Biomedical Engineering Reference
In-Depth Information
Matrix A Matrix B
Dual
Matrix A
Mean rate per minute
Matrix B
1000
1000
Botulinum toxin-A
900
900
800
800
Referene "A"
700
700
Referene "B"
600
600
500
500
Matrix "B"
50 ng/ml
400
400
300
300
Volume
adjustment
to 1 ml
Matrix "A"
100 ng/ml
200
200
100
100
0
0
0 5 0 5
100
125
150
175
200
225
250
275
300
325
350
375
400
425
450
Matrix A
1000
Mean rate per minute
Matrix B
1000
Native
Botulinum toxin-A
900
900
800
800
Reference "A"
700
700
Reference "B"
600
600
500
500
Matrix "B"
50 ng/ml
400
400
300
300
Matrix "A"
100 ng/ml
Volume
adjustment
to 1 ml
200
200
100
100
0
0
0
25
50
75
100
125
150
175
200
225
250
275
300
325
350
375
400
425
450
FIGURE 6.12
Dual network array experiment showing responses to 100 ng/ml (Matrix A) and 50 ng/ml (Matrix B) botulinum
toxin-A. Time to 50% activity decay is 1.9 and 2.9 h for the high and low concentrations, respectively. The con-
centrations respond to approximately 660 and 320 picomoles. The lowest concentration at which responses were
repeatable was 2 ng/ml. Real-time computer display (CNNS NACTAN program).
glutamate release occurred after 150-210 min. These results agree well with the evolution
of activity changes depicted in Figure 6.11 where burst rates reach a maximum at 35 min
followed by a spike rate maximum at 60-100 min. Activity is lost (>90%) at 240 min.
6.3.3
Life Support Stability and Medium Biochemistry
The stability of the native activity and the repeatability of the responses are directly related to
the stability of the culture life support provided. Temperature, pH, and osmolarity of the
medium must be held as constant as possible. Small changes of pH (7.3-7.5) are tolerated, but
may affect activity in a subtle manner that has not yet been quantitatively described.
Temperature will directly affect the episode means as well as standard deviation of the minute
means. Although any temperature between 35 and 38°C can be used as reference, this value
must be kept within
0.2°C during the course of a compound evaluation. One interesting fea-
ture of the networks is that they tolerate exposure to hypothermic conditions at room tem-
perature (20-22°C), even showing in many cases spontaneous activity although
substantially reduced from that observed at physiologic temperatures. Like other cells,
