé afin de rechercher l'existence d'une variabilité phénotypique dans sept populations naturelles de Juniperus oxycedrus L. à l'aide d'une analyse descriptive et comparative des aiguilles, des galbules et des stomates. Les surfaces épidermiques ont été également examinées dans le but de mieux caractériser cette essence. Un total de vingt-trois caractères morphologiques, quantitatifs et qualitatifs, a été étudié. L'observation et l'évaluation des caractères macro-et micro-morphologiques ont été réalisées sous loupe binoculaire, au microscope optique et au microscope électronique à balayage. L'analyse de la variance montre que les sept populations étudiées présentent une diversité morphologique considérable aux niveaux intra-et inter-populationnels pour les variables aiguilles, galbules et stomates, tandis que l'analyse multivariée a permis de séparer l'ensemble des populations étudiées en groupes bien distincts selon leurs caractères phénotypiques en mettant en évidence des corrélations entre les variables morphologiques et les caractéristiques environnementales. Par ailleurs, des variations micro-morphologiques ont été observées pour les surfaces épidermiques, incluant une variation dans la densité stomatique, la taille des stomates, l'occurrence de cire épicuticulaire, et des modifications dans la structure de l'épiderme

Culture conditions have an impact on the maturation of traceable, transplantable mouse embryonic stem cell-derived otic progenitor cells.

International audienceThe generation of replacement inner ear hair cells (HCs) remains a challenge and stem cell therapy holds the potential for developing therapeutic solutions to hearing and balance disorders. Recent developments have made significant strides in producing mouse otic progenitors using cell culture techniques to initiate HC differentiation. However, no consensus has been reached as to efficiency and therefore current methods remain unsatisfactory. In order to address these issues, we compare the generation of otic and HC progenitors from embryonic stem (ES) cells in two cell culture systems: suspension vs. adherent conditions. In the present study, an ES cell line derived from an Atoh1-green fluorescent protein (GFP) transgenic mouse was used to track the generation of otic progenitors, initial HCs and to compare these two differentiation systems. We used a two-step short-term differentiation method involving an induction period of 5 days during which ES cells were cultured in the presence of Wnt/transforming growth factor TGF-β inhibitors and insulin-like growth factor IGF-1 to suppress mesoderm and reinforce presumptive ectoderm and otic lineages. The generated embryoid bodies were then differentiated in medium containing basic fibroblast growth factor (bFGF) for an additional 5 days using either suspension or adherent culture methods. Upon completion of differentiation, quantitative polymerase chain reaction analysis and immunostaining monitored the expression of otic/HC progenitor lineage markers. The results indicate that cells differentiated in suspension cultures produced cells expressing otic progenitor/HC markers at a higher efficiency compared with the production of these cell types within adherent cultures. Furthermore, we demonstrated that a fraction of these cells can incorporate into ototoxin-injured mouse postnatal cochlea explants and express MYO7A after transplantation

Exogenous Isoprene Confers Physiological Benefits in a Negligible Isoprene Emitter (Acer monspessulanum L.) Under Water Deficit

International audienceIsoprene, the main volatile released by plants, is known to protect the photosynthetic apparatus in isoprene emitters submitted to oxidative pressures caused by environmental constraints. Whether ambient isoprene contributes to protect negligible plant emitters under abiotic stress conditions is less clear, and no study has tested if ambient isoprene is beneficial during drought periods in plant species that naturally release negligible isoprene emissions. This study examines the effect of exogenous isoprene (20 ppbv) on net photosynthesis, stomatal conductance and production of H2O2 (a reactive oxygen species: ROS) in leaves of Acer monspessulanum (a negligible isoprene emitter) submitted to three watering treatments (optimal, moderate water stress and severe water stress). Results showed that A. monspessulanum exhibited a net photosynthesis increase (+30%) and a relative leaf H2O2 decrease when saplings were exposed to an enriched isoprene atmosphere compared to isoprene-free conditions under moderate water deficit. Such physiological improvement under isoprene exposure was not observed under optimal watering or severe water stress. These findings suggest that when negligible isoprene emitters are surrounded by a very high concentration of isoprene in the ambient air, some plant protection mechanism occurs under moderate water deficit probably related to protection against ROS damage eventually impeding photosynthesis drop