2,133 research outputs found
Protestant letter networks in the reign of Mary I: A quantitative approach
Sebastian E. Ahnert was supported by The Royal Society, UK
Millimolar concentrations of free magnesium enhance exocytosis from permeabilized rat pheochromocytoma (PC 12) cells
The role of Mg2+ during the final steps of exocytosis was investigated using rat pheochromocytoma cells (PC12) permeabilized with bacterial pore forming toxins. Concentrations of free Mg2+ between 0.2 and 2 mM slightly lowered the basal but greatly enhanced the [3H]dopamine release elicited by 8 ΌM free Ca2+. Maximal effects were obtained at approximately 1 mM free Mg2+. At higher concentrations Mg2+ was less potent. Similar effects of Mg2+ were obtained in cells permeabilized either for small molecules (by α-toxin) or for large ones (by streptolysin O). It is concluded that millimolar concentrations of cytoplasmic Mg2+ play an important role in Ca2+ triggered exocytosis
Reductive chain separation of botulinum A toxin â a prerequisite to its inhibitory action on exocytosis in chromaffin cells
Cleavage of the disulfide bond linking the heavy and the light chains of tetanus toxin is necessary for its inhibitory action
on exocytotic release ofcatecholamines from permeabi1ized chromaffin cells [(1989) FEBS Lett. 242, 245-248; (1989) J.
Neurochern., in press]. The related botulinum A toxin also consists of a heavy and a light chain linked by a disulfide
bond. The actions ofboth neurotoxins on exocytosis were presently compared using streptolysin O-permeabilized bovine
adrenal chromaffin cells. Botulinum A toxin inhibited Ca2 +-stimulated catecholamine release from these cells. Addition
of dithiothreitollowered the effective doses to values below 5 nM. Under the same conditions, the effective doses of tetanus
toxin were decreased by a factor of five. This indicates that the interchain S-S bond of botulinum A toxin must
also be split before the neurotoxin can exert its effect on exocytosis
Odeint - Solving ordinary differential equations in C++
Many physical, biological or chemical systems are modeled by ordinary
differential equations (ODEs) and finding their solution is an every-day-task
for many scientists. Here, we introduce a new C++ library dedicated to find
numerical solutions of initial value problems of ODEs: odeint (www.odeint.com).
odeint is implemented in a highly generic way and provides extensive
interoperability at top performance. For example, due to it's modular design it
can be easily parallized with OpenMP and even runs on CUDA GPUs. Despite that,
it provides a convenient interface that allows for a simple and easy usage.Comment: 4 pages, 1 figur
Models for the two-phase flow of concentrated suspensions
A new two-phase model for concentrated suspensions is derived that
incorporates a constitutive law combining the rheology for non-Brownian
suspension and granular flow. The resulting model exhibits a yield-stress
behavior for the solid phase depending on the collision pressure. This property
is investigated for the simple geometry of plane Poiseuille flow, where an
unyielded or jammed zone of finite width arises in the center of the channel.
For the steady states of this problem, the governing equations are reduced to a
boundary value problem for a system of ordinary differential equations and the
conditions for existence of solutions with jammed regions are investigated
using phase-space methods. For the general time-dependent case a new drift-flux
model is derived using matched asymptotic expansions that takes into account
the boundary layers at the walls and the interface between the yielded and
unyielded region. The drift-flux model is used to numerically study the dynamic
behavior of the suspension flow including the appearance and evolution of an
unyielded or jammed region
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