Neurovascular embolization: in vitro evaluation of a mechanical detachable platinum coil system.

The authors evaluated a mechanically detachable platinum coil system intended for neurovascular use. The introduction characteristics, ease of delivery, ease of retrieval, and detachability were studied with fluoroscopic guidance with in vitro silicone models. All the coils passed easily through the microcatheter. The detachment maneuver occurred within 20 seconds with 20 or fewer rotations of the pusher wire. One of 229 coils detached prematurely but only after deliberate and extreme manipulation. The detachment system is safe, reliable, and consistent and will be useful for interventional neuroradiologists.

Cell death, survival and proliferation in Tetrahymena thermophila. Effects of insulin, sodium nitroprusside, 8-Bromo cyclic GMP, NG-methyl-L-arginine and methylene blue.

Cells of the ciliate Tetrahymena thermophila produce compounds that act as autocrine (paracrine) survival and/or growth factors. 8-Bromo cyclic GMP, sodium nitroprusside, hemin, protoporphyrin IX, human recombinant and bovine insulin were tested for their ability to substitute for the cell-produced factors and stimulate cell survival and proliferation. The cells were inoculated into conical flasks in a nutritionally complete, chemically defined medium at known cell densities from 5 to 5000 cells/ml. In unsupplemented medium cells at 5 to 500 cells/ml ('low initial cell density cultures') died within 8 h, whereas cells at 1000 and 5000 cells/ml ('high initial cell density cultures') proliferated with lag phases lasting for up to 4 h. In the presence of insulin compounds, hemin, protoporphyrin IX, or 8-bromo cyclic GMP, cells also proliferated at all low initial cell densities. Sodium nitroprusside was effective over two separate concentration ranges: at the nanomolar levels as well at low pico- to femtomolar levels. At initial population densities of up to 50 cells/ml the cells at both concentrations of sodium nitroprusside survived about 4-fold longer than the controls. At 500 initial cells/ml, cells at the high concentrations of sodium nitroprusside survived about 4-fold longer than those of the control cultures; they proliferated in the low concentrations of sodium nitroprusside. Concentrations of hemin, too low to have any effects on their own, had synergistic effects with sodium nitroprusside. NG-methyl-L-arginine inhibited proliferation at high initial cell densities. This inhibitory action was reduced by high concentrations of L-arginine, protoporphyrin IX, sodium nitroprusside, or 8-bromo cGMP, but not by insulin. Methylene blue inhibited cell proliferation at high initial cell densities. This inhibition was circumvented by addition of 8-bromo cGMP. The findings that insulin-related material may be released from Tetrahymena and that insulin and sodium nitroprusside increase intracellular cGMP in these cells are discussed in relation to the presented results. Together these observations suggest that cGMP is responsible for supporting cell survival in Tetrahymena and switching the cells into their proliferative mode, and that cell-produced signal molecules and insulin stimulate an NO-dependent guanylate cyclase into producing cGMP.

Insulin produces a biphasic response in Tetrahymena thermophila by stimulating cell survival and activating proliferation in two separate concentration intervals.

Cells of Tetrahymena may produce autocrine signal molecules with effects on survival and proliferation. Here we have tested the effects of human recombinant and bovine insulin, and the B22-B30 fragment of bovine insulin over a wide range of concentrations (10(-5)-10(-18) M) on cell survival and proliferation in a synthetic nutrient medium. The cells were grown in conical flasks at low initial cell densities (40 and 400 cells/ml). Insulin prevented rapid cell death and/or promoted cell proliferation over two separate concentration ranges: down to nanomolar levels and again in the low pico- and femtomolar range. At an initial population density of 400 cells/ml the cells multiplied at both concentration intervals. At 40 or fewer organisms/ml the cells multiplied in the high concentration interval, whereas in the low interval they survived for about four times longer than those in the control cultures. B22-B30 added to cultures of 40 initial cells/ml produced a stimulation of cell survival in the low pico- and high femtomolar range. In the presence of hemin (50 nM) cells at 400 initial organisms/ml multiplied at insulin concentrations down to about 3 nM and again from 300 am to 10 pM. In some cases, hemin plus insulin activated cell proliferation between the two concentration intervals as well. At 40 cells/ml the cells not only survived but proliferated in the femtomolar range. Cells in cultures supplemented with both hemin and B22-B30 multiplied at the low concentration interval (from about 100 fM to 10 pM).