Comparison of spatial scale variability of shoot density and epiphytic leaf assemblages of Halophila stipulacea and Cymodocea nodosa on the Eastern Coast of Tunisia

Abstract

A study was undertaken to compare the patterns of spatial variability, epiphytic percentage cover, and distribution of epiphytic fauna and flora between the two adjacent seagrasses Cymodocea nodosa and the invasive species Halophila stipulucea. Samples were taken at six stations separated by 600?m and exposed to different current conditions. The stations G2 and G5 were affected by a high current tide, while G4 was directly exposed to the northern marine currents. The station G3 was situated in the middle of a Posidonia oceanica bed and was less exposed to hydrodynamism, whereas the other stations were relatively protected. Results indicate that for both H. stipulacea and C. nodosa, shoot density and epiphytic cover biomass decreased when exposed to high levels of hydrodynamic activity. In terms of epiphytic leaf assemblages, our results showed significant differences for the two host plants in their mean cover and for the six stations at the largest and smallest spatial scale. Our observations highlight the dominance of Rhodophyta and the low number of epiphytic species and the epiphytic cover on H. stipulacea compared to C. nodosa. In addition, results indicate the absence of two taxa Hydrozoans and Annelida in the epiphytic assemblage of H. stipulacea leaves.     

Analysis of Bitter Orange Petitgrain Essential Oil by Combined Gas Chromatography-Mass Spectrometry

Candida catenulata CBS 1904, the previous type strain of C. ravautii, was selected as the best strain for the production of threo-O_s-isocitric acid from water-insoluble carbon sources, non-carbohydrates. The addition of surfactants, lipophilic polyoxyethylene nonyl phenyl ethers, was essential for the acid production, because the cell surface of the strain was less lipophilic. «-Alkanes, ranging from C_n to C_l4, gave the acid in high yields. The acid was produced in ajar fermentor in an about 90% yield on a weight basis as to «-tetradecane supplied. The acid was easily recovered, as crystals of its monopotassium salt, from the concentrated culture broth filtrate.     

Aphid (Hemiptera: Aphidoidea) diversity in Tunisia in relation to seed potato production

Winged morphs of aphids were investigated from 2002 to 2004 in 4 Tunisian regions of potato seeds production in order to know the aphid diversity and the potential vectors of Potato Virus Y. This is a very important contribution to the knowledge of aphid fauna in Maghreb. A total of 50,030 aphids were caught using yellow water traps and one suction trap. 130 taxa were identified including 103 species. Ten species are well represented in all regions prospected and typical species were also observed in every region. Some differences in species diversity appeared between regions which are discussed considering weather condition and vegetation.     

Daily Changes of Plasma Corticosterone by an 8-h Daytime Feeding Occur Without Body Weight Loss or Severe Food Restriction in the Rat

Different studies have reported that daytime feeding entrains the circadian rhythm of corticosterone secretion in rats. However, it remained unclear whether calorie restriction or daytime feeding access have an effect. The aim of our study is to evaluate the effect of an 8-h daytime feeding access on the circadian rhythm of plasma corticosterone. Eleven adult male Wistar rats were assigned to two different conditions of access to food: ad lib feeding for one week and daytime feeding for the following two weeks. On the 7th, 14th and 21st day, blood samples were collected every 4 h from 08:00 to 04:00. Food intake and body weight were recorded daily. During daytime feeding, rats ingested 88% of the amount of food ingested over 24 h in the ad lib feeding period. However, body weight increased significantly from the first day to the end of experiment. Peak plasma corticosterone was 12 h shifted during daytime feeding period compared to the ad lib condition. This study showed that an 8-h daytime feeding entrained the circadian rhythm of plasma corticosterone without body weight loss or severe food restriction.     

The potential of antagonistic moroccan Streptomyces isolates for the biological control of damping‐off disease of pea (Pisum sativum L.) caused by Aphanomyces euteiches

Three hundred and fifty‐nine isolates of actinobacteria collected from different Moroccan soils were evaluated for their in vitro antimicrobial activity against the oomycete pathogen Aphanomyces euteiches, the causal agent of damping‐off of pea and other legumes. Eighty‐seven isolates (24%) had an inhibitory in vitro effect against A. euteiches. Fourteen bioactive isolates with the greatest inhibitory effect against A. euteiches and no inhibitory effect on plant beneficial rhizobia were tested for their ability to protect pea seeds and seedlings against the damping‐off disease using culture supernatants or spore suspensions as treatments. The two most protective isolates, OB21 and BA15, significantly reduced, compared to untreated control plants, damping‐off by 33% and 47%, respectively. The two bioactive isolates were classified as species of the genus Streptomyces based on 16S rDNA analysis and morphological and chemical characteristics.     

