1. Models in stress research
Brest, 2016/08/29/14:00
MEMS Summer school

2. Contents Stress Research - in biology - in energetics - in stress
Meta-models

3. Stress stress factor too little enough too much
too little
enough
too much
No stress for a range of factor values
Stress = difference from no-stress
Consequence:
We need to know the no-stress situation
to recognize stress, including `variability’

4. Arrhenius relationship
stress
ln pop growth rate, h-1
103/T, K-1
103/TH
103/TL

6. Space-time scales system earth space ecosystem population individual
Each process has its characteristic domain of space-time scales
molecule
cell
individual
population
ecosystem
system earth
time
space
When changing the space-time scale,
new processes will become important
other will become less important
This can be used to simplify models,
by coupling space-time scales
Complex models are required
for small time and big space scales and vv
Models with many variables & parameters
hardly contribute to insight

7. Biochemical ↔ Pools many compounds few pools need for selection
conservation laws
cannot be used
wide range in scales
complex dynamics
easy connection
with molecular level
with literature
few pools
use of homeostasis
conservation laws
can be used
narrow range in scales
simple dynamics
complex connection
with molecular level
with literature
Bridge calls for intermediary levels of organisation

8. Homeostasis strong homeostasis weak homeostasis structural homeostasis
constant composition of pools (reserves/structures)
generalized compounds, stoichiometric constraints on synthesis
weak homeostasis
constant composition of biomass during growth in constant environments
determines reserve dynamics (in combination with strong homeostasis)
structural homeostasis
constant relative proportions during growth in constant environments
isomorphy .work load allocation
thermal homeostasis
ectothermy  homeothermy  endothermy
acquisition homeostasis
supply  demand systems
development of sensors, behavioural adaptations
Homeostasis is the ability to run metabolism independent from environmental conditions.
This can obviously not be perfect, all organisms require food and/or nutrients.
We need 5 difference homeostasis concepts to capture the extent organisms sport homeostasis.

9. Static vs Dynamic Budgets
Net production models
time-dependent static models
no damping by reserve
Assimilation models
dynamics by nature
reserve damps food fluctuations

10. Criteria for general energetic models
Quantitative
Based on explicit assumptions that together specify all quantitative aspects to allow for mass and energy balancing
Consistency
Assumptions should be consistent in terms of internal logic, with physics and chemistry, as well as with empirical patterns
Simplicity
Implied model(s) should be simple (numbers of variables and parameters) enough to allow testing against data
Generality
The conditions species should fulfill to be captured by the model(s) must be explicit and make evolutionary sense
Explanatory
The more empirical patterns are explained, the better the model

11. Stress by chemical compounds
Par values depend on internal concentration: transport
1 compartment
1-1 compartment
internal conc
external conc
partition coef =
vol environ
vol organism
dim(partition coef) =
vol organism
time × vol environ 1
time
dim(accum rate) =
dim(elim rate) =

12. n,n-compartment models 6.3a
1,1-comparment
model
film
model
Compound can cross,
interface between media with different rates vice versa
sub-layers with equal rates for all sublayers

13. Meta models models for parameter values Null model:
group pars in either intensive or extensive
find a simple function of pars that contains 1 extensitive par x
example: max struct length for standard DEB model,
example: bioconc factor for 1 compartment model
find ratios of extensive pars that are intensive and contains x
this links all extensive parameters to x
write property of interest as function of pars and study how is scales with x

14. Primary parameters standard DEB model
The are all standard DEB model parameters for an individual with a max structural length of 1 cm at 20°C
Simple rules apply for individuals of different max length and/or temperature.
Kooijman 1986
J. Theor. Biol.
121:

15. Primary parameters 1-1 compartment, film model
time to reach x-level saturation
film model
Kooijman et al 2007
SAR & QSAR Environ. Res.
18:

16. DEB tele course 2017 Audience: thank you for your attention
Free of financial costs;
Some 108 or 216 h effort investment
Program for 2017:
Feb/Mar general theory (5w)
May symposium in Tromso (N) (8d +3 d)
Target audience: PhD students
We encourage participation in groups
who organize local meetings weekly
Software package DEBtool for Octave/ Matlab
freely downloadable
Slides of this presentation are downloadable from
Cambridge Univ Press 2009
Audience:
thank you for your attention