Laser microfabricated model surfaces for controlled cell growth

The relatively recent applications of microelectronics technology into the biological sciences arena has drastically revolutionized the field. New foreseeable applications include miniaturized, multiparametric biosensors for high performance multianalyte assays or DNA sequencing, biocomputers, and substrates for controlled cell growth (i.e. tissue engineering). The objectives of this work were to investigate a new method combining microphotolithographical techniques with laser excimer beam technology to create surfaces with well defined 3-D microdomains in order to delineate critical microscopic surface features governing material-cell interaction. Another obvious application of this study pertains to the fabrication of cell-based biosensors. Microfabricated surfaces were obtained with micron resolution, by "microsculpturing" polymer model surfaces using a laser excimer KrF beam coupled with a microlithographic projection technique. The laser beam after exiting a mask was focused onto the polymer target surface via an optical setup allowing for a 10-fold reduction of the mask pattern. Various 3-D micropatterned features were obtained at the micron level. Reproducible submicron features could also be obtained using this method. Subsequently, model osteoblast-like cells were plated onto the laser microfabricated surfaces in order to study the effects of particular surface microtopography on preferential cell deposition and orientation. Preferential cell deposition was observed on surfaces presenting "smooth" microtopographical transitions. This system may provide an interesting model for further insights into correlations between 3-D surface microtopography and cell response with new applications in the field biosensor, biomaterial and pharmaceutical engineering sciences (e.g. new cell based biosensors, controlled synthesis of immobilized cell derived active ingredients).     

The metabolic (under)groundwork of the lily bulb toward sprouting

Large bulbs of Lilium longiflorum have an obligatory cold requirement to flower. Bulb cooling is widely used to induce and accelerate flowering. However, in‐depth investigations of the effect of bulb cooling on major landmarks of plant development are lacking. It has been demonstrated that low temperature induces carbohydrate degradation, yet integrative studies on metabolic changes occurring in the bulb are not available. We detected that cold exposure mainly hastened bulb sprouting, rather than floral transition or blooming. Metabolite profiling of cooled and non‐cooled bulbs was carried out, revealing cold‐induced accumulation of soluble sugars, lipids and specific amino acids, and a significant reduction in tricarboxylic acid (TCA)‐cycle elements. We observed that metabolic pathways located in the cytosol – including glycolysis, lipid synthesis and part of the gamma‐Aminobutyric acid (GABA) shunt – were enhanced by cold exposure, while mitochondrial metabolism – namely the TCA cycle – was reduced by cold. We suggest a physiological model accounting for this metabolic discrepancy.     

Human Immunodeficiency Virus Type 1 Intergroup (M/O) Recombination in Cameroon

Here we describe, for the first time, recombinants between two highly divergent major groups of human immunodeficiency virus type 1 (HIV-1), M and O, within a Cameroonian woman infected with three different HIV-1 strains, a group O virus, a subtype D virus, and a recently reported IBNG (A/G)-like recombinant virus. Using nested extra-long PCR amplification, we sequenced from the pol region to the env region including accessory genes of the viral genome obtained from the patient's uncultured peripheral blood mononuclear cells and examined the phylogenetic position of each gene. Compared with sequential blood samples obtained in 1995 and 1996, there were multiple segmental exchanges between three HIV-1 strains (O, D, and IBNG) and all the recombinants appeared to be derived from a common M/O ancestor. Importantly, recombination between groups M and O occurred, even though the homology between these two groups is 69, 76, 68, and 55% in the gag, pol, vif-vpr, and env regions, respectively. Recombination between strains with such distant lineages may contribute substantially to generating new HIV-1 variants.