Heat treatment results in a loss of transgene-encoded activities in several tobacco lines.

Heat treatment (37 degrees C) of transgenic tobacco (Nicotiana tabacum) plants led to a reversible reduction or complete loss of transgene-encoded activities in about 40% of 10 independent transformants carrying the luciferase-coding region fused to the 355 cauliflower mosaic virus or the soybean small subunit promoter and the nopaline synthase promoter driving the neomycin phosphotransferase gene, whereas the other lines had temperature-tolerant activities. Temperature sensitivity or tolerance of transgene-encoded activities was heritable. In some of the lines, temperature sensitivity of the transgene-encoded activities depended on the stage of development, occurring in either seedlings (40% luciferase and 50% neomycin phosphotransferase) or adult plants (both 40%). The phenomenon did not correlate with copy numbers or the homo- or hemizygous state of the transgenes. In lines harboring a temperature-sensitive luciferase activity, reduction of bioluminescence was observed after 2 to 3 h at 37 degrees C. Activity was regained after 2 h of subsequent cultivation at 25 degrees C. Irrespective of the reaction to the heat treatment, the level of luciferase RNA was slightly increased at 37 degrees C. Only in lines showing temperature sensitivity of transgene-encoded activities was the amount of luciferase and neomycin phosphotransferase strongly reduced. In sterile culture, heat treatment for 15 d did not cause visible damage or changes in plant morphology. In all plants tested a slight induction of the heat-shock response was observed at 37 degrees C.     

Temporal and spatial trends in heavy metal concentrations in the marine mussel Mytilus edulis from the Western Scheldt estuary (The Netherlands)

Since the first North Sea Conference (1984, Bremen), all countries bordering the North Sea made commitments to reduce discharge of hazardous substances into the North Sea. From Belgium and The Netherlands, large reductions (upto 90) in heavy metal emissions from land-based sources have been reported between 1985 and 2000. Recently, some studies in the Western Scheldt estuary (WS) have shown that total metal concentration in the water, sediments and suspended particles have decreased compared to levels in the 70s. However, data on aquatic organisms is still very limited and it is therefore difficult to confirm whether the reductions in pollution input and generally improving water quality in the WS have a corresponding impact on the levels of heavy metals in aquatic organisms. The current study measured metal concentrations in the soft tissues of mussels, Mytilus edulis (known to be good indicators of environmental metal pollution) during the period 1996–2002. Spatial (salinity and pollution gradients), temporal and seasonal variations were also studied. Results showed a down-stream decreasing trend for the metals studied (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) during all sampling campaigns. There was also a significant seasonal effect on tissue metal concentrations, with a peak observed around spring in both WS and the nearby less polluted Eastern Scheldt (ES). On temporal trends, a clear drop of metals in mussels was observed in the early 80s coinciding with the start of the efforts to reduce chemical pollution input into the North Sea. Since those early reductions, metal concentrations in mussels generally remained unchanged upto mid 90s. However, in recent times metal concentration in mussels have increased significantly, for example Cd in 2002 was almost 10 times the values in 1983 and similar to levels seen during the peak in the 70s. Other metals also increased in the 90s also reaching levels seen in the 70s. As there is no indication of recent increase in metal input into the estuary, we suggest that increased metal concentrations observed in mussels in recent years especially in the upper estuary are most likely a result of changes in physical and chemical speciation and metal bioavailability. Such changes may be caused by changes in some water quality parameters in the estuary (i.e. increased dissolved oxygen, concentration of organic matter), resulting in conditions that favour releases of sediment-bound metals into the water column. The relationship between metal content and season showed very similar annual profiles in the polluted WS and less polluted ES. Thus, seasonal variations in metal concentrations appear to be largely controlled by biological processes, while total body burdens are dependent on environmental levels and bioavailability.     

On feeding and nutrition in Fungiacava eilatensis (Bivalvia, Mytilidae), a commensal living in fungiid corals

The enlarged inhalant siphon of Fungiacava eilatensis opens into the coelenteron of species of fungiid corals with which it lives in commensal association. Material consisting of mucus, zooxanthellae, nematocysts, plankton and inorganic matter, is taken exclusively from the coelenteron. The very mobile foot possibly assists in food collection and in the removal of pseudofaeces; but, with large ctenidia, the bivalve is a typical ciliary feeder. Experiments with labelled zooxanthellae reveal that these are taken into the gut of Fungiacava with subsequent metabolic incorporation of products derived from them. The other prime source of food must be phytoplankton carried in with the feeding currents of the coral, itself carnivorous so that there is no competition for food between commensal and host. The Fungia zooxanthella– Fungiacava association operates as a "Troika" the productivity of which is autoregulated in proportion to the number of bivalves present. The inorganic wastes of the bivalve (as well as those of the coral) are utilized by the zooxanthellae, resultant increase in the algal component becoming available as food to the bivalve. Losses in the cycle are balanced by intake of exogenous food.     

Phosphorylation of the acetylcholine receptor by protein kinase C and identification of the phosphorylation site within the receptor delta subunit

Purified acetylcholine receptor is rapidly and specifically phosphorylated by partially purified protein kinase C, the Ca2+/phospholipid-dependent enzyme. The receptor delta subunit is the major target for phosphorylation and is phosphorylated on serine residues to a final stoichiometry of 0.4 mol of phosphate/mol of subunit. Phosphorylation is dose-dependent with a Km value of 0.2 microM. Proteolytic digestion of the delta subunit phosphorylated by either protein kinase C or the cAMP-dependent protein kinase yielded a similar pattern of phosphorylated fragments. The amino acids phosphorylated by either kinase co-localized within a 15-kDa proteolytic fragment of the delta subunit. This fragment was visualized by immunoblotting with antibodies against a synthetic peptide corresponding to residues 354-367 of the receptor delta subunit. This sequence, which contains 3 consecutive serine residues, was recently shown to include the cAMP-dependent protein kinase phosphorylation site (Souroujon, M. C., Neumann, D., Pizzighella, S., Fridkin, M., and Fuchs, S. (1986) EMBO J. 5, 543-546). Concomitantly, the synthetic peptide 354-367 was specifically phosphorylated in a Ca2+- and phospholipid-dependent manner by protein kinase C. Furthermore, antibodies directed against this peptide inhibited phosphorylation of the intact receptor by protein kinase C. We thus conclude that both the cAMP-dependent protein kinase and protein kinase C phosphorylation sites reside in very close proximity within the 3 adjacent serine residues at positions 360, 361, and 362 of the delta subunit of the acetylcholine receptor.