Differential expression of thrombospondin,collagen, and thyroglobulin by thyroid-stimulating hormone and tumor-promoting phorbol ester in cultured porcine thyroid cells

In the present study, we have investigated the potential regulation of thyroglobulin (Tg) and extracellular matrix components synthesis by thyroid-stimulating hormone (TSH) and tetradecanoyl phorbol-13-acetate (TPA) on thyroid cells. Porcine thyroid cells isolated by trypsin-EGTA digestion of thyroid glands were maintained in serum containing medium on poly (L-lysine)-coated dishes. Cells differentiated into follicular or vesicular-like structures were distinguished by their ability to organify Na[¹²⁵l] and to respond to TSH stimulation. After an incubation of the cells with radiolabeled proline or methionine, two major proteins were identified, p450–480 and p290 (so named because of their molecular masses). Tg (p290) synthesis was demonstrated by the synthesis of [¹³¹l]-labeled polypeptides with electrophoretic properties identical to those of authentic Tg molecules. P450–480 resolved to Mr 190,000 under reducing sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) conditions. It was identified as thrombospondin by its reactivity with a monoclonal anti-human thrombospondin and by peptide sequencing of some of its tryptic fragments that displayed identity to thrombospondin l. Collagen synthesis was demonstrated by the formation of radioactive hydroxyproline and by the synthesis of pepsin-resistant polypeptides ranging from Mrs 120,000 to 200,000. When the cells were cultured in the presence of 100 nM TPA, the culture medium contents of thrombospondin and collagen were increased by 2.7 and 1.6-fold, respectively, whereas Tg content was decreased by a factor 3.9. In contrast, the acute treatment of control cells with TPA induced a decrease in both Tg and collagen content by factors 3.0 and 1.5, respectively, and an increase in thrombospondin content by a factor 2.5. In the presence of 100 nM TPA, TSH (1 mU/ml) did not counteract the stimulating effect of TPA on extracellular matrix components synthesis. In contrast, when cells were cultured in the presence of TSH alone at concentrations higher than 0.1 mU/ml, collagen and thrombospondin in the medium were decreased by a factor 2.0 and 1.9, respectively, and TSH preferentially activated Tg synthesis. However, no acute response to TSH was observed in cells incubated for 2 days without effectors (control cells). On TSH differentiated cells, TPA decreased both collagen and Tg accumulation by factor 1.2 and 1.8, respectively, whereas it increased the one of thrombospondin by a factor 2. These results, together with the stimulating effect of TPA on TSH mediated cell proliferation, argue for a role of thrombospondin in cell adhesion and migration events within the thyroid epithelium. © 1994 Wiley-Liss, Inc.     

Using Adeno-associated Virus as a Tool to Study Retinal Barriers in Disease

Müller cells are the principal glial cells of the retina. Their end-feet form the limits of the retina at the outer and inner limiting membranes (ILM), and in conjunction with astrocytes, pericytes and endothelial cells they establish the blood-retinal barrier (BRB). BRB limits material transport between the bloodstream and the retina while the ILM acts as a basement membrane that defines histologically the border between the retina and the vitreous cavity. Labeling Müller cells is particularly relevant to study the physical state of the retinal barriers, as these cells are an integral part of the BRB and ILM. Both BRB and ILM are frequently altered in retinal disease and are responsible for disease symptoms.There are several well-established methods to study the integrity of the BRB, such as the Evans blue assay or fluorescein angiography. However these methods do not provide information on the extent of BRB permeability to larger molecules, in nanometer range. Furthermore, they do not provide information on the state of other retinal barriers such as the ILM. To study BRB permeability alongside retinal ILM, we used an AAV based method that provides information on permeability of BRB to larger molecules while indicating the state of the ILM and extracellular matrix proteins in disease states. Two AAV variants are useful for such study: AAV5 and ShH10. AAV5 has a natural tropism for photoreceptors but it cannot get across to the outer retina when administered into the vitreous when the ILM is intact (i.e., in wild-type retinas). ShH10 has a strong tropism towards glial cells and will selectively label Müller glia in both healthy and diseased retinas. ShH10 provides more efficient gene delivery in retinas where ILM is compromised. These viral tools coupled with immunohistochemistry and blood-DNA analysis shed light onto the state of retinal barriers in disease.     

Contribution of microwave accelerated distillation in the extraction of the essential oil of Zygophyllum album L.

Introduction – The aerial parts of Zygophyllum album L. are used in folk medicine as an antidiabetic agent and as a drug active against several pathologies. In this work we present the chemical composition of Algerian essential oils obtained by microwave accelerated distillation (MAD) extraction, a solventless method assisted by microwave. Objective – Under the same analytical conditions and using GC‐FID and GC‐MS, the chemical composition of the essential oil of Zygophyllum album L. extracted by MAD was compared with that achieved using hydrodistillation (HD). Methodology – The extracted compounds were hydrosoluble, and they were removed from the aqueous solution by a liquid extraction with an organic solvent. Results – Employing MAD (100°C, 30 min), the essential oil contained mainly oxygenated monoterpenes with major constituents: carvone and α‐terpineol. However, most of the compounds present in the hydrodistilled volatile fraction were not terpene species, with β‐damascenone as a major constituent. Conclusion – The MAD method appears to be more efficient than HD: after 30 min extraction time, the obtained yields (i.e. 0.002%) were comparable to those provided by HD after 3 h extraction. MAD seems to be more convenient since the volatile fraction is richer in oxygenated monoterpenes, species that are recognised for their olfactory value and their contribution to the fragrance of the essential oil. Copyright © 2010 John Wiley & Sons, Ltd.