j et al 10 the preparations of e granulosus protoscolex stored in liquid nitrogen are ground manually before being taken up in a solution of 4 2m guanidium thiocyanate 2 n lauroylsarcosine 10 mm edta ph 8 5 2 mercaptoethanol and 20 mm sodium acetate ph 4 5 this preparation is homogenised ultraturax before being sonicated and centrifuged at 10 000 rpm for 20 min sorvall rotor hb 4 the supernatant is then placed on a cushion of 2 ml of caesium chloride solution cscl density 1 72 10 mm edta ph 8 50 mm sodium acetate ph 5 5 the tubes are centrifuged at 28 000 rpm beckman rotor sw41 for 20 hours at 20 u00b0 c the rna pellet is then taken up in water and precipitated with absolute ethanol at 20 u00b0 c 4 preparation of the cdna library in phage lambda gt11 vector starting with 300 u03bcg of total rna extracted from e granulosus protoscolices the complementary dna strand is synthesised through the action of reverse transcriptase by means of an oligo dt primer the rna is then attacked with ribonuclease h which perforates it the remaining pieces of rna then serve as initiators for the action of e coli dna polymerase i which consequently synthesises the second strand of the cdna the use in the final phase of t4.