Table 2.

Reverse transcriptase (RT) activity in cultured sporocysts

Exp.	Sample	RT activity, OD405
A	Lysis buffer (no extract)	0.065
	Sporocyst extract	0.121
	Viral RT control	0.907
B	Lysis buffer (no extract)	0.076
	RT control	0.750
	Viral RT control + sporocyst extract	0.156
	Extract from mouse cells expressing RT	0.188

Experiments were carried out as described in the text. Positive reverse transcriptase control contained 1 ng of purified viral enzyme. Extract volume added to reverse transcriptase control in Exp. B was 20 μl. Mouse cells expressing reverse transcriptase were genetically altered retroviral packing cells (83psiAM, ATTC CLR 8859).