Key Role of Polyphosphoinositides in Dynamics of Fusogenic Nuclear Membrane Vesicles

The role of phosphoinositides has been thoroughly described in many signalling and membrane trafficking events but their function as modulators of membrane structure and dynamics in membrane fusion has not been investigated. We have reconstructed models that mimic the composition of nuclear envelope precursor membranes with naturally elevated amounts of phosphoinositides. These fusogenic membranes (membrane vesicle 1(MV1) and nuclear envelope remnants (NER) are critical for the assembly of the nuclear envelope. Phospholipids, cholesterol, and polyphosphoinositides, with polyunsaturated fatty acid chains that were identified in the natural nuclear membranes by lipid mass spectrometry, have been used to reconstruct complex model membranes mimicking nuclear envelope precursor membranes. Structural and dynamic events occurring in the membrane core and at the membrane surface were monitored by solid-state deuterium and phosphorus NMR. “MV1-like” (PC∶PI∶PIP∶PIP2, 30∶20∶18∶12, mol%) membranes that exhibited high levels of PtdIns, PtdInsP and PtdInsP2 had an unusually fluid membrane core (up to 20% increase, compared to membranes with low amounts of phosphoinositides to mimic the endoplasmic reticulum). “NER-like” (PC∶CH∶PI∶PIP∶PIP2, 28∶42∶16∶7∶7, mol%) membranes containing high amounts of both cholesterol and phosphoinositides exhibited liquid-ordered phase properties, but with markedly lower rigidity (10–15% decrease). Phosphoinositides are the first lipids reported to counterbalance the ordering effect of cholesterol. At the membrane surface, phosphoinositides control the orientation dynamics of other lipids in the model membranes, while remaining unchanged themselves. This is an important finding as it provides unprecedented mechanistic insight into the role of phosphoinositides in membrane dynamics. Biological implications of our findings and a model describing the roles of fusogenic membrane vesicles are proposed

ECRH in the Levitated Dipole Experiment

Abstract. It has been previously shown in mirror experiments that the use of multiple-frequency ECRH increased the pressure of trapped, high-energy electrons [l]. In the initial phases of the Levitated Dipole Experiment (LDX), ECRH will be applied with multiple frequencies between 2.45 and 28 GHz in order to produce a population of energetic electrons at high ft. The pressure profile will be controlled by adjusting the relative power of the ECRH sources. The effect of the pressure profile on plasma stability and confinement is a principal area of study for the LDX experiment. Ray tracing in the LDX geometry using a finite temperature code indicates that single-pass absorption can be obtained. ECRH has several other uses within LDX, such as formation and control of convective cells and the study of heating of over-dense thermal plasmas

Recombinant adenovirus infection process, Ontario Quebec Biotech meeting, \uc9cole Polytechnique, Montreal, Quebec, June 2000.

NRC publication: Ye

Study of adenoviral amplification using a fluorescence probe for online GFP monitoring

NRC publication: Ye

Use of an online GFP sensor for the bioprocess monitoring of recombinant adenovirus production

NRC publication: Ye

Ecological interactions in a shallow sand-pit lake (Lake Créteil, Parisian Basin, France): a modelling approach

A large data set (n = 154) of phytoplankton production and biomass in relation to physico-chemical environmental factors was collected from 1979 to 1986 in a recently created sand-pit lake (Paris suburbs). These data are well suited to interpret the oligotrophication observed along the 8 years period, characterized by a regular decrease in chlorophyll (from 16 to 4 μg l-1 as annual averages). A model describing the ecological functioning of the lake has been established. Biological processes related to phyto-, bacterio- and zooplankton as well as sediment-water interactions, are described within several submodels. Most of the parameters involved were determined by in situ measurements in this or similar environments The model provides a good simulation of observed data and confirms that the reduction of nutrient loading, resulting from the diversion - in 1981 - of a sewer previously discharging into the lake, was responsible for the oligotrophication of the system. The model allows to explore the response of planktonic compartments accross a gradient of nutrient loading. The role of hydrology is also tested. The systematic run of the model with and without zooplankton leads to a better understanding of top-down control. © 1994 Kluwer Academic Publishers.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

A critical examination of the possible application of zinc stable isotope ratios in bivalve mollusks and suspended particulate matter to trace zinc pollution in a tropical estuary

The application of zinc (Zn) isotopes in bivalve tissues to identify zinc sources in estuaries was critically assessed. We determined the zinc isotope composition of mollusks (Crassostrea brasiliana and Perna perna) and suspended particulate matter (SPM) in a tropical estuary (Sepetiba Bay, Brazil) historically impacted by metallurgical activities. The zinc isotope systematics of the SPM was in line with mixing of zinc derived from fluvial material and from metallurgical activities. In contrast, source mixing alone cannot account for the isotope ratios observed in the bivalves, which are significantly lighter in the contaminated metallurgical zone (δ66ZnJMC = +0.49 ± 0.06‰, 2σ, n = 3) compared to sampling locations outside (δ66ZnJMC = +0.83 ± 0.10‰, 2σ, n = 22). This observation suggests that additional factors such as speciation, bioavailability and bioaccumulation pathways (via solution or particulate matter) influence the zinc isotope composition of bivalves

Basalt petrology, zircon ages and sapphire genesis from Dak Nong, southern Vietnam

Basalts associated with sapphire deposits are widespread in Europe, Africa, Asia and Australia. In Vietnam, blue, green and yellow sapphires are recovered from eluvial and alluvial placers hosted in basaltic fields of the Dak Lak Province. Two distinct basalt suites are recognized in this field: a tholeiitic suite without any xenocrysts and an alkaline suite with mantle and lower crustal xenocrysts. The sapphires are enriched in Fe (0.43 to 1.26 wt.%), with moderate contents of Cr (33-1582 ppm), Ti (35-1080 ppm), Ga (149-308 ppm) and V (28- 438 ppm) and they are poor in Zn and Mg. Their O-isotope compositions range from 6.0 to 6.9 parts per thousand and are not in equilibrium with the alkali basalts which have delta(18)O values between 5.0 and 5.7 parts per thousand. The U-Pb dating of zircons recovered from the basaltic placers provides evidence of two eruptional events: one at similar to 6.5 Ma followed by another one at similar to 1 Ma. The petrography of the basalts and the oxygen isotopic composition of the sapphires suggest that the sapphires are xenocrysts and that they crystallized in a deep magma chamber, at the lower continental lithosphere and the upper mantle boundary, in evolved melts issued from the fractionation of alkali basaltic magmas contaminated with lower crustal fluids