230
D. Lloyd
2. For the separation of incompatible processes within the same cellular compartment e.g., H 2 S production and oxidative metabolism in a protozoon, Acanthamoeba castellanii [93, 99], and in yeast [72, 125, 153].
3. Oscillations in enzyme reactions lower the average concentrations involving
potentially toxic reaction products (e.g. H 2 O 2 , superoxide, and other reactive O 2
species (e.g. in the peroxidase-oxidase reaction), Hauser et al. [58]. Superoxide
radical anions (O 2
− ) act as signals, but in excess are responsible for oxidative
damage.
4. Oscillations may increase the thermodynamic efficiency of metabolism by
lowering energy dissipation [79, 122, 123], and/or be a necessary accompaniment
of the low-entropy state of cells [60].
5. Signaling: e.g., Ca
2+ oscillations transmit stimulus-specific information to downstream signaling machinery involving Ca
2+ dependent protein phosphorylation
[120]. Protein phosphatases and protein kinases are involved in the complex and
highly dynamic and specific signaling functions in normal, inflamed, [19], and
cancerous cells [51–56]. Out of phase expression of multiple isoenzymes may
be involved: e.g., in cultured erythroleukemia cells distinct temporal oscillatory
expression of 3 isoforms have been characterized [54, 56], and in the ras oncogene during proliferation and differentiation [56]. Regulation of the dynamics
may be crucial to the control of cell function and transformation. Oscillations
may encode information (frequency-encoding is more accurate than amplitude
encoding) in signal transduction chains or networks. Spatial reorganization is
required during differentiation, e.g., in the segmentation of embryos and insects
the ‘somite clock’.
6. Synchronization of intra- and extra-cellular processes. In heart and brain synchronization of coupled oscillators is vital for concerted signaling, action and
responses over wide spatial scales. Thus, time-frequency wavelet transforms of
several non-invasive measurements of cardiovascular signals within and between
neuronal (EEC) recordings indicate strengths and directions of interactions
between the two systems and in principle can be used to assess the state of
the organism under anesthesia [154].
7. Most biological receptors are phasic in their nature and therefore oscillating
signals can be rapidly sensed without membrane modification [122]: i.e., speed
of response can be faster from an appropriately rapidly oscillating signal.
14.1.5 Rhythms and Clock-Like Timekeepers
Rhythms are self-sustained oscillations, emergent and persistent, even if their characteristics (frequency, phase or amplitude) may become temporarily modified (as just
described for oscillations). However, their unregulated and hence unperturbed “freerunning” periods are robust and their periods, phase and amplitudes fully recoverable
when restraints or stimuli are removed. Biological clock-like synchronisers, e.g. the
D. Lloyd
2. For the separation of incompatible processes within the same cellular compartment e.g., H 2 S production and oxidative metabolism in a protozoon, Acanthamoeba castellanii [93, 99], and in yeast [72, 125, 153].
3. Oscillations in enzyme reactions lower the average concentrations involving
potentially toxic reaction products (e.g. H 2 O 2 , superoxide, and other reactive O 2
species (e.g. in the peroxidase-oxidase reaction), Hauser et al. [58]. Superoxide
radical anions (O 2
− ) act as signals, but in excess are responsible for oxidative
damage.
4. Oscillations may increase the thermodynamic efficiency of metabolism by
lowering energy dissipation [79, 122, 123], and/or be a necessary accompaniment
of the low-entropy state of cells [60].
5. Signaling: e.g., Ca
2+ oscillations transmit stimulus-specific information to downstream signaling machinery involving Ca
2+ dependent protein phosphorylation
[120]. Protein phosphatases and protein kinases are involved in the complex and
highly dynamic and specific signaling functions in normal, inflamed, [19], and
cancerous cells [51–56]. Out of phase expression of multiple isoenzymes may
be involved: e.g., in cultured erythroleukemia cells distinct temporal oscillatory
expression of 3 isoforms have been characterized [54, 56], and in the ras oncogene during proliferation and differentiation [56]. Regulation of the dynamics
may be crucial to the control of cell function and transformation. Oscillations
may encode information (frequency-encoding is more accurate than amplitude
encoding) in signal transduction chains or networks. Spatial reorganization is
required during differentiation, e.g., in the segmentation of embryos and insects
the ‘somite clock’.
6. Synchronization of intra- and extra-cellular processes. In heart and brain synchronization of coupled oscillators is vital for concerted signaling, action and
responses over wide spatial scales. Thus, time-frequency wavelet transforms of
several non-invasive measurements of cardiovascular signals within and between
neuronal (EEC) recordings indicate strengths and directions of interactions
between the two systems and in principle can be used to assess the state of
the organism under anesthesia [154].
7. Most biological receptors are phasic in their nature and therefore oscillating
signals can be rapidly sensed without membrane modification [122]: i.e., speed
of response can be faster from an appropriately rapidly oscillating signal.
14.1.5 Rhythms and Clock-Like Timekeepers
Rhythms are self-sustained oscillations, emergent and persistent, even if their characteristics (frequency, phase or amplitude) may become temporarily modified (as just
described for oscillations). However, their unregulated and hence unperturbed “freerunning” periods are robust and their periods, phase and amplitudes fully recoverable
when restraints or stimuli are removed. Biological clock-like synchronisers, e.g. the