The generally positive response to our target article indicates that most of the commentators accept our contention that light adaptation consists of multiple and possibly redundant mechanisms. The commentaries fall into three general categories. The first deals with putative mechanisms that we chose not to emphasize. The second is a more extended discussion of the role of calcium in adaptation. Finally, additional aspects of cGMP involvement in adaptation are considered. We discuss each of these points in turn.

This article evaluates each of the reactions known to be involved in visual transduction as a potential site for the regulation of light adaptation. Extensive evidence suggests that calcium acts as a feedback messenger at several different points and recent work suggests a role for cGMP in regulating the primary excitatory pathway. A conclusion is that adaptation is likely to be regulated by multiple and redundant mechanisms. The goal of future experimentation will be to determine the relative importance of each (...) of these. (shrink)

(No abstract is available for this citation).

The nondecay probability of an unstable particle at a definite moment of time is investigated provided this particle existed at all earlier observation moments separated with the time interval Δ. Using the usual postulates for quantum measurements it is proved that this probability is described by the exponential function of Δ>0, and it tends to 1 as Δ → 0. An approximate formula is found for the effective decay width Γ(Δ) appearing in the case of multiple measurements. It is shown (...) that Γ(Δ) → 0 as Δ → 0. For Δ → ∞, the width Γ(Δ) → Γ0, with Γ0 being the standard decay with in Weisskopf-Wigner theory. At finite δ's Γ(Δ) may be smaller or greater than Γ0 depending on the parameters of the theory. (shrink)

The development of cancer therapies is a long and arduous process. Because it can take several years for a cancer agent to pass clinical testing and be approved for use, terminal cancer patients rarely have the time to see these experimental therapies become widely available. For most terminal cancer patients the only opportunity they have to access an experimental drug that could potentially improve their prognosis is by joining a clinical trial. Unfortunately, several aspects of clinical trial methodology that are (...) set in place in order to optimise drug development for the benefit of future generations of cancer patients, pose significant limitations to current patient participation. Therefore, several terminal cancer patients believe that they should have the right to access experimental agents that have passed initial safety testing without having to participate in clinical trials. However, granting off-trial access to patients could be detrimental to the scientific process of drug development, and thus could pose significant risks to the health of future patients relying on sound research. Examining this matter through two divergent ethical lenses, rights-based ethics and communitarian ethics, may provide new insight into the issues surrounding the balance between the autonomous rights of current terminal cancer patients, and the needs of future patients and the values of society. (shrink)