Phytoplankton distribution in the upwelling areas of the Moroccan Atlantic coast localized between 32°30'N and 24°N

Marine phytoplankton was studied in January and July 2002 along of four transects: 32°30′N, 29°N, 24°30′N and 24°N. A total of 142 taxa were recorded in this area. The maximal specific richness, both in summer and in winter, was registered around Dakhla (24°N). The global spatiotemporal variability of species richness and specific diversity showed that the most structured and species-rich populations are situated in the coastal areas. The vertical variation of the two parameters showed homogeneity between depth levels. The maximal phytoplanktonic densities are recorded in the southern transects due to the permanent upwelling activity in the southern Atlantic coast. The bathymetric distribution of densities was more heterogeneous during summer, characterized by a high intensity of upwelling. The species Thalassionema nitzschioides, Asterionellopsis glacialis, Melosira, Chaetoceros and Leptocylindrus minimus are indicators of upwelling.     

Ecdysteroids in spinach (Spinacia oleracea L.): biosynthesis, transport and regulation of levels

Many plant species produce phytoecdysteroids (PEs: i.e. analogues of insect steroid hormones). There is increasing evidence that PEs are used as a chemical defence by plants against non-adapted insects and nematodes. PEs are good candidates for the development of an environmentally safe approach to crop protection. Most crop species do not accumulate PEs. However, many arguments support the idea that most, if not all, plant species have the genetic ability to produce PEs, but the biosynthetic pathway is not active. A better understanding of the PE biosynthetic pathway and its regulation is consequently necessary. Spinach is one of the very few crop plants which produce large amounts of PEs, of which 20-hydroxyecdysone is the major component. Labeling experiments with radiolabeled precursor (mevalonic acid), putative ecdysteroid intermediates and 20-hydroxyecdysone itself have allowed investigation of PE biosynthesis and transport during spinach development. Biosynthesis takes place in older leaf sets ("sources"), but not in the young developing ones, which in contrast accumulate (acting as "sinks") the PEs produced by the older leaves. PEs are thus continuously redistributed within the developing plant, as its leaf set number increases. The biosynthetic pathway has been analyzed using excised leaves and various labeled precursors, and a preferential sequence of the last steps has been established. Although they do not produce PEs, apical leaf sets are nevertheless able to perform several putative terminal steps of PE biosynthesis. The regulatory mechanisms of PE synthesis appear to involve a direct negative feedback of 20-hydroxyecdysone (the major PE in spinach) on its own synthesis; thus, a sustained synthesis in older leaves requires that they can export the PE they produce.     

North African wetland lakes: characterization of nine sites included in the CASSARINA Project

Exploitation of land and water resources has increased rapidly in North Africa during the 20th century, paralleling regional population growth. As part of the CASSARINA Project (see Flower, 2001), the environmental status of nine wetland lakes in Morocco, Tunisia, and Egypt was evaluated. All are conservationally important habitats and several are Ramsar Sites (internationally recognized bird reserves) and several support significant fisheries. All are shallow (<2 m in depth) but vary greatly in area.Where available, documentary information on relevant 20th century changes is given. Survey transects for aquatic vegetation were established and used to provide baseline ecological information on the aquatic plant communities during 1997–1999. Unusually, one site (Tunisian Megene Chitane) supported acidophilous vegetation (some taxa being nationally rare). Aquatic macrophytes declined catastrophically at two sites during the 1990s. Merja Bokka was drained in 1998 and, at Garaet El Ichkeul, fringing Phragmites and Scirpus spp. were lost, mainly as a result of salinity changes. Elsewhere, fringing macrophytes remain (extensively so in the Nile Delta lakes) common, despite major land reclamation and water quality problems, or are degraded by grazing (Merja Zerga). Marginal vegetation during 1997/98 changed markedly at Megene Chitane due to water level lowering.Documentary records indicated that throughout the 20th century, reclamation and hydrologic modifications, mainly for agricultural purposes, affected all nine sites. The loss of lake area by reclamation is substantial for the Nile Delta lakes (Edku, Burullus and Manzala). For the western sites, some data indicate increasing salinity in the most recent decade but the Delta lakes have become generally fresher during the 20th century, as supply of Nile water for irrigation increased.Despite intense human disturbance, many of the remaining CASSARINA sites still support regions of high aquatic diversity. Spatial scale monitoring of the larger sites for seasonal and inter-annual changes in open water area and in aquatic plant abundances is a key requirement for integrated environmental change assessment in the 21st century.     

Biodiversity characteristics of Teucrium polium species in Saudi Arabia

Teucrium (Lamiaceae) is a large and polymorphic genus distributed mainly in Europe, North Africa and in the temperate parts of Asia. In this study, the anatomical features of the leaf and stem of Teucrium polium are investigated. Teucrium has 19 taxa in Iran, which mainly grow in the Irano-Turanian region between 700 and 2000 m above sea level. T. polium belonging to sect. Polium, is a perennial herb growing on Lorestan province. The leaves clearly exhibit xeromorphy due to features such as thick cuticle layer, thick outer epidermal cell wall, high density of trichomes and thick palisade layer of the mesophyll. Anatomical studies on T. polium revealed that the stem shares the general characteristics of the Labiatae family. The aim of our approach was to study the morphological and taxonomical parameters for T. polium in Saudi Arabia. The results of this study showed that there was no influence of environment on the structure of stomata and trichomes as studying species with T.polium. In conclusion our study shows we have studied the geographical distribution of the species in Saudi Arabia and in the world.     

Effects of lactoferrin on intestinal epithelial cell growth and differentiation: an in vivo and in vitro study

This study was designed to analyse the effects of human (h) and bovine lactoferrin (bLF) on the growth and differentiation of intestinal cells using the mice model supplemented with Lactoferrin (LF) and the enterocyte-like model of Caco-2 cells which spontaneously differentiate after confluency. In mice, bLF supplementation increased jejunal villus height and the expression of several intestinal brush border membrane enzymes activities. Addition of bLF or hLF to undifferentiated Caco-2 cells was able to increase cell proliferation with confluency being reached more rapidly. Moreover, when Caco-2 cells were grown in the presence of LF for 3 weeks, brush-border membrane-associated enzyme activities i.e. sucrase, alkaline phosphatase and neutral aminopeptidase, as well as the l-glutamate transporter expression were all increased indicating an increased Caco-2 cell differentiation. Accordingly, cDNA Atlas array and Western blot analysis of cell cycle proteins shown a decreased expression of Cdck2 and an increased TAF1 expression; these proteins being implicated in the regulation of numerous genes related to cellular proliferation and differentiation. These modifications were associated with an inhibition of Caco-2 cell spontaneous apoptosis. Altogether, our results indicate that LF increase in vivo and in vitro enterocyte differentiation. In addition, LF was found to increase in vitro enterocyte proliferation resulting in higher cell density in cell flasks, an effect that was likely partly due to a reduction of the cellular apoptosis. The different stimulation patterns observed for the different parameters associated with cell differentiation in relationship with specific gene regulation is discussed.     

Interspecific incompatibility in Populus: inhibition of tube growth and behaviour of the male germ unit inP. deltoides×P. alba cross

Summary In order to better understand the cellular events controlling interspecific incompatibility in the genus Populus, the incompatible cross betweenP. deltoides andP. alba has been investigated both at the light and electron microscopic levels. Stained in decolourized aniline blue and observed by epifluorescence microscopy, most incompatible pollen grains are seen to germinate at the stigma surface. Numerous incompatible pollen tubes reach the base of the style where they are arrested 19 h after pollination. Ultrastructural observations on in vivo growing incompatible pollen tubes confirm these data. Very few cytoplasmic modifications are seen within living pollen tubes reaching the lower end of the style or within arrested ones, except the presence of polymorphic plastids. In this predominantly tricellular system, the male germ unit (MGU) is apparently initiated at pollen maturity as an association between the vegetative nucleus and sperm cells. It is maintained during pollen tube growth within the style and persists within arrested incompatible pollen tubes. The unique observation of an association between a dividing generative cell at metaphase and the vegetative nucleus is also reported. Arrested pollen tubes are characterized by apical deformations and accumulation of callose within their thickened cell walls. These cytological data provide additional information on the cellular events associated with interspecific incompatibility in Populus.Abbreviations DAPI 4,6-diamino-2-phenylindole - FCR fluorochromatic reaction - MGU male germ unit     

Lymph nodes are innervated by a unique population of sensory neurons with immunomodulatory potential

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Rational conversion of noncontinuous active region in proteins into a small orally bioavailable macrocyclic drug-like molecule: The HIV-1 CD4:gp120 paradigm

Rational conversion of noncontinuous active regions of proteins into a small orally bioavailable molecule is crucial for the discovery of new drugs based on inhibition of protein–protein interactions. We developed a method that utilizes backbone cyclization as an intermediate step for conversion of the CD4 noncontinuous active region into small macrocyclic molecules. We demonstrate that this method is feasible by preparing small inhibitor for human immunodeficiency virus infection. The lead compound, CG-1, proved orally available in the rat model.