A Kinetic Model of the Inositol Trisphosphate Receptor Based on Single-Channel Data

In many cell types, the inositol trisphosphate receptor is one of the important components controlling intracellular calcium dynamics, and an understanding of this receptor is necessary for an understanding of calcium oscillations and waves. Based on single-channel data from the type-I inositol trisphosphate receptor, and using a Markov chain Monte Carlo approach, we show that the most complex time-dependent model that can be unambiguously determined from steady-state data is one with three closed states and one open state, and we determine how the rate constants depend on calcium. Because the transitions between these states are complex functions of calcium concentration, each model state must correspond to a group of physical states. We fit two different topologies and find that both models predict that the main effect of [Ca²⁺] is to modulate the probability that the receptor is in a state that is able to open, rather than to modulate the transition rate to the open state.     

Long-term cultivation of immortalised mouse hepatocytes in a high cell density,fixed-bed reactor

An immortalised mouse hepatocyte line was grown in culture flasks and in a small-scale fixed-bed system to determine growth characteristics and a suitable carrier type. The cells were then cultivated in a 40 ml fixed-bed reactor over 75 days at a perfusion rate of 6.25 ml medium per ml fixed-bed and day. A cell density of approx. 8.5.107 cells per ml carrier was reached at the end of the experiment proving that a stable cultivation was possible over a long period of time with constant consumption and production rates.     

Linked transcripts of the genes for leader and N message are synthesized in vitro by vesicular stomatitis virus

Synthesis of vesicular stomatitis virus RNA in the presence of the β, γ imido analog of ATP lead to the inhibition of normal message synthesis and resulted in the appearance of two electrophoretically distinct RNA species. Comparison of T1-oligonucleotide fingerprint patterns indicated that the major product contained oligonucleotides characteristic of both leader RNA and N message suggesting that it arose by read through of the leader-N gene junction with subsequent termination at the 3′ end of the N gene.