Biomedical Engineering Reference
In-Depth Information
a
b
Collection of animals with liquid
Place animals on a plate with defined regions
12345678
d
c
Visualize data or calculate index
Score distribution of the animals
N
i=1
Σ
Si
0.5
thermal gradient
no gradient
TTX mean = S =
N
0.4
0.3
N
i=1
0178
counter
2
Σ
(Si - S)
N - 1
0.2
TTX deviation =
0.1
0
Si : Score of individual i
N : Total number of animals on a TTX plate
12345
678
region
Fig. 1.1
Protocol of population behavioral analysis for
C. elegans
. (
a
) Cultivated animals were
collected and washed with liquid. Several buffers were used depending on the purpose of experi-
ments. (
b
) Collected animals were placed on assay plate. Extra liquid were removed by tissue
paper to prevent the worms from swimming. (
c
) Score the distribution of animals in the assay plate
after certain assay time. (
d
) Visualize scored data and/or calculate characteristic index. Statistical
analysis should be needed to discriminate the difference between the different conditions
probabilistic property of animal behavior. In this section, we describe about
population assay for
C. elegans
in which we use relatively a large number of ani-
mals for each experiment. Such assay systems enable to provide well-reproducible
data even with rather small number of trials. Due to small body size and prolifi c
nature, population assay for
C. elegans
is easy and practical in laboratory
experiments. Thus, the population analysis for
C. elegans
can reduce time and cost
to validate the focusing behavioral character, as compared with single animal analy-
sis described in the later section.
1.2.1
Protocol of Population Analysis
Exact protocols of population assay vary depending on its purpose. We thus sum-
marize here four main steps of population assay shown in Fig.
1.1
. First, a large
number of animals are collected from cultivating plate (Fig.
1.1a
). Liquids such
as wash buffer (0.02 % gelatin, 50 mM NaCl, and 25 mM pH 6.0 potassium
phosphate) or NG buffer (0.3 % NaCl, 1 mM CaCl
2
, 1 mM MgSO
4
, and 25 mM
pH 6.0 potassium phosphate) are used for this collection step. Note that the buf-
fer composition sometimes affects behavioral assay so that the selection of buf-
fer should be carefully considered. Usually this collection step includes aiming
to wash off the food sticking to the animal body. Second, the collected animals
are gently placed on an assay plate with defi ned regions (Fig.
1.1b
). The assay
plate should be kept with constant and stable environment during assay. Since
behavior is affected by any kinds of stimuli around the plate, experimenters
should be attentive to keep the assay environment strictly controlled in fi ne
