Antibody:	Anti-smooth muscle alpha-Actin (clone 1A4)
Detection system:	Secondary antibody coupled to horseradish peroxidase

Structure	Cell Type	Level	Pattern	Image	Note
TS19: 6th arch artery		Present		2a	Both 6th arch arteries showed solid and continuous expression between their origin in the pulmonary trunk and the dorsal aortae.
TS19: dorsal aorta	aortic smooth muscle cell	Present		2a	Three to five heavily stained layers of primary smooth muscle cells were seen.

Structure	Cell Type	Level	Pattern	Image	Note
TS19: 4th arch artery		Present		2b , 2c	Expression showed a clear discontinuity: most proximal parts downstream of the left cardiac outflow tract, expressed in a continuous pattern of two to three cell layers; in the distal half, positive peri-endothelial cells were only sparsely present and did not form a continuous layer.
TS19: aortic sac	aortic smooth muscle cell	Present		2b	Expressed in a primary tunica media of approximately two to three cell layers thick.
TS19: dorsal aorta		Present		2b	Three to five heavily stained layers of primary smooth muscle cells were seen.

Structure	Level	Pattern	Image	Note
TS19: 3rd arch artery	Present		2e	Expression was continuous along the entire length, with exception of a small area near the vagal nerve and junction with the dorsal aorta.

Structure	Cell Type	Level	Pattern	Image	Note
TS21: arch of aorta	aortic smooth muscle cell	Present	Regionally restricted	3b , 3a	Groups of cells that clearly lacked expression partially interrupt the media of the arch, which had otherwise attained a solid media of approximately five to six peri-endothelial layers of primary smooth muscle cells. The non- or weakly stained cells between the vagal and recurrent laryngeal nerves were separated from the endothelium by a single layer of actin-positive cells.

Structure	Cell Type	Level	Pattern	Image	Note
TS21: arch of aorta	aortic smooth muscle cell	Present	Regionally restricted	3c	A similar phenomenon of groups of non-staining cells was observed near the junction of the prospective brachiocephalic, subclavian and common carotid arteries.

Structure	Cell Type	Level	Pattern	Image	Note
TS20: arch of aorta	aortic smooth muscle cell	Present	Regionally restricted	3e	Groups of cells that clearly lacked expression partially interrupt the media of the arch, which had otherwise attained a solid media of approximately five to six peri-endothelial layers of primary smooth muscle cells.

Structure	Cell Type	Level	Pattern	Image	Note
TS23: arch of aorta	aortic smooth muscle cell	Present	Regionally restricted	4a	Groups of cells that previously had not stained had somewhat shifted in position towards the periphery of the media.

Structure	Level	Pattern	Image	Note
TS24: arch of aorta	Present	Regionally restricted	4e	The nonmuscular aortic ring was not as prominent as before, and appeared to have shifted towards more peripheral layers.

Structure	Cell Type	Level	Pattern	Image	Note
TS28: arch of aorta	aortic smooth muscle cell	Present	Regionally restricted	5c , 5a	The aortic B-segment between the dotted lines was clearly aberrant in showing optically lower staining levels caused by reduced cellular volume and increased elastic matrix.

Structure	Level	Pattern	Image	Note
TS28: right subclavian artery	Present	Regionally restricted	5e	Reduced positive tissue in a circular segment just downstream from the bifurcation of the brachiocephalic artery into the right carotid artery and subclavian artery (proximal part).

Structure	Cell Type	Level	Pattern	Image	Note
TS28: right subclavian artery	aortic smooth muscle cell	Present		5f	In the further downstream of the subclavian artery, homogeneous expression along its entire circumference was seen.

Structure	Cell Type	Level	Pattern	Image	Note
TS28: arch of aorta	aortic smooth muscle cell	Present	Regionally restricted	5g	Expression at the B-segment was much lower. Expression in a small number of cells in the B-segment was absent. The relative cellular volume/ matrix ratio was much smaller than elsewhere.

Structure	Cell Type	Level	Pattern	Image	Note
TS28: arch of aorta	aortic smooth muscle cell	Present		5h	Expression at the C-segment was much higher.

Structure	Cell Type	Level	Pattern	Image	Note
TS28: arch of aorta	aortic smooth muscle cell	Present	Regionally restricted	7a	Expression at the B-segment was much lower. Expression in a small number of cells in the B-segment was absent.

Structure	Level	Pattern	Image	Note
TS19: pulmonary artery	Present			The small pulmonary arteries showed a thin line of peri-endothelial expression.
TS19: 3rd arch artery	Present			Expressed in a primary tunica media of approximately two to three cell layers thick.
TS19: 4th arch artery	Present			Expressed in a primary tunica media of approximately two to three cell layers thick.
TS19: 6th arch artery	Present			Expressed in a primary tunica media of approximately two to three cell layers thick.

Structure	Cell Type	Level	Pattern	Image	Note
TS27: arch of aorta	aortic smooth muscle cell	Present	Regionally restricted		Areas with absence of immunoreactivity in outer media cell layers were seen.