. 2014 Mar 6;9(3):e90887. doi: 10.1371/journal.pone.0090887

Table 2. Principal component analysis of sperm cryotolerance with parameters (x) evaluated after incubation at 37°C for 30 min.

Component	Variance	Combinations of variables	a_ij	a_ij ²
1	59.49%	% Viable spermatozoa (SYBR-14⁺/PI⁻)	0.92	0.85
		Free cysteine radicals in sperm nucleoproteins	−0.91	0.83
		% Spermatozoa with fragmented DNA	−0.89	0.79
		% Non-viable spermatozoa with high lipid disorder (M540⁺/PI⁺)	−0.85	0.72
		% Viable spermatozoa without changes in m.p. (YO-PRO-1^−/PI⁻)	0.85	0.72
		% Membrane intact spermatozoa (PNA-FITC^−/PI⁻)	0.84	0.71
		% Viable spermatozoa with low lipid disorder (M540^−/PI⁻)	0.82	0.67
		% TMOT	0.81	0.66
		% Non-viable spermatozoa (YO-PRO-1^+/−/PI⁺)	−0.81	0.66
		% Viable spermatozoa with high lipid disorder (M540⁺/PI⁻)	−0.80	0.64
		% Membrane damaged spermatozoa that present o.a.m. (PNA-FITC⁺/PI⁺)	−0.80	0.64
		VAP	0.79	0.62
		% Viable spermatozoa with low intracellular Ca²⁺ levels (Fluo3-AM^−/PI⁻)	0.79	0.62
		VCL	0.78	0.61
		VSL	0.77	0.59
		% Viable spermatozoa with early changes in m.p. (YO-PRO-1⁺/PI⁻)	−0.75	0.56
		% Non-viable spermatozoa with low intracellular Ca²⁺ levels (Fluo3-AM^−/PI⁺)	−0.71	0.50
		% PMOT	0.70	0.49
		GMFI Fluo3-AM⁺	−0.64	0.41
2	11.95%	% Membrane damaged spermatozoa with lost o.a.m. (PNA-FITC^−/PI⁺)	−0.86	0.74
		% Viable spermatozoa with high intracellular Ca²⁺ levels (Fluo3-AM⁺/PI⁻)	−0.67	0.45
		% Viable spermatozoa with high intracellular peroxide levels (DCF⁺/PI⁻)	0.59	0.35
		Non-viable spermatozoa with high intracellular Ca²⁺ levels (Fluo3-AM⁺/PI⁺)	−0.57	0.32
3	8.30%	GMFI E⁺/PI⁻	0.84	0.71
		GMFI E⁺/Total	−0.64	0.41
4	6.78%	GMFI DCF⁺/PI⁻	0.98	0.96
		GMFI DCF⁺/Total	0.68	0.46
5	4.71%	% LIN	0.87	0.76
		% STR	0.79	0.62
		% WOB	−0.62	0.38
Total	91.23%

Each cryotolerance index was calculated as follows: Inline graphic .

(m.p.: membrane permeability; o.a.m.: outer acrosome membrane; GMFI: Geometric mean of fluorescence intensity; arbitrary units).