232
J. KIRK, and J. S. ORR
Ziehen, or frequency jump, effect. In a system of coupled electronic oscillators, the resonance condition for the system as a whole occurs when the
reactance is zero, and this condition is satisfied for two frequencies. The
system will be stable in one or other of the two frequencies, depending on
its energy. As the energy changes through some critical value, the system
can jump from one meta-stable state to the other. The two modes of oscillation shown in figure 3 can be compared with the two meta-stable states of
the electronic analogue, and the disturbance at 150 days represents the
frequency jump or transient involved in the transition from one mode to
the other.
The analogy between this electronic system of coupled oscillators, and
the behaviour of the mathematical formulation of the red cell system with
its two interacting control loops, appears to be very close, and an analysis
of the latter system in the light of this analogy may prove of considerable
interest and value.
References
1. HULSE, E. V.: Brit. J. Haemat. 9, 365 (1963).
2. ORR, J. S., J. KIRK, K. G. GRAY and J. R. ANDERSON: Brit. J. Haemat. 15,23
(1968).
3. PORTEOUS, D. D., and L. G. LAJTHA: Brit. J. Haemat. 12, 177 (1966).
Discussion
KIEFER:
Is there experimental evidence for a stem-cell specific chalone?
KIRK:
Not exactly, but BULLOUGH and LAURENCE (1964) described an experiment
on the inhibitory effects of chalone in mouse epidermal tissue. The form of
this inhibition effect has been carried over and applied to stem cells.
KIEFER:
How would the behaviour of your model system be changed if the other ways
of differentiation were accounted for by more feedback loops?
KIRK:
The behaviour would not be basically changed, but other differentiation channels would cause more fluctuations in the stem cell population and compete
to some extent with red cell differentiation channels.
KIEFER:
The integration step of one day is in the order of the mitotic cycle time of the
stem cells. Is it not likely to introduce artefacts by such a long integration step?
KIRK:
The one-day integration step has a great deal to recommend it owing to
diurnal effects in the system. Calculations on a small section of the system
with an integration step of 1/5 of a day introduced a difference of less than
6 %; also the integration effect is of the order of 1/20 of the frequency of the
loops. Thus, it is very unlikely that any artefacts are introduced.
J. KIRK, and J. S. ORR
Ziehen, or frequency jump, effect. In a system of coupled electronic oscillators, the resonance condition for the system as a whole occurs when the
reactance is zero, and this condition is satisfied for two frequencies. The
system will be stable in one or other of the two frequencies, depending on
its energy. As the energy changes through some critical value, the system
can jump from one meta-stable state to the other. The two modes of oscillation shown in figure 3 can be compared with the two meta-stable states of
the electronic analogue, and the disturbance at 150 days represents the
frequency jump or transient involved in the transition from one mode to
the other.
The analogy between this electronic system of coupled oscillators, and
the behaviour of the mathematical formulation of the red cell system with
its two interacting control loops, appears to be very close, and an analysis
of the latter system in the light of this analogy may prove of considerable
interest and value.
References
1. HULSE, E. V.: Brit. J. Haemat. 9, 365 (1963).
2. ORR, J. S., J. KIRK, K. G. GRAY and J. R. ANDERSON: Brit. J. Haemat. 15,23
(1968).
3. PORTEOUS, D. D., and L. G. LAJTHA: Brit. J. Haemat. 12, 177 (1966).
Discussion
KIEFER:
Is there experimental evidence for a stem-cell specific chalone?
KIRK:
Not exactly, but BULLOUGH and LAURENCE (1964) described an experiment
on the inhibitory effects of chalone in mouse epidermal tissue. The form of
this inhibition effect has been carried over and applied to stem cells.
KIEFER:
How would the behaviour of your model system be changed if the other ways
of differentiation were accounted for by more feedback loops?
KIRK:
The behaviour would not be basically changed, but other differentiation channels would cause more fluctuations in the stem cell population and compete
to some extent with red cell differentiation channels.
KIEFER:
The integration step of one day is in the order of the mitotic cycle time of the
stem cells. Is it not likely to introduce artefacts by such a long integration step?
KIRK:
The one-day integration step has a great deal to recommend it owing to
diurnal effects in the system. Calculations on a small section of the system
with an integration step of 1/5 of a day introduced a difference of less than
6 %; also the integration effect is of the order of 1/20 of the frequency of the
loops. Thus, it is very unlikely that any artefacts are introduced.