Effect of sulphate deficiency on the plasma membrane polypeptide composition of Brassica napus

Highly purified oilseed rape (Brassica napus) root plasma membranefractions were prepared and their polypeptide patterns analysedby two-dimensional gel electrophoresis. Sulphur starvation enhancesthe sulphate uptake capacity of B. napus roots. The relativeabundance of several polypeptides increased significantly andspecifically after sulphur starvation. Several of them (37,38, 60, and 65 kDa), found in sulphur-starved plants, were moreabundant in a phase-partitioned membrane fraction treated withTriton X-100/KBr, indicating that they are intrinsic polypeptides.One polypeptide (47 kDa) was identified in the in vitro translationproducts of the roots mRNAs as specific for S-starved plants.It was also present among the intrinsic polypeptides specificfor —S plants. These plasma membrane polypeptides mightbe involved in sulphate uptake. Key words: Sulphate, sulphur-starvation, plasma membrane, polypeptides, root, transport     

Origin and development of river zooplankton: example of the Marne

Zooplankton composition and growth in the river Marne (France)were studied on a space scale of 300 km in July 1991. There werethree distinct areas along the river: the immediate reservoir outlet(pK 652), the natural river called middle Marne (from pK 652to pK 799 downstream) and the channeled river (from pK 799 topK 975 downstream). A typical lake community, characterized both byan abundance of microcrustaceans and a high zooplanktonconcentration was found immediately downstream of the reservoir Marne(Der-Chantecocq Lake). Here, large microcrustaceans (copepods,daphnids), and large rotifers (Keratella cochlearisrobusta and Polyarthra dolichoptera-vulgaris) rapidlydisappeared, and small rotifer species (<120 m) dominated theplankton. Their populations (specially Keratella c. cochlearis)proliferated in the middle Marne as far as 100 km downstream(up to 288 ind. l-1) but were considerably reduced (20 to35 ind. l-1) where the river is channeled, algal resourcesdecline and turbidity increases.The dominance of small organisms such as rotifers, in riverplankton is assumed to be the result of fish predation on largezooplankton as well as of a short generation time which allowstheir in situ reproduction, in spite of a short residencetime of the water.     

Compartmentalized coculture of porcine arterial endothelial and smooth muscle cells on a microporous membrane

Summary Endothelial and smooth muscle cells were harvested from porcine pulmonary arteries and grown to two passages from primary culture in serum-containing medium. Thereafter, the cells were plated on the opposite sides of a microporous poly-(ethylene terephthalate) membrane and cultivated in a chemically defined, serum-free medium. The membrane with pores of 1 μm diameter allowed the passage of molecules and the extension of cell processes, while maintaining separate homogeneous cell populations. Pores of 3 μm diameter permitted the crossing of smooth muscle cells through the membrane. The coating of the polymer with constituents of the extracellular matrix optimized cell adhesion. Morphological analysis of the model showed typical cobblestone pattern and ultrastructure of endothelial cells, which lost rapidly the expression of von Willebrand factor but kept that of angiotensin-converting enzyme. Smooth muscle cells were spindle shaped and specific α-actin was revealed by immunochemistry and quantitated by enzyme-linked immunosorbent assay (ELISA). Their ultrastructure featured an intermediate contractile-synthetic phenotype. Permeability studies to different molecules showed a marked reduction of the albumin clearance. Finally, in coculture in the presence of endothelial cells, the smooth muscle cells proliferation was increased, whereas it was not the case in autologous cocultures. In conclusion, such a coculture model may help to a better understanding of the interactions between endothelial and smooth muscle cells that may be important in the pathogenesis of vascular diseases.     

Plant hormones and plant growth regulators in plant tissue culture

Summary This is a short review of the classical and new, natural and synthetic plant hormones and growth regulators (phytohormones) and highlights some of their uses in plant tissue culture. Plant hormones rarely act alone, and for most processes— at least those that are observed at the organ level—many of these regulators have interacted in order to produce the final effect. The following substances are discussed: (a) Classical plant hormones (auxins, cytokinins, gibberellins, abscisic acid, ethylene and growth regulatory substances with similar biological effects. New, naturally occurring substances in these categories are still being discovered. At the same time, novel structurally related compounds are constantly being synthesized. There are also many new but chemically unrelated compounds with similar hormone-like activity being produced. A better knowledge of the uptake, transport, metabolism, and mode of action of phytohormones and the appearance of chemicals that inhibit synthesis, transport, and action of the native plant hormones has increased our knowledge of the role of these hormones in growth and development. (b) More recently discovered natural growth substances that have phytohormonal-like regulatory roles (polyamines, oligosaccharins, salicylates, jasmonates, sterols, brassinosteroids, dehydrodiconiferyl alcohol glucosides, turgorins, systemin, unrelated natural stimulators and inhibitors), as well as myoinositol. Many of these growth active substances have not yet been examined in relation to growth and organized developmentin vitro.     

Abdominal Visceral Fat is Associated with a BclI Restriction Fragment Length Polymorphism at the Glucocorticoid Receptor Gene Locus

Several investigations have suggested that body fat distribution is influenced by nonpathologic variations in the responsiveness to Cortisol. Genetic variations in the glucocorticoid receptor (GRL) could therefore potentially have an impact on the level of abdominal fat. A restriction fragment length polymorphism (RFLP) has previously been detected with the BelI restriction enzyme in the GRL gene identifying two alleles with fragment lengths of 4.5 and 2.3 kb. This study investigates whether abdominal fat areas measured by computerized tomography (CT) are associated with this polymorphism in 152 middle-aged men and women. The less frequent 4.5-kb allele was found to be associated with a higher abdominal visceral fat (A VF) area independently of total body fat mass (4.5/4.5 vs. 2.3/2.3 kb genotype; men: 190.7 ± 30.1 vs. 150.7 ± 33.3 cm², p=0.04; women: 132.7 ± 37.3 vs. 101.3 ± 34.5 cm², p=0.06). However, the association with AVF was seen only in subjects of the lower tertile of the percent body fat level. In these subjects, the polymorphism was found to account for 41% (p=0.003) and 35% (p=0.007), in men and women, respectively, of the total variance in AVF area. The consistent association between the GRL polymorphism detected with BelI and AVF area suggests that this gene or a locus in linkage disequilibrium with the BelI restriction site may contribute to the accumulation of AVF.     

Parasites, biodiversity and ecosystem stability

The influence of parasites in ecosystems, especially on biodiversity, is discussed. Various examples illustrate the role that parasites play in the outcome of interspecific competition, in the success of invading species, and in the separation of emerging species. Parasites can be stabilizers or destabilizers, depending on factors such as susceptibility of hosts and size of the ecosystem. Parasites play a major role each time something disturbs living beings at the populational and/or specific level, as they do at the individual level.