Dynamic changes in soluble interleukin-2 receptor levels during treatment of Graves' disease. Correlation with disease activity

The activation of T lymphocyte is accompanied by the release of soluble interleukin-2 receptors (sIL-2R) which can be assessed in biological fluids. A prospective study of the dynamic changes in sIL-2R levels was performed in the serum of 10 patients undergoing a medical treatment for Graves' disease. All patients received carbimazole during the study and, when necessary, L-thyroxine to compensate hypothyroidism. sIL-2R levels were measured before (M0) and after the 1st (M1), 3rd (M3) and 6th month (M6) of treatment. The levels of sIL-2R were high at M0 and M1, and decreased significantly between M1 and M3 (p = 0.03). At M0, the levels of sIL-2R were highly correlated with triiodothyronine (T3) levels (p = 0.0003), early [131I] uptake (p = 0.007) and, to a lesser degree, with anti-thyrotropin receptor antibody levels (p = 0.02). At M6, no correlation was found anymore. We conclude that sIL-2R levels are increased in patients with untreated Graves' disease. They are highly correlated with the markers of Graves' disease activity and decrease during medical treatment.     

Scanning and transmission electron microscopy of three strains of Bifidobacterium.

Scanning and transmission electron microscopy was applied for a morphological study of three strains of Bifidobacterium grown on solid or liquid media. The pronounced pleomorphism of the cultures previously observed by light microscopy was confirmed. A possible sequence of the morphological events during transformation from one to another pleomorphic form is proposed for B. bifidum and B. longum. Ultrastructural differences such as the formation of extensive mesosomal complexes in B. longum and characteristic plasmalemma particles only observed in the B. bifidum mutant are described and discussed.     

Glucosylceramide Biosynthesis is Involved in Golgi Morphology and Protein Secretion in Plant Cells

Lipids have an established role as structural components of membranes or as signalling molecules, but their role as molecular actors in protein secretion is less clear. The complex sphingolipid glucosylceramide (GlcCer) is enriched in the plasma membrane and lipid microdomains of plant cells, but compared to animal and yeast cells, little is known about the role of GlcCer in plant physiology. We have investigated the influence of GlcCer biosynthesis by glucosylceramide synthase (GCS) on the efficiency of protein transport through the plant secretory pathway and on the maintenance of normal Golgi structure. We determined that GlcCer is synthesized at the beginning of the plant secretory pathway [mainly endoplasmic reticulum (ER)] and that d ,l ‐threo‐1‐phenyl‐2‐decanoyl amino‐3‐morpholino‐propanol (PDMP) is a potent inhibitor of plant GCS activity in vitro and in vivo. By an in vivo confocal microscopy approach in tobacco leaves infiltrated with PDMP, we showed that the decrease in GlcCer biosynthesis disturbed the transport of soluble and membrane secretory proteins to the cell surface, as these proteins were partly retained intracellularly in the ER and/or Golgi. Electron microscopic observations of Arabidopsis thaliana root cells after high‐pressure freezing and freeze substitution evidenced strong morphological changes in the Golgi bodies, pointing to a link between decreased protein secretion and perturbations of Golgi structure following inhibition of GlcCer biosynthesis in plant cells.     

N-hexanoyl-L-homoserine lactone, a mediator of bacterial quorum-sensing regulation, exhibits plant-dependent stability and may be inactivated by germinating Lotus corniculatus seedlings

The half-life of N-hexanoyl-l-homoserine lactone (C6-HSL) was determined under various pH and temperature conditions, and in several plant environments. C6-HSL was sensitive to alkaline pH, a process that was also temperature-dependent. In addition, C6-HSL disappeared from plant environments, i.e. axenic monocot and dicot plants cultivated under gnotobiotic, hydroponic conditions, albeit with variable kinetics. The disappearance was rapid at the root system of legume plants such as clover or Lotus, and slow or non-existent at the root system of monocots such as wheat or corn. These variable kinetics were not dependent upon pH changes that may have affected the growth media of the plants. Furthermore, C6-HSL did not accumulate in the plant, and the plant did not produce inhibitors of the C6-HSL signal. HPLC analyses revealed that C6-HSL disappeared from the media, and hence, Lotus exhibited a natural C6-HSL inactivating ability. This ability was not specific for C6-HSL and allowed the degradation of other N-acyl-homoserine lactones such as 3-oxo-C6-HSL, 3-oxo-octanoyl-HSL and 3-oxo-decanoyl-HSL. Preliminary investigation revealed that the inactivating ability is temperature-dependant and possibly of enzymatic origin.