Table 1.

Quantification of neurexin and neuroligin expression in the E5 chicken embryo

Class	Range of wall thickness (μm), by SMA staining	Number of vessels in the class	Range of vessel length (μm)	Range of vessel diameter (μm)	α-SMA staining intensity	NRXN staining intensity	NLGN staining intensity	Representative vessels of the class
1	0–4	17	20–250	4.5–135	0/+	+	+	Arteries and veins of the primary cephalic plexus
2	4–6	13	21–270	5–250	+	+	+	Intersomitic vessels
3*	6–10*	17*	34–1650*	13–115*	++	++	++	Dorsal aorta, subcardinal vein, primary cephalic plexus
4*	>10*	10*	52–1130*	33–116*	+++	++	++	Aortic arches

Medial sagittal sections from 6 entire E5 chicken embryos were immunohistochemically stained and blood vessels throughout the sections were evaluated for their expression of α-SMA, neurexin, and neuroligin. Next, various morphological parameters were measured, and the vessels were separated into 4 classes based on the thickness of the SMA staining in their walls. Arbitrary values of expression were reported for each marker: +++, strong; ++, good; +, weak. Data show that neurexin and neuroligin expression almost perfectly matches that of α-SMA.

*Examples of blood vessels included in classes 3 and 4 are presented in Fig. 2A